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Effect of Silicon Content and Shake-Out Time on Hardness and Grain Size Properties of GL 250 Cast Iron

Journal of Minerals and materials Characterization and engineering 2011年第3期10卷 257-266页

作者： P. Atanda G. Oluwadare O. Oluwole Industrial Chemistry Department Bells University Nigeria. Materials Science and Engineering Dept. Obafemi Awolowo University Nigeria Mechanical Engineering Dpartment University of Ibadan Nigeria

The properties of cast iron grade GL 250 are dependent on the microstructures developed during casting. These microstructures are in turn dependent on the composition of the alloy, type of mould and other numerous casting practice variables such as shake-out time, pouring temperature, mould ambient conditions and inoculating technique. In this work, the effect of silicon content and shake-out time on the grain size (GS) and hardness properties of GL 250 cast iron was studied using a pouring temperature of 1400℃ and sand mould casting. Using charge materials consisting of pig iron and other additives, GL 250 castings containing silicon contents of 1.7, 2.1 and 2.7% were casted using a constant pouring temperature of 1400℃, molding sand of specified properties and ambient mould temperature of 32℃. Results showed that type A flake type was obtained at 30mins shakeout time for all samples for the C.I composition under study. Increasing shake-out time decreased hardness and increased carbide grain size. Increasing silicon content was observed to increase grain size and reduce free graphite but with resultant decrease in hardness. Two mathematical relationships were derived. One related grain-size to silicon content and shakeout time while the second related Brinnel Hardness to Silicon content and shake-out time. They are: Grain Size=0.40 Si+0.17Shake-out Time-0.15 and BHN=-60.53Si-7.15Shake-out Time+329.35 at 1400℃ pouring temperature in a molding sand of specified properties and sand mould ambient temperature of 32℃.

关键词： Shake-out time Silicon content Hardness Grain-Size GL 250 C.I

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Effect of Long Range Interaction on Diffusion in Cu/NiFe TernaryAlloy Composition Modulated Thin Films

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MRS Online Proceedings Library 2011年第1期37卷 537-543页

作者： Jharna Chaudhuri Thomas Tsakalakos Mechanical Engineering Department Wichita State Univ. Wichita USA Dept. of Mechanics and Materials Science College of Engineering Rutgers The State University of New Jersey Piscataway USA

Composition modulated (with wavelengths between 1.6 to 4.98 nm) Cu/NiFe ternary alloy thin films containing 53 at % Cu, 40 at % Ni, and 7 at % Fe were prdduced by the vapor-phase growth technique. The inter-diffusivities in these films were measured at temperatures 320°C, 345°C, and 400°C from the growth or decay rate of satelite peak intensities. $${\widetilde{\rm{D}}_{\rm{B}}}$$ as a function of dispersion relation B2 exhibited anomalous behavior at certain wavelengths at which an enhanced elastic modulus effect is also observed. This anomalous behavior was directly attributed to the long range interaction.

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Nucleation and Growth of Gallium Nitride Films on Si and Sapphire Substrates Using Buffer Layers

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MRS Online Proceedings Library 2011年第1期423卷 287-292页

作者： N.R. Perkins M.N. Horton D. Zhi R.J. Matyi Z.Z. Bandic T.C. McGill T.F. Kuech Materials Science Program University of Wisconsin Madison USA Department of Materials Science and Engineering University of Wisconsin Madison USA Department of Applied Physics California Institute of Technology Pasadena USA Dept. of Chemical Engineering University of Wisconsin Madison USA

We have investigated the nucleation and growth of gallium nitride (GaN) films on silicon and sapphire substrates using halide vapor phase epitaxy (HVPE). GaN growth was carried out on bare Si and sapphire surfaces, as well as on MOVPE-grown GaN buffer layers. HVPE growth on MOVPE GaN/AIN buffer layers results in lower defect densities as determined by x-ray than growth directly on sapphire. HVPE GaN films grown directly on sapphire exhibit strong near-edge photoluminescence, a pronounced lack of deep level-based luminescence, and x-ray FWHM values of 16 arcsec by an x-ray θ-2θ scan. The crystallinity of GaN films on sapphire is dominated by the presence of rotational misorientation domains, as measured by x-ray ω-scan diffractometry, which tend to decrease with increasing thickness or with the use of a homoepitaxial MOVPE buffer layer. The effect of increasing film thickness on the defect density of the epilayer was studied. In contrast, the HVPE growth of nitride films directly on silicon is complicated by mechanisms involving the formation of silicon nitrides and oxides at the initial growth front.

