^{19th World Congress on} Materials Science and Engineering June 11-13, 2018 Tryp Barcelona Aeropuerto, Barcelona, Spain

Biography:

Arnaud Caron is a materials scientist with expertise in the multi-scale mechanical behavior of materials, surfaces and micro-components. Since 2015 Arnaud Caron is Assistant Professor in the School of Energy, Materials and Chemical Engineering at KoreaTech, Republic of Korea. Arnaud Caron obtained his engineering degree in Materials Science in 2004 from the University of Saarland, Germany and was awarded with the Schiebold Medal. In 2009 he earned his doctoral degree in Materials Science from the University of Saarland, Germany. From 2006 to 2015 Arnaud Caron worked as a research associate at the Institute of Micro- and Nanomaterials of the University of Ulm, Germany, the WPI-Advanced Institute of Materials Research, Japan and the Leibniz – Institute for New Materials, Germany.

Abstract:

Understanding and controlling the surface mechanical behavior of materials is crucial for the development of new devices. We have investigated the effects of chemistry on the friction and wear behavior of face centered cubic metal and alloy surfaces in contact with a single asperity by friction force microscopy. In the low load regime below 10 nN, we show that sliding friction behaviors of different metallic couples is governed by their thermodynamic affinity. Comparing the friction behavior of miscible and immiscible couples we find that in the first case friction is governed by adhesion while the friction force is almost independent on the normal load. In the latter case of immiscible couples, adhesion is found to be low and the friction force increases with the normal load. At larger loads, friction and wear of pure fcc metals is found to scale with the ratio of the surface energy to the hardness, which describes both contributions involved into the ploughing process: the resistance of the material to flow ahead of a penetrating asperity and the formation of a fresh surface behind the asperity. Finally, we show how the tribological response of a Ag-Cu nano-eutectic alloy surface is affected to its solidification velocity. It is found that both the microstructural length-scale and the solubility of both elements into one another determine the wear response of this alloy.

Recent Publications

1. Ko HE, Kwan SG, Park HW, Caron A (2017) Chemical effects on the sliding friction of Ag and Au(111). Friction; doi.org/10.1007/s40544-017-0167-5.

2. Kang SJ, Rittgen KT, Kwan SG, Park HW, Bennewitz R, Caron A (2017) Importance of surface oxide for the tribology of a Zr-based metallic glass. Friction 5: 115-122; doi.org/10.1007/s40544-017-0149-7.

3. Caron A (2016) Quantitative hardness measurement by instrumented AFM-indentation. Journal of Visualized Experiments 117; doi: 10.3791/54706.

4. Caron A, Bennewitz R (2015) Lower Nanometer-scale size limit for the deformation of a metallic glass by shear transformations revealed by quantitative AFM indentation. Beilstein journal of nanotechnology 6:1721-1732; doi: 10.3762/bjnano.6.176.

5. Caron A, Louzguine-Luzgin DV, Bennewitz R (2013) Structure vs chemistry: friction and wear of Pt-based metallic surfaces. ACS Applied materials and interfaces 13:11341-11347; doi:10.1021/am403564a.

Biography:

Nobufumi Ueshima received his PhD from Osaka University in 2014. He subsequently joined the faculty of Department of Metallurgy, Tohoku University, as an assistant professor. He has his expertise in computational material science, and focuses on the application of Phase-Field Modeling and KWN modeling for simulating precipitation kinetics of second phase in metallic materials. He has expanded his expertise to plastic deformation of metals after years of experience in research in Tohoku University. He also focuses on relationship between microstructure and plastic deformation in metallic materials. He has developed a methodology to observe the relationship between grain distribution and strain distribution to investigate microstructure-deformation relationship.

Abstract:

It has been highly demanded to miniaturize lead frames, sockets and any kind of connecting element made of copper or its alloys. Miniaturization increases the ratio of grain size to parts size. In such a case, individual grain size and orientation effect on the deformation behavior becomes significant, which causes ununiform deformation and decrease in formability. To understand the mechanism of the ununiform deformation in detail, strain localization during tensile test of oligo-crystalline Cu-Al plate has been investigated.

Cu-Al alloys were melted by induction furnace and cast into stainless steel mold. Dog-bone specimens were cut from the cast alloys. The cooling rate after casting was controlled to obtain various grain sizes, which enables us to see the effect of grain distribution on strain localization in visible scale by optical microscopy. Crystal orientation of the grains was analyzed by EBSD. A random pattern was painted on the surface of the specimen and the painted surface was recorded during tensile test to analyze strain distribution by digital image correlation (DIC) method.

Figure 1 shows the equivalent strain distributions of the reduction section during tensile test. Nominal tensile strain calculated from DIC analysis was 0.1. Strain was localized in specific grains before reaching its highest strength. Schmid's factor of the grains was analyzed. We found that the strain does not always localize at high Schmid's factor grains. When high Schmid's factor grain is surrounded by low Schmid's factor grains, the high Schmid's factor grain cannot deform largely. In contrast, strain was localized relatively low Schimid's factor grains chained over the width of the specimen. In such a case, interlocking among grains seems to be relatively weak since the edge of the specimen can move freely, which may be the reason for the strain localization.

Figure 1: Strain Distribution of oligo-crystalline Cu plate at 0.1 of tensile strain. The black lines show the grain boundaries measured by EBSD. The numbers are grain index. We can see strain localization at grain 4 and 6.

Recent Publications

1. Ueshima N, Maeda T, Oikawa K (2017) Effect of Cu addition on precipitation and growth behavior of MnS in silicon steel sheets. Metall. Mater. Trans. A 48:3843-3851.

2. Ueshima N, Liu XT, Utsumi H, Chiyokubo T, Horio K, Oikawa K (2017) Influence of Cu and Mg addition on age-related deterioration in strength and creep behavior of Zn-12Al die casting alloy, Int. J. Mater. Res. (formerly Z. Metallkd.) 108:151-154.

3. Ueshima N, Yoshiya M, Yasuda H, Fukuda T, Kakeshita T (2015) Numerically-quantified two dimensionality of microstructure evolution accompanying variant selection of FePd. Mater. Res. Exp. 2:076502(13pages).

4. Ueshima N, Yoshiya M, Yasuda H, Fukuda T, Kakeshita T (2014) Impact of interplay between magnetic field, transformation strain, and coarsening on variant selection in L1₀-type FePd. J. Appl. Phys. 115:073501(10pages).

5. Ueshima N, Shikatani T, Yoshiya M, Yasuda H (2013) Effect of Spatial Distribution of Local Magnetization on Microstructure Formation in L1₀-type Ferromagnetic Alloys under External Magnetic Field. Trans. Mater. Res. Soc. Jpn. 38:673-676.

Biography:

Floricica Barvinschi is Associate Professor at Politehnica University Timisoara, Romania. She has a PhD thesis in heat transport numerical modeling during the growth of CaF₂ and BaF₂ crystals by VB method. A part of her PhD thesis was conducted by Prof.dr. Thierry Duffar, INP Grenoble, at that time engineer at CEA Grenoble, France. Continuing a very good collaboration, Floricica .Barvinschi has been invited several times to the CEA Grenoble and INP Grenoble for scientific researches and/or for teaching.

Abstract:

Statement of the Problem: A method for the Vertical Bridgman (VB) solidification of InSb in a silica ampoule is modeled with COMSOL Multiphysics software, using time-dependent thermal conditions. Axial-symmetric numerical simulations of temperature, velocity field in the melt, under normal gravity, and capillarity at the melt-gas-crucible interface resemble those used in an induced pressure difference dewetting VB configuration. The VB technique has some drawbacks that are linked to the use of a crucible in intimate contact with the growing crystal. Methodology & Theoretical Orientation: In order to avoid the sticking of the crystal on the crucible, which can result in crystal or crucible breakage, a pressure difference is built up inside a sealed growth ampoule by a temperature variation.  Detached growth  is a small gap between the growing crystal and the crucible wall. The contact-free growth reduces mechanical stress in the crystal, resulting in a reduction of the defect density. Findings: In the present paper we extend our previous steady-state model by including the calculation of the energy, momentum and mass transport, plus the interfacial phenomena at the melt-gas-crucible interface, under normal gravity, while applying a time dependent step-type temperature distribution on the outer part of the crucible. Conclusion & Significance: Several systematically studies on this subject have been reported during time, both experimental and numerical. In order to model the flow of two different, immiscible fluids, where the exact position of the interface is of interest, we have applied the phase-field method. The purpose of this study is to include in a single model the transport phenomena (energy, momentum, mass) and the interfacial phenomena at the melt-crystal-crucible and respectively melt-gas-crucible interfaces. All these new models were developed numerically. The validation of modeling was made by comparing Lamine Sylla`s results, reported in his PhD thesis.

Figure 1: Vertical Bridgman model and transient boundary conditions.

Recent Publications

1. Barvinschi P, Barvinschi F (2011) Coupled Heat Transfer and Fluid Dynamics Modeling of InSb Solidification. AIP Conference Proceedings 1387:190-197.

2. Sylla L  (2008) Etude Experimentale et Thermodynamique du Procédé de Démouillage Appliqué aux Semiconducteurs. PhD Thesis  INP Grenoble France.

3. Duffar T (Ed.) (2010) Crystal Growth Processes Based on Capillarity. Czochralski. Floating Zone. Shaping and Crucible Techniques  J. Wiley & Sons Ltd. Chichester UK.

4. Barvinschi B, Barvinschi P (2015) Numerical investigation of crystal growth in a vertical Bridgman configuration using a mushy zone model. JOAM 17 (3-4): 431-438.

5. Gallien B, Sylla L, Bengulescu M, Barvinschi F, Duffar T (2013) Study of crystal-crucible detachment: GaSb in SiO₂. CrystEngCom 15: 2329-2336.

6. Stelian C, Yeckel A, Derby J J (2009) Influence of thermal phenomena on crystal reattachment during dewetted Bridgman growth. J.Cryst.Growth 311: 2572-2579.

Acknowledgments: This work was supported in part by the strategic grant POSDRU/21/1.5/G/13798, inside POSDRU Romania 2007-2013, co-financed by the European Fund-Investing in People.

Biography:

Alberto Monsalve G. has his expertise in steel processing and materials characterization. He is a full time teacher in Metallurgical Department in Universidad de Santiago de Chile and part time teacher in Academia Poitécnica Aeronáutica and Universidad Técnica Federico Santa María, Chile. He works for local industry in the solution of failure problems and give supervision to different postgraduates’ programs in Chile and other countries.

Abstract:

The objective of the present study is to analyze the microstructure and mechanical properties of a TWIP steel at different temperatures. For this purpose, tensile tests were performed in a Fe-22Mn-0.65C TWIP (Twinning-induced plasticity) steel in a temperature range between 25 °C and 400 °C. The microstructure after deformation was characterized via optical microscopy. It was observed that the microstructure consists of mainly deformation twins at low temperatures, whereas dislocation bands are the predominating feature at high temperatures. The yield stress, ultimate tensile strength, total elongation, strain hardening index and the area reduction were measured at different temperatures. The analysis of mechanical data suggests a transition of deformation mechanism from twinning at low temperature to dislocation slip at high temperatures. The work hardening rate and area reduction variations with temperature are discussed and correlated to the decrease of twinning contribution to the deformation mechanism. The role of other process, such as dynamic strain aging and precipitation hardening, are discussed. A thermodynamic-based description for the dependence of Yield stress with temperature was developed, suggesting two acting work hardening mechanisms. This is consistent with the computed activation energy for each mechanism. The stacking fault energy (SFE) was computed by means of Olson and Cohen model, at different temperatures finding that at temperatures higher than 325°C, dislocation glide was the predominant deformation mechanism, which is in accordance with experimental results. Twinning-volume fraction (TVF) in samples tested at different temperatures were computed, finding a decrease in TVF as testing temperatures increases, which in agreement with previous experimental features.

Recent Publications

1. B. De Cooman, Y. Estrin, S. Kim (2018) Twinning-induced plasticity (TWIP) steels. Acta Materialia 142: 283-362.

2. A. Saleh, A. Gazder (2016) A re-evaluation of “The micromechanics of twinning in a TWIP steel”. Materials Science and Engineering A 649:184-189.

3. E. Galindo-Nava, P. Rivera-Díaz-del-Castillo (2017) Understanding martensite and twin formation in austenitic steels: A model describing TRIP and TWIP effects. Acta Materialia 128:120-134.

4. B. De Cooman, O. Kwon, K. Chin (2012) State-of-the-knowledge on TWIP steel. Materials Science and Technology 28:513-527.

5. O. Bouaziz, S. Allain, C. Scott, P. Cugy, D. Barbier (2011) High manganese austenitic twinning induced plasticity steels: A review of the microstructure properties relationships. Current Opinion in Solid State and Materials Science 15:141-168.

Biography:

Felix Gunkel is a young investigator based at Institute of Electronic Materials (IWE2) at RWTH Aachen University, Germany. His research interests comprise thermodynamics and solid state chemistry of complex oxides on the nanoscale. His current work addresses tailored functionality of crystal defects in oxides for nano-electronic devices, energy applications, and gas sensors.

With background is fundamental and applied physics, Dr. Gunkel started his scientific career at Institute of Solid State Physics, Forschungszentrum Jülich, Jülich, Germany in 2010. He received his PhD from the faculty of electronic engineering at RWTH Aachen University in 2013. After continuing his scientific work in his postdoctoral career at Stanford University and Forschungszentrum Jülich, he is now leading a research team at RWTH Aachen University, Germany, with a research focus of thermodynamic engineering of device properties and material functionality on the nanoscale.

Abstract:

Perovskite oxides exhibit a plethora of fascinating electronic material properties covering an exceptionally wide range of phenomena in solid state and surface physics. This has led to tremendous efforts to functionalize these materials in applications for energy technology, gas sensing, and electronics. Layered in an atomically defined epitaxial heterostructures and superlattices, diverse properties of perovskites can be combined on the nanoscale level. In such structures, even new functionality can arise at interfaces of layered materials, exhibiting properties that are absent in the bare bulk materials.

In our approach, we utilize atomically-defined layer growth to obtain desired material properties. However, on top of that, we employ thermodynamic engineering of crystal defects as a unique approach to functionalize material properties at surfaces and interfaces: Even at material synthesis conditions close to perfection, device properties are often determined by imperfection, hence, by lattice disorder and crystal defects. As we discuss, we can intentionally control defect structure in nanoscale devices, by developing and utilizing thermodynamic routes to trigger surface and interface reactions in confined systems.

While historically defects were seen as something to be avoided, a change of paradigm is required in the field of complex oxides today: In these materials, we can promote functionality, such as metallicity in nominally insulating compounds, by atomic defect-management. Therefore, rather than avoiding defect formation, it is an essential necessity to control and to utilize defect formation in oxides on the nanoscale.

Here, we discuss fundamental aspects of lattice disorder effects in bulk oxides, and elaborate the special character of defect formation in thin films, surfaces and interfaces. Focusing on SrTiO₃ as a perovskite model system, we will crosslink fundamental perspectives on lattice disorder to actual applications, addressing different examples, such as resistive switching memories, high-mobility electron gases and induced magnetism, oxygen sensors, and electro-catalysts.

Recent Publications

1. F. Gunkel, et al., “Defect-control of anomalous and conventional electron transport in NdGaO₃/SrTiO₃ heterostructures”, Physical Review X, 6, 031035 (2016)

2. F. Gunkel et al., “Ordering and phase control in epitaxial (Pr,Ba)CoO_3- catalysts for oxygen evolution reaction”, ACS Catalysis 7 (10), 7029–7037 (2017)

3. M. Andrä et al., “Oxygen partial pressure dependence of space charge formation in donor doped SrTiO₃”, APL Materials 5, 056106 (2017)

4. F. Gunkel et al., “Mobility modulation and suppression of defect-formation in two-dimensional electron systems by charge transfer management”, ACS Applied Materials & interfaces 9 (12), 10888  (2017)

5. R. Meyer et al., “Dynamics of the metal-insulator transition of donor-doped SrTiO₃”, Physical Review B 94, 115408 (2016)

6. F. Gunkel et al., “Defect concentration profiles at complex oxide interfaces”, Physical Review B 93, 245431 (2016)

Biography:

Rapoport is the Head of the Center for Materials Engineering and the Laboratory of Tribology at the Holon Institute of Technology. Friction and wear research of nanomaterials is known both nationally and internationally. Friction and wear properties of fullerene-like nanoparticles were studied at first in the laboratory of Prof. Rapoport. Prof. Rapoport is a principal investigator in several research grants sponsored by the Israel Ministry of Science, the Bi-national Israel- USA and Germany-Israel Funds. Prof. Rapoport is the author more than 100 publications. He is Vice-President of the Tribology Council in Israel.

Abstract:

Friction and wear are the crucial problems affecting the life time of moving mechanical parts. The main goal of this work is to study: the evolution of the microstructure after friction with lubricant of four fcc metals (Ag, Cu, Ni and Al and the effect of stacking fault energy (SFE) on grain size and wear loss. Friction surfaces were carefully examined with a field emission scanning electron microscope. The cross sectional TEM lamellae were prepared from the pins using a focused ion beam (FIB). Cross-sectioning of the specimens was done in the longitudinal and transverse directions (parallel and perpendicular to direction of friction).Deformation twinning followed by a limited recovery within a surface of Ag led to formation of relatively thick top layer of ultra-fine equiaxial grains. Surface regions of Cu and Ni  samples consisted of inhomogeneous microstructure with wide range of grain sizes. With a depth lamellar structure was formed parallel to direction of friction for Ag, Cu and Ni. Subdivision of grains into subgrains with high dislocation density is clearly observed within a lamellar structure. Steady state values of grain size, ds and hardness, Hs after friction in lubricant conditions are explained by a balance between hardening and dynamic recovery in surface layers strongly depending on the g_SFE and temperature.

Typical HAADF STEM images of Ag presenting general view of deformation microstructure with a gradient of grain size. The white arrow shows direction of friction. Black arrows show the pores in top layers.

Biography:

Luis M. Angelats Silva has experience in electrochemical corrosion of metallic materials. Within its diverse research in materials science and technology, it is currently looking for alternatives to improve corrosion resistance by using natural polysaccharides as non-toxic inhibitors for human health and the environment. His experience in electrochemical studies has allowed him to develop diverse methods and/or techniques that allow him to evaluate, through accelerated corrosion tests, the efficiency of inhibition of these polysaccharides in alloy steels widely used in high temperature pipes.

Abstract:

Statement of the Problem: The high efficiency of corrosion inhibition of synthetic organic inhibitors in the industries of chemical cleaning, acid etching, acidification of oil wells and acid desalination is well recognized. However, most of these inhibitors are toxic to the environment and human health. This has forced to look for more secure corrosion inhibitors called "green corrosion inhibitors" due to its non-toxicity, biodegradability and low cost. In recent years, the use of natural polysaccharides as an environmentally safe corrosion inhibitor has received special attention. For this reason, the present study, evaluates the mucilage of Linum usitatissimum, which contains a high content of polysaccharides, as a corrosion inhibitor of ASTM A335 grade P11 steel in HCl -1.0 M.  Methodology & Theoretical Orientation: All the corrosion tests were carried out at least in triplicate to evaluate the reproducibility of the same, by means of the techniques of: weight loss tests, Tafel extrapolation, resistance to linear polarization, electrochemical impedance spectroscopy and electrochemical frequency modulation. For the electrochemical tests the Gamry Reference 3000 potentiostat was used. Figure 1 shows part of the tests carried out at 65°C. Findings: Considering the five techniques, it was observed that the average inhibition efficiencies for a dosage of 0.5g/L of mucilage were 77.3%, 81.2% and 88.6% at temperatures of 25ºC, 45ºC and 65°C, respectively. Higher dosages only generated a slight increase in inhibition efficiency. Additionally, it was also found that an increase in temperature produced an increase in the adsorption constant and a decrease in the standard free energy of adsorption. The standard enthalpy of adsorption was positive and the apparent activation energy decreased with increasing mucilage concentration. Conclusion & Significance: From the results, we conclude that the Linum mucilage acts as a good corrosion inhibitor of P11 steel in HCl-1.0 M. Its efficiency increased with the increase in temperature. Likewise, it was determined that the adsorption of mucilage on steel P11 occurs through a chemical adsorption, acting as a mixed type inhibitor.

Figure 1. Corrosion tests of P11 steel in HCl-1.0 M containing different concentrations of Linum mucilage (g/L) at 65ºC. (a) Potentiodynamic polarization curves, (b) Intermodulation spectra and (c) Nyquist diagram.

Recent Publications

1. Finšgar, M., Jackson, J. (2014) Application of corrosion inhibitors for steels in acidic media for the oil and gas industry: A review. Corrosion Science, v. 86:17–41.

2. Sharma, S.K., Sharma, A. (2011) Green corrosion inhibitors: status in developing countries. In: Sharma S.K. (ed.) Green corrosion chemistry and engineering, Wiley–VCH, Weinheim, p. 157-180.

3. Peter, A., Obot, I.B., Sharma, S.K. (2015). Use of natural gums as green corrosion inhibitors: an overview. International Journal of Industrial Chemistry, 6:53-164.

4. Bentrah H, Rahali Y, Chala A. (2014) Gum Arabic as an eco-friendly inhibitor for API 5L X42 pipeline steel in HCl medium. Corr. Sci. 82: 426-431.

5. Roy P, Karfa P, Adhikari U, Sukul D. (2014) Corrosion inhibition of mild steel in acidic medium by polyacrylamide grafted Guar gum with various grafting percentage: Effect of intramolecular synergism. Corr. Sci. 88: 246-253.

Biography:

Sezai Elagoz is currently a full Professor in the Department of Nanotechnology Engineering and the director of the Nanophotonics Research and Application Center at Cumhuriyet University, Turkey. He received his M.Sc and Ph.D. degrees from University of Michigan in 1993. He has published more than 60 peer-reviewed articles and his currently research interest includes semiconductor crystal growth for quantum cascade lasers, high brightness InGaN/GaN based light emitting diodes, high efficiency tandem solar cells and short wave infrared detectors.

Abstract:

InGaAs/InAlAs superlattices (SLs) are very attractive and suitable for QCL applications due to the availability of lattice matching on InP substrate and large conduction band offset. When InxGa1-xAs and InyAl1-yAs compounds are lattice matched to InP substrate, this allows fabricating QCL devices with an emission wavelength at λ>4µm. Similarly, to go larger wavelengths, the same materials can be used by utilizing a technique known as strain-balancing to overcome the difficulties arise from lattice mismatch. Precise thickness control, alloy composition control and repeatability of the SLs are the most critical issues to be dealt with in growth studies to obtain the desired device structures. The thinnest layer thickness is a few monolayers and the device performance is quite sensitive to interface roughness. Molecular beam epitaxy (MBE) is the generally preferred growth technique due to the requirement of having very thin layers with sharp interfaces. However, QCL also includes thick layers such as claddings for which MOCVD suits the best. For these reasons, it is worth efforts to find a way to grow the whole structure via MOCVD. Using special growth conditions and smaller mass flow controllers (MFCs) it is possible to precisely control the gas flow quantity dilution and injection of metalorganic sources. Transmission Electron Microscope (TEM), Scanning Tunneling Electron Microscope (STEM) and similar techniques are widely used to determine the exact thickness of epitaxially grown SLs. However, these techniques are destructive, relatively expensive, time consuming and require an elevated level of expertise for the sample preparations as well as the sample measurement. The high-resolution x-ray diffraction is a non-destructive, economic, quick and robust technique than electron microscopes and depending on the scan type it is quite sensitive to thickness change, alloy composition and interface quality and, as we demonstrate, it can be used to find the thicknesses for very thin layers.

Figure-1 10 stage strain balanced QCL structure grown by MOCVD

Recent Publications

1. Demir I, Elagoz S (2017) V/III ratio effects on doping of high quality InAlAs for Quantum Cascade Laser structures. Superlattices and Microstructures 104:140-148.

2. Demir I, Robin Y, McClintock R, Elagoz S, Zekentes K, Razeghi M, (2017) Direct growth of thick AlN layers on nanopatterned Si substrates by cantilever epitaxy. Physica Status Solidi (a) 214 (4): 1600363.

3. Demir I, Elagoz S (2016) Interruption time effects on InGaAs/InAlAs superlattices of quantum cascade laser structures grown by MOCVD. Superlattices and Microstructures 100:723-729.

4. Demir I, Elagoz S (2016) Growth of InGaAs/InAlAs superlattices by MOCVD and precise thickness determination via HRXRD. Gazi University Journal of Science 29(4):947-951.

5. Tansel T, Hostut M, Elagoz S, Kilic A, Ergun Y, Aydinli A (2016) Demir I, Elagoz S (2016) Electrical performance of InAs/AlSb/GaSb superlattice photodetectors. Superlattices and Microstructures 91:1-7.

Biography:

Hajo Dieringa has his expertise in developing magnesium alloys and magnesium based metal matrix composites. Since 2000 he is working at the Institute of Materials Science at GKSS Research Centre, now Helmholtz-Zentrum Geesthacht. He is deputy head of the department "Magnesium Processing" and coordinated the work package "Metal Matrix Nanoconposites" in the large scale EU project Exomet. In addition to composites, Hajo Dieringa also developed creep-resistant magnesium alloys.

Abstract:

Magnesium-based metal matrix nanocomposites (MMNCs) are promising materials for small-series applications, for example in automotive engineering or the aviation industry. For some years now, ceramic nanoparticles have been so inexpensive that they only represent a negligible increase in the cost of a nanocomposite material. The magnesium sand casting alloy Elektron21 and the die-casting alloy AM60 were reinforced with AlN nanoparticles with a diameter of 80 nm. To break up particle clusters in the melt, an ultrasound assisted casting process was used. Cavitation and acoustic streaming are generated by ultrasound, and an indirect chill casting process in a permanent mould results in a microstructure free of pores. The grain size, tensile mechanical properties and compression creep resistance were investigated. We found that the nano-AlN addition refines the microstructure of AM60 significantly. Mechanical testing shows an outstanding increase in tensile yield strength, ultimate tensile strength and ductility of AM60+1AlN compared to the unreinforced AM60. By contrast we observed no grain refinement and no tensile strengthening of Elektron21, although the creep resistance was improved by one order of magnitude. This demonstrates how differently two magnesium alloys can respond to reinforcement with 1% AlN in their structures and properties. In case of AM60-MMNCs remelting trials were performed and showed that the nanoparticles remain in the melt with only a marginal loss of grain refinement and loss of strength occurring for each remelting.

Recent Publications

1. Saboori A, Padovano E, Pavese M, Dieringa H, Badini C (2017) Effect of Solution Treatment on Precipitation Behaviors, Age Hardening Response and Creep Properties of Elektron21 Alloy Reinforced by AlN Nanoparticles; Materials 10:1380-1397.

2. Dieringa H, Katsarou L, Buzolin R, Szakács G, Horstmann M, Wolff M, Mendis Ch, Vorozhtsov S, StJohn D (2017) Ultrasound Assisted Casting of an AM60 Based Metal Matrix Nanocomposite, Its Properties, and Recyclability; Metals 7:388-400.

3. Daudin R, Terzi S, Mallmann C, Sanchez Martin R, Lhuissier P, Boller E, Pacureanu A, Katsarou L, Dieringa H, Salvo L (2017)  Indirect improvement of high temperature mechanical properties of a Mg based alloy Elektron21 by addition of AlN nanoparticles; Materials Science & Engineering 688:76-82.

4. Katsarou L, Mounib M, Lefebvre W, Vorozhtsov S, Pavese M, Badini C, Molina-Aldareguia J M, Cepeda Jimenez C, Pérez Prado M T, Dieringa H (2016) Microstructure, mechanical properties and creep of magnesium alloy Elektron21 reinforced with AlN nanoparticles by ultrasound-assisted stirring; Materials Science & Engineering A 659:84-92.

5. Dieringa H, Das S, Eskin D, Fan Z, Katsarou L, Horstmann M, Kurz G, Mendis C, Hort N, Kainer KU (2015) Twin-roll Casting after Intensive Melt Shearing and Subsequent Rolling of an AM30 Magnesium Alloy with Addition of CaO and SiC; Materials Science Forum 828-829:35-40.

6. Sillekens W, Jarvis DJ, Vorozhtsov A, Bojarevics V, Badini CF, Pavese M, Terzi S, Salvo L, Katsarou L, Dieringa H (2014) The ExoMet Project: EU/ESA Research on High-Performance Light-Metal Alloys and Nanocomposites; Metallurgical and Materials Transactions A 45:3349-3361.

7. Dieringa H (2011) Properties of magnesium alloys reinforced with nanoparticles and carbon nanotubes: a review; Journal of Materials Science 46:289-306.

Biography:

Sergiu Cojocaru is a senior researcher at the Department of Theoretical Physics of the National Institute of Physics and Nuclear Engineering, Romania. He authors over 100 scientific publications in several areas of Condensed Matter Theory. His current interests are in Nanophysics and, in particular, the physical effects of confinement on the properties of nanomaterials.

Abstract:

Vibrational excitations in nanomaterials are very sensitive to confinement and boundary conditions since both the typical wavelengths and mean-free-paths may easily exceed the size of a nanodevice. Then multiple reflections from the surfaces drastically modify the vibration properties as compared to bulk materials. These have major implications for the broad range of devices [1-3]. Thus, in ultrahigh sensitivity radiation detectors, electronic microrefrigerators or microcalorimeters [4,5] an essential part of the design is the coupling and energy exchange between vibrational modes (or their quantum version, phonons) and electron excitations in ultrathin quasi-two-dimensional structures:

It has been shown both experimentally and theoretically that in such devices the transfer of energy per unit time (or energy flux) between electrons and phonons (in a stationary case, for instance, electrons may thermalize at a higher effective temperature than phonons, or inverse) can be engineered to vary in orders of magnitudes depending on the specific requirements [6-8].

The problem becomes more complicated for a layered structure composed of materials with significantly different acoustic characteristics when the interface effects cannot be neglected (e.g., Copper film deposited on Silicon Nitride membrane). Unlike the composite materials with layer stacking along the direction of propagation of excitations, the “lateral” symmetry with respect to this direction in our case is absent. This difficulty, however, can be viewed as an opportunity for a new kind of behavior.

For a better understanding of this situation a new theoretical approach is proposed that allows to substantially simplifying the description of the governing equations and in, some cases, to obtain analytical expressions for both the spectra and amplitudes of the normal modes. These are shown to become gapped when the system is sufficiently thin for the physically relevant wavelengths to reach the nanometer range. The only truly acoustic waves which account for the low energy – low temperature properties in a composite system are the Lamb compressional (dilatational) and flexural (bending) modes. These modes are described in an analytical form. An additional possibility to engineer the behavior of phonon modes and their coupling to electrons is revealed by the possibility to localize the vibration amplitudes in one or another layer, near to the surfaces or the interface, depending on the thickness of the layers and material parameters.

Recent Publications

1. Kargar F, Debnath B, Kakko J-P, Saynatjoki A, Lipsanen H, Nika D L, Lake R K, Balandin A A (2016) Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires, Nature Comm. 7:13400.

2. Cleland A (2003) Foundations of Nanomechanics, Springer.

3. M. A. Stroscio and M. Dutta (2004) Phonons in Nanostructures, CUP.

4. Kupiainen A, Muratore-Ginanneschi P, Pekola J, Schwieger K (2016) Fluctuation relation for qubit calorimetry, Phys. Rev. E 94:062127.

5. Muhonen J T,  Meschke M, Pekola J P (2012) Micrometre-scale refrigerators, Rep. Prog. Phys. 75: 046501.

6. Karvonen J, Maasilta I (2007) Influence of Phonon Dimensionality on Electron Energy Relaxation, Phys. Rev. Lett. 99: 145503.

7. Cojocaru S, Anghel D-V (2016)  Low-temperature electron-phonon heat transfer in metal films, Phys. Rev. B 93:115405.

8. Anghel D-V, Cojocaru S (2017) Electron–phonon heat exchange in quasi-two-dimensional nanolayers, Eur. Phys. J. B 90: 260.

Biography:

Jaspreet Kaur Randhawa research area includes drug delivery systems for CNS and cancers treatment: The main theme of our research includes drug delivery based on solid lipid nanoparticles (SLNs) for controlled drug release. The ability to incorporate drugs into nanocarriers offers a new prototype in drug delivery that could be used for secondary and tertiary levels of drug targeting. SLNs hold great promise for reaching the goal of controlled and site specific drug delivery. Similarly we are also working on stimuli responsive drug carrier for cancer and in the development of various nanostructures of metal oxides, and screen their glucose sensing activity to for low cost glucometer.

Abstract:

Schizophrenia is a neurological disorder and Paliperidone the antipsychotic drug with poor water solubility is potent drug used for its treatment. Solid lipid nanoparticles (SLN) based drug delivery system offer the potential for encapsulating lipophilic drugs. Three different lipids and surfactants formulations were prepared by ultrasonic homogenization method. The selection of the lipids and surfactant was based on their proven compatibility to enhance their BBB permeability and their neuro protective behaviour. The release kinetics was based on dynamic dialysis method. Detailed release mechanism analysis and its relation to the properties of system is very important. Analysis of the release kinetic data with mathematical analysis could provide a great impact on the development of solid lipid nanoparticles drug delivery system. Paliperidone a newly developed antipsychotic, which was unexpored due to low bioavailability was formulated as nanoparticles in lipid matrix analyzed for drug release kinetics. To observe the best release kinetic model, the First order, Baker-Lonsdale, Hixson-Crowell, Korsmeyer-Peppas model, and Higuchi model were implemented. Korsmeyer-Peppas model given the best fit for the release kinetics of Paliperidone from the various solid lipid nanoparticles system prepared. The results express the Gelucire based SLNs principle suitability for a prolonged release formulation. The neuro protective effects of paliperidone, on the cell survival of human neuroblastoma SH-SY5Y and RAW 264.7 macrophages was also observed for various drug concentration. GSLNs based system show 85 % cell viability from lower to higher dose.

Recent Publications

1. Jaspreet Kaur Randhawa, (2013) High melting lipid based approach for drug delivery: Solid lipid nanoparticlesMaterials Science and Engineering: C, , 33, 1842-1852.

2. Jaspreet Kaur Randhawa(2013) Preparation and characterization of Paliperidone loaded solid lipid nanoparticles, Colloids and Surfaces B: Biointerfaces, , 102, 562-568.

3. Jaspreet Kaur Randhawa (2014) Paliperidone-loaded spherical solid lipid nanoparticles   RSC Advances, 4, 30186-30192.

4. Jaspreet Kaur Randhawa (2015) RSC Advances, , 5, 68743-68750.

5. Jaspreet Kaur Randhawa (2017) Curcumin encapsulated zeolitic imidazolate frameworks as stimuli responsive drug delivery system and their interaction with biomimetic environment, 7:12598.

Biography:

VALERIO F. GILI went to the University of studies of Rome “La Sapienza”, where he studied Physics and took his bachelor degree in 2012. He received the Master degree in Physics at the University of studies of Rome in 2014, doing an experimental thesis on quantum optics with Paolo Mataloni and Fabio Sciarrino. He now attends PhD. Study in the Laboratoire Matériaux et Phénomènes Quantiques at Paris Diderot University.

Abstract:

Aluminium gallium arsenide (AlGaAs) is a promising material for monolithic photonics. Besides having a high optical Kerr coefficient, this III-V semiconductor alloy has a high ; it is a mature laser material; and its direct band-gap can be varied with the Al molar fraction, making it not only linearly transparent from 0.7 µm to 16 µm, but also two-photon-absorption free at 1.55 µm. Several types of AlGaAs high-contrast nonlinear integrated photonic structures have been demonstrated in the last years, spanning from nanowires [1,2] to high-  resonators [3,4] and multi-pole nanoantennas [5]. To confine photons at sub-wavelength scales, such devices rely on a high-refractive-index core clad by a far lower index in two or three dimensions, and therefore they typically consist of semiconductor nanostructures that either lie on an oxide substrate or are suspended in air. Here we focus on the former case, which seems more promising because of its superior heat-sink behaviour and mechanical stability. Our devices, from the nano- to the micro-scale, share the same fabrication protocol: they are grown by molecular-beam-epitaxy on {100} non-intentionally doped GaAs wafer, with a few hundred nanometres layer of Al_0.18Ga_0.82As on top of an aluminium-rich substrate, to be oxidized at a later stage (see Figure 1). In order to improve the eventual adhesion between AlOx and the adjacent crystalline layers, such substrate consists of AlAs layer of about 1μm of thickness sandwiched between proper matching layers. A number of nonlinear optics results have been allowed by this class of devices, ranging from second harmonic generation to down-conversion in optical nanoantennas, and from radiation pattern engineering with subwavelengths photonic molecules to frequency conversion in waveguides and resonators. We will provide an overview of this new and exciting research field, along with a few perspectives.

Fig. 1: Monolithic AlGaAs-on-AlOx nanoantennas: (a) scanning-electron-microscope picture of a part of the array; (b) schematics of a single nanoantenna.

Recent Publications

1. Scaccabarozzi L et al. (2009) Enhanced second-harmonic generation in AlGaAs/AlxOy tightly confining waveguides and resonant cavities. Opt. Lett. 31: 3626-3629.

2. Morais N et al. (2017) Directionally induced quasi-phase matching in homogeneous AlGaAs waveguides. Opt. Lett.

3. Mariani S et al. (2014) Second-harmonic generation in AlGaAs microdisks in the telecom range. Opt. Lett. 39: 3062-3065.

4. Pu M et al. (2016) Efficient frequency comb generation in AlGaAs-on-insulator. Optica 3: 823-826.

5. Gili V F et al. (2016) Monolithic AlGaAs second-harmonic nanoantennas. Opt. Express 24: 15965-15971.

Biography:

Golibjon Berdiyorov is a Scientist in Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University. He has an experience in performing theoretical investigations on structural, optoelectronic and transport properties of molecular and low-dimensional systems. Currently, he is interested in conducting material science research with a focus on predicting novel materials for photovoltaics, energy storage applications and membranes materials for water treatment. In his studies he mostly uses first principles methods (such as Density Functional theory in combination with the non-equilibrium Green’s function formalism) and other atomistic scale methods such as force field based molecular dynamics. He has published more than 100 research articles, which have already received more than 1600 citations. He was awarded for his research including the best research award at University of Antwerp.

Abstract:

MXenes, a new family of low-dimensional materials, have received a lot of interest due to their unique physical, chemical, and mechanical properties [1]. MXenes have already shown a great potential in storage applications due to their impressive capacitive performance [2]. Here, we study the electronic and transport properties of Ti₃C₂ MXene using density-functional theory (DFT) in combination with the nonequilibrium Green’s function formalism [3, 4]. Fluorinated, oxidized and hydroxylated surfaces are considered. We found that the surface termination has a considerable impact on the electronic transport [3]. For example, the fluorinated sample shows the largest transmission, whereas surface oxidation results in considerable reduction of the electronic transmission. Such enhanced transmission originates from the extended electronic states and smaller variations of the electrostatic potential profile. We also study the effect of lithium and sodium ion adsorption on the electronic transport properties of the MXene [4]. Optical properties of MXene are also affected bysurface functionalization [5]. For example, in the visible range of the spectrum, the oxidized sample shows larger absorption, whereas surface fluorination results in weaker absorption as compared to pristine MXene.

Recently, MXene nanosheets have also emerged as ultrathin and high-flux sieving membranes [6]. In addition to ultrafast water flux, both hydration radius and charge dependent transport of ions have been observed. MXenes are also shown to be highly resistive to biofouling [7]. Here we present the results of our DFT calculations to explore the possible mechanisms for the charge-selective ionic transport through Ti₃C₂X₂ (X=O, OH or F) Mxene [8, 9]. We show that the charge selectivity originates from the charged nature of the MXene layers: the system shows dynamic response to the intercalating ions, even in their hydrated states, by changing the interlayer spacing. We also address the stability of MXene membranes and discuss the possibilities of enhancing their stability by molecular and nanoparticle intercalations. We present the results of our atomistic scale calculations for structural, electronic water sieving properties of hydrophobic graphene and hydrophilic MXene monolayers (see Fig. 1).

Fig 1. Atomistic structure of graphene (top) and Ti₃C₂(OH)₂ MXene (bottom) bilayer with intercalating water molecules.

Recent Publications

1. M. Naguib, V. N. Mochalin, M. W. Barsoum, Y. Gogotsi, 25th Anniversary Article: MXenes: A New Family of Two-Dimensional Materials, Adv. Mater. 26, 992 (2014).

2. J.-C. Lei, X. Zhang, Z. Zhou, Recent advances in MXene: Preparation, properties, and applications, Front. Phys. 10, 276 (2015).

3. G. R. Berdiyorov, Effect of surface functionalization on the electronic transport properties of Ti₃C₂ MXene, Europhys. Lett. 111, 67002 (2015).

4. G. R. Berdiyorov, Effect of lithium and sodium adsorption on the electronic transport properties of Ti₃C₂ MXene, Appl. Sur. Scie. 359, 153 (2015).

5. G. R. Berdiyorov, Optical properties of functionalized Ti₃C₂T₂ (T = F, O, OH) MXene: First-principles calculations, AIP Advances 6, 055105 (2016).

6. C. E. Ren, K. B. Hatzell, M. Alhabeb, Z. Ling, K. A. Mahmoud, Yury Gogotsi, Charge- and Size-Selective Ion Sieving Through Ti₃C₂ T x MXene Membranes, J. Phys. Chem. Lett. 6 (2015) 4026-4031.

7. K. Rasool, K. A. Mahmoud, D. J. Johnson, M. Helal, G. R. Berdiyorov, and Y. Gogotsi, Efficient Antibacterial Membrane  based on Two-Dimensional Ti₃C₂T_x (MXene) Nanosheets, Scientific Reports 7, 1598  (2017).

8. G. R. Berdiyorov, M. E. Madjet, and K. A. Mahmoud, Ionic transport through Ti₃C₂(OH)₂ MXene: first principles calculations, Applied Physics Letters 108,113110 (2016).

9. G. R. Berdiyorov and K. A. Mahmoud, Effect of surface termination on ion intercalation selectivity of bilayer Ti₃C₂T₂ (T=F, O and OH) Mxene, Applied Surface Sciences 416, 725-730 (2017).

Biography:

Gennady N. Panin (Ph.D.) is a professor at the Academy of Nanotechnologies (NITA), the Department of Physics at Dongguk University and a senior research fellow at the Institute of Microelectronic Technology of the Russian Academy of Sciences (IMT RAS). He graduated from the Moscow National University with a degree in Applied Physics and Electronics with honors and received his doctorate in physics of semiconductors and solid state electronics at the IMT RAS in 1994. He worked as a research fellow at the Institute of Solid State Physics, Halle, Germany, in 1986 and at the Faculty of Physics of Materials at the University of Complutense, Madrid, Spain, in 1994-1996 and as a research professor (2000-2008), Professor ( 2008-2017), Vice-Director (2012-2017) of QSRC at Dongguk University, Seoul. His research interests include the physics of quantum structures and multifunctional nanomaterials based on layered multiferroics and graphene to create new photonic and electronic devices for use in nano-information technologies.

Abstract:

Statement of the Problem: Memristive systems based on two-dimensional (2D) crystals such as graphene, graphene oxide, molybdenum disulphide, etc., 1-5, are considered as a new type of electronic elements with extremely low energy consumption and with ultra-high scalability for processing and storage of information. The unique electronic and optical properties of 2D crystals demonstrate the enormous potential for creating ultra-high density nano-and bioelectronics for innovative imaging systems. The purpose of this study is to develop memristors with a floating photogate so-called photomemristors^2,3 based on graphene and nanocrystals. Findings: A new concept of the formation of self-assembled nanoscale photomemristive heterojunctions of graphene, graphene oxide and zinc oxide in the form of two-terminal memristors with a floating photogate for bioelectronics and optoelectronics is demonstrated. Methodology & Theoretical Orientation: Photocatalytic oxidation of graphene with nanocrystals of zinc oxide is proposed as an effective method of creating two-dimensional memristive systems with photoresistive switching for synaptic nonvolatile memory of ultrahigh density. Conclusion & Significance: Two-dimensional photomemristive systems with a floating photogate exhibit multiple states controlled in a wide range of electromagnetic radiation, and can be used as neurohybrid systems for neuromorphological calculations, image processing, and pattern recognition needed to create artificial intelligence.

a - Schematic electronic diagram of the G/ZnO NP interface under UV irradiation. Electron-hole pairs generated in ZnO (3.3 eV) under UV irradiation (reaction 1) are separated by a built-in electric field at the G/ZnO NP interface, providing a flow of holes into the graphene; b - resistive states of the G/GO photomemristor, which are switched by the Set/Reset voltage of -3.8/3.3 V in the dark and -3.5/4 V with light pulses and read at 2.5 V.

Acknowledgements

This work was supported by Basic Science Research Program through the NRF of Korea funded by the Ministry of Education (No. 2017R1D1A1B03035102).

Recent Publications

1. Gennady N. Panin et al (2011) Resistive Switching in Al/Graphene Oxide/Al Structure. Jpn. J. Appl. Phys. 50:070110

2. Olesya O. Kapitanova, Gennady N. Panin et al (2017) Formation of Self-Assembled Nanoscale Graphene/Graphene Oxide Photo-memristive Heterojunctions using Photocatalytic Oxidation. Nanotechnology 28:204005.

3. Wei Wang, Gennady N. Panin et al (2016) MoS₂ memristor with photoresistive switching. Scientific Reports 6:31224.

4. Wei Wang, Olesya O. Kapitanova, Pugazhendi Ilanchezhiyan, Sixing Xi, Gennady N. Panin, Dejun Fu, Tae Won Kang (2018)  Self-assembled MoS₂/rGO nanocomposites with tunable UV-IR absorption. RSC Advances 8:2410.

5. Xiao Fu, P. Ilanchezhiyan,a  G. Mohan Kumar,  Hak Dong Cho,  Lei Zhang,  A. Sattar Chan,  Dong J. Lee,  Gennady N. Panin  and  Tae Won Kang (2017) Tunable UV-visible absorption of SnS₂ layered quantum dots produced by liquid phase exfoliation. Nanoscale 9:1820.

Biography:

Raquel Lizárraga  is a researcher at the department of Materials Science and Engineering at the Royal Institute of Tecknology in Seden. She has large expertise in ab initio calculations. She has great knowledge on magnetism of transition metals and rare earth systems. She has also studied materials with lack of periodic order, such as glassy systems. She has used an ab-initio method, the stochastic quenching method to study the amorphous structure of glassy materials. Recently she has studied the problem of Co substitution in cemented carbides. By studying stacking fault energies she has been able to identified possible alternative substitutions for Co, which is an important industry problem.

Abstract:

The stacking fault energy is closely related to structural phase transformations and can help to understand plastic deformation mechanisms in materials. Here we perform first principles calculations of the stacking fault energy in the face centered cubic (fcc) Cobalt-based binary alloys Co_1-xM_x, where M = Cr, Fe, Ni, Mo, Ru, Rh, Pd and W. We investigate the concentration range between 0 and 30 at. % of the alloying element.

The results are discussed in connection to the phase transition between the low-temperature hexagonal close packed (hcp) and the fcc structures observed in Co and its alloys. By analyzing the stacking fault energies, we show that alloying Co with Cr, Ru, and Rh promotes the hcp phase formation while Fe, Ni and Pd favor the fcc phase instead. The effect of Mo and W on the phase transition differs from the other elements, that is, for concentrations below 10 % the intrinsic stacking fault energy is lower than that for pure fcc Co and the energy barrier is higher, whereas above 10\% the situation reverses.

We carry out also thermodynamic calculations using the Calphad method. The trends of the ab initio stacking fault energy are found to agree well with those of the molar Gibbs energy differences and the phase transition temperature in the binary phase diagrams and give a solid support for the phase stability of these alloys.

Recent Publications

1. L. Tian, R. Lizárraga et al. (2017)  A First Principles Study of the Stacking Fault Energies for fcc Co-based Binary Alloys. Acta Materialia 136:215-223.

2. R. Lizárraga et al.  (2017) First Principles Theory of the hcp-fcc Phase Transition in Cobalt. Scientifc Reports 7:3778

3. R. Lizárraga (2016) Structural and magnetic properties of the Gd-based bulk metallic glasses GdFe₂, GdCo₂, and GdNi₂ from first principles. Phys. Rev. B 94:174201.

4. M. Araujo et al. (2014) Disorder-induced room temperature Ferromagnetism in Glassy Chromite. Scientific Reports 4:4686.

5. A. Lindmaa, R. Lizárraga et al. (2013) Exchange interactions in paramagnetic amorphous and disordered crystalline CrN-based systems. Phys. Rev. B 88:054414.

Biography:

Takashi Tokumasu is a professor of Institute of Fluid Science, Tohoku University. He has his expertise in analyzing nanoscale flow phenomena. Especially, he is focusing on the effect of quantum characteristics of molecules on macroscopic flow and thermodynamic phenomena. Moreover, he applies this technique and knowledge to the development of materials for next generation fuel cells. He performs large scale molecular dynamics simulations to analyze such nanoscale flow phenomena. He developed a molecular model which can treat proton hopping by classical molecular dynamics method (Mabuchi, Fukushima and Tokumasu, 2015). By using this model the relation between nanoscale structures of material and nanoscale flow phenomena of reactant and product materials can be analyzed. He also analyzes the transport mechanism of ions in solid materials.

Abstract:

Polymer Electrolyte Fuel Cells (PEFC) are expected to be as one of next-generation power supply systems due to its low environmental damage, high efficiency, and availability for dispersed power systems and emergency use. Transport resistance of reactant and product materials such as proton, oxygen and water is the determining factor of its efficiency and therefore it is necessary to analyze the transport phenomena of proton, oxygen and water in PEFC as fast as possible to increase its performance and efficiency. Computational Fluid Dynamics (CFD) based on macroscopic transport equations is often used as a conventional numerical analysis. A Membrane Electrode Assembly (MEA) of PEFC, however, consists of Gas Diffusion Layers (GDL), Micro Porous Layers (MPL), Catalyst Layers (CL), and a Polymer Electrolyte Membrane (PEM), where many nanoscale structures are constructed. In such flow fields, the characteristics of transport phenomena in MEA cannot be analyzed at the macroscopic point of view. Molecular simulation is a powerful tool to analyze these phenomena. In this study these nanoscale transport phenomena are analyzed by large scale Molecular Dynamics (MD) simulations and the relation between the nanoscale structures and the transport phenomena is analyzed in detail (Figure 1). Especially, the transport phenomena of proton in PEM which has highly anisotropic water structures, oxygen permeability, oxygen scattering and proton diffusivity of ionomer in CL, and the transport phenomena of nanoscale water droplet in MPL were simulated.  In the analysis of proton transfer in PEM and ionomer, we considered not only Vehicle mechanism but also Grotthus mechanism and the diffusivity of proton at various water contents was estimated. This information leads to a new design concept of materials for next generation polymer electrolyte fuel cells.

Recent Publications

1. Kurihara Y, Mabuchi T, Tokumasu T (2017) Molecular Analysis of Structural Effect of Ionomer on Oxygen Permeation Properties in PEFC. J. Electrochem. Soc. 164: F628-F637.

2. Mashio T, Ohma A, Tokumasu T (2016) Molecular Dynamics Study of Ionomer Adsorption at a Carbon Surface in Catalyst Ink. Electrochimica Acta 202: 14-23.

3. Fukushima A, Mima T, Kinefuchi I, Tokumasu T (2015) Molecular Dynamics Simulation of Channel Size Dependence of the Friction Coefficient between a Water Droplet and a Nanochannel Wall. J. Phys. Chem. C 119: 28396-28404

4. Mabuchi T, Fukushima A, Tokumasu T (2015) A Modified Two-state Empirical Valence Bond Model for Proton Transport in Aqueous Solutions. J. Chem. Phys. 143: 014501.

5. Sakai H, Tokumasu T (2015) Quantum Chemical Analysis of the Deprotonation of Sulfonic Acid in a Hydrocarbon Membrane Model at Low Hydration Levels. Solid State Ionics 274: 94-99.

Biography:

A. Jiménez-Suárez has his expertise in the optimization of manufacturing processes of nanoreinforced matrices and multiscale reinforced composites with multifunctional capabilities. His research started with optimization of mechanical routes of dispersion for carbon nanofibers and carbon nanotubes with improved electrical and mechanical conductivities as well as better barrier properties. Afterwards this research is translated into graphene nanoparticles based nanocomposites and the use of these nanoreinforced matrices to manufacture multiscale reinforced composites. These multifunctional composites showed improved interlaminar shear strength and self-sensing capabilities for structural health monitoring (SHM). Finally, recent publications are related to parametric modeling of properties as a function of morphological aspects of nanoreinforcements and manufacturing processing parameters and the introduction of carbon nanostructures in polymer matrices to be used in 3D printing technologies to obtain multifunctional materials with SHM, anti-icing, de-icing capabilities among others.

Abstract:

The use of 3D printing technologies has attracted the interest of the industrial and scientific community during last decades. The possibility  of quick and non-costly redesign can be used also for repairing and easy replacement structures after in service wear. Present work used Direct Write technology to print nanoreinforced resin circuits on continuous fiber reinforced polymers (CFRPs). The use of a carbon nanostructure resin would allow electrical conductivity through the resin circuit which could be used for structural health monitoring (SHM) and/or self-heating by Joule effect. This last effect could be used to create the first layer of a multilayer coating with anti-icing purposes taking advantage of the self-heating capability of this coatings by Joule effect.

Previous research has allow the selection of graphene nanoparticles (GNP) and carbon nanotubes (CNT) as nanoreinforcements to modify the epoxy resin and allow Joule effect heating. Nevertheless, the characteristics of Direct Write 3D printing technology as well as morphology of the printed lines, do not allow the direct extrapolation of results obtained in bulk nanocomposites to the printed circuits. Thus, it requires an optimization of the carbon nanostructures contents to allow resin flow through the injector as well as the formation of conductive nanoparticle networks.

The morphology of the printed circuit, the voltage applied and the  type and content of carbon nanoparticles need to be tuned in order to improve the anti-icing purpose. The study has determined that the greatest influence is the carbon nanotube content followed by the voltage and circuit morphology. The selected conditions allowed to  melt the frozen distilled water built-up on a fiber reinforced polymer composite similar to those that could be find in wind turbine blades.

Fig. 1. Image of the 3D printed circuits based on nanoreinforced epoxy resin with carbon nanostructures

Recent Publications

1. Moriche R, Jiménez-Suárez A, Sánchez M, Prolongo S.G, Ureña A. (2018) Sensitivity, influence of the strain rate and reversibility of GNPs based multiscale composite materials for high sensitive strain sensors. Compos Sci Tech 155:100-107.

2. Fernandez Sanchez-Romate X.X, Molinero J, Jiménez-Suárez A, et al. (2017) Carbon nanotube-doped adhesive films for detecting crack propagation on bonded joints: A deeper understanding of anomalous behaviors. ACS Applied Materals and Interfaces 9:43267-43274.

3. Moriche R, Jiménez-Suárez A, Sánchez M, Prolongo S.G, Ureña A. (2017) Graphene Nanoplatelets coated lass fibre fabrics as strain sensors. Compos Sci Tech 146:59-64.

4. Prolongo S.G, Moriche R, Del Rosario G, Jiménez-Suárez A et al. (2016). Joule effect self-heating of epoxy composites reinforced with graphitic nanofillers. Journal of Polymer Research 23:189.

5. Jiménez-Suárez A, Campo M, Prolongo. S.G et al. (2016). Effect of filtration in functionalized and non-functionalized CNTs and surface modification of fibers as an effective alternative approach. Composites Part B: Engineering 94:286:291.

Biography:

Alice W M Chan received her Bachelor Degree in Chemistry from the Chinese University in Hong Kong in 2016. She is now a postgraduate student with the supervision of Prof. Jimmy C Yu in the same institution. Her main research interest is in Environmental Chemistry, focusing on photocatalysis and supercapacitor.

Abstract:

Supercapacitors are of attractive for energy storage applications, such as back-up power supplies for batteries and boosting power for vehicle acceleration. Researchers are seeking for materials which outperform the high-capacitance ruthenium oxide in terms of its cost and abundance cost effective application in the reality. One of the suitable materials is manganese dioxide, which theoretical capacitance is as high as 1370 F/g. However, the experimental capacitances of the synthesized manganese oxides were usually below 500 F/g even if the material was fabricated with other materials (e.g. gold, graphene oxide, etc. ) for property enhancement.

In this research, manganese oxides nanoparticles (~10nm) are synthesized by hydrothermal treatment of manganese (II) acetylacetonate in ethanol. The electrode for measurement is prepared in a similar way by putting a piece of nickel foam in the reaction mixture. Although the particles are of low crystallinity, its capacitance is over 700 F/g at 18 A/g as confirmed by the measurement in galvanostatic charge/discharge method. Other analyses and characterizations of the pseudocapacitor are done by including CV, ICP, TEM and XRD etc.

Biography:

Yang Liu received her B,Sc. Degree from Xiamen University in 2019, She is currently pursuing her PhD degree in the Department of Chemistry, The Chinese University of Hong Kong. Her research interests primarily focuse on photocatalytic hydrogen evolution, removal of organic pollutants and nitrogen fixation over phosphorus-based photocatalysts.

Abstract:

Charge polarization is an interesting phenomenon. We have abserved this effect in crystalline red phosphorus (P). A relatively large-scale (up to 100×10×0.3 μm³) single crystal red P microbelts were prepared on liquid bismuth (Bi) substrate via a thermal vaporization method. Under visible light illumination, the P microbelts become highly charge polarized. Electrons accumulate on the two ends which become negatively charged, while the middle of the microbelts becomes positive. Water can be reduced to hydrogen on the two ends with higher electrons density. Such polarization can suppress the charge recombination and thus enhances charge transfer efficiency. Compared with amorphous P where charge carriers are randomly distributed, the photocatalytic efficiency of P microbelts exhibits a 10 times enhancement. The polarization property of P microbelts is confirmed by facet-selective photo-reduction of platinum (Pt) and theoretical calculations.

Recent Publications

1. Y. Q. Chen, C. Q. Yang, T. Li, M. Zhang, Y. Liu, M. A. Gauthier, Y. B. Zhao and C. L. Wu* (2015) The Interplay of Disulfide Bonds, α-Helicity, and Hydrophobic Interactions Leads to Ultrahigh Proteolytic Stability of Peptides. 16 (8) 2347–2355

Biography:

Sajid Ali has his expertise in DFT and quantum chemistry approaches for simulating the material properties. He also uses group theory analysis to study the defect induced properties of Materials. His recent(PhD) work is majorly focused on studying the mechanism of Quantum Emsission from Defects in Hexagonal Boron Nitride.  He is currently a final year PhD student at University of Technology Sydney Australia. and has already published a number of papers in high quality journals

Abstract:

Hexagonal boron nitride (h-BN) is a wide band gap (~6 eV) 2-dimensional (2-D) material with the potential to host many such colour centres [1-8] that are promising candidates for quantum applications. Defects can dramatically alter the electronic and magnetic properties of the host Semiconductor. While both nitrogen (N_v) and boron (B_v) vacancies can act as paramagnetic centres in h-BN [9], electron paramagnetic resonance (EPR) studies indicate that N_v are more important [10-15].  Two types of paramagnetic centres have been identified: (i) three-boron centres (TBC) in which an unpaired electron interacts with three equivalent boron (B¹¹) nuclei, producing 10-line EPR spectra, and (ii) one-boron centres (OBC) in which an unpaired electron interact with only a single B¹¹, producing 4-line EPR spectra.

A-priori calculations using density-functional theory (DFT) can provide useful tools for the interpretation of EPR by comparing the experimental and calculated hyperfine constants [16-20]. We consider detailed models of the TBC and OBC defects in h-BN, as well as proposing many new defect centres, particularly defects involving introduced carbon impurity atoms one’s which are thought of being responsible for single photon emission in hBN. We do Group-theoretical analysis to suggest new directions for experimental studies. Key properties of 9 possible defect sites in hexagonal boronitride (h-BN), V_N, V_N^-1, C_N, V_NO_2B, V_NN_B, V_NC_B, V_BC_N, V_BC_NSi_N, and V_NC_BSi_B, are predicted using density-functional theory (DFT) that are corrected by applying results from high-level ab initio calculations. Detailed consideration of the available excited states, allowed spin-orbit couplings, zero-field splitting, and optical transitions is made for the two related defects V_NC_B(Fig.1.) and V_BC_N. We propose that ground-state spin polarization and long-lived quantum memory in h-BN can be achieved for V_BC_N and V_NC_B respectively.

FIG.1. (a) Key DFT orbitals from the (1)¹A₁ closed-shell ground-state electronic structure of V_NC_B. The states are labelled according to the symmetry of Irreducible representation as per C_2v point group. x(y,z)-axis are perpendicular(in the) to the plane of defect.  (b) HSE06 adiabatic energies of low lying states of V_NC_B  as calculated by DFT, with, in (), these energies corrected according to ab initio CCSD(T), EOMCCSD, and CASPT2 calculations for a model compound [23].  Allowed transition polarizations d, spin-orbit couplings l driving non-radiative transitions and zero-field splittings are also indicated.

Recent Publications

1. A. Sajid, J. R. Reimers, and M. J. Ford, Physical Review B 97, 064101 (2018).

2. J. Reimers, A. Sajid, R. Kobayashi, and M. Ford, Journal of chemical theory and computation  (2018).

3. (A.Sajid, S. A. Tawfik)^{Equal Authors}, M. Fronzi, M. Kianinia, T. T. Tran, C. Stampfl, I. Aharonovich, M. Toth, and M. J. Ford, Nanoscale  (2017).

4. G. Grosso, H. Moon, B. Lienhard, A. Sajid, D. K. Efetov, M. M. Furchi, P. Jarillo-Herrero, M. J. Ford, I. Aharonovich, and D. Englund, Nature Communications 8, 705 (2017).

5. i. Zhu, L. L. C Lem, T. Nguyen, K. Fair, A. Sajid, M. J Ford¹, M. R. Phillips¹ and C. Ton-That

Biography:

Nick Gerasimchuk is Full Professor of Inorganic Chemistry at Missouri State University (USA). His research interests and expertise lay in the following areas: 1) the 1D coordination polymers as cytotoxic NIR emitters for theranostic applications; 2) mixed valence compounds; 3) novel antimicrobials based on silver and antimony oximates; 4) physical methods of investigation of inorganic and coordination compounds, including small molecules crystallography of inorganic and coordination compounds; 5) equipment design for synthetic inorganic/materials chemistry.

Abstract:

Mixed valence solids such as oxides based on molybdenum blues and tungsten bronzes recently found useful applications as semiconductors and catalysts. Despite some considerable efforts in the past, many of these interesting systems were not sufficiently investigated. We attempted systematic studies in this area of solid state chemistry and prepared several new systems for their subsequent investigations and evaluation of practical applications in the outlined above fields. Thus, interactions between well mixed fine powders of As2O3, P2O5, MoO3, WO3 and Nb2O5 at different stoichiometry in quartz ampoules under vacuum at ~1000oC in the presence of metallic molybdenum (or niobium) within several weeks lead to shiny dichroic crystalline  materials formed in cooler parts of the reaction vessel. An addition of small quantities of metals – Mo or Nb – was done with the aim of partial reduction of their highly oxidized Mo(VI), W(VI) or Nb(V) species to corresponding Mo(V), W(V) and Nb(IV) centers in order to form mixed valence solids. Sublimed crystals were investigated using a variety of techniques including XRD methods (powder, single crystals), spectroscopy (visible diffusion reflectance, IR, Raman and EPR), second harmonic generation (SHG), TG/DSC under N2 and air atmosphere, and electrical conductivity studies.

Results evidenced the formation of new, complex solids of previously unknown compositions that all crystallized in non-centrosymmetric, polar space groups. There were Mo(V) and Nb(IV) species detected in lattices by the EPR spectroscopy (Figure 1) both in coupled state, and as isolated centers of slightly different symmetry.

Thermogravimetric data and careful ICP analyses studies allowed accurate determination of content of solids and % of reduced metal ions. All new solids exhibit strong SHG effect based on YAG 1064 nm tests.

Structures of new solids and aspects of their practical usefulness are discussed.

Figure 1. The EPR spectra of Nb(IV) species in crystalline Nb5P3O18 (A) and Mo12P4O45 powder at 80K showing both Mo(V) and trapped oxygen radical in the lattice (B).

Recent Publications

1. Cheadle, C.; Ratcliff, J.; Berezin, M.; Pal’shin, V.; Nemykin, V.N.; Gerasimchuk, N. Dalton Trans, 2017, 46(39), 13562-13581.

2. Solntsev, P.V.; Anderson, D.R.; Rhoda, H.M.; Belosludov, R.V.; Fathi-Rasekh,  M.;  Maligaspe,  E.;  Gerasimchuk,  N.N.;  Nemykin, V.N. Crystal Growth & Design, 2016, 16 (2), 1027–1037.

3. Pariyar, A.; Gopalakrishnan, S.; Stansbery, J.; Patel, L. R.; Liang, X.; Gerasimchuk, N.; Choudhury, A. RSC Advances. 2016, 6, 38533- 38540.

4. Haleya, A.L.; Broadbent, L.N.; McDaniel, L.S.; Heckman, S.T.; Hinkle, C.H.; Gerasimchuk, N.N.; Hershberger, J.C.; Mebi, C.A. Polyhedron, 2016, DOI:10.1016/j.poly.2015.12.031

5. He, S.; Toukrakis, G.; Berezin, O.; Gerasimchuk, N.; Zhang, H.; Zhou, H.; Izraely, A.; Akers, W.J.; Berezin, M.Y. J. Mater. Chemistry, C. 2016, DOI: 10.1039 /c6tc001225.

6. Li, Y.; Dutta, T.; Gerasimchuk, N.; Wu, S.; Shetye, K.; Jin, L.; Wang, R.; Zhu, D-M.; Peng, Z. ACS Appl. Mater. Interfaces, 2015, 7 (18), 9372−9384.

Biography:

Richard Weihrich is professor for chemistry of materials and resources (CMR) at the institute of materials resource management (MRM) of the University of Augsburg, Germany. He studied chemistry in Regensburg with Diploma, PhD and habilitation thesis. Therein he developed the combined use of methods of experimental and theoretical chemistry to discover and to exploit novel materials.

Abstract:

Statement of the Problem: Megatrend developments from digitalisation to environmental challenges and the scarcity of resources drive an increasing need for new materials. They should be smart, low dimensional (from 3D to 2D and nano size) and highly functional – Phosphorene is a good example. Materials and their processing should also be “green” and resource efficient. This causes a still puzzling question to find the “right” material within the large number of possible combinations of chemical elements from a systematic approach. Methodology & Theoretical Orientation: We report on the combination of soft experimental chemistry and computational materials design within the phase diagram A-M-Ch. First, we focus on main group metals A like Phosphorous (P) [1, 2] and Phosphorene allotropes with a systematical understanding of structures and properties. Next we ask for the understanding and design of ternary materials like helical SnIP [3], pyrites MACh, and half perovskites AM_3/2X [4,5]. Findings: From our cooperative work phosphorene like P_xA_1-x and helical SnIP were recently described as smart 2D and 1D semiconductors with tunable band gaps. Within ternary A-M-X compounds superconducting parkerites and shandite like Sn₂Co₃S₂ and became a highly fascinating 2D system for spintronic, thermodynamic and skyrmionic properties. From computational chemistry and experiment a rational design to tune specific properties upon substitution could be reached. Further a guided synthesis could be reached by predicting stable and metastable compositions and structures. With the scheme of energy diagrams formation and decay of compositions as well as the formation of competing products are predicted. Novel results on new 3D and 2D materials are presented, that are reached by novel soft and conversion synthesis. Conclusion & Significance: the combination of modern computational and synthetic inorganic chemistry leads an efficient way to green materials design.

Combination of green and applied ressource efficient computer and experimental chemistry.

Recent Publications

1. F. Bachhuber, J. von Appen, R. Dronskowski, P. Schmidt, T. Nilges, A. Pfitzner, R. Weihrich, The extended range of phosphorus allotropes Angew. Chem. Int. Ed., 2014, 53, 2014, 11629-11633.

2. D. Pfister, C. Ott, K. Schäfer, B. Gerke, R. Pöttgen, O. Janka, M. Baumgartner, R. Weihrich, A. Efimova, A. Hohmann, P. Schmidt, S. Venkatachalam, L. van Wüllen, T. Nilges Inorganic double helices in semiconducting Material, Adv. Mater 2016, 28. 9783DOI: 10.1002/adma.201603135.

3. B. Liu, M. Köpf, A. A. Abbas, X. Wang, Q. Guo, Y. Jia, F. Xia, R. Weihrich, F. Bachhuber, F. Pielnhofer, H. Wang, R. Dhall, S. B. Cronin, M. Ge, X. Fang, T. Nilges, C. Zhou, Black Arsenic-Phosphorus: Layered Anisotropic Infrared Semiconductors with Highly Tunable Compositions and Properties, Adv. Mater 2015, 27, 4423-29.

4. R. Weihrich, W. Yan, J. Rothballer · Ph. Peter, S. M. Rommel, S. Haumann, F. Winter, Ch. Schwickert, R. Poettgen, Tuneable anisotropy and magnetism in Sn₂Co₃S_2–xSe_x – probed by ¹¹⁹Sn Mößbauer Spectroscopy and DFT studies, Dalton Trans., 2015, 44, 15855 – 15864.

5. F. Bachhuber, A. Krach, A. Furtner, T. Söhnel, J. Rothballer, R. Weihrich, Phase Stabilities of pyrite-related MTCh Compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te): A systematic DFT study, J. Solid State Chem. 2015; 226, 29-35.

Biography:

Ludek Frank is a senior researcher at the Institute of Scientific Instruments of the Czech Academy of Sciences. He has expertise in the methodology of electron microscopy and spectroscopy with an emphasis on low-energy electron applications. Currently he is studying the scanning transmission electron energy at near-zero energies of electrons and its application in material as well as biomedical sciences. Eliska Mikmekova is a staff researcher at the same Institute and head of the Group of Microscopy and Spectroscopy of Surfaces. She has expertise in the generation and diagnostics of ultrafine layers and 2D crystals. She is also developing and promoting the method of electron-stimulated desorption of adsorbed hydrocarbons.

Abstract:

Graphene sheets, including multilevel stacks, are nearly fully transparent for electrons at energies standard in electron microscopes. Graphene has even been considered an ideal substrate for the deposition of, for example, organic macromolecules for their observation in a scanning (transmission) electron microscope (SEM/STEM). The cathode lens principle with a negatively biased sample in the SEM/STEM enables one to obtain an arbitrarily low energy of electrons securing an ultimately reduced interaction volume providing the image information. The image contrast has been found to be sufficient for distinguishing graphene flakes at tens and units of eV in the STEM, and the electron transmissivity surprisingly showed values in units of percent only in this energy range. Expectations based on the usual extension of the inelastic mean free path of electrons below some 50 eV have not been confirmed. The electron transmissivity at tens of eV has proven a reliable tool for counting the graphene layers as an alternative to Raman spectroscopy providing much enhanced lateral resolution. Graphene layers grown by the CVD method on substrates exhibit contrasts connected with electron reflectivity fluctuations below about 8 eV and also in a second band around 15 eV in the ultra-low-energy SEM. This phenomenon can also be employed for counting the graphene layers because we get n-1 minima of reflectivity on n graphene layers. Observation at ultra-low electron energies, in particular under standard high-vacuum conditions, faces surface contamination owing to the electron-beam-induced deposition of carbon from spontaneously adsorbed hydrocarbon precursors. This fatal phenomenon mostly prevents us from performing true surface studies under the standard high vacuum (10^-6 to 10^-7 mbar). However, electrons bombarding surfaces at tens of eV have proven themselves to release hydrocarbon molecules instead of decomposing them, so ultimately cleaned surfaces are obtained.

Recent Publications

1. Mikmeková E, Bouyanfif H, Lejeune M, Hovorka M, Unčovský M, Frank L (2013) Very low energy electron microscopy of graphene flakes. Journal of Microscopy 251:123-127.

2. Frank L, Mikmeková E, Müllerová I, Lejeune M (2015) Counting graphene layers with very slow electrons. Applied Physics Letters 106:013117, 1-5.

3. Mikmeková E, Frank L, Müllerová I, Li BW, Ruoff RS, Lejeune M (2016) Study of multi-layered graphene by ultra-low energy SEM/STEM. Diamond & Related Materials 63:136-142.

4. Frank L, Mikmeková E, Lejeune M (2017) Treatment of surfaces with low-energy of electrons. Applied Surface Science 407:105-108.

5. Frank L, Hovorka M, Mikmeková Š, Mikmeková E, Müllerová I, Pokorná Z (2012) Scanning electron microscopy with samples in an electric field. Materials 5:2731-2756.

Biography:

Ruiwen Xie has her expertise in first principles calculations. She is now a PhD student in Royal Institute of Technology, Sweden. She has a great knowledge of mechanical properties of stainless steels. She is also working in collaboration with Sandvik Coromant which is a world’s leading supplier of tools and tooling solutions. Her calculations with the ab-initio method will help optimize the process of quality control for industrial products.

Abstract:

The measurement of the magnetic saturation in reference to the pure Co is utilized for quality control in cemented carbides. This measurement is an estimation of binder phase components. WC-Co cemented carbides, in which Co is chosen as a binder, are relatively tough and fatigue-resistant composite materials used widely for cutting tools and rock drilling inserts. However, a substitution for Co as a binder is in urgent demand due to its health threat and fluctuating price. This work aims to investigate the correlation between the COM value and binder phase components for a new binder Ni₈₅Fe₁₅ (at. %) through first principles calculations. The magnetic behavior of Ni/WC interface and the binder segregation are also studied.

The equation for calculating the COM value of WC-Ni₈₅Fe₁₅ cemented carbides is constructed. The COM value is decreased by W and C compositions dissolved into the binder phase. We further compare theoretically predicted COM values with experimental measurements for several cemented carbides. And theoretical results agree well with experimental values. The interface investigation shows that spin polarized Ni atoms around the Ni(111)/WC(0001) interface possess lower magnetic moments than bulk Ni atoms. The segregation near the impurity W in the binder phase indicates that the W prefers Fe instead of Ni. Factors that would affect the magnetic behavior of WC-Ni₈₅Fe₁₅ alloys are analyzed.

Recent Publications

1. Dai, J. H., Xie, R. W., Chen, Y. Y., & Song, Y. (2015). First principles study on stability and hydrogen adsorption properties of Mg/Ti interface. Physical Chemistry Chemical Physics, 17(25), 16594-16600.

2. Chen, Y., Dai, J., Xie, R., Song, Y., & Bououdina, M. (2017). First principles study of dehydrogenation properties of alkali/alkali-earth metal doped Mg7TiH16. Journal of Alloys and Compounds, 728, 1016-1022.

3. Chen, Y., Dai, J., Xie, R., & Song, Y. (2016). A first-principles study on interaction of Mg/Ni interface and its hydrogen absorption characteristics. Surface Science, 649, 133-137.

4. Dai, J., Chen, Y., Xie, R., Hu, Z., & Song, Y. (2016). Influence of alloying elements on the stability and dehydrogenation properties on Y(BH4)3 by first principles calculations. International Journal of Hydrogen Energy, 41(3), 1662-1671.

Biography:

Alessandra Fava is graduated in “Materials Science” and in “Science and Technology of materials” at the University of Rome “Tor Vergata”, Rome, Italy in 2014. Nowadays she is in third year of her PhD in Industrial Engineering at the University of Rome “Tor Vergata”. Her current research focuses on a mechanical and a microstructural characterization of oxide dispersion strengthened (ODS) steel produced by low-energy mechanical alloying (LEMA) in order to study the effect of the LEMA on the ODS structure and the involved strengthening mechanisms.

Abstract:

Oxide dispersion strengthened (ODS) steels are promising materials for high temperature applications, in particular in fission and fusion nuclear reactors. In comparison to common reduced activation ferritic/martensitic steels they exhibit better resistance to neutron irradiation and creep owing to an uniform dispersion of nano-oxides particles (~ 5 nm) and a very fine grain structure (~ 500 nm). These features are shown in Figure 1.

ODS steels are commonly prepared by high-energy mechanical alloying (HEMA) of a mixture of steel powder and Y₂O₃ particles followed by a consolidation stage consisting of hot extrusion (HE) or hot isostatic pressing (HIP). The samples are then submitted to annealing around 1100 °C for 1-2 hours. Recently, the present authors proposed a novel method based on low-energy mechanical alloying (LEMA).

In general ODS microstructure is quite complex and several mechanisms contribute to the mechanical strengthening with different effects depending on the temperature. The present work analyses the role played by each single mechanism at increasing temperature by considering the specific microstructural features.

ODS steels prepared through different routes and process parameters display different grain size distribution and homogeneity of particles dispersion, factors which strongly affect the mechanical properties.

Yield stress values measured in tensile tests performed at increasing temperature up to 700 °C, either from literature or achieved by us, have been examined and the following strengthening mechanisms have been taken into account to fit the experimental data: (i) solid solution; (ii) Bailey-Hirsch; (iii) Hall-Petch; (iv) Orowan; (v) Arzt-RÅ‘sler-Wilkinson and (vi) Coble creep.

The analyses evidence advantages and drawbacks of different preparation routes and suggest some criteria for further improving the mechanical properties of these materials.

Figure 1: Fine grain structure (a) and nano-oxides particles (b).

Recent Publications

1. Zhao Q, Yu L, Liu Y, Huang Y, Ma Z, Li H, Wu J (2017) Microstructure and tensile properties of a 14Cr ODS ferritic steel. Materials Science and Engineering A 680:347-350.

2. Shen J, Li Y, Li F, Yang H, Zhao Z, Kano S, Matsukawa Y, Satoh Y, Abe H (2016) Microstructural characterization and strengthening mechanisms of a 12Cr-ODS steel. Materials Science and Engineering A 673:624-632.

3. Li Y, Shen J, Li F, Yang H, Kano S, Matsukawa Y, Satoh Y, Fu H, Abe H, Muroga T (2016) Effects of fabrication processing on the microstructure and mechanical properties of oxide dispersion strengthening steels. Materials Science & Engineering A 654: 203–212.

4. De Sanctis M, Fava A, Lovicu G, Montanari R, Richetta M, Testani C, Varone A (2017) Mechanical characterization of a nano-ODS steel prepared by low-energy mechanical alloying. Metals 7

5. Frelek-Kozak M, Kurpaska L, Wyszkowska E, Jagielski J, Jozwik I, Chmielewski M (2018) Evaluation of consolidation method on mechanical and structural properties of ODS RAF steel. Applied Surface Science 446:215-221.

Biography:

Dipanjana De has her focus on the advancement and enhancement of the mechanical and electrical properties of the nanocomposites. She has enhanced the mechanical properties of Zirconium toughened alumina (ZTA) by incorporating carbon nanotubes (CNT) and developed lightweight high-strength CNT-reinforced epoxy composite. Recently, she is working on the enhancement of the electrical properties of BFO-ZnO nanocomposite, with an aim to create nanomaterals with amplified magnetoelectric coupling.  As a student, she is always looking forward for opportunities to enhance her knowledge and skills regarding nanomaterials/nanophysics.

Abstract:

The use of carbon nanotubes (CNTs) in the Zirconium Toughened Alumina (ZTA) matrix composite results in enhanced mechanical properties. In this study, the ceramic matrix composites – ZTA (containing 80 vol% of pure Al₂O₃ and 20 vol% of yttria stabilized zirconia (YSZ)) is furthermore mixed with different proportions of MWCNTs. The addition of YSZ in monolithic ceramic results in the reinforcement of the pure alumina Al₂O₃, thus overcoming brittleness of monolithic ceramics. It, too, results in corrosion resistance and temperature stability. The resulting reinforced composite is ZTA. Our main aim is to improve the mechanical properties of ZTA such as fracture toughness and micro-hardness. It is observed that CNTs are better than SiC for reinforcement. Due to its large aspect ratio (diameter Ì´ 20-30 nm and length Ì´ 1-2μm) and tensile strength, CNTs are the most preferred reinforcing material used for binary composites. Carbon fiber-reinforced epoxy composites modified with carbon nanotubes (CNTs) were fabricated and characterized. Here, Araldite is mixed with Aradur (hardener) to create a strong epoxy composite. Furthermore, MWCNTs are added in the composite to produce a light-weight, strong composite. A process for preparing carbon nanotube (CNT) dispersions for reinforcement of CNT in epoxy resin for improved mechanical properties has been reported. Mechanical property evaluations were then performed for the cured CNT-epoxy nano-composites and compared to the base epoxy resin matrix. This research may help to propose a further positive solution for fabricating CNTs-epoxy reinforced nanocomposites.

Recent Publications

1. Bocanegra-Bernal MH, Echeberria J, Ollo J, Garcia-Reyes A, Dominguez-Rios C, Reyes-Rojas A, Aguilar-Elguezabal A (2014) A comparison of the effects of multiwall and single-wall carbon nanotube additions on the property of Zirconia toughened alumina. Carbon 49:1599-1607

2. Echeberria J, Rodriguez N, Vanmeensal K, Reyes-Rojas A, Garcia-Reyes A, Dominguez-Rios C, Aguilar-Elguezabal A, Bocanegra-Bernal MH (2012) Hard and Tough carbon nanotube reinforced zirconium-toughened alumina composite prepared by spark plasma sintering. Carbon 50:706-717

3. Akin Ipek (2015) Investigation of the microstructure, mechanical properties and cell viability of zirconia-toughened alumina composites reinforced with carbon nanotubes. Journal of the Ceramic Society of Japan 123 [5] 405-413

4. Galusek Dušan, Galusková Dagmar (2015) Alumina Matrix Composites with Non-Oxide Nanoparticle Addition and Enhanced Functionalities. Nanomaterials 5: 115-143

5. Popov Valentin N. (2004) Carbon nanotubes: properties and application. Materials Science and Engineering R 43: 61–102

Biography:

Andrés Muñoz Chemical Engineering, Universidad Nacional de Colombia, Medellín, Colombia, 2010. Specialization on Integral Management, Politécnico Colombiano Jaime Isaza Cadavid, Colombia, 2014. MSc, Master in Chemical Engineering, Universidad de Antioquia, Colombia, In progress, throughout his career has developed skills to perform calculations and engineering reports, measurements and commissioning of thermal systems, field operation analysis, process and equipment measurements, specialized software CFD simulations (ANSYS), Development of calculation models in Visual Basic excel, analysis of energy consumption and balances of matter and energy. He has developed his experience in HATCH-NDISA in projects for companies in the food, paper, mining and cement sectors. He has also participated in research projects in university, company and state alliances in the development of prototypes in the field of nanotechnology, catalysis and environmental control.

Abstract:

Carbon nanotubes are materials of great scientific and technological interest that has called attention of many scientists, since the discovery of them by Ijima in 1991[1]; This great interest due to their unique physical and chemical properties such as chemical corrosion resistance, thermal stability, high thermal and electrical conductivity, low density and high mechanical strength.

The present work shows an experimental fluidized bed catalytic chemical vapor deposition reactor (see Figure), as the best technology to produce carbon nanotubes, using a clean process that allows the simultaneous production of hydrogen, based on catalytic decomposition of ethanol, which is a renewable carbon source, and a catalyst based on nickel. Operational parameters as initial catalyst amount, fluidization velocity, temperature and residence time, was analyzed and optimized for the experimental design, making the respective experiments to obtain a kinetic model of the reactor.

As results was found that the granulometric distribution size of the catalyst have an impact in the yield of the reaction, being increased as the size down; the nature and behavior of the catalyst inside the reactor affect the requirements to keep the fluidization regimen, increasing the inlet flow of gases when agglomeration of catalyst is created with the increase of the temperature inside the reactor; the time of reaction, to obtain the same yield is decreased while the gas concentration of the ethanol is increased in the inlet gases; the outer diameter of the CNTs strongly depends on the reaction temperature; an increase of the reaction temperature leads to an increase in H2 production, this associated with the thermal decomposition of the ethanol and the CNT production; finally the TEM micrographs show that the nanotubes were multi-walled for the range of conditions studied. The production of carbonaceous materials (mainly carbon nanotubes) was between 1 g/g catalyst and 14 g/g catalyst.

Materials, catalysts, and reaction products was characterized using analytical techniques such as XRD, TGA, SEM, TEM.

Figure. Design and laboratory experimental set up of the fluidized bed Reactor for the production of CNT.

Recent Publications

1. Q. Weizhong et al., “Production of carbon nanotubes in a packed bed and a fluidized bed,” AIChE J., vol. 49, no. 3, pp. 619–625, 2003.

2. E. M. S. Dresselhaus, G. Dresselhaus, and P. Avouris, Carbon Nanotubes, vol. 4216, no. 2001. 2003.

3. R. Philippe et al., “Catalytic production of carbon nanotubes by fluidized-bed CVD,” Chem. Vap. Depos., vol. 13, no. 9, pp. 447–457, 2007.

4. A. Morançais et al., “A parametric study of the large scale production of multi-walled carbon nanotubes by fluidized bed catalytic chemical vapor deposition,” Carbon N. Y., vol. 45, no. 3, pp. 624–635, 2007.

Biography:

Ismail Altuntas has continued PhD in Solid State Physics in Cumhuriyet University, Turkey. During his PhD studies he worked at Microelectronic Materials and Device Laboratory-Virginia Commonwealth University USA under the supervision of Prof. Dr. Hadis Morkoç. Currently, he is a research assistant at Nanophotonics Research and Application Center at Cumhuriyet University. His research interest covers high quality III-V semiconductor thin films (InGaAs, InAlAs, InP, AlN, AlGaN, GaN etc) growth by MOCVD and detailed characterization to produce electronic and optoelectronic devices.

Abstract:

GaN based materials including light emitting diodes, blue laser diodes and high-power microwave transistors have received much attention over the past few years. An important problem of these structures is the high levels of structural defects, mostly dislocations, due to the lack of a suitable lattice-matched substrate So far, the substrate of choice has been mainly sapphire (Al2O3) substrates, which has a large lattice mismatch with GaN or AlN. As a result, (0001) GaN layers epitaxially grown on sapphire subtrates include high concentrations of misfit and threading dislocations. In this study, epitaxial GaN layers have been grown on both conventional sapphire and patterned sapphire substrates by using an MOCVD system and high resolution XRD scans and photoluminescence measurements are performed to compare the effect of patterned sapphire substrates on the dislocation density.

Biography:

Stiliyana Pereva – graduated The National High-School of Mathematics and Sciences with profile in chemistry, biology and mathematics. This followed to a bachelor degree in Computational Chemistry at Sofia’s University. Meanwhile I started to work in the group of prof. DSc Tony Spassov at the Department of Applied Inorganic Chemistry, which led me to obtaining my master degree in Materials Science with special interest in Cyclodextrins (CDs): their inclusion complexes, and especially their application in pharmaceutical industry. In April, 2017 I become a PhD in Solid State Chemistry, successfully defending my Thesis on “Inclusion compounds based on Cyclodextrins “. Now I’m working on new ways to improves the complex formation between cyclodextrins and some drugs, conducting experiments and applying the methods of Quantum-chemistry for a better understanding on the complex mechanism.

Abstract:

Cyclodextrin (CDs) have a vast and important applications in many fields of natural sciences – chemistry, pharmacy, gas storage, catalysis, foods, cosmetics. This interest and nearly 40 years of research on CDs is due to their structure – they have a hydrophobic cavity and a hydrophilic exterior, thus they can be hosts of molecules with proper size, which can be entrapped into their cavity. Ibuprofen and naproxen are non-steroidal anti-inflammatory drugs with high bioavailability and permeability, but low water solubility.

Very few researches investigate the complex efficiency and how this can improve the solubility of the drugs in water, their properties and also shed a light to the mechanism of complex formation. We propose a modified ball milling method (with the use of a solvent), which is very effective, compared to the classical pharmaceutical methods – it’s cheap, environmentally friendly and can be applied in an industrial scale. With the help of thermal analysis (Differential Scanning Calorimetry and Thermal Gravimetry), we were able for a first time to quantitatively determine how efficient is this modified synthetic method. We proved that for ibuprofen complexes 1 molecule ibuprofen, replaces 7 molecules water from the cavity of the cyclodextrin.

Recent Publications

1. Pereva, S., Himitliiska, T., Spassov, T., Stoyanov, S.D., Arnaudov, L.N., Dudev, T. (2015) Cyclodextrin-Based Solid-Gas Clathrates., Journal of Agricultural and Food Chemistry, 63, Issue 29, Pages 6603-6613.

2. Pereva, S., Sarafska, T., Bogdanova, S., Spassov, T. (2016), Efficiency of "cyclodextrin-ibuprofen" inclusion complex formation., Journal of Drug Delivery Science and Technology, 35, Pages 34-39.

3. Angelova S., Nikolova V., Pereva S., Spassov T., Dudev T. (2017) α-Cyclodextrin: How Effectively Can Its Hydrophobic Cavity Be Hydrated?, J Phys Chem B., (39):9260-9267.

Biography:

Tamara Aleksandrov Fabijanic is employed as a research assistant at the Laboratory for the Mechanical Properties of the Faculty of Mechanical Engineering and Naval Architecture. She gained PhD in 2014 by defending her dissertation titled "Development of Reference Vickers Hardness Blocks by Powder Metallurgy Process". In addition to teaching and scientific work in the field of materials, she also participates in the field of testing and calibration of force and hardness and testing of mechanical properties. In the area of scientific metrology as an employee of the Laboratory for Testing Mechanical Properties, a national standard for force and hardness, intensively cooperates with the most prestigious European institutes through various interlaboratory comparisons of force and hardness measurements. She has been trained scientifically and professionally in Croatia and abroad, the most important being Physikalische Technische Bundesanstalt, Braunschweig and Fraunhoffer IIKTS, Dresden.

Abstract:

Niobium Nb micro alloyed low carbon steel contains small amounts of Nb as an alloying element (0.02-0.1 wt%), which has a significant impact on many material properties. Niobium shows a strong affinity for nitrogen and carbon and causes the formation of niobium carbide and niobium nitride within the structure of the steel which improve the grain refining, retardation of recrystallization, and precipitation hardening [1-5].  Those precipitates are dispersed in the form of small Nb (CN) precipitates, which are arranged in fine lines [1, 4]. Consequently, the toughness, yield point and ultimate tensile strength, formability, and weldability of the micro alloyed steel are increased with small decrease in elongation and ductility [1-5].

The mechanical properties of Nb micro alloyed low carbon steel were researched in the paper. For the purpose of research the low alloyed steels with different Nb content; 0.035 wt. %Nb and 0.06 wt. %Nb were selected. The tensile test with the combination of digital image correlation (DIC) and thermography were used to study the thermomechanical behaviour of materials.  The test pieces were cut from the hot rolling strip which were air cooled and thermomechanically treated. The test pieces of low carbon steel were tested for the comparison. The test pieces with the original gauge length L₀ of 45 mm, original width b₀ of 20 mm were prepared. The tensile test was performed in accordance with ISO 6892-1:2009 at room temperature. Two different strain rates; 5mm/min and 20 mm/min were applied in order to research the potential of Nb micro alloyed low carbon steels for improved energy absorption. The highest values of yield strength and tensile strength and the lowest values of elongation were measured for the test pieces with 0.06 wt. %Nb. The strength measured at different strain rates did not change for both Nb micro alloyed steels and low carbon steel indicating that materials do not show positive strain rate  sensitivity.

Recent Publications

1. Jandrlić, Ivan; Rešković, Stoja; Brlić, Tin: Distribution of stress in deformation zone of niobium microalloyed steel, Metals and materials international, 2018; 1-6

2. S. Shanmugama, N.K. Ramisetti, R.D.K. Misra , T. Mannering, D. Panda, S. Jansto: Effect of cooling rate on the microstructure and mechanical properties of Nb-microalloyed steels, Materials Science and Engineering A, 460–461 (2007) 335–343

3. D. Bhattacharya, Microalloyed steels for the automotive industry. Tecnologia em Metalurgia, Materiais e Mineração 11(4), 371–383 (2014)

4. M.I. Equbal, P. Talukdar, V. Kumar, R.K. Ohdar, Deformation behavior of micro-alloyed steel by using thermo mechanical simulator and finite element method. Proc. Mater. Sci. 6, 674–681 (2014)

5. W.B. Morrison, Overview of microalloying in steel, in The Proceedings of the Vanitec Symposium, Guilin, China 2000, The Vanadium International Technical Committee (Vanitec Limited, Westerham Kent, England, 2000), pp. 25–35

Biography:

Simone Borri has completed his PhD in 2007 from University of Firenze, Italy. He is researcher at CNR-National Institute of Optics since 2010. He worked as researcher for LENS, the European Laboratory for Nonlinear Spectroscopy, and IFN, the italian Institute for Photonics and Nanotechnologies. His main expertise is development of coherent sources and techniques for high-sensitivity and high-resolution molecular spectroscopy in the mid infrared. During his scientific activity he developed mid-IR and THz sources based on nonlinear frequency generation, and worked on trace-gas sensors based on cavity-enhanced absorption spectroscopy, photoacoustic sensing, Doppler-free spectroscopy, high-precision spectroscopy on molecular beams. He studied the noise properties of quantum cascade lasers, and developed locking techniques for linewidth narrowing, using also novel optical devices like crystalline whispering gallery mode resonators.

Abstract:

Material Science and Optics are intrinsically related from the earlier study on radiation-matter interaction.

Over the last years, photonics has rapidly evolved towards more compact and sophisticated devices from the visible-near infrared (VIS-NIR) towards Mid and Far Infrared (MIR and THz). The challenge is the realization of integrated structures as a powerful technology for “packing” sources, detectors, electronics and optics into single and low costs platforms.

In particular MIR and THz spectral region are very attractive for scientific and applicative reasons:this spectral zone is the “so-called” fingerprint region in which many substances exhibitvery strong characteristic absorptions: simple molecules (CO₂, H₂O, H₂S, etc.), complex molecules (dioxins, explosives, organic fluids, etc.).

Key light sources for mid infrared sensing and spectroscopy are coming from Material Science Research:Interbandand Quantum Cascade Lasers.For spectroscopic and metrology it is very important to have stable sources with narrow linewidth. In this view, a new class of materials (nonlinear crystals) and devices enable frequency conversion,in order to realize optical referencesusing VIS-NIR sources or Laser Frequency Combs.

A new Physics and new classes of devices are coming from research in crystalline Whispering Gallery Mode Resonators (WGMRs). These devices enable nonlinear generation of optical frequency combs, recently exploited in the Telecom region (making use of micro-resonators where light is coupled in and out by opticalfibers). Such WGMRs are also providing outstanding performance in laser stabilization, even in the mid infrared-MIR spectral range. They can also be used for direct sensing in gaseous or liquid compounds, with innovative applications in the field of medicine, human health and study of capillarity phenomena and viscous-elastic properties of fluids.

Here, we report our recent researchactivity on crystalline and liquid WGMRs, used as powerful tool for nonlinear optics, bio-chemical sensing and mid-IR laser frequency stabilization,passive and active optical cavity-assisted surface-plasmon-resonance sensors as well ason nonlinear crystals for generation of metrological mid-IR coherent light. These results open the way to new classes of compact MIR sources with a number of applications in Space missions, Metrology, Chemistryand Fundamental Physics.

                    Figure 1: High-Q crystalline Whispering Gallery Mode Resonators have undergone an impressive development in the last years, demonstrating ultimate performance in laser stabilization from UV to MIR spectral range.                    

Recent Publications

1. G. Insero, C. Clivati, D. D'Ambrosio, P. De Natale, G. Santambrogio, P. Schunemann, J.-J. Zondy, and S. Borri, “Difference frequency generation in the mid-infrared with orientation-patterned gallium phosphide crystals”, Opt. Lett. 41 (2016), 5114

2. M. Siciliani de Cumis, S. Borri, G. Insero, I. Galli, A. Savchenkov, D. Eliyahu, V. Ilchenko, N. Akikusa, A. Matsko, L. Maleki, and P. De Natale, “Microcavity-Stabilized Quantum Cascade Laser”, Laser Photon. Rev. 10, 153 (2016).

3. S. Borri, M. Siciliani de Cumis, G. Insero, S. Bartalini, P. CancioPastor, D. Mazzotti, I. Galli, G. Giusfredi, G. Santambrogio, A. Savchenkov, D. Eliyahu, V. Ilchenko, N. Akikusa, A. Matsko, L. Maleki, and P. De Natale, “Tunablemicrocavity-stabilized quantum cascade laser for mid-IR high-resolutionspectroscopy and sensing”, Sensors 16, 238 (2016).

4. G. Gagliardi, M. Salza, S. Avino, P. Ferraro, P. De Natale, “Probing the Ultimate Limit of Fiber-opticStrainSensing“, Science 330, 1081 (2010)

5. A. Giorgini, S. Avino, P. Malara, P. De Natale, G. Gagliardi, “Fundamentallimits in high-Q dropletmicroresonators”, Sci. Rep. 7, 41997 (2017)

6. Consolino, A. Taschin, P. Bartolini, S. Bartalini, P. Cancio, A. Tredicucci, H.E. Beere, D.A. Ritchie, R. Torre, M.S.Vitiello, and P. De Natale, “Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers”, Nature Communications 3, 1040 (2012)

Biography:

Mina Yoon received her PhD degree in Theoretical Condensed Matter Physics in 2004, from Michigan State University. She is a Research Scientist at ORNL and a Joint Professor of Physics at University of Tennessee, Knoxville. The primary focus of her research lies in the fundamental understanding of growth mechanisms, novel properties, functionalization, and potential technological applications of surface-based and low-dimensional materials. Especially, her interest is in utilizing these materials as light, environmentally friendly, and efficient energy storage/generation and optoelectronic application by making use of their unique low-dimensional properties. Her theoretical approach ranges from atomistic modeling by first-principles quantum mechanical approaches and many-body potential approaches, to continuum elasticity theory and phenomenological modeling.

Abstract:

We discover new class of electrides [1,2], the first electride with nontrivial band topology, based on 1D building blocks by coupling materials database searches and first-principles-calculations-based analysis. This new class of electrides, composed of 1D nanorod building blocks, has crystal structures that mimic β-TiCl₃ with the position of anions and cations exchanged. Unlike the weakly coupled nanorods of β-TiCl₃, Cs₃O and Ba₃N retain 1D anionic electrons along the hollow inter-rod sites; additionally, strong inter-rod interaction in C₃O and Ba₃N induces band inversion in a 2D superatomic triangular lattice, resulting in nontrivial band topology of Dirac nodal lines [2].  This new material could be served as an ideal template to explore various quantum phases. Using a tight-binding Hamiltonian based on two-dimensional (2D) honeycomb lattices, we construct a phase diagram in terms of exchange coupling and spin-orbit coupling (SOC), which spans four different phases, such as topological insulator, large/small gap quantum anomalous Hall (QAH) insulator, and ferromagnetic semiconductor [3]. We reveal that 2D honeycomb lattices consisting of some post-transition metals, such as Sn, Pb, and Bi, undertake ferromagnetic transition as the lattice constant increases and significant changes in SOC strength, which makes them an ideal material to explore the versatile phases solely by changing lattice constants.  First-principles density functional calculations demonstrate that 2D honeycomb SnF can show QAH effect with SOC gap of ~0.25eV and Curie temperature (T_c) of ~780K [3]. Our calculations propose a new avenue to the room-temperature QAH effect in realistic 2D materials systems.

Recent Publications

1. First-Principles Prediction of Themodynamically Stable Two-Dimensional Electrides, W. Ming, M. Yoon, M.-H. Du, F. Liu, K. Lee, and S. W. Kim, J. Am. Chem. Soc. 138, 15336 (2016).

2. First-Principles Prediction of New Electrides with Nontrivial Band Topology Based on One-Dimensional Building Blocks, Changwon Park, Sung Wng Kim, Mina Yoon, Phys. Rev. Lett. 120, 26401 (2018).

3. Quantum Phase Engineering of Two-Dimensional Post-Transition Metals: Toward a High-Temperature Quantum Anomalous Hall Insulators, L. Zhang, C. Park, and M. Yoon (2018, to be published).

Biography:

Michael Kaplan is a physics and chemistry researcher and educator. From 2005 he is a tenured professor of Simmons College (Boston, USA). His expertise is related to the structural phase transitions, acoustic and magnetic properties of materials, ferroelectricity, non-destructive testing of materials, ultrasound, multiferroics, smart materials. He is co-author (with Benjamin Vekhter) of a book Cooperative Phenomena in Jahn-Teller Crystals (Plenum Press, 1995), co-editor (with George Zimmerman) of a book Vibronic Interactions: Jahn-Teller Effect in Crystals and Molecules, NATO Science Series (Kluvers Academic Publishers, 2001), author and co-author of about 300 refereed articles and 40 patents registered in Germany, UK, France, Japan, USSR, USA.

Abstract:

Microscopic theory of structural phase transitions based on the cooperative Jahn-Teller effect is considered for finite size crystal samples in the shape of a plate.  In these samples one size – thickness 2h – is significantly smaller than two others. In such crystal plate the electron and phonon spectra are different from ones of the regular 3-dimensional crystal. The vibrational spectrum difference is in the focus of attention in this presentation. This difference is especially big for the long wave acoustic vibrations with the wavelength 𝜆 2h.

Structural phase transitions are caused by the intersite electron interactions mediated by the crystal acoustic and optical vibrations – virtual phonon exchange. If the major contribution to these interactions is related to the acoustic vibrations, the theory modifications caused by sample surfaces are especially significant. The theory peculiarities for crystal plates are connected with the existence of the Lamb (symmetric LS and antisymmetric LA) and horizontal (symmetric SH and antisymmetric AH) vibrational modes. The mutual orientation of the crystal symmetry axes and the crystal plate surface (crystal cut type) is of primary importance in defining the acoustic wave family most significant in the mechanism of structural phase transition.

Thermodynamic and dynamic aspects of the cooperative Jahn-Teller effect in tetragonal symmetry crystal plates with the major role of the Lamb waves or horizontal waves in the mechanism of the ferroelastic phase transition are under discussion.

Biography:

Ilkay Demir received his PhD degree in Solid State Physics from the Cumhuriyet University, Turkey. During his PhD studies he worked at Center for Quantum Devices-Northwestern University USA under the supervision of Prof. Dr. Manijeh Razeghi. Currently, he is a research assistant at Nanophotonics Research and Application Center at Cumhuriyet University. His research interest covers high quality  III-V semiconductor thin films (InGaAs, InAlAs, InP, AlN, AlGaN, GaN etc) growth by MOCVD and detailed characterization to produce electronic and optoelectronic devices.

Abstract:

The UV capabilities of III-nitride materials are of special interest for civilian applications such as air and water sterilization, efficient white lighting, high density optical data storage and military applications such as biological agent detection and non-line-of-sight communication etc. In recent years AlN has received a great deal of attention for use as a template layer for deep UV emitter and detector applications because of its promising features such as UV transparency, good thermal stability and high thermal conductivity. Generally, the surface morphology and defect density of AlGaN and the upper quantum-well active layer of DUV devices depend significantly on the crystalline quality of the underlying AlN template; therefore, obtaining AlN with a smooth surface and low threading dislocation (TD) density is critical to improve DUV device performance. In this study we report pulsed atomic layer epitaxy growth of high crystalline quality, thick (~2µm) and crack-free AlN material on c-sapphire substrates via a sandwich method using metal organic chemical vapor deposition. This method involves the introduction of a relatively low temperature (1050 °C) 1500 nm thick AlN layer between two 250 nm thick AlN layers which are grown at higher temperature (1170 °C). The surface morphology and crystalline quality remarkably improve using this sandwich method. A 2 µm thick AlN layer was realized with 33 arcsec and 136 arcsec FWHM values for symmetric (0002) and asymmetric (10-15) reflections of w-scan, respectively, and it has an root-mean square surface roughness of ~0.71 nm  for a 5 x 5 um² surface area.

Biography:

Nicolas Reyren got his PhD in 2009 at the University of Geneva (Switzerland). He joined the CNRS at the Unité Mixte de Physique CNRS/Thales (France) as a junior researcher in 2013. He is interested by spin-orbit related phenomena in the context of spintronics, such as Edelstein effect, Dzyaloshinskii-Moriya interaction and skyrmions.

Abstract:

Magnetic skyrmions are small whirling magnetic textures with non-trivial topology, which are usually stabilized by the Dzyaloshinskii-Moriya interaction (DMI). As they are potentially the smallest magnetic textures in magnetic thin films stable at room temperature, they attracted a lot of attention due to their potential applications for memory devices [1].

In 2016, we have shown that sub-100nm skyrmions can be stabilized at room temperature using Ir|Co|Pt-based in 10 repetition multilayers in order to increase the magnetic volume compared to single layer systems, while keeping large DMI (about 2 mJ/m²) [2]. Moreover, we also demonstrated the possibility to nucleate them using current pulses [3-5], and to detect them using anomalous Hall effect [4,5]. In the studied geometry, the topological Hall effect is negligible compared to the anomalous Hall effect, which is sufficient to detect single skyrmions in 500-nm-wide tracks, as we could verify by simultaneous magnetic force microscopy (MFM) measurements (see Fig.1).

Up to now, the spin torque induced skyrmion velocity remains low, partly due to the imperfect materials (with textured crystalline grains) [3]. We indeed also realized that the magnetic textures of the skyrmions along the thickness of the multilayers were more complex than initially thought, contrasting with most of the previous models considering 2D magnetic textures. The internal structure of the skyrmions can be refined using simulations and x-ray resonant magnetic scattering (XRMS) [4,6] at the L₃ Co edge.

This new insights should allow us to better engineer the multilayer stacking sequence in order to achieve skyrmion motion at lower current densities and get closer to potential applications.

Recent Publications

1. Fert A, Reyren N, Cros V (2017) Magnetic skyrmions: advances in physics and potential applications. Nature Rev. Materials 2:17031-1-15.

2. Moreau-Luchaire C, Moutafis C, Reyren N, et al. (2016) Additive interfacial chiral interaction in multilayers for stabilization of small individual skyrmions at room temperature. Nature Nanotechnology 11:444-448.

3. Legrand W, Maccariello D, Reyren N, et al. (2017) Room-Temperature Current-Induced Generation and Motion of sub-100 nm Skyrmions. Nano Letters 17:2703-2712.

4. Reyren N, Bouzehouane K, Chauleau J-Y, et al. (2017) Skyrmions in magnetic multilayers: chirality, electrical detection and current-induced motion. Proc. of SPIE 10357:1035724-1-9.

5. Maccariello D, Legrand W, Reyren N, et al. (2017) Electrical signature of individual magnetic skyrmions in multilayered systems. arXiv:1706.05809.

6. Chauleau J-Y, Legrand W, Reyren N, et al. (2017) Chirality in magnetic multilayers probed by the symmetry and the amplitude of dichroism in X-ray resonant magnetic scattering. arXiv:1709.08009.

Biography:

Henri Jaffrès completed his Ph.D. at the Physics Department of the Institut National des Sciences Appliquées (INSA) - University Toulouse III, France, in 1999. Then he joined the Unité Mixte  de Physique CNRS-Thales, Palaiseau, France as a postdoc (2000–2001) before joining the CNRS at the same institute. His work focuses on spintronics, spin injection, spin transport, and spin transfer in semiconductor spintronics devices with electrical and optical detection in III-V heterostructures, as well as spin-Hall  effect  and spin-pumping  in group  IV  semiconductors.

Abstract:

Spin-Hall Effects at short lengthscale in bulk heavy metals like Pt or W [1] and spin-orbit related phenomena like Inverse-Edelstein Effect [2-3] at interfaces are presently at the basis of new spintronics functionalities. Combined with RF-spin-pumping Ferromagnetic Resonance (FMR) pumping, spin-orbit give rise to AC and DC spin-to-charge current conversion. Those combined techniques enable to probe the interface quality and physical properties. In the same way, in an extented description out-of FMR resonance, it was recently reported that THz emission of relatively high power may be realized in the same kind of heterostructures composed of ferromagnetic (FM) and non-FM metal films via dynamical spin-to charge conversion and time- dependent spectroscopy (TDS) [4-6].

In that mind, we will present our last results of THz emission provided by optimized growth bilayers composed of a high-spin orbit   material   in   contact   with   a   ferromagnetic   layerCo/Pt, NiFe/Au:W). Those bilayers state-to-the art model systems in experiments combining RF-spin pumping and spin-to-charge conversion by ISHE [7-8]. Here, experiments consist in exciting magnetization and spin-currents within the FM layer via femtosecond laser excitation and measuring, in the picosecond timescale, the relaxation of the correlated spin and charge currents responsible for THz dipolar emission. The THz emission provided by these spintronics bilayers reaches the power of ZnTe semiconductor technology. We will display the first THz emission results obatined on a-Sn/InSb topological insulators.

Moreover, in order to study the SHE spin-current profiles and address their properties in those [Co,Ni]N/Pt and [Co,Ni]N/Au:W multilayers, we have analyzed their Anomalous Hall effect (AHE) signals showing up a characteristic AHE spin-inversion from Pt to Au:W samples. We analyze our results in the series of samples: the exact conductivity profile across the multilayers via the 'extended' Camley-Barnas approach [9] and the spin current profile generated by spin-Hall effect. We will discuss the role of the generalized spin-mixing conductance on the spin-transport properties and spin-orbit torques.

Figure 1 | Time-Domain-Spectroscopy (TDS) THz signals of Pt(4nm)/Co(2nm)/Quartz bilayer systems obtained by femtosecond (100 fs) laser excitation (400 mW). The fs laser exciation causes magnetization precession associated to a spin-current (spin displacement). This is transformed afterward to a lateral charge current responsible for dipole oscillations and THz emission. The signal is compared to a reference ZnTe characteristic THz emission (amplitude x 0.5).

Recent Publications

1. J. Sinova, S. O. Valenzuela, J. Wunderlich, C. H. Back, and T. Jungwirth, Rev.Mod. Phys. 87, 1213

2. J. C. Rojas Sánchez, L. Vila, G. Desfonds, S. Gambarelli et al., Nat. Comm. 4, 2944 (2013)

3. J.-C. Rojas-Sánchez, S. Oyarzún, Y. Fu, A. Marty et al., Phys. Rev.Lett. 116, 096602 (2016)

4. T.J. Huisman et al, Nat. Nano., DOI 10.1038 (Nnano2015) 331 (2015).

5. T.Seifert, and All Efficient metallic spintronic emitters of ultrabroadband terahertz radiation Nature photonics 10:483488, (2016).

6. D. Yang et al.. ‘Powerful and tunable thz emmiters based on the Fe/Pt magnetic heterostructure’, Adv. Opt. Mat.(2016).

7. J. C Rojas Sanchez et al., Phys Rev Lett. 112, 106602 (2014).

8. P. Laczowski et al., Applied Physics Letters 104 (14), 142403, 2014. 28 (2014). P. Laczowski et al., Phys. Rev. B 92, 214405 (2015)

9. R. E. Camley, J. Barnas, Phys. Rev. Lett. 63, 664 (1989); J. Barnas, A. Fuss, R. E. Camley,    P.    Grünberg,    and    W.    Zinn,    Phys.    Rev.    B    42,    8110   (1990)

Biography:

Jose Luis Pau is an Associate Professor of the Applied Physics Department at Universidad Autónoma de Madrid, Spain. Currently, he is involved in the development of electronic devices based on novel materials, semiconductor nanostructures and bidimensional materials. The device technology developed at his group also exploits the properties of surface plasmons and polaritons in metal nanostructures and thin films to enhance device performance. Optoelectronic devices and (bio)sensors are the main targets as part of advanced technologies for future communications, food quality sensors and biomedical systems.

Abstract:

Zinc nitride (Zn₃N₂) is a material with an antibixbyite structure in its crystal form and a band gap energy of 1.23 eV. It is deposited by radio frequency magnetron sputtering and molecular beam epitaxy (MBE) at low temperatures (T < 500 K) using reactive N₂ plasma and tends to form polycrystalline films. Despite its low temperature growth, it presents high mobilities (100 cm²/V·s, in sputtering samples, and 350 cm²/V·s, in MBE samples) and low resistivities (10^-2-10^-3 Ω·cm). Those are attractive features for applications in flexible electronics for which common substrates do not often tolerate high temperature growth.

An intrinsic property of the material is its metastability in ambient conditions. The as-grown material has a black appearance but, through the reaction with the water molecules in air, it oxidizes completely to produce a translucent whitish film of ZnO. As a result of the transformation, the material becomes electrically insulating. Through our extensive work on the material characteristics, a good correlation between the transformation span and the storage conditions was found. Thus, at a constant temperature, the lifetime of the nitride layer reduces as the relative humidity increases.

The irreversible characteristic of the nitride degradation makes our devices suitable for potential applications in industry. In particular, the thickness of the Zn₃N₂ layer can be tuned to adapt the device lifetime to the degradation time of a perishable product in transit during long-distance transportation or long-time storage. These products suffer sudden changes on the ambient conditions that could spoil them or diminish their quality. The device is fabricated on polyethylene substrates and can be read out either optically or electronically.

In order to further develop the technology, we investigated material passivation using a ZnO layer on top of the nitride. The results indicate that the cap layer improves the stability of the electrical characteristics, enabling the fabrication of thin film transistors, which deliver good output characteristics and field effect mobilities close to those achieved in amorphous Si technology.

Recent Publications

1. Gómez-Castaño M, Redondo-Cubero A, Vázquez L, Pau JL (2016) Analysis of Zinc Nitride Resistive Indicators under Different Relative Humidity Conditions. ACS Appl. Mater. Interfaces 8:29163-29168.

2. Redondo-Cubero A, Gómez-Castaño M, García Núñez C, Domínguez M, Vázquez L, Pau JL, Zinc Nitride Thin Films: Basic Properties and Applications. Oxide-based Materials and Devices VIII, San Francisco, CA, USA, 29 Jan - 1 Feb 2017, 101051B.

3. Domínguez MA, Pau JL, Gómez-Castaño M, Luna-López JA, Rosales P (2016) High mobility thin film transistors based on zinc nitride deposited at room temperature. Thin Solid Films 619:261-264.

4. García Núñez C, Pau JL, Ruíz E, Piqueras J (2012) Thin film transistors based on zinc nitride as a channel layer for optoelectronic devices. Appl. Phys. Lett. 101:253501.

5. García Núñez C, Pau JL, Hernández MJ, Cervera M, Piqueras J (2011) On the true optical properties of zinc nitride. Appl. Phys. Lett. 99:232112.

Biography:

Hiroyuki Aoki is a Senior Scientist in Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency. He obtained his degrees of BE, ME, and PhD from Kyoto University in 1996, 1998, and 2001, respectively. He became an Assistant Professor of Department of Polymer Chemistry, Kyoto University in 2001 and promoted to an Associate Professor in 2006. In 2016, he moved to J-PARC as a Senior Scientist. His research interests are focused on structure and dynamics of polymer materials at the single molecule scale. He was awarded Inoue Research Award for Young Scientist from Inoue Foundation for Science (2002), Young Scientist Lectureship Award (2008), SPSJ Award for the Outstanding Paper in Polymer Journal (2008), and SPSJ Science Award from Society of Polymer Chemistry, Japan (2016)

Abstract:

Polymer materials have been used widely in our daily life, and they are used often as an ultra thin film with a thickness less than 100 nm. Such the thickness is comparable to the size of a single polymer chain; therefore, the conformation and molecular motion in an ultra-thin film should be constrained. Becuase the unique properties of polymer materials originate from the large degree of freedom of a polymer chain, various properties of an ultra-thin film would be different from those in a bulk state. However, the details on the polymer dynamics in a confined space is still unclear because the limitation of experimental methods. In this work, the dynamics in polymer thin films was studied through single molecule observation.

A fluorescent perylenediimide (PDI) molecule was incorporated at the center of a poly(alkyl methacrylate) chain for the selective observation of the segmental motion at the chain center. The emission from the PDI moiety was observed by fluorescence microscopy in a defocus condition, which probe the translational and orientational motion of a single fluorescent molecule in real time. The detailed analysis of the molecular motion revealed that the diffusion rate of the in-plane rotation was similar for the thin film and the bulk; on the other hand, the out-of-plane motion was restricted in a thin film. This result indicates that the spatial restriction in an ultra-thin film thinner than the unperturbed chain dimension alters the dynamics of individual molecules in a polymer system.

Recent Publications

1. Aoki H, Mori K, Ito S (2012) Conformational analysis of single polymer chains in three dimensions by super-resolution fluorescence microscopy. Soft Matter 8: 4930–4935.

2. Aoki H, Takahashi T, Tamai Y, Sekine R, Aoki S, Tani K, Ito S (2009) Poly(methacrylate)s Labeled by Perylene Diimide: Synthesis and Applications in Single Chain Detection Studies. Polym. J. 41: 778–783.

3. Ube T, Aoki H, Ito S, Horinaka J, Takigawa T, Masuda T (2009) Affine deformation of single polymer chain in poly(methyl methacrylate) films under uniaxial extension observed by scanning near-field optical microscopy. Polymer 50: 3016–3021.

4. Ube T, Aoki H, Ito S, Horinaka J, Takigawa T, Masuda T (2011) Relaxation of Single Polymer Chain in Poly(methyl methacrylate) Films under Uniaxial Extension Observed by Scanning Near-Field Optical Microscopy. Macromolecules 44: 4445–4451

Ube T, Aoki H, Ito S, Horinaka J, Takigawa T (2012) Relaxation of single polymer chain in binary molecular weight blends observed by scanning near-field optical microscopy. Soft Matter 8: 5603–5611.

Biography:

Nikolay Shadrinov completed his undergraduate studies at North-Eastern Federal University, Russia in 2007, and earned his Ph.D. from Institute of oil and Gas Problems of the Siberian Branch of the Russian Academy of Sciences (IOGP SB RAS), Russia in 2012. Nikolay is a senior researcher in the materials sciences laboratory at the IOGP SB RAS. His research interests lie in the area of rubber composites development and structural researches, ranging from theory to design to implementation.

Abstract:

Statement of the Problem: Rubber has an excellent sealing ability and can be successfully used as sealing elements of different systems. There are no fields of industry where the rubber is not used. But sometimes the use of rubber has limitations due to insufficient strength, resistance to wear and oil, etc. The application of the fillers into rubber mix is one of the usual ways to improve up of physical and mechanical properties of rubbers specifically hardness, tensile straight, modulus. The properties of filled rubbers strongly depend on the interaction between the filler particles and the polymer matrix. There is a close correlation between the structure of filler and the modulus of a rubber product compounded with that filler. But still the reinforcing mechanism of rubber with active fillers is not completely studied. The purpose of this study is to describe the mechanism of rubber reinforcement with the use of atomic force microscopy (AFM). Methodology & Theoretical Orientation: AFM is perfect technique that allows us to see and measure surface structure with unprecedented resolution and accuracy. So, we employed AFM to study the surface properties of the supramolecular structure deformation of rubber composites under uniaxial stretching. Findings: The influence of single-wall carbon nanotubes (SWCNT) on the properties of nitrile butadiene rubber (NBR).  It was estimated that a small amount of SWCNT (less than 1 mass. part) into NBR does not lead to a change in the physical and mechanical and basic technical properties. A significant increase in strength characteristics is observed only at 2.5 and 5.0 mass. part of SWCNT. AFM allowed us to visualize of the deformation of the spatial grid structures formed by SWCNT, microcracks formation and to estimate the dependences of the Poisson's ratio and the surface roughness on the degree of uniaxial tension.

Recent Publications

1. Dorozhkin V.P., Muradyan V.E., Mokhnatkin A.M., Mukhtarov A.R., Mokhnatkina E.G. (2017) Single-wall carbon nanotubes in vulcanisates based on different rubbers: Investigation of the dynamic mechanical characteristics. International Polymer Science and Technology 44(6): 31-37.

2. Boonbumrung A., Pongdhorn S., Sirisinha C. (2016) Reinforcement of Multiwalled Carbon Nanotube in Nitrile Rubber: In Comparison with Carbon Black, Conductive Carbon Black, and Precipitated Silica. Journal of Nanomaterials. 1-8.

3. Sato Y., Hasegawa K., Motomiya K., Namura M., Ito N., Jeyadevan B., Tohji K. (2016) Reinforcement of rubber using radial single –walled carbon nanotube soot at its shock dampening properties. Carbon 46: 1509-1512.

4. Bagrov D.V., Yarysheva A.Y., Rukhlya E.G., Yarysheva L.M., Volynskii A.L., Bakeev  N.F. (2014) Atomic force microscopic study of the structure of high-density polyethylene deformed in liquid medium by crazing mechanism. Journal of Microscopy. 253: 151–160.

5. Morozov I.A. (2016) Structural−Mechanical AFM Study of Surface Defects in Natural Rubber Vulcanizates. Macromolecules 49(16): 5985-5992.

Biography:

A.S.A Khiar has her expertise in Solid State Ionics particularly in the development of solid biopolymer electrolytes. Her research focuses on the enhancement of conductivity of various SBE based on chitosan, methylcellulose and starch based electrolytes. A.S.A Khiar is currently a lecturer at the Faculty of Science and Technology, Universiti Sains Islam Malaysia.

Abstract:

Statement of the Problem: Polymer electrolyte is an ionic conductor containing inorganic salt dissolved in polymer host. Among other, liquid-based electrolyte are commonly used in electrochemical devices due to its high conductivity. Nevertheless, some drawbacks of liquid electrolyte could cause safety and environmental issues. Hence, solid biopolymer electrolyte (SBE) are proposed to overcome the problems. However, one drawback is the low conductivity of SBE has hindered their applications. Thus, this work was carried out to enhance the conductivity of SBE based on methylcellulose/chitosan blend doped with 1-butyl-3-methyl imidazolium bis (trifluoro sulfonyl) imide (BMIMTFSI) ionic liquid and ammonium triflate (NH₄TF) salt.

Material and Method: A mixture of MC/CS/45 wt% BMIMTFSI containing different weight percentage of NH₄TF was prepared by using solution casting technique. Electrochemical Impedance Spectroscopy (EIS) was used to measure ionic conductivity over a wide range of frequency between 50Hz-1MHz and at temperatures between 298 K and 378 K.

Findings: Maximum conductivity achieved is 7.67 x 10^-4 Scm^-1with 25 wt% of NH₄TF at ambient temperature. Dielectric data shows that the increase in conductivity could be due to the increase in number of charge carriers while modulus study confirms the non-Debye behavior. Conductivity study at elevated temperatures suggest that samples are Arrhenius in nature.

Conclusion & Significance: MC/CS/45 wt% BMIMTFSI /25 wt% NH₄TF polymer electrolyte was successfully prepared. The sample achieve a maximum conductivity of 7.67 x 10^-4 Scm^-1 at ambient. The increase in conductivity could be attributed to increase in mobile ions while the decrease could be attributed to ion association.  Temperature helps to assist ion movement and provide alternative pathway for the cation hoping, hence boost the conductivity.

Figure 1: Conductivity plot as a function  Figure 2: Log conductivity

                 Versus of salt content                                   1000/T

Recent Publications

1. Chinnam, P. R., Hanjun Zheng, Stephanie L. Wunder. (2015). Blends of Pegylated Polyoctahedralsilsesquioxanes (POSS-PEG) and Methyl Cellulose as Solid Polymer Electrolytes for Lithium Batteries. Electrochim Acta.  170:191–201.

2. Radzir N.N.M. (2015). An investigation of polymer electrolyte based on poly (glycidyl methacrylate) doped withimidazolium ionic liquid. J. Mater. Environ. Sci. 6:1436-1443.

3. Ramlli M. A. & M. I. N. Isa. (2015). Structural and ionic transport properties of protonic conducting solid biopolymer electrolytes based on carboxymethyl cellulose doped with ammonium fluoride. J. Phys. Chem. B5: 748 – 752.

4. Kadir M. F. Z. (2017). Biopolymeric electrolyte based on glycerolized methyl cellulose with NH4Br as proton source and potential application in EDLC. Ionics. https://doi.org/10.1007/ s11581-017-2330-4.

5. Ariffin N. A., & A. S. A. Khiar. Effect (2015) of BMITFSI to the electrical properties of Methylcellulose/chitosan/NH₄TF based polymer electrolyte. Proc. of SPIE 2015; 9668: 96681J.

Biography:

Maryam Alimoradi Jazi is a PHD candidate at the University of Utrecht, Netherlands.

Abstract:

Colloidal semiconductor nanocrystals have gained interest because their optical and electronic properties can be tuned by varying shape, size and composition. Recently, 2D square and honeycomb superstructure of  lead- and cadmium-chalcogenide quantum dots (QDs) have been prepared. These superstructures are formed by assembling PbSe nanocrystals in a monolayer at the toluene suspension air/interface after which the nanocrystals attach via their four vertical {100}  facets [1],[2]. Theoretical studies show that these 2-D systems have profoundly distinct band structures compared to other continious nanosheets with the appearance of Dirac cones in the case of the honeycomb [3],[4]. Strong electronic coupling via the atomic connections of the QDs in the superstructure may result in a higer mobility compared to the self-assembled lead chalcogenide QDs that are less strongly coupled due to the (in)organic ligands [5].

In our research, we use electrolyte-gated transistors (Figure 1a) to study the optoelectronic properties and transport characteristics of 2-D PbSe superstructures [6]. The potential of the gate electrode determines the Fermi level with respect to the conduction band (CB) or valance band (VB) of the superstructure. First, to monitor the stability of the superlattice under electron injection we measure the differential capacitance as a function of gate voltage. From the total injected charge and an estimation of the number of nanocrystal sites in the gated part of the PbSe superlattice we calculate charge density of the superstructure. Second, the conductivity of the network is measured as a function of the Fermi level position. Finally, the mobility of the system is calculated from conductivity and charge density. As an alternative methode to quantify electron injection into the PbSe superlattice, the optical absorbsion measurent is done while sweeping the potential. Furthermore, actual position of the Fermi level can also be obtained by measuring the inter-band light absorption quenching which monitors the precise occupation of the bands (Figure1b). In our recent work, we report the first study of electron transport in a 2-D system with a square geometry in which band occupation is assured by the high electron denity of 8 electron per nanocrystal site.The electron mobility between 5 and 18 cm²/Vs is observed for these supersructures [7].­­

Figure. 1 a) electrolyte gated transistor, b) Interband light absorption quenching

Recent Publications

1. W.H. Evers et al., Nano Lett., 13, 2317-2323 (2013).

2. M.P. Boneschanscher et al., Science, 344, 1377 (2014).

3. E. Kalesaki et al., Phys. Rev. X 4, 011010 (2014).

4. E. Kalesaki et al., Phys. Rev. B 88, 115431 (2013).

5. W.H. Evers et al., Nature Communications 6, 8195 (2015).

6. D. Vanmaekelbergh et al., Electrochemica Acta, 53, 1140-1149 (2007).

7. M.Alimoradi Jazi et al., Nano Lett., 17, 5238-5243 (2017)

Biography:

Tan Lay Poh is an Assoc Prof in the School of Materials Science and Engineering, NTU, Singapore. Her training is on Polymer Engineering and has been working on biodegradable polymers and biopolymers for the past decade. She has published extensively in the top journals of biomaterials and tissue engineering.

Her research interest focuses on developing engineering platforms to investigate cell-material interactions that eventually guide the development of 3D scaffolds and cell culture platforms for soft tissue engineering.  For 3D systems, we have developed highly porous fibrous scaffold that mimics ECM physical properties. Hydrogel is also a major focus of our group where we develop ECM bio-chemistry mimicking systems which could be applied individually or combined with the fibrous platform to form hybrid ECM mimicking systems.

Abstract:

Material surface is an important and versatile avenue for manipulation of cell-material interaction which eventually leads to modulation of cellular behavior. In our laboratory, we work on surface patterning to modulate cellular morphology with the hypothesis that cellular morphology has an intimate relationship with the cellular behavior. We also study the physical cues including physical stiffness, coupled with surface patterning in modulating stem cell differentiation. In particular, we found that micropatterning micro islets on polymeric substrate could directly modulate stem cell fate. Here we will show the stem cell differentiation into skeletal muscle lineage through micropatterning. We have designed patterns of 1 by 7 micron that are attached with ITG-β1 antibodies. hMSCs were then cultured on this biofunctionalized patterned substrate. After 2 weeks of culture, myotubes were observed and the relevant markers were positively exhibited. This micropatterning technique could also be adopted as a generic method to steer cellular behavior such as cell migration or polarization in wound healing applications.

(a) Schematic illustrating top- and cross-section view of micropatterned substrate.(b) Phase contrast image of fabricated gold micropatterned substrate (Scale bar: 10 µm). (c) Confocal image of PEG passivated gold micropatterned substrate displaying precise immobilization of ITG-β1 antibodies to the gold micropattern lanes (Scale bar: 20 µm). (d) Immunofluorescent staining of F-actin (red) and β-MHC (green) from both cell groups validated the myotubes formation on patterned substrate (Scale bar:100 µm).

Recent Publications

1.  Li, Huaqiong; Wen, Feng; Chen, Huizhi; Tan LP (2016),  Micropatterning Extracellular Matrix Proteins on Electrospun Fibrous Substrate Promote Human Mesenchymal Stem Cell Differentiation Toward Neurogenic Lineage;  ACS Applied Materials & Interfaces Volume: 8 Issue: 1 Pages: 563-573

2. Tay, Chor Yong; Wu, Yun-Long; Cai, Pingqiang; Tan LP et al. (2015),  Bio-inspired micropatterned hydrogel to direct and deconstruct hierarchical processing of geometry-force signals by human mesenchymal stem cells during smooth muscle cell differentiation,  NPG Asia Materials Volume: 7

3. Tijore, Ajay; Cai, Pingqiang; Nai, Mui Hoon; Tan LP et al (2015); Role of Cytoskeletal Tension in the Induction of Cardiomyogenic Differentiation in Micropatterned Human Mesenchymal Stem Cell,  Advanced Healthcare Materials Volume: 4 Issue: 9 Pages: 1399-1407.

4. Tijore, Ajay; Wen, Feng; Lam, Chee Ren Ivan; LP Tan (2014) Modulating Human Mesenchymal Stem Cell Plasticity Using Micropatterning Technique, PLOS ONE Volume: 9 Issue: 11 Article Number: e113043

5. Tijore, Ajay; Hariharan, Srivats; Yu, Haiyang;.LP Tan (2014),  Investigating the Spatial Distribution of Integrin beta(1) in Patterned Human Mesenchymal Stem Cells Using Super-Resolution Imaging, ACS APPLIED MATERIALS & INTERFACES Volume: 6 Issue: 18 Pages: 15686-15696.

Biography:

Guy Antou, assistant professor since 2005 at IRCER institute (Univ. of Limoges), mainly deal with the experimental characterization, the modeling and the numerical simulation of the thermomechanical behavior (in particular viscoplastic) of ceramic materials during their elaboration by pressure-assisted sintering or in service (creep). His scientific production (h index: 10) is now composed of 29 publications in international journals, 4 invited conferences, 55 oral communications, 3 grants, etc. He was co-responsible of 5 national or international projects (ANR, French MOD, CEA, CNRS contract).

Abstract:

The Spark Plasma Sintering (SPS) process can lead to significant temperature and stress gradients within the graphite tools and the powder bed during the densification treatment. The establishment of the temperature and stress fields depends on the geometry of the used tools, the applied uniaxial stress, the considered temperature range and the thermos-physical properties of the sample. The identification of these gradients and the determination of their amplitude are necessary to precisely know the experimental conditions applied to the powder and to evaluate the possible thermomechanical gradients that may appear within the sample, especially in the case of large parts. The thermomechanical conditions seen by the powder bed directly impact the densification mechanisms and, finally, the microstructure and working properties of the sintered bodies.

In this context, the optimization and prediction of the thermo-physical properties of the SPS process depend on reliable numerical models that can simulate the consolidation process. An electro-thermo-mechanical numerical model of the SPS process has thus been developed [1]. Concerning the electrothermal part, the input electrical data of the model were measured experimentally thanks to the development of a specific instrumentation. The main operating characteristics of the pulse generator have been highlighted as well as the effect of pulsed current on Joule heating kinetics at the start of sintering [2]. From a thermomechanical point of view, based on a robust experimental approach to identify powder densification mechanisms [3-4], the constitutive law has been integrated into the numerical model [1].

This approach coupling experimentation and simulation has been applied to the study of scaling-up problems in SPS, considering for example alumina pellets with a diameter greater than 50 mm (Fig. 1). The results of the numerical model have been correlated with microstructural features of the sintered compounds, especially in terms of spatial distribution of relative density.

Fig. 1. Calculated temperature distribution throughout the complete die/punches/powder set-up at the end of the isothermal stage (t=1470s).

Recent Publications

1. Diatta J, Antou G, Pradeilles N, Maître A (2017) Numerical modeling of spark plasma sintering—Discussion on densification mechanism identification and generated porosity gradients. J Eur Ceram Soc 37:4849-4860.

2. Diatta J, Antou G, Courreges F, Georges M, Pradeilles N, Maître A (2017) Effect of the current pulse pattern during heating in a spark plasma sintering device: Experimental and numerical modeling approaches. J Mater Proc Tech 246:93-101.

3. Antou G, Guyot P, Pradeilles N, Maître A (2015) Identification of densification mechanisms of pressure-assisted sintering: Application to hot pressing and spark plasma sintering of alumina. J Mater Sci 50:2327-2336.

4. Antou G, Guyot P, Pradeilles N, Maître A (2015) New Approach of the Evolution of Densification Mechanisms During Spark Plasma Sintering: Application to Zirconium (Oxy-)Carbide Ceramics. Scr Mater 101:103-106.

5. Kozak K, Dosi A, Bucko M, Chlubny L, Lis J, Antou G, Chotard T (2017) Investigation of the mechanical behavior of MAX phases by acoustic emission technique. Mater Sci Eng A 707:73-80.

Biography:

Pantilimon Mircea Cristian is an environmental and materials science engineer with an aim at research that can be introduced into the industrial sector. He has followed training and education during his undergraduate and graduate studies in foreign countries such as Italy and South Korea. The focus of his research is to develop better materials that can be used by the populace and that can have a very low impact on the wellbeing of both humanity and the environment.

Abstract:

Increasing biocompatibility of implant materials is an important factor in developing better and long-lasting implants that function in a very close manner to actual tissue and bone. Various alloys have been used due to their biocompatibility, such as: stainless steels, titanium based alloys and nickel or cobalt alloys. Depending on the alloying elements used it is possible to modify the material properties to fit into various niches of use such as pacemaker devices, stents, biosensors, dental or bone implants and others. Some alloying elements show higher biocompatibility than others and the commonly used alloys include elements that can be detrimental to human health such as Nickel, Vanadium and Cobalt. Using materials such as Nb, Fe and Zr in order to replace the commonly used metals reduces the risks of accumulation of various substances that can damage tissue and lead to health complications. The proposed alloys are elaborated in a Five Celles levitation melting furnace under argon atmosphere in order to create a more homogeneous material with reduced defects and inclusions. The cast alloys are then analyzed through modern methods such as SEM, XRD, EDS and their mechanical properties such as hardness and strength and these properties are compared to that of bone in order to determine mechanical reliability.

Recent Publications

1. Bang, I.-H., S.-Y. Cho, M. Pantilimon and S.-J. Lee (2018). "NO2 Gas Sensing Properties of Nano-Sized WO3 Powders Prepared by a Polyvinyl Alcohol Solution Route." Journal of Nanoscience and Nanotechnology 18(3): 2185-2188.

2. Matei, E., A. Predescu, C. Drăgan, C. Pantilimon and C. Predescu (2017). "Characterization of Magnetic Nanoiron Oxides for the Removal of Metal Ions from Aqueous Solution." Analytical Letters 50(17): 2822-2838.

3. Matei, E., M. Rapa, A. A. Andras, A. M. Predescu, C. Pantilimon, A. Pica and C. Predescu (2017). "Recycled Polypropylene Improved with Thermoplastic Elastomers." International Journal of Polymer Science 2017: 10.

4. Pantilimon, M. C., T.-S. Kang and S.-J. Lee (2017). "Synthesis of Nano-Sized Tungsten Oxide (WO3) Powder by a Polymer Solution Route." Science of Advanced Materials 9(2): 280-284.

5. Pantilimon, M. C., T. S. Kang and S.-J. Lee (2016). "Synthesis of nano-sized indium oxide (In2O3) powder by a polymer solution route." Ceramics International 42(3): 3762-3768.

Biography:

Bakhtawar Ghafoor has her expertise in biomaterials and medical implants coatings. She has done her MS in Biomedical Sciences and currently she is doing PhD in Biomedical Sciences from National University of Sciences and Technology, Pakistan. She has worked on coatings for medical implants, electrospun mats for wound healing and on the synthesis of films for different biomedical applications.

Abstract:

Statement of the Problem: The integrity of injured tissue and prevention from microbes at the site of wound is important factor for healing the target site. Currently, the main aims of wound dressings are to come up with natural material based environment which will not only prevent environmental intervention but also help in reducing microbial attack along with accelerating wound healing. The aim of this study was the synthetization and characterization of natural composite films that possess natural antimicrobial agent and can release it in a sustained manner. In this study CMC (CarboxyMethyl Cellulose), PVA (Polyvinyl Alcohol) and Basil seed gum were used for the preparation of a nature composite and Hermal seed extract was added as an anti-microbial agent.

Methodology & Theoretical Orientation: For the fabrication of films, solvent casting method is used. The different ratios of PVA, CMC and basil gum is used to synthesis the films with constant amount of drug. Afterwards, films were subjected to drug release testing along with antimicrobial and SEM analysis.

Findings: The SEM analysis of successfully fabricated films showed accumulation of drug over the surface of the films which resulted in initial burst release of Hermal and later slow release. The films showed good results against various bacterial strains.

Conclusion & Significance: The intrinsic antibacterial property of Hermal extract is combined with swelling property of PVA, basil seed gum and CMC. The composite films were screened drug release and antibacterial activity against P. aeruginosa, E. coli, S. aureus and B. subtilis. According to the results obtained from antibacterial and drug release studies, the composition with the ratio of CMC/Gum 3:1 with Hermal extract is considered to be better among all other ratios used. Thus, this composition can be considered as a potent candidate for coatings and wound healing applications.

Recent Publications

1. Boateng, J., & Catanzano, O. (2015). Advanced therapeutic dressings for effective wound healing—a review. Journal of pharmaceutical sciences, 104(11), 3653-3680.

2. Capanema, N. S., Mansur, A. A., Carvalho, S. M., Mansur, L. L., Ramos, C. P., Lage, A. P., & Mansur, H. S. (2018). Physicochemical properties and antimicrobial activity of biocompatible carboxymethylcellulose‐silver nanoparticle hybrids for wound dressing and epidermal repair. Journal of Applied Polymer Science, 135(6).

3. MogoÅŸanu, G. D., & Grumezescu, A. M. (2014). Natural and synthetic polymers for wounds and burns dressing. International journal of pharmaceutics, 463(2), 127-136.

4. Singh, B., Sharma, S., & Dhiman, A. (2013). Design of antibiotic containing hydrogel wound dressings: biomedical properties and histological study of wound healing. International journal of pharmaceutics, 457(1), 82-91.

5. Shaw, G. S., Biswal, D., Banerjee, I., Pramanik, K., Anis, A., & Pal, K. (2017). Preparation, characterization and assessment of the novel gelatin–tamarind gum/carboxymethyl tamarind gum-based phase-separated films for skin tissue engineering applications.

Polymer-Plastics Technology and Engineering, 56(2), 141-152.

Biography:

Hafsa Inam is a PhD student of Biomedical Engineering and Sciences at School of Mechanical and Manufacturing Engineering, NUST, H-12 Islamabad, Pakistan. She completed her Masters in Biomedical Sciences in 2017 from School of Mechanical and Manufacturing Engineering SMME, NUST, H-12 Islamabad Pakistan. As a part of her MS research program, she completed her research project entitled ‘Magnetically Targeted Drug Delivery Approach using Imaging Technology and PID Feedback Loop System’. After completing her MS, she is working as a research associate on a project funded by Ignite. Pakistan.

Abstract:

Statement of the Problem: Coronary Heart Diseases lead towards the stenosis where the plaques are accumulated under coronary artery endothelium layer. This deposition blocks the coronary artery and does not allow smooth flow of blood to the walls of the heart. The design of stent has great influence on late lumen loss along with neointimal proliferation which affects the rate of restenosis. It is revealed that design of stent also affect the platelet activation and thrombogenesis. The purpose of this study is to design and fabricate a new coronary stent design with Auxetic geometry which will complement the body’s vascular system anisotropic properties. Based on previous studies, we can hypothesize that the new Auxetic design of stent will allow good anchorage with arterial walls. When expanded through an inflated balloon, the special feature of this design allows maintaining vascular patency by expanding in two directions simultaneously.

Findings: During longitudinal expansion there is no foreshortening in the Auxetic stent. This is an advantage over existing coronary stents where foreshortening cause the problem of stent migration. The 3.3 % elastic recoil shows that the luminal patency will effectively be maintained by the coronary artery. Having no foreshortening and minimal recoiling in the present stent will might avert the stent from migration problem while being expanded in the coronary artery which will reduce the chances of thrombogenesis and restenosis.

Conclusion & Significance: Auxetic design the stent has anisotropic properties that make it a great match for coronary vessel anisotropic structural properties. When expanded radially through balloon catheter the auxetic stent size increases in both radial and longitudinal directions exhibiting no foreshortening. It is believed that auxetic stent will prevent stent migration and will effectively maintain the luminal patency of the coronary artery due to the auxetic property of the stent design.

Recent Publications

1. Skousen, D. J., Jones, K. N., Kowalski, T., Bowden, A. E., & Jensen, B. D. (2017). Exploration of Carbon-Filled Carbon Nanotube Vascular Stents. In Microactuators and Micromechanisms (pp. 103-114). Springer, Cham.

2. Wu, W., Song, X., Liang, J., Xia, R., Qian, G., & Fang, D. (2017). Mechanical properties of anti-tetrachiral auxetic stents. Composite Structures.

3. Bukhari, F., Ansari, U., Najabat Ali, M., Akhtar, H., Asif, S., Mohammad, U., & Mir, M. (2017). A biaxial strain–based expansion mechanism for auxetic stent deployment. Journal of applied biomaterials & functional materials, 15(3), 196-205.

4. Bhullar, S. K., Ko, J., Cho, Y., & Jun, M. B. (2015). Fabrication and Characterization of Nonwoven Auxetic Polymer Stent. Polymer-Plastics Technology and Engineering, 54(15), 1553-1559.

5. Carneiro, V. H., & Puga, H. (2015, February). Modeling and elastic simulation of auxetic magnesium stents. In Bioengineering (ENBENG), 2015 IEEE 4th Portuguese Meeting on (pp. 1-4). IEEE.

Biography:

Mariam Mir has completed her MS in Biomedical Sciences from National University of Sciences and Technology and University of Engineering and Technology (NUST) and currently she is doing her PhD in Biomedical Sciences from NUST. She has a vast experience in research and her research interest includes biomedical implants, biomaterials and development of drug delivery mechanisms.

Abstract:

Statement of the Problem: Changes in pH in the physiological environment are an important parameter in assessment of the normal functioning of the body. pH sensors such as pH glass electrodes, fiber optic pH sensors and sensors made from metal oxide have many limitations such as conformance to body contours and single point measurements. To address these limitations, there is a need for a planar, biocompatible and point of care pH sensor array that can conform with body contours and possibly provide a map of pH levels. This study focuses on the design and fabrication of a hydrogel based pH sensor array for physiological applications.

Methodology & Theoretical Orientation: The development of this conductometric pH sensor array has been carried out on the basis of measurement of the conductance of a pH-responsive composite (Chitosan/Gelatin) hydrogel. Since the sensitivity of a hydrogel based conductometric measurements can be dependent upon size and separation of the sensors, both these parameters have been investigated in detail. The design of the pH sensor array is dependent on the electrode density, which is a function of both the optimized size and separation of electrodes. The final electrode density was thus calculated and used for an optimized design of the pH sensor array. For fabrication, copper conductive layer tracts with pH sensitive gel casting, on a polyimide substrate have been used.

Conclusion & Significance: Conductometric tests carried out on the pH sensor array and results show good sensitivity and resolution in the physiological pH range (pH 4 - 10). The pH sensor array may be used for physiological mapping for both in vitro and in vivo measurements.

Recent Publications

1.  Chen Y, Mun SC, Kim J. A wide range conductometric pH sensor made with titanium dioxide/multiwall carbon nanotube/cellulose hybrid nanocomposite. Sensors Journal, IEEE. 2013; 13(11):4157- 62.

2. Dhandayuthapani B, Krishnan UM, Sethuraman S. Fabrication and characterization of chitosan‐gelatin blend nanofibers for skin tissue engineering. Journal of Biomedical Materials Research Part B: Applied Biomaterials. 2010; 94(1):264-72.

3. Vaughan SS, Patel MM. pH-sensitive hydrogels based on semi- interpenetrating network (semi-IPN) of chitosan and polyvinyl pyrrolidone for clarithromycin release. Drug development and industrial pharmacy. 2011; 37(10):1160-9.

4. Berger J, Resist M, Mayer JM, Felt O, Peppas N, Gurny R. Structure and interactions in covalently and ionically crosslinked chitosan hydrogels for biomedical applications. European Journal of Pharmaceutics and Biopharmaceutics. 2004; 57(1):19-34.

5. C. D. Tran and T. M. Mututuvari, ‘‘Cellulose, chitosan, and keratin composite materials. Controlled drug release,’’ Langmuir, vol. 31, no. 4, pp. 1516–1526, 2014.