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FA:HP24 Multiblock Copolymers with Locally High Ionic Concentration for Anion Exchange Membranes
E.A. WEIBER, DAVID MEIS, PATRIC JANNASCH, Lund University, Department of Chemistry, Lund, Sweden
With the use of alkaline membrane fuel cells (AMFCs) there is a possibility to utilize low temperature fuel cell technology without the need of scarce and expensive noble metal catalysts. With this technology there is, however, a need to enhance the stability and ionic conductivity of anion-exchange membranes (AEMs) before AMFCs can be a viable alternative to the more studied proton-exchange membrane fuel cells. In the presented work we have aimed to improve the anionic conductivity by synthesizing multiblock copolymers containing blocks with exceptionally high local ion exchange capacity (IEC). Thus, a series of AEMs, based on poly(arylene ether sulfone)s, with IECs in the hydrophilic domain in the range between 4.9 and 5.8 meq./g has been produced. The high IEC was achieved by incorporating tri- and tetramethylhydroquinone into the polymer backbone, thus enabling the attachment of three and four ionic groups respectively on single aromatic rings. The structure− morphology− property relationships and the performance of these copolymers and AEMs will be presented.
FB:HP15 Atomistic Models of Long-term Hydrogen Diffusion in Metals
M.P. ARIZA1, K.G. WANG2, M. ORTIZ3, 1Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Sevilla, Spain; 2Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA; 3Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
The effective and efficient storage of hydrogen is one of the key challenges in developing a hydrogen economy. Intensive research has been focused on developing and optimizing metal-based nanomaterials for high-speed, high-capacity, reversible hydrogen storage applications. Notably, the absorption and desorption of hydrogen in nanomaterials is characterized by an atomic, deformation-diffusion coupled process with a time scale of the order of seconds to hours – far beyond the time windows of existing simulation technologies such as Molecular Dynamics (MD) and Monte Carlo (MC) methods. In this work, we present a novel deformation-diffusion coupled computational framework, which allows the long-term simulation of such slow processes and also maintains a strictly atomistic description of the material. We first propose a theory of non-equilibrium statistical thermodynamics for multi-species based on Jayne’s maximum entropy principle and the meanfield approximation approach. This non-equilibrium statistical thermodynamics model is then coupled with novel discrete kinetics laws, which governs the diffusion of mass – and possibly also conduction of heat – at atomic scale. Finally, this thermo-chemo-mechanical coupled system is solved numerically using a staggered procedure.
FB:HP16 Effect of Pulverization of Hydrogen Storage Alloys on Micro-scale Structural Changes in the Packed Bed
M. OKUMURA, Y. SAITO, Y. MATSUSHITA, H. AOKI, Tohoku University, Japan; Y. KAWAKAMI, Takasago Thermal Engineering Co., Ltd., Japan; K. TAKI, Nihon Visual Science, Inc., Japan
Packing structures of two kinds of hydrogen storage alloy beds (i.e. Mm-Ni-Co-Mn-Al and Ti-Fe-Mn) were observed by an X-ray computed tomography, and the structural changes before and after hydrogen absorption were investigated. In the Mm-Ni-Co-Mn-Al bed, large particles and small particles which filled a void between the large particles were observed after hydrogen absorption. It appears that some of the large particles were pulverized by swelling with hydrogen absorption and the shape drastically changed. On the other hand, small cracks on cross-sections of Ti-Fe-Mn particles in the bed were observed after hydrogen absorption. These cracked particles seemed to maintain their shape during swelling with hydrogen absorption. The structural change of the Ti-Fe-Mn bed was little in comparison with the Mm-Ni-Co-Mn-Al bed because small particles were not generated in the Ti-Fe-Mn bed. The generation of small particles in the packed bed of hydrogen storage alloys would cause the large structural change.
FB:HP17 A Millimeter Scale Reactor Integrated PEM Fuel Cell Energy System with an On-board Hydrogen Production, Storage and Regulation Unit for Autonomous Small Scale Applications
A. BALAKRISHNAN, C. MUELLER, H. REINECKE, Laboratory for Process Technology, IMTEK-Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany
The research and development of new on-board energy sources for autonomous microsystems have gained popular interest in the past few decades. Hydrogen based PEM fuel cells systems, where hydrogen is produced from chemical hydrides and supplied to the fuel cell are one of the top most preferred candidates for such on-board sources due to their high volumetric energy density and integration capabilities. One of the major drawbacks in the state-of-the-art is the complexity of the system design e.g., pumps, valves and gas-liquid separators. Here in this work, we present a millimeter scale reactor integrated PEM fuel cell energy source with an on-board hydrogen production reactor (realized by chemical hydride), and further more passive buffering, regulation unit (realized by metal hydride) of hydrogen. Palladium (Pd) metal hydride has the property to adsorb and desorb hydrogen at ambient and elevated temperatures this allows the Pd to replaces active valves and gas-liquid separators. A stacked system of reactor-buffer/regulator-PEM fuel cell is built up. The system is driven by the hydrolysis of the chemical hydride (NaBH4) in the alkaline medium with Nickel mesh Platinum catalyst (Ni-Pt) for the hydrolysis reaction, where the produced hydrogen gas from the reactor diffuses (due to the pressure difference) through the buffer/regulator and evenly distributes onto the anode of the PEM fuel cell. The system is “self-buffering” in nature so any change in electrical load can be handled during system operation. The operational behaviour of the integrated buffer/regulator in the complete system is investigated with the hydrogen produced from the chemical hydrides and pure hydrogen gas. Furthermore the hydrogen production in the hydrolysis reaction is controlled by the interaction between the Ni-Pt and the liquid medium so a new control mechanism for the chemical hydride hydrolysis reaction is proposed using a shape memory alloy (SMA) and a bimetallic (BM) catalyst structures. Such an approach of using a SMA and a BM can pave the way for the realization of the independent system which is self-sustainable in nature (custom defined).
FD:HP06 Capacitive Energy Harvesting System for Low-grade Heat
WEIYI LU, YU QIAO, University of California, San Diego, La Jolla, CA, USA; HYUCK LIM, Applied Materials, Inc.
Harvesting and storing useful electricity from ambient thermal gradients/fluctuations, particularly low-grade heat (LGH) sources with temperature lower than 250 C, is an important research area. Usually, direct thermal energy conversion is achieved by using thermoelectric materials. Their energy conversion efficiencies, although already close to the upper limits, are still far from satisfactory. In order to meet the increasingly high functional requirements, new mechanisms must be investigated.
Recently, a novel thermal-to-electric energy harvesting system based on capacitive effects of nanoporous electrodes was developed by our team. With a relatively small temperature difference of only 40C, the output voltage could be higher than 100 mV. The energy density was ~2 J/g, much higher than that of many conventional thermoelectrics. This concept may open a new area of study for energy harvesting, conversion, and storage of LGH.
FD:HP07 Influence of Gamma Irradiation on Properties of Selected Thermoelectric Materials
K. WOJCIECHOWSKI1, M. ANDRZEJEWSKA1, K. PYTEL2, T. KROK2, M. DOROSZ2, J. MIETELSKI3, W. GIESZCZYK3, R. KOPEC3, M. BROZEK3, 1Thermoelectric Research Laboratory, Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Poland; 2National Centre for Nuclear Research, Poland; 3Nuclear Physical Chemistry Department, Institute of Nuclear Physics, Polish Academy of Sciences, Poland
The aim of the work was a comparative study of the influence of gamma irradiation on thermoelectric and structural properties of selected thermoelectric materials: PbTe, Bi2Te3, CoSb3 and Mg2Si. Polycrystalline samples of these materials were exposed to radiation doses from 80 to 2500 kGy emitted by fuel rods used in the EWA research reactor in the National Centre for Nuclear Research in Poland. The radiation doses were measured using thermoluminescent detectors MTS. Analyses of changes of microstructure were done using scanning electron microscope SEM with EDX analyzer; structural studies were performed using X-ray diffraction XRD method. Measurements of thermoelectric properties were performed using Scanning Thermoelectric Microprobe STM. Carrier concentration was determined through 5-probe Hall method before and after the exposition to ionizing radiation.
The study confirmed a strong influence of gamma radiation on transport properties of the studied thermoelectric materials. With the increase in radiation dose a significant increase in carrier concentration for CoSb3, Bi2Te3, Sb2Te3 and PbTe was observed. The only exception was Mg2Si for which a decrease in carrier concentration was noticed. The results are correlated with thermoelectric and structural properties of materials.
FD:HP08 Fabrication and Thermoelectric Properties of Te Substituted BiCuSeO
T. SATO, Graduate School, Kogakuin University, Hachioji, Tokyo, Japan; H. KOHRI, T. YAGASAKI, Faculty of Engineering, Kogakuin University, Japan
BiCuSeO has nano-layered structure and consists of conducting [Cu2Se2]2- layer and insulating [Bi2O2]2+ layer. We expect this crystal structure to show large Seebeck coefficient due to the quantum confinement of electron in conducting nano-layer. In this study, the fabrication conditions and the thermoelectric properties of BiCuSeO were investigated. In addition, Te substituted BiCuSeO in order to reduce the thermal conductivity was fabricated, and was investigated the influence of Te substitutions of Se site on their thermoelectric properties.
BiCuSe1-xTexO(x=0, 0.05, 0.10) were fabricated by solid state reaction. Crystalline phase was identified by XRD. Seebeck coefficient α was measured by large temperature difference method. The measurement atmosphere was the air, and the cold side temperature was kept at 300 K, and the hot side temperature was changed from 320 to 540 K.
From the results of XRD, BiCuSeO single phase was obtained in the non-substituted sample. On the other hands, the peaks of the second phase were recognized in the Te substituted samples. The non-substituted sample showed the highest α 456 μV/K at 460 K in hot side temperature. The peak temperature and maximum value of the α were decreased with increasing Te substitution amount.
FF:HP19 Effect of Al-doping on the Structural and Magnetic Properties of ErFe2 Laves-phase Compounds for Magnetocaloric Applications
J. CWIK1, Y. KOSHKIDKO2, A MICHAILOWA3, N. KOLCHUGINA3, K. NENKOV1, 4, 1International Laboratory for High Magnetic Fields and Low Temperatures, Wroclaw, Poland; 2Vysoka Skola banska - Technical University of Ostrava, Ostrava-Poruba, Czech Republic; 3Baikov Institute of Metallurgy and Materials Science, RAS, Moscow, Russia; 4lFW Dresden, lnstitute of Metallic Materials, Dresden, Germany
In this work we report on the structural, magnetic and magnetocaloric properties of several polycrystalline ErFe2-xAlx)( intermetallic compounds (0.36≤x ≤1.125).
Powder X-ray diffraction study at room temperature showed that the compounds in the Fe rich region crystallize in the C15 cubic Laves phase structure, while for the ones in the intermediate region the hexagonal C14 structure was observed. Magnetic and magnetocaloric properties of polycrystalline ErFe2-xAlx intermetallic compounds were investigated experimentally using magnetic and heat capacity measurements; the Landau theory was applied also to clarify peculiarities of magnetic phase transition in the compounds. The Curie temperature Tc decreases from 275 to 55 K as the Al content increases to x = 1.125. The isothermal entropy change -ΔSmag was calculated according to magnetic measurements using thermodynamic
Maxwell's relation. A large entropy change has been observed for all concentrations. Under an external fìeld change from 0 to 4 T, the maximum entropy change fluctuates within 9 J/kg K. Heat capacity measurements allowed us to determine the adiabatic temperature change in magnetic fields up to maximum 2 T. The maximum ΔTad value varies within 0.5 and 1 K for a magnetic field change of 2 and 1 T, respectively. The effect of increasing Al amount in the ErFe2-xAlx intermetallic compounds on their magnetic and magnetocaloric properties is discussed.
FF:HP20 Tomographic Imaging of Metal vs. Polymer Matrix Magnetocaloric Composites
A. WASKE1, A. FUNK1,3, M. KRAUTZ2, B. WEISE1,3, B. PULKO4, K. SKOKOV5, O. GUTFLEISCH5, J. ECKERT1,3, 1Institute of Complex Materials, IFW Dresden, Dresden, Germany; 2Institute for Metallic Materials, IFW Dresden, Dresden, Germany; 3Institute for Material Science, TU Dresden, Dresden, Germany; 4University of Ljubljana, Faculty of Mechanical Engineering, Ljubljana, Slovenia; 5Material Science, TU Darmstadt, Darmstadt, Germany
Magnetocaloric materials could one day be the basis of a new magnetic cooling concept for consumer use, replacing conventional refrigeration technology. The research in magnetocalorics focused on the discovery and development of materials with large or giant magnetocaloric effects (MCE) over the last few decades. Such alloys show a first order phase transition, with a simultaneous and abrupt structural and magnetic changes. However, bulk MCE-materials often show mechanical instability upon magnetic field cycling due to the large strain that is associated with this kind of phase transition. By using a composite containing a polymer or metal matrix and powderized magnetocaloric material, this problem could be overcome. Furthermore, such composites show good workability to produce various geometries (e.g. thin plates, spheres) and also offer the possibility to form complex composite designs.
We will show results on magnetocaloric properties obtained by magnetometry and direct ΔTad measurements. 3D computed tomographic imaging was employed to ensure precise determination of the volume fraction of all relevant phases (active material, matrix, pores). Using this approach, we determine the performance of the composites as a function of magnetocaloric material fraction.
FG:HP07 CuZnSnSe Nanotubes and Nanowires by Template Electrosynthesis
R. INGUANTA, M. BATTAGLIA, S. PIAZZA, C. SUNSERI, Laboratorio di Chimica Fisica Applicata, Dipartimento di Ingegneria Chimica, Gestionale, Informatica, Meccanica, Università di Palermo, Palermo, Italy
Copper zinc tin sulphide, or CZTS, is one of the most inexpensive and interesting semiconductor employed in solar cells. Moreover, its components are not toxic and earth abundant and this material presents useful properties as absorber also when composition is different from the stoichiometric one. Among the different methods to obtain CZTS, the electrochemical route appears of great interest because easy to conduct. Up to date, literature data show that non-uniformity in composition and/or presence of secondary phases, prevent the formation of electrochemical CZTS thin-film of high quality.
In this work we present an extensive investigation aimed to find suitable conditions to grow CZTS with good performance: this implies the simultaneous electrodeposition of elements having different standard electrochemical potential. In particular attention was focused on template electrosynthesis in order to obtain regular and ordered array of nanowires. Synthesis of nanostructured absorber materials is of great technological interest because photovoltaic devices employing nanostructures display higher values of energy conversion efficiency compared to conventional thin-film devices. Besides, this morphology provides excellent light trapping, and increases defects tolerance.
FG:HP08 Single-side Boron Profile Control in n-type Silicon Wafer and Photovoltaic Design by PC1D Calculations
WOON JO CHO, JIN DONG SONG, IL KI HAN, Center for Opto-Electronic Conversion System, Korea Institute of Science and Technology, Seoul, Korea
Efficiency limitation of silicon solar cell, the most commercialized photovoltaics, has been studied with the point of view of dopant complexes as boron-oxygen defects and boron-iron defects. These defects are commonly found in B-doped p-based Czochralski wafers. B-doped single crystal silicon wafers reportedly suffer both a light-induced degradation and a lifetime decrease of minority carrier electrons which origin from the boron related defects [1]. To avoid these degradation, boron doped emitter structures in n-type silicon wafers are recommended.
For a selective emitter photovoltaic design, we carried out the boron diffusion in n-type silicon wafer using our borosilicate glass as a boron source. With our experimental profiles of boron concentration, we calculated the photovoltaic parameters for the single-side boron emitter on P-doped n-type silicon wafer by PC1D program. We could obtain the cell efficiency of 15 ~ 21 % according to our single-side boron diffusion profiles for wafer base resistivity of 1 ohm-cm, wafer thickness of 250 micrometer and rear junction depth of 5 micrometer. The controlled boron profiles in p-emitter and the design parameters for high efficiencies will be discussed.
[1] Daniel L. Meier, et al. IEEE J. Photovoltaics 1, 123-129 (2011)
FH:HP11 (Ga1-xInx)2O3 Layers Grown by Metal Organic Vapour Phase Epitaxy
M. BALDINI, D. GOGOVA, R. SCHEWSKI, M. ALBRECHT, M. SCHMIDBAUER, Z. GALAZKA, G. WAGNER, Leibniz Institute for Crystal Growth, Berlin, Germany
Among Transparent Semiconductor Oxides (TSOs), monoclinic β-Ga2O3 is one of the most interesting compound, by virtue of its high break-down field (~8 MV/cm), which allows to minimize conduction losses in high-power devices, and its large direct band gap (4,9 eV) that turns into a high transparency, up to mid-UV wavelengths [1, 2]. By partially substituting Ga with In, it is possible to modulate the energy gap of the material towards the lower value of In2O3 (3,75 eV), opening the field to a broad spectrum of applications [3, 4].
Here, we report on the growth of (Ga1-xInx)2O3 layers on (100) Ga2O3 and (0001) Al2O3 substrates, performed in a vertical metal organic vapour phase epitaxy (MOVPE) reactor. The growth pressure, explored in a wide range, turned out to have a fundamental role in the critical In incorporation process, by increasing the amount of In introduced in the Ga2O3 lattice at higher pressure values. The employment of In during the growth contributed to limit the concentration of structural defects, both in hetero- and homoepitaxial layers. This behavior has been explained, in analogy with the growth of (In)GaN [5, 6], by the tendency of In to float on the surface of Ga2O3, delivering a surfactant effect that promotes a step-flow growth mode.
[1] Fleischer M., Meixner H., Sensors and Actuators B 1991, 4, 437-441.
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[3] A. Wang, N.L. Edleman, J.R. Babcock, T.J. Marksa, M.A. Lane, P.R. Brazis, and C.R. Kannewurf, J. Mater. Res. 2002, 17, 3155.
[4] T. Oshima, S. Fujita, phys. stat. sol. (c), 2008, 5, 3113
[5] S. Keller, S. Heikman, I. Ben-Yaacov, L. Shen, S.P. DenBaars, U. K. Mishra, Appl. Phys. Lett. 2001, 79, 3449
[6] J.E. Northrup, C.G. Van de Walle, Appl. Phys. Lett. 2004, 84, 4322.
FI:HP09 White Light Emitting Nanocomposite Films Constituted of Lanthanide Orthophosphates Nanophosphors Dispersed in Silicon
A. GARRIDO HERNÁNDEZ1,2, A. POTDEVIN2, D. BOYER2, G. CHADEYRON2, A. GARCÍA MURILLO1, F. DE J. CARRILLO ROMO1, R. MAHIOU2, 1Instituto Politécnico Nacional, CIITEC IPN, México D.F, México; 2Institut de Chimie de Clermont-Ferrand, UMR 6296 CNRS / UBP / ENSCCF, Aubiere Cedex, France
Rare-earth doped lanthanides orthophosphates represent a class of materials with significant technological importance. Recently, new applications of nanoscale phosphors, including biolabelling, optical imaging or luminescent transparent layers have attracted intensive interests. As a result, several synthesis methods leading to LnPO4 nanocrystals with controlled shape have been developed. It is well known that the reduction of particles size or the modification of their shape can dramatically modify their physico-chemical properties.
In this work Eu3+, Tb3+ and Dy3+ doped GdPO4 were successfully synthetized by a new hydrothermal method leading respectively to red, green and blue nanophosphors. Their structural characterization was performed by X-ray diffraction and infrared spectroscopy. Transmission electron microscopy images have revealed the achievement of nanomaterials with a narrow size distribution. Their photoluminescent properties and quantum efficiencies were investigated upon excitation in the UV range. Luminescent composite films were prepared by dispersing a mixture of these fluorescent nanomaterials in a silicon matrix by the coatmaster technique. Finally their chromaticity coordinates were determined to assess the ability for producing white light upon UV excitation.
FK:HP18 Carbon Nano/Microcoils-Polyurethane Composites Shielding Materials for Electromagnetic Interference
GI-HWAN KANG, SUNG-HOON KIM, Center for Green Fusion Technology and Department of Engineering in Energy & Applied Chemistry, Silla University, Busan, South Korea
Due to the increasingly demand of light weight and moldable process, polymer-matrix composites for shielding materials of electromagnetic interference (EMI) are strongly attractive for portable electronic devices, avionic electronics and etc. In this respect, carbon materials (such as carbon fibers, carbon nanotubes, carbon blacks, carbon coils, graphites, and so on) are noticed as the promising candidates for EMI shielding materials. In this work, carbon nano/microcoils (CNCs/CMCs) were deposited on Al2O3 substrate using C2H2/H2 for source gases and SF6 for an incorporated additive gas under thermal chemical vapor deposition system. The CNCs/CMCs-polyurethane (PU) composites were obtained by dispersing the CNCs/CMCs in PU solvent with dimethylformamide additive. We investigated the electromagnetic wave shielding properties of the CNCs/CMCs-PU composites in the frequency range of 0.25-1.5 GHz and discussed the shielding effectiveness of the CNCs/CMCs-PU composites according to the weight percent of CNCs/CMCs in CNCs/CMCs-PU composites and the thickness of the CNCs/CMCs-PU composites layers. Based on these results, the main mechanism for the SE is suggested.