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Group IV Nanocrystals for Silicon Photovoltaics

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MRS Online Proceedings Library 2011年第1期1305卷 1-6页

作者： X. Liu S. Saini M. Vanhoutte J. Bakalis W. Yau A. Eshed L. C. Kimerling N. Pervez I. Kymissis C. W. Wong Dept. of Physics CUNY-Graduate Center New York United States Dept. of Physics CUNY-Queens College Flushing United States Dept. of Materials Science and Engineering Massachusetts Institute of Technology Cambridge United States Depts. of Electrical Engineering & Mechanical Engineering Columbia University New York United States

Silicon nanocrystals (nc-Si), have been shown to act as opto-electronic centers enabling light emission by carrier recombination, when precipitated in a silicon nitride (Si3N4) host. In this work, nc-Si and Germanium nanocrystals (nc-Ge) are studied in sputtered films of Si3N4 and SiGeN for application as tandem cell layers in a Si solar cell. The samples are annealed in a nitrogen gas and forming gas ambient, from 500 ºC to 900 ºC, to investigate the influence of temperature on photoluminescence and photoconductivity.

关键词： photovoltaic photoconductivity sputtering

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Beam Induced Lateral Epitaxy: a new way to Lateral Growth in Molecular Beam Epitaxy

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MRS Online Proceedings Library (OPL) 2011年第1期799卷 Z2.4-Z2.4页

作者： Shigeya Naritsuka Koji Saitoh Takashi Suzuki Takahiro Maruyama Meijo University Dept. of Materials Science and Engineering Nagoya 468–8502 Japan Meijo University 21st century COE program “NANO FACTORY”

We developed a new technique of epitaxial lateral growth without using oxide masks called beam induced lateral epitaxy (BILE). In this technique, molecular beams are directed at a nearly glancing angle with respect to a substrate that has pre-fabricated truncated ridges. By using BILE we grew GaAs laterally from the side of ridges on a GaAs substrate. The growth behavior of BILE strongly depended on both incident angle of the Ga beam and the crystal orientation of the truncated ridges. The formation of facets on the lateral growth front controlled the grown shape of the layers. By using a (111) B substrate with BILE, we grew a smooth, flat (111) B facet on the top of the layer.

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Single Asperity Plowing of Metallic and Polymeric Surfaces in an Atomic Force Microscope: An Overview of Recent Developments

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MRS Online Proceedings Library 2011年第1期522卷 391-397页

作者： S. R. Schmid L. G. Hector J. Elings H. Hampel H. Piehler Aerospace and Mechanical Engineering Dept. University of Notre Dame Notre Dame USA Surface Science Division Alcoa Technical Center Alcoa Center USA Digital Equipment Corp. Santa Barabara USA Materials Science and Engineering Dept. Carnegie Mellon University Pittsburgh USA

Previous experimental and theoretical work in plowing phenomena have primarily focused on the effects of many asperities and hence wear phenomena due to a single asperity have not been adequately investigated. In response to this apparaent lack of information around single asperity plowing effects, two of the authors [1] developed an experimental technique wherein the plowing motion of a pyramidal diamond indentor affixed to a stainless steel cantilever is controlled by the piezoelectric transducers of an atomic force microscope and appropriate software macros. Using the mathematical model of Azarkhin and Richmond [2], they were able to estimate the friction stress developed between the substrate and the indentor as well as the material flow stress for selected aluminum alloys. In particular, the measured ridge heights gave an estimate of friction factor for a particular plow track, and the measured normal and plowing forces lead to an estimate of flow strength. The plow track morphologies were found to depend upon material hardness and specific alloying agents in the material, with the softer materials exhibiting oscillatory ridges due to the development of a built-up edge of the indentor, and the harder materials exhibiting detached ridges due to their reduced fracture toughness [3]. The purpose of the present article is to present an overview of recent developments in single asperity plowing of selected metal surfaces in an atomic force microscope. We shall discuss results from dry plowing experiments as well as plowing experiments in the presence of selected boundary additives. Corresponding theoretical modeling developments will also be discussed as well as the roll of indentation size effect in single asperity plowing. We shall also present results of plowing experiments on HMWPE which is used in orthopaedic prostheses. Finally, some discussion about ongoing work will be presented.

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Single molecule studies of unstructured protein function and dynamics

Single molecule studies of unstructured protein function and...

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Frontiers in Optics, FiO 2011

作者： Nath, Abhinav O'Hern, Corey Miranker, Andrew D. Rhoades, Elizabeth Dept. of Molecular Biophysics and Biochemistry Yