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Finite-temperature elasticity of fcc Al: Atomistic simulations and ultrasonic measurements

Physical Review B 2011年第6期84卷 064101-064101页

作者： Hieu H. Pham Michael E. Williams Patrick Mahaffey Miladin Radovic Raymundo Arroyave Tahir Cagin Department of Chemical Engineering Texas A&M University College Station TX 77843 USA Department of Mechanical Engineering Texas A&M University College Station TX 77843 USA Department of Industrial and Systems Engineering Texas A&M University College Station TX 77843 USA Materials Science and Engineering Program Texas A&M University College Station TX 77843 USA

Though not very often, there are some cases in the literature where discrepancies exist in the temperature dependence of elastic constants of materials. A particular example of this case is the behavior of C12 coefficient of a simple metal, aluminum. In this paper we attempt to provide insight into various contributions to temperature dependence in elastic properties by investigating the thermoelastic properties of fcc aluminum as a function of temperature through the use of two computational techniques and experiments. First, ab initio calculations based on density functional theory (DFT) are used in combination with quasiharmonic theory to calculate the elastic constants at finite temperatures through a strain-free energy approach. molecular dynamics (MD) calculations using tight-binding potentials are then used to extract the elastic constants through a fluctuation-based formalism. Through this dynamic approach, the different contributions (Born, kinetic, and stress fluctuations) to the elastic constants are isolated and the underlying physical basis for the observed thermally induced softening is elucidated. The two approaches are then used to shed light on the relatively large discrepancies in the reported temperature dependence of the elastic constants of fcc aluminum. Finally, the polycrystalline elastic constants (and their temperature dependence) of fcc aluminum are determined using resonant ultrasound spectroscopy (RUS) and compared to previously published data as well as the atomistic calculations performed in this work.

关键词： THERMOELASTICITY DENSITY functionals molecular dynamics FLUCTUATIONS (Physics) POLYCRYSTALLINE semiconductors

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Application of X-ray synchrotron microscopy instrumentation in biology

Application of X-ray synchrotron microscopy instrumentation ...

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2nd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications, ANIMMA 2011

作者： Gasperini, F.M. Pereira, G.R. Granjeiro, J.M. Calasans-Maia, M.D. Rossi, A.M. Perez, C.A. Lopes, R.T. Lima, I. Medical Science Program Fluminense Federal University Niterói Brazil Department of Metallurgical and Materials Engineering Federal University of Rio de Janeiro Brazil Molecular and Cell Biology Department Fluminense Federal University Niterói Rio de Janeiro Brazil Oral Surgery Department Fluminense Federal University Niterói Rio de Janeiro Brazil Biomaterials Laboratory Brazilian Center of Physics Research Rio de Janeiro Brazil Brazilian Synchrotron Laboratory Campinas São Paulo Brazil Nuclear Engineering Laboratory Federal University of Rio de Janeiro Brazil

ISBN: (纸本)9781457709265

X-ray microfluorescence imaging technique has been used as a significant tool in order to investigate minerals contents in some kinds of materials. The aim of this study was to evaluate the elemental distribution of calcium and zinc in bone substitute materials (nanohydroxyapatite spheres) and cortical bones through X-Ray Microfluorescence analysis with the increment of Synchrotron Radiation in order to evaluate the characteristics of the newly formed bone and its interface, the preexisting bone and biomaterials by the arrangement of collagen fibers and its birefringence. The elemental mapping was carried out at Brazilian Synchrotron Light Laboratory, Campinas - Sao Paulo, Brazil working at D09-XRF beam line. Based on this study, the results suggest that hydroxyapatite-based biomaterials are biocompatible, promote osteoconduction and favored bone repair. © 2011 IEEE.

关键词： Bone

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Phonon transport and thermoelectricity in defect-engineered InAs nanowires

Phonon transport and thermoelectricity in defect-engineered ...

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2011 MRS Fall Meeting

作者： Weathers, Annie Moore, Arden L. Pettes, Michael T. Salta, Daniel Kim, Jaehyun Dick, Kimberly Samuelson, Lars Linke, Heiner Caroff, Philippe Shi, Li Department of Mechanical Engineering University of Texas at Austin Austin TX United States Material Science and Engineering Graduate Program University of Texas at Austin Austin TX United States Center for Nano and Molecular Science University of Texas at Austin Austin TX United States Division of Solid State Physics Lund University S-22100 Lund Sweden Polymer and Materials Chemistry Lund University S-22100 Lund Sweden Institut d'Electronique de Microelectronique et de Nanotechnologie UMR CNRS 8520 F-59652 Villeneuve d'Ascq France