FK:HP19 High-Yield, Single-step Separation of Metallic and Semiconducting SWCNTs Using Block Copolymers at Low Temperatures
C.M. HOMENICK, A. ROUSINA-WEBB, FUYONG CHENG, M.B. JAKUBINEK, P.R.L. MALENFANT, B. SIMARD, Security and Disruptive Technologies Portfolio, National Research Council Canada, Ottawa, Ontario, Canada
Electronic type separation of SWCNT material is necessary to facilitate the development of carbon nanotube electronics. A convenient, high-yield, single-step separation of metallic and semiconducting SWCNTs has been developed using block copolymers and density gradient ultracentrifugation. In particular by varying the centrifugation temperature and dissolved oxygen content under acidic conditions, extraction efficiencies of up to 65% were achieved with both metallic and semiconducting SWCNT electronic purity exceeding 99% as determined by absorption spectroscopy. It was demonstrated that lowering the temperature during the DGU separation, which is expected to increase the difference in densities between metallic and semiconducting nanotube complexes, results in higher purity and yield. Semiconducting and metallic bands are separated simply with a disposable pipette such that specialized fractioning equipment is not required for effective isolation of enriched SWCNTs.
FK:HP20 New Physical Mechanism of Diamond Growth in Low Pressure Microwave Plasma
A. KROMKA et al, Institute of Physics ASCR, Prague, Czech Republic
Diamond is recognized as a promising semiconductor material with multifunctional features. Presently, there is an inherent demand on its growth over large areas (>100cm2) due to increased industrial interest. Here we investigate large area diamond growth by pulsed linear antenna microwave plasma at low pressures (<500Pa). We show that decrease of pressure from 200 to 6 Pa results in an enlargement of diamond grains from nanoscale (<20nm) to polycrystalline character. At the same time, the growth accelerated by factor 3x and film quality is improving. Adding of CO2 is needed to suppress re-nucleation process. Employing “extremely” high CO2 concentration (80%) results in a formation of porous layer consisting of randomly oriented diamond nanowires. We conclude that growth conditions in linear plasma at low pressure are more sensitive to the gas composition and density of active species in the substrate vicinity as well as to microwave energy rather than to temperature of electrons (<2eV). The growth model supported by optical emission spectra of plasma and Langmuir probe measurements implies that the concentration of atomic hydrogen plays a crucial role in well-known hydrogen rich growth conditions and the gas pressure is the key process parameter controlling the growth regime.
FK:HP21 Structural Characterization and Thermophysical Properties of Ag-C Composites
N. SOBCZAK, M. HOMA, J. SOBCZAK, A. GAZDA, R. NOWAK, K. PIETRZAK, K. FRYDMAN, D. WÓJCIK-GRZYBEK, A. STRONY-NEDZA, Foundry Research Institute, Krakow, Poland
Silver-based metal matrix composites have been produced by powder metallurgy using different carbon materials such as carbon nanopowder, graphene oxide, long and short carbon nanotubes. Their structural characterization has been done by optical, scanning electron microscopy and computed tomography. Thermophysical properties of materials (specific heat, coefficient of thermal expansion, thermal diffusivity and thermal conductivity) have been measured using calorimetry, dilatometry and laser flash analysis. The relationships between materials structure and corresponding thermophysical properties have been examined. The results obtained show that effective homogenization of initial Ag-C powder mixture is a critical factor for the production of composite materials of required properties.
FM:HP14 Silicon-on-Insulator Based Metal-Insulator-Semiconductor Structures as Non-volatile Memory and Photo Diodes with Light Enhanced Memory and Responsivity in 245 nm to 880 nm
V. MIKHELASHVILI, D. CRISTEA, G. EISENSTEIN, Electrical Engineering Dept., Technion, Haifa, Israel; G. ATIYA, W.D. KAPLAN, Material Engineering Dept., Technion, Haifa, Israel
We study planar systems of nonvolatile memory (NVM) Metal-Insulator-Semiconductor (MIS) and MIS devices based on substrate of Silicon on Insulator. The MIS diode is comprised of 3.1 nm thermal SiO2 and 20 nm atomic layer deposited HfO2 films. Pt nanocrystals, embedded between insulator films deliver charge trap sites, essential for the NVM function. The electrical and optical characteristics of the structures are considered before and after voltage stress in wavelength range of 245 nm to 880 nm. With no voltage stress and under illumination the NVM MIS structure operates as an optically triggered memory cell in a non-equilibrium depletion state. The total charge densities in both write/erase regimes (at ±5 V) reach 4.5x1013 cm-2. The post voltage stressed NVM MIS, analogous with MIS structure, operates as a photo detectors with identical spectral responsivity (R). However, in contrast with voltage stressed MIS structure an unexpected illumination and voltage sweep amplitude dependent hysteresis of current-voltage characteristic in depletion mode is observed. The values of R of structures without antireflection coating (ARC) at edge wavelengths of 245 nm and 880 nm reach ~0.11 A/W and change from R~0.2 to 0.27 A/W in the 405 nm to 630 nm range. ARC improves the R up to about 25%. The measured bandwidth at 3 db level is about 2.5 MHz. A photo to dark currents ratio larger than 5x104 is achieved. The studied devices can be potentially integrated on a complementary MIS structures.
FN:HP08 STM Investigation of Ferromagnet/Superconductor Hybrid Structures
M. IAVARONE1, S. MOORE1, J. FEDOR1, V. NOVOSAD2, J. PEARSON2, G. KARAPETROV3, 1Temple University, Physics Department, Philadelphia, PA, USA; 2Argonne National Laboratory, Materials Science Division, Argonne, IL, USA; 3Drexel University, Physics Department, Philadelphia, PA, USA
In magnetically coupled, planar ferromagnet-superconductor (F/S) hybrid structures, magnetic domain walls can be used to spatially confine the superconductivity. As opposed to the situation of a superconductor in a uniform applied magnetic field, the nucleation of the superconducting order parameter in F/S structures is governed by the inhomogeneous magnetic field distribution. The interplay between the superconductivity localized at the domains walls and far from the walls leads to effects such as a re-entrant superconductivity and reverse domain superconductivity with the critical temperature depending upon location. Here, we use scanning tunnelling microscopy to directly image the nucleation of superconductivity at the domain wall in F/S structures realized with Co-Pd multilayers and Pb thin films. Moreover we have investigated the effect of magnetic domain width on the vortex configuration as well as on the domain wall superconductivity. Our results demonstrate that such F/S structures are attractive model systems that offer the possibility to control the strength and the location of the superconducting nucleus by applying an external magnetic field.
FO:HP12 Self-assembly Mechanism of Magnetoplasmonic Nanoparticles under a Static Magnetic Field
JAEBEOM LEE, SOO HYUNG KIM, Pusan National University, Miryang, Rep. of Korea
One-dimensional (1D) assemblies of nanoparticles (NPs) are a burgeoning area of research due to their potential in electronics, photonics and sensing applications. They are also essential focus of quantum mechanical study because they may establish liaison between nanoscale quantum properties and meso- or macroscale physical properties depending on longitudinal or horizontal observation. Developing a reliable technique to organize nanoscale building blocks into ordered assemblies is of particular interest in a range of practical applications. Herein, a method is proposed for the subtle control of 1D assembly of multifunctional magnetoplasmonic NPs by applying an external static magnetic field. Au-coated Fe3O4 core–shell nanoparticle (Fe3O4@Au NP) was used as a unit to assemble magnetoplasmonic nanowires (MPNWs), which shows superparamagnetic, plasmonics property, and excellent electrical conductivity. The length of these MPNWs was controllable from several tens to hundreds of microns on unique experimental conditions: concentration of particles, magnetic field intensity, and temperature. Molecular dynamics (MD) simulations were carried out in order to consolidate the hypothesis of the formation mechanism of MPNWs.
E.A. WEIBER, DAVID MEIS, PATRIC JANNASCH, Lund University, Department of Chemistry, Lund, Sweden
With the use of alkaline membrane fuel cells (AMFCs) there is a possibility to utilize low temperature fuel cell technology without the need of scarce and expensive noble metal catalysts. With this technology there is, however, a need to enhance the stability and ionic conductivity of anion-exchange membranes (AEMs) before AMFCs can be a viable alternative to the more studied proton-exchange membrane fuel cells. In the presented work we have aimed to improve the anionic conductivity by synthesizing multiblock copolymers containing blocks with exceptionally high local ion exchange capacity (IEC). Thus, a series of AEMs, based on poly(arylene ether sulfone)s, with IECs in the hydrophilic domain in the range between 4.9 and 5.8 meq./g has been produced. The high IEC was achieved by incorporating tri- and tetramethylhydroquinone into the polymer backbone, thus enabling the attachment of three and four ionic groups respectively on single aromatic rings. The structure− morphology− property relationships and the performance of these copolymers and AEMs will be presented.
FB:HP15 Atomistic Models of Long-term Hydrogen Diffusion in Metals
M.P. ARIZA1, K.G. WANG2, M. ORTIZ3, 1Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Sevilla, Spain; 2Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA; 3Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
The effective and efficient storage of hydrogen is one of the key challenges in developing a hydrogen economy. Intensive research has been focused on developing and optimizing metal-based nanomaterials for high-speed, high-capacity, reversible hydrogen storage applications. Notably, the absorption and desorption of hydrogen in nanomaterials is characterized by an atomic, deformation-diffusion coupled process with a time scale of the order of seconds to hours – far beyond the time windows of existing simulation technologies such as Molecular Dynamics (MD) and Monte Carlo (MC) methods. In this work, we present a novel deformation-diffusion coupled computational framework, which allows the long-term simulation of such slow processes and also maintains a strictly atomistic description of the material. We first propose a theory of non-equilibrium statistical thermodynamics for multi-species based on Jayne’s maximum entropy principle and the meanfield approximation approach. This non-equilibrium statistical thermodynamics model is then coupled with novel discrete kinetics laws, which governs the diffusion of mass – and possibly also conduction of heat – at atomic scale. Finally, this thermo-chemo-mechanical coupled system is solved numerically using a staggered procedure.
FB:HP16 Effect of Pulverization of Hydrogen Storage Alloys on Micro-scale Structural Changes in the Packed Bed
M. OKUMURA, Y. SAITO, Y. MATSUSHITA, H. AOKI, Tohoku University, Japan; Y. KAWAKAMI, Takasago Thermal Engineering Co., Ltd., Japan; K. TAKI, Nihon Visual Science, Inc., Japan
Packing structures of two kinds of hydrogen storage alloy beds (i.e. Mm-Ni-Co-Mn-Al and Ti-Fe-Mn) were observed by an X-ray computed tomography, and the structural changes before and after hydrogen absorption were investigated. In the Mm-Ni-Co-Mn-Al bed, large particles and small particles which filled a void between the large particles were observed after hydrogen absorption. It appears that some of the large particles were pulverized by swelling with hydrogen absorption and the shape drastically changed. On the other hand, small cracks on cross-sections of Ti-Fe-Mn particles in the bed were observed after hydrogen absorption. These cracked particles seemed to maintain their shape during swelling with hydrogen absorption. The structural change of the Ti-Fe-Mn bed was little in comparison with the Mm-Ni-Co-Mn-Al bed because small particles were not generated in the Ti-Fe-Mn bed. The generation of small particles in the packed bed of hydrogen storage alloys would cause the large structural change.
FB:HP17 A Millimeter Scale Reactor Integrated PEM Fuel Cell Energy System with an On-board Hydrogen Production, Storage and Regulation Unit for Autonomous Small Scale Applications
A. BALAKRISHNAN, C. MUELLER, H. REINECKE, Laboratory for Process Technology, IMTEK-Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany
The research and development of new on-board energy sources for autonomous microsystems have gained popular interest in the past few decades. Hydrogen based PEM fuel cells systems, where hydrogen is produced from chemical hydrides and supplied to the fuel cell are one of the top most preferred candidates for such on-board sources due to their high volumetric energy density and integration capabilities. One of the major drawbacks in the state-of-the-art is the complexity of the system design e.g., pumps, valves and gas-liquid separators. Here in this work, we present a millimeter scale reactor integrated PEM fuel cell energy source with an on-board hydrogen production reactor (realized by chemical hydride), and further more passive buffering, regulation unit (realized by metal hydride) of hydrogen. Palladium (Pd) metal hydride has the property to adsorb and desorb hydrogen at ambient and elevated temperatures this allows the Pd to replaces active valves and gas-liquid separators. A stacked system of reactor-buffer/regulator-PEM fuel cell is built up. The system is driven by the hydrolysis of the chemical hydride (NaBH4) in the alkaline medium with Nickel mesh Platinum catalyst (Ni-Pt) for the hydrolysis reaction, where the produced hydrogen gas from the reactor diffuses (due to the pressure difference) through the buffer/regulator and evenly distributes onto the anode of the PEM fuel cell. The system is “self-buffering” in nature so any change in electrical load can be handled during system operation. The operational behaviour of the integrated buffer/regulator in the complete system is investigated with the hydrogen produced from the chemical hydrides and pure hydrogen gas. Furthermore the hydrogen production in the hydrolysis reaction is controlled by the interaction between the Ni-Pt and the liquid medium so a new control mechanism for the chemical hydride hydrolysis reaction is proposed using a shape memory alloy (SMA) and a bimetallic (BM) catalyst structures. Such an approach of using a SMA and a BM can pave the way for the realization of the independent system which is self-sustainable in nature (custom defined).
FD:HP06 Capacitive Energy Harvesting System for Low-grade Heat
WEIYI LU, YU QIAO, University of California, San Diego, La Jolla, CA, USA; HYUCK LIM, Applied Materials, Inc.
Harvesting and storing useful electricity from ambient thermal gradients/fluctuations, particularly low-grade heat (LGH) sources with temperature lower than 250 C, is an important research area. Usually, direct thermal energy conversion is achieved by using thermoelectric materials. Their energy conversion efficiencies, although already close to the upper limits, are still far from satisfactory. In order to meet the increasingly high functional requirements, new mechanisms must be investigated.
Recently, a novel thermal-to-electric energy harvesting system based on capacitive effects of nanoporous electrodes was developed by our team. With a relatively small temperature difference of only 40C, the output voltage could be higher than 100 mV. The energy density was ~2 J/g, much higher than that of many conventional thermoelectrics. This concept may open a new area of study for energy harvesting, conversion, and storage of LGH.
FD:HP07 Influence of Gamma Irradiation on Properties of Selected Thermoelectric Materials
K. WOJCIECHOWSKI1, M. ANDRZEJEWSKA1, K. PYTEL2, T. KROK2, M. DOROSZ2, J. MIETELSKI3, W. GIESZCZYK3, R. KOPEC3, M. BROZEK3, 1Thermoelectric Research Laboratory, Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Poland; 2National Centre for Nuclear Research, Poland; 3Nuclear Physical Chemistry Department, Institute of Nuclear Physics, Polish Academy of Sciences, Poland
The aim of the work was a comparative study of the influence of gamma irradiation on thermoelectric and structural properties of selected thermoelectric materials: PbTe, Bi2Te3, CoSb3 and Mg2Si. Polycrystalline samples of these materials were exposed to radiation doses from 80 to 2500 kGy emitted by fuel rods used in the EWA research reactor in the National Centre for Nuclear Research in Poland. The radiation doses were measured using thermoluminescent detectors MTS. Analyses of changes of microstructure were done using scanning electron microscope SEM with EDX analyzer; structural studies were performed using X-ray diffraction XRD method. Measurements of thermoelectric properties were performed using Scanning Thermoelectric Microprobe STM. Carrier concentration was determined through 5-probe Hall method before and after the exposition to ionizing radiation.
The study confirmed a strong influence of gamma radiation on transport properties of the studied thermoelectric materials. With the increase in radiation dose a significant increase in carrier concentration for CoSb3, Bi2Te3, Sb2Te3 and PbTe was observed. The only exception was Mg2Si for which a decrease in carrier concentration was noticed. The results are correlated with thermoelectric and structural properties of materials.
FD:HP08 Fabrication and Thermoelectric Properties of Te Substituted BiCuSeO
T. SATO, Graduate School, Kogakuin University, Hachioji, Tokyo, Japan; H. KOHRI, T. YAGASAKI, Faculty of Engineering, Kogakuin University, Japan
BiCuSeO has nano-layered structure and consists of conducting [Cu2Se2]2- layer and insulating [Bi2O2]2+ layer. We expect this crystal structure to show large Seebeck coefficient due to the quantum confinement of electron in conducting nano-layer. In this study, the fabrication conditions and the thermoelectric properties of BiCuSeO were investigated. In addition, Te substituted BiCuSeO in order to reduce the thermal conductivity was fabricated, and was investigated the influence of Te substitutions of Se site on their thermoelectric properties.
BiCuSe1-xTexO(x=0, 0.05, 0.10) were fabricated by solid state reaction. Crystalline phase was identified by XRD. Seebeck coefficient α was measured by large temperature difference method. The measurement atmosphere was the air, and the cold side temperature was kept at 300 K, and the hot side temperature was changed from 320 to 540 K.
From the results of XRD, BiCuSeO single phase was obtained in the non-substituted sample. On the other hands, the peaks of the second phase were recognized in the Te substituted samples. The non-substituted sample showed the highest α 456 μV/K at 460 K in hot side temperature. The peak temperature and maximum value of the α were decreased with increasing Te substitution amount.
FF:HP19 Effect of Al-doping on the Structural and Magnetic Properties of ErFe2 Laves-phase Compounds for Magnetocaloric Applications
J. CWIK1, Y. KOSHKIDKO2, A MICHAILOWA3, N. KOLCHUGINA3, K. NENKOV1, 4, 1International Laboratory for High Magnetic Fields and Low Temperatures, Wroclaw, Poland; 2Vysoka Skola banska - Technical University of Ostrava, Ostrava-Poruba, Czech Republic; 3Baikov Institute of Metallurgy and Materials Science, RAS, Moscow, Russia; 4lFW Dresden, lnstitute of Metallic Materials, Dresden, Germany
In this work we report on the structural, magnetic and magnetocaloric properties of several polycrystalline ErFe2-xAlx)( intermetallic compounds (0.36≤x ≤1.125).
Powder X-ray diffraction study at room temperature showed that the compounds in the Fe rich region crystallize in the C15 cubic Laves phase structure, while for the ones in the intermediate region the hexagonal C14 structure was observed. Magnetic and magnetocaloric properties of polycrystalline ErFe2-xAlx intermetallic compounds were investigated experimentally using magnetic and heat capacity measurements; the Landau theory was applied also to clarify peculiarities of magnetic phase transition in the compounds. The Curie temperature Tc decreases from 275 to 55 K as the Al content increases to x = 1.125. The isothermal entropy change -ΔSmag was calculated according to magnetic measurements using thermodynamic
Maxwell's relation. A large entropy change has been observed for all concentrations. Under an external fìeld change from 0 to 4 T, the maximum entropy change fluctuates within 9 J/kg K. Heat capacity measurements allowed us to determine the adiabatic temperature change in magnetic fields up to maximum 2 T. The maximum ΔTad value varies within 0.5 and 1 K for a magnetic field change of 2 and 1 T, respectively. The effect of increasing Al amount in the ErFe2-xAlx intermetallic compounds on their magnetic and magnetocaloric properties is discussed.
FF:HP20 Tomographic Imaging of Metal vs. Polymer Matrix Magnetocaloric Composites
A. WASKE1, A. FUNK1,3, M. KRAUTZ2, B. WEISE1,3, B. PULKO4, K. SKOKOV5, O. GUTFLEISCH5, J. ECKERT1,3, 1Institute of Complex Materials, IFW Dresden, Dresden, Germany; 2Institute for Metallic Materials, IFW Dresden, Dresden, Germany; 3Institute for Material Science, TU Dresden, Dresden, Germany; 4University of Ljubljana, Faculty of Mechanical Engineering, Ljubljana, Slovenia; 5Material Science, TU Darmstadt, Darmstadt, Germany
Magnetocaloric materials could one day be the basis of a new magnetic cooling concept for consumer use, replacing conventional refrigeration technology. The research in magnetocalorics focused on the discovery and development of materials with large or giant magnetocaloric effects (MCE) over the last few decades. Such alloys show a first order phase transition, with a simultaneous and abrupt structural and magnetic changes. However, bulk MCE-materials often show mechanical instability upon magnetic field cycling due to the large strain that is associated with this kind of phase transition. By using a composite containing a polymer or metal matrix and powderized magnetocaloric material, this problem could be overcome. Furthermore, such composites show good workability to produce various geometries (e.g. thin plates, spheres) and also offer the possibility to form complex composite designs.
We will show results on magnetocaloric properties obtained by magnetometry and direct ΔTad measurements. 3D computed tomographic imaging was employed to ensure precise determination of the volume fraction of all relevant phases (active material, matrix, pores). Using this approach, we determine the performance of the composites as a function of magnetocaloric material fraction.
FG:HP07 CuZnSnSe Nanotubes and Nanowires by Template Electrosynthesis
R. INGUANTA, M. BATTAGLIA, S. PIAZZA, C. SUNSERI, Laboratorio di Chimica Fisica Applicata, Dipartimento di Ingegneria Chimica, Gestionale, Informatica, Meccanica, Università di Palermo, Palermo, Italy
Copper zinc tin sulphide, or CZTS, is one of the most inexpensive and interesting semiconductor employed in solar cells. Moreover, its components are not toxic and earth abundant and this material presents useful properties as absorber also when composition is different from the stoichiometric one. Among the different methods to obtain CZTS, the electrochemical route appears of great interest because easy to conduct. Up to date, literature data show that non-uniformity in composition and/or presence of secondary phases, prevent the formation of electrochemical CZTS thin-film of high quality.