ISBN: (纸本)9781627482219

There have been reports of improvements in the thermoelectric figure of merit through the use of nanostructured materials to suppress the lattice thermal conductivity. Here, we report on a fundamental study of the combined effects of defect planes and surface scattering on phonon transport and thermoelectric properties of defect-engineered InAs nanowires. A microfabricated device is employed to measure the thermal conductivity and thermopower of individual suspended indium arsenide nanowires grown by metal organic vapor phase epitaxy. The four-probe measurement device consists of platinum resistance thermometers and electrodes patterned on two adjacent SiNx membranes. A nanowire was suspended between the two membranes, and electrical contact between the nanowire and the platinum electrodes was made with the evaporation of a Ni/Pd film through a shadow mask. The exposed back side of the device substrate allows for characterization of the crystal structure of the suspended nanowire with transmission electron microscopy (TEM) following measurement. The 100-200 nm diameter zincblende (ZB) InAs nanowire samples were grown with randomly spaced twin defects, stacking faults, or phases boundaries perpendicular to the nanowire growth direction, as revealed by transmission electron microscopy (TEM) analysis. Compared to single-crystal ZB InAs nanowires with a similar lateral dimension, the thermal conductivity of the defect-engineered nanowires is reduced by fifty percent at room temperature. © 2012 materials Research Society.

关键词： Nanowires

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Tunable Photoluminescence from Graphene Oxide†

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Angewandte Chemie 2012年第27期124卷

作者： Chih‐Tao Chien Shao‐Sian Li Wei‐Jung Lai Yun‐Chieh Yeh Hsin‐An Chen I‐Shen Chen Li‐Chyong Chen Kuei‐Hsien Chen Takashi Nemoto Seiji Isoda Mingwei Chen Takeshi Fujita Goki Eda Hisato Yamaguchi Manish Chhowalla Chun‐Wei Chen Department of Materials Science and Engineering National Taiwan University No. 1 Sec. 4 Roosevelt Road Taipei 10617 (Taiwan) Center for Condensed Matter Sciences National Taiwan University No. 1 Sec. 4 Roosevelt Road Taipei 10617 (Taiwan) Institute of Atomic and Molecular Sciences Academia Sinica No. 1 Sec. 4 Roosevelt Road Taipei 10617 (Taiwan) Institute for Chemical Research Kyoto University Uji Kyoto 611‐0011 (Japan) Institute for Integrated Cell‐Material Sciences Kyoto University 606‐8501 Kyoto (Japan) WPI Advanced Institute for Materials Research Tohoku University 2‐1‐1 Katahira Aoba‐ku Sendai Miyagi 980‐8577 (Japan) Department of Materials Science and Engineering Rutgers University 607 Taylor Road Piscataway NJ 08854 (USA)

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Metamorphic solar cells employing chemical mechanical polishing and MOVPE regrowth

Metamorphic solar cells employing chemical mechanical polish...

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2011 37th IEEE Photovoltaic Specialists Conference

作者： L. J. Mawst P. Dudley J. Kirch T. Kim S. Ruder T. F. Kuech R. Tatavarti Department of Electrical and Computer Engineering University of Wisconsin-Madison Madison WI USA Materials Science Program University of Wisconsin-Madison Madison WI USA Department of Chemical and Biological Engineering University of Wisconsin-Madison Madison WI USA Microlink Devices Inc. Niles IL USA

We have investigated the MOVPE growth of In x Ga 1-x As metamorphic buffer layer (MBL) structures with a focus on techniques to improve the surface morphology and determine the influence of morphology on subsequently grown single-junction device structures. To improve the surface roughness of the underlying MBL, chemical-Mechanical Polishing (CMP) is employed and MOVPE regrowth of single-junction (SJ) solar cells on top of the polished surface is performed. AFM image analysis indicates the CMP process is effective in reducing the step-graded In x Ga 1-x As MBL surface roughness from ~7-10 nm (as-grown) to 2.3 nm post CMP. A post-CMP ozone/HF treatment was found to be effective in removing silica residue remaining on the surface from the CMP process, allowing for the growth of films on top of the MBL surface subjected to CMP. Improved short circuit current density (J sc ) and external quantum efficiency (QE) were obtained from SJ (1eV) devices which employ the CMP process compared with those on as-grown MBLs.

关键词： Surface roughness Rough surfaces Surface treatment Surface morphology Indium gallium arsenide Epitaxial layers Epitaxial growth

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Enhanced interfacial adhesion, mechanical, and thermal properties of natural flour-filled biodegradable polymer bio-composites

Enhanced interfacial adhesion, mechanical, and thermal prope...

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作者： Kim, Hee-Soo Lee, Byoung-Ho Lee, Sena Kim, Hyun-Joong Dorgan, John R. Research and Development Institute Research 2 Team Woongjin Chemical Co. Ltd Suwon 443-270 Korea Republic of Laboratory of Adhesion and Bio-Composites Program in Environmental Materials Science Seoul National University Seoul 151-921 Korea Republic of Research Institute for Agriculture and Life Sciences Seoul National University Seoul 151-921 Korea Republic of Colorado Center for Biorefining and Biofuels Department of Chemical and Biochemical Engineering Colorado School of Mines Golden CO 80401-1887 United States

This study examined the interfacial adhesion, mechanical, and thermal properties of compatibilizing agent-treated and non-treated biocomposites as a function of the type of compatibilizing agent. The tensile strength, interfacial adhesion, and heat deflection temperature (HDT) of maleic anhydride-grafted poly(butylene succinate) (PBS-MA) and maleic anhydride-grafted poly(lactic acid) (PLA-MA)-treated biocomposites are greater than those of untreated maleic anhydride-grafted poly(styrene-b-ethylene-co-butylene-b-styrene) triblock copolymer (SEBS-MA) and maleic anhydride-grafted polypropylene (MAPP)-treated biocomposites. The storage modulus (E′) values and the tan Εmax temperatures (T g) of PBS-MA and PLA-MA-treated biocomposites were slightly higher than that of the untreated biocomposites. © Akadémiai Kiadó, Budapest, Hungary 2010.

关键词： Maleic anhydride

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Theoretical Insight into the Mechanisms of Ethanol Electro-oxidation with PtSn Electrodes

Theoretical Insight into the Mechanisms of Ethanol Electro-o...

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第十一届全国量子化学会议

作者： Hui-Fang Wang Zhi-Pan Liu College of Chemistry Chemical Engineering and Materials Science Suzhou University 199 RenAi Road Suzhou 215123. Jiangsu P. R. China Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Department of Chemistry Fudan University Shanghai 200433 China Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Department of Chemistry Fudan University Shanghai 200433 China

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Phonon Transport and Thermoelectricity in Defect-Engineered InAs Nanowires

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MRS Online Proceedings Library 2011年第1期1404卷 36-43页

作者： Weathers, Annie Moore, Arden L. Pettes, Michael T. Salta, Daniel Kim, Jaehyun Dick, Kimberly Samuelson, Lars Linke, Heiner Caroff, Philippe Shi, Li Department of Mechanical Engineering The University of Texas at Austin Austin USA Center for Nano and Molecular Science The University of Texas at Austin Austin USA Material Science and Engineering Graduate Program The University of Texas at Austin Austin USA The Nanometer Structure Consortium (nmC@LU) and Division of Solid State Physics Lund University Lund Sweden Polymer & Materials Chemistry Lund Sweden Institut d’Electronique de Microelectronique et de Nanotechnologie UMR CNRS 8520 France

关键词： thermoelectric nanostructure thermal conductivity

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Synthesis of new antibacterial ZnO powders by hydrothermal treatment and their characterization

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Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 2010年第2期57卷 106-111页

作者： Matsuoka, Sho Kato, Masaki Hirota, Ken Tsukagoshi, Kazuhiko Department of Molecular Chemistry and Biochemistry Doshisha University Kyo-Tanabe 610-0321 Japan Department of Chemical Engineering and Materials Science Faculty of Science and Engineering Doshisha University Kyo-Tanabe 610-0321 Japan

Homogeneous ZnO powders with antibacterial activity have been synthesized by hydrothermal treatment at 160 ∼ 190°C under 1.01 ∼1.09 MPa for 10 ∼ 50 h using Zn(NO3)2·6H 2O, hexamethylenetetramine ((CH2)6N 4) and ethanol. Their particle morphology and specific surface areas have been characterized in relation with the synthesis conditions. A luminol chemiluminescence (CL) measurement has been applied to evaluate their antibacterial activity under dark conditions. Experimental results revealed that the ZnO nanorod powders (a length≤ 500nm and a diameter*C/20h/1.09 MPa, showed the highest photon counts of 3.75x 105, which value was ten times higher than that (3.59 x 104 counts) of conventional ZnO powders commercially available.

关键词： Powders

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Characteristics of Step-Graded In_xGa_(1-x)As and InGaP_ySb_(1-y) Metamorphic Buffer Layers on GaAs Substrates

Characteristics of Step-Graded In_xGa_(1-x)As and InGaP_ySb_...

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Compound Semiconductor Week

作者： J. Kirch P. Dudley T. Kim K. Radavich S. Ruder L. J. Mawst T. F. Kuech S. D. LaLumondiere Y. Sin W. T. Lotshaw S. C. Moss Department of Electrical and Computer Engineering University of Wisconsin - Madison Materials Science Program University of Wisconsin - Madison Department of Chemical and Biological Engineering University of Wisconsin - Madison Electronics and Photonics Lab The Aerospace Corporation

ISBN: (纸本)9781457717536

Step-graded InGaP_ySb_(1-y) and In_xGa_(1-x)As metamorphic buffer layer (MBL) structures are grown on GaAs substrates by metal-organic chemical vapor deposition (MOCVD). AFM analysis indicates that graded group V InGaP_ySb_(1-y) MBLs exhibit significantly lower surface roughness (～4.7nm) compared with more conventional graded group III In_xGa_(1-x)As MBLs, which typically have rms surface roughness in the range of 7-14nm. To reduce the surface roughness of the In_xGa_(1-x)As MBL, a post growth chemical-Mechanical Polishing (CMP) procedure is implemented. AFM image analysis indicates the CMP process is effective in reducing the step-graded In_xGa_(1-x)As MBL surface roughness from ～7.3 nm (as-grown) to 2.3 nm post CMP. Preliminary studies indicate that bulk InGaAs layers regrown on top of the MBL subjected to CMP exhibit improved static and transient PL characteristics compared with those deposited on as-grown MBLs.

关键词： III-V semiconductors Defects Optical devices

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