In this work we present an extensive investigation aimed to find suitable conditions to grow CZTS with good performance: this implies the simultaneous electrodeposition of elements having different standard electrochemical potential. In particular attention was focused on template electrosynthesis in order to obtain regular and ordered array of nanowires. Synthesis of nanostructured absorber materials is of great technological interest because photovoltaic devices employing nanostructures display higher values of energy conversion efficiency compared to conventional thin-film devices. Besides, this morphology provides excellent light trapping, and increases defects tolerance.
FG:HP08 Single-side Boron Profile Control in n-type Silicon Wafer and Photovoltaic Design by PC1D Calculations
WOON JO CHO, JIN DONG SONG, IL KI HAN, Center for Opto-Electronic Conversion System, Korea Institute of Science and Technology, Seoul, Korea
Efficiency limitation of silicon solar cell, the most commercialized photovoltaics, has been studied with the point of view of dopant complexes as boron-oxygen defects and boron-iron defects. These defects are commonly found in B-doped p-based Czochralski wafers. B-doped single crystal silicon wafers reportedly suffer both a light-induced degradation and a lifetime decrease of minority carrier electrons which origin from the boron related defects [1]. To avoid these degradation, boron doped emitter structures in n-type silicon wafers are recommended.
For a selective emitter photovoltaic design, we carried out the boron diffusion in n-type silicon wafer using our borosilicate glass as a boron source. With our experimental profiles of boron concentration, we calculated the photovoltaic parameters for the single-side boron emitter on P-doped n-type silicon wafer by PC1D program. We could obtain the cell efficiency of 15 ~ 21 % according to our single-side boron diffusion profiles for wafer base resistivity of 1 ohm-cm, wafer thickness of 250 micrometer and rear junction depth of 5 micrometer. The controlled boron profiles in p-emitter and the design parameters for high efficiencies will be discussed.
[1] Daniel L. Meier, et al. IEEE J. Photovoltaics 1, 123-129 (2011)
FH:HP11 (Ga1-xInx)2O3 Layers Grown by Metal Organic Vapour Phase Epitaxy
M. BALDINI, D. GOGOVA, R. SCHEWSKI, M. ALBRECHT, M. SCHMIDBAUER, Z. GALAZKA, G. WAGNER, Leibniz Institute for Crystal Growth, Berlin, Germany
Among Transparent Semiconductor Oxides (TSOs), monoclinic β-Ga2O3 is one of the most interesting compound, by virtue of its high break-down field (~8 MV/cm), which allows to minimize conduction losses in high-power devices, and its large direct band gap (4,9 eV) that turns into a high transparency, up to mid-UV wavelengths [1, 2]. By partially substituting Ga with In, it is possible to modulate the energy gap of the material towards the lower value of In2O3 (3,75 eV), opening the field to a broad spectrum of applications [3, 4].
Here, we report on the growth of (Ga1-xInx)2O3 layers on (100) Ga2O3 and (0001) Al2O3 substrates, performed in a vertical metal organic vapour phase epitaxy (MOVPE) reactor. The growth pressure, explored in a wide range, turned out to have a fundamental role in the critical In incorporation process, by increasing the amount of In introduced in the Ga2O3 lattice at higher pressure values. The employment of In during the growth contributed to limit the concentration of structural defects, both in hetero- and homoepitaxial layers. This behavior has been explained, in analogy with the growth of (In)GaN [5, 6], by the tendency of In to float on the surface of Ga2O3, delivering a surfactant effect that promotes a step-flow growth mode.
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[4] T. Oshima, S. Fujita, phys. stat. sol. (c), 2008, 5, 3113
[5] S. Keller, S. Heikman, I. Ben-Yaacov, L. Shen, S.P. DenBaars, U. K. Mishra, Appl. Phys. Lett. 2001, 79, 3449
[6] J.E. Northrup, C.G. Van de Walle, Appl. Phys. Lett. 2004, 84, 4322.
FI:HP09 White Light Emitting Nanocomposite Films Constituted of Lanthanide Orthophosphates Nanophosphors Dispersed in Silicon
A. GARRIDO HERNÁNDEZ1,2, A. POTDEVIN2, D. BOYER2, G. CHADEYRON2, A. GARCÍA MURILLO1, F. DE J. CARRILLO ROMO1, R. MAHIOU2, 1Instituto Politécnico Nacional, CIITEC IPN, México D.F, México; 2Institut de Chimie de Clermont-Ferrand, UMR 6296 CNRS / UBP / ENSCCF, Aubiere Cedex, France
Rare-earth doped lanthanides orthophosphates represent a class of materials with significant technological importance. Recently, new applications of nanoscale phosphors, including biolabelling, optical imaging or luminescent transparent layers have attracted intensive interests. As a result, several synthesis methods leading to LnPO4 nanocrystals with controlled shape have been developed. It is well known that the reduction of particles size or the modification of their shape can dramatically modify their physico-chemical properties.
In this work Eu3+, Tb3+ and Dy3+ doped GdPO4 were successfully synthetized by a new hydrothermal method leading respectively to red, green and blue nanophosphors. Their structural characterization was performed by X-ray diffraction and infrared spectroscopy. Transmission electron microscopy images have revealed the achievement of nanomaterials with a narrow size distribution. Their photoluminescent properties and quantum efficiencies were investigated upon excitation in the UV range. Luminescent composite films were prepared by dispersing a mixture of these fluorescent nanomaterials in a silicon matrix by the coatmaster technique. Finally their chromaticity coordinates were determined to assess the ability for producing white light upon UV excitation.
FK:HP18 Carbon Nano/Microcoils-Polyurethane Composites Shielding Materials for Electromagnetic Interference
GI-HWAN KANG, SUNG-HOON KIM, Center for Green Fusion Technology and Department of Engineering in Energy & Applied Chemistry, Silla University, Busan, South Korea
Due to the increasingly demand of light weight and moldable process, polymer-matrix composites for shielding materials of electromagnetic interference (EMI) are strongly attractive for portable electronic devices, avionic electronics and etc. In this respect, carbon materials (such as carbon fibers, carbon nanotubes, carbon blacks, carbon coils, graphites, and so on) are noticed as the promising candidates for EMI shielding materials. In this work, carbon nano/microcoils (CNCs/CMCs) were deposited on Al2O3 substrate using C2H2/H2 for source gases and SF6 for an incorporated additive gas under thermal chemical vapor deposition system. The CNCs/CMCs-polyurethane (PU) composites were obtained by dispersing the CNCs/CMCs in PU solvent with dimethylformamide additive. We investigated the electromagnetic wave shielding properties of the CNCs/CMCs-PU composites in the frequency range of 0.25-1.5 GHz and discussed the shielding effectiveness of the CNCs/CMCs-PU composites according to the weight percent of CNCs/CMCs in CNCs/CMCs-PU composites and the thickness of the CNCs/CMCs-PU composites layers. Based on these results, the main mechanism for the SE is suggested.
FK:HP19 High-Yield, Single-step Separation of Metallic and Semiconducting SWCNTs Using Block Copolymers at Low Temperatures
C.M. HOMENICK, A. ROUSINA-WEBB, FUYONG CHENG, M.B. JAKUBINEK, P.R.L. MALENFANT, B. SIMARD, Security and Disruptive Technologies Portfolio, National Research Council Canada, Ottawa, Ontario, Canada
Electronic type separation of SWCNT material is necessary to facilitate the development of carbon nanotube electronics. A convenient, high-yield, single-step separation of metallic and semiconducting SWCNTs has been developed using block copolymers and density gradient ultracentrifugation. In particular by varying the centrifugation temperature and dissolved oxygen content under acidic conditions, extraction efficiencies of up to 65% were achieved with both metallic and semiconducting SWCNT electronic purity exceeding 99% as determined by absorption spectroscopy. It was demonstrated that lowering the temperature during the DGU separation, which is expected to increase the difference in densities between metallic and semiconducting nanotube complexes, results in higher purity and yield. Semiconducting and metallic bands are separated simply with a disposable pipette such that specialized fractioning equipment is not required for effective isolation of enriched SWCNTs.
FK:HP20 New Physical Mechanism of Diamond Growth in Low Pressure Microwave Plasma
A. KROMKA et al, Institute of Physics ASCR, Prague, Czech Republic
Diamond is recognized as a promising semiconductor material with multifunctional features. Presently, there is an inherent demand on its growth over large areas (>100cm2) due to increased industrial interest. Here we investigate large area diamond growth by pulsed linear antenna microwave plasma at low pressures (<500Pa). We show that decrease of pressure from 200 to 6 Pa results in an enlargement of diamond grains from nanoscale (<20nm) to polycrystalline character. At the same time, the growth accelerated by factor 3x and film quality is improving. Adding of CO2 is needed to suppress re-nucleation process. Employing “extremely” high CO2 concentration (80%) results in a formation of porous layer consisting of randomly oriented diamond nanowires. We conclude that growth conditions in linear plasma at low pressure are more sensitive to the gas composition and density of active species in the substrate vicinity as well as to microwave energy rather than to temperature of electrons (<2eV). The growth model supported by optical emission spectra of plasma and Langmuir probe measurements implies that the concentration of atomic hydrogen plays a crucial role in well-known hydrogen rich growth conditions and the gas pressure is the key process parameter controlling the growth regime.
FK:HP21 Structural Characterization and Thermophysical Properties of Ag-C Composites
N. SOBCZAK, M. HOMA, J. SOBCZAK, A. GAZDA, R. NOWAK, K. PIETRZAK, K. FRYDMAN, D. WÓJCIK-GRZYBEK, A. STRONY-NEDZA, Foundry Research Institute, Krakow, Poland
Silver-based metal matrix composites have been produced by powder metallurgy using different carbon materials such as carbon nanopowder, graphene oxide, long and short carbon nanotubes. Their structural characterization has been done by optical, scanning electron microscopy and computed tomography. Thermophysical properties of materials (specific heat, coefficient of thermal expansion, thermal diffusivity and thermal conductivity) have been measured using calorimetry, dilatometry and laser flash analysis. The relationships between materials structure and corresponding thermophysical properties have been examined. The results obtained show that effective homogenization of initial Ag-C powder mixture is a critical factor for the production of composite materials of required properties.
FM:HP14 Silicon-on-Insulator Based Metal-Insulator-Semiconductor Structures as Non-volatile Memory and Photo Diodes with Light Enhanced Memory and Responsivity in 245 nm to 880 nm
V. MIKHELASHVILI, D. CRISTEA, G. EISENSTEIN, Electrical Engineering Dept., Technion, Haifa, Israel; G. ATIYA, W.D. KAPLAN, Material Engineering Dept., Technion, Haifa, Israel
We study planar systems of nonvolatile memory (NVM) Metal-Insulator-Semiconductor (MIS) and MIS devices based on substrate of Silicon on Insulator. The MIS diode is comprised of 3.1 nm thermal SiO2 and 20 nm atomic layer deposited HfO2 films. Pt nanocrystals, embedded between insulator films deliver charge trap sites, essential for the NVM function. The electrical and optical characteristics of the structures are considered before and after voltage stress in wavelength range of 245 nm to 880 nm. With no voltage stress and under illumination the NVM MIS structure operates as an optically triggered memory cell in a non-equilibrium depletion state. The total charge densities in both write/erase regimes (at ±5 V) reach 4.5x1013 cm-2. The post voltage stressed NVM MIS, analogous with MIS structure, operates as a photo detectors with identical spectral responsivity (R). However, in contrast with voltage stressed MIS structure an unexpected illumination and voltage sweep amplitude dependent hysteresis of current-voltage characteristic in depletion mode is observed. The values of R of structures without antireflection coating (ARC) at edge wavelengths of 245 nm and 880 nm reach ~0.11 A/W and change from R~0.2 to 0.27 A/W in the 405 nm to 630 nm range. ARC improves the R up to about 25%. The measured bandwidth at 3 db level is about 2.5 MHz. A photo to dark currents ratio larger than 5x104 is achieved. The studied devices can be potentially integrated on a complementary MIS structures.
FN:HP08 STM Investigation of Ferromagnet/Superconductor Hybrid Structures
M. IAVARONE1, S. MOORE1, J. FEDOR1, V. NOVOSAD2, J. PEARSON2, G. KARAPETROV3, 1Temple University, Physics Department, Philadelphia, PA, USA; 2Argonne National Laboratory, Materials Science Division, Argonne, IL, USA; 3Drexel University, Physics Department, Philadelphia, PA, USA
In magnetically coupled, planar ferromagnet-superconductor (F/S) hybrid structures, magnetic domain walls can be used to spatially confine the superconductivity. As opposed to the situation of a superconductor in a uniform applied magnetic field, the nucleation of the superconducting order parameter in F/S structures is governed by the inhomogeneous magnetic field distribution. The interplay between the superconductivity localized at the domains walls and far from the walls leads to effects such as a re-entrant superconductivity and reverse domain superconductivity with the critical temperature depending upon location. Here, we use scanning tunnelling microscopy to directly image the nucleation of superconductivity at the domain wall in F/S structures realized with Co-Pd multilayers and Pb thin films. Moreover we have investigated the effect of magnetic domain width on the vortex configuration as well as on the domain wall superconductivity. Our results demonstrate that such F/S structures are attractive model systems that offer the possibility to control the strength and the location of the superconducting nucleus by applying an external magnetic field.
FO:HP12 Self-assembly Mechanism of Magnetoplasmonic Nanoparticles under a Static Magnetic Field
JAEBEOM LEE, SOO HYUNG KIM, Pusan National University, Miryang, Rep. of Korea
One-dimensional (1D) assemblies of nanoparticles (NPs) are a burgeoning area of research due to their potential in electronics, photonics and sensing applications. They are also essential focus of quantum mechanical study because they may establish liaison between nanoscale quantum properties and meso- or macroscale physical properties depending on longitudinal or horizontal observation. Developing a reliable technique to organize nanoscale building blocks into ordered assemblies is of particular interest in a range of practical applications. Herein, a method is proposed for the subtle control of 1D assembly of multifunctional magnetoplasmonic NPs by applying an external static magnetic field. Au-coated Fe3O4 core–shell nanoparticle (Fe3O4@Au NP) was used as a unit to assemble magnetoplasmonic nanowires (MPNWs), which shows superparamagnetic, plasmonics property, and excellent electrical conductivity. The length of these MPNWs was controllable from several tens to hundreds of microns on unique experimental conditions: concentration of particles, magnetic field intensity, and temperature. Molecular dynamics (MD) simulations were carried out in order to consolidate the hypothesis of the formation mechanism of MPNWs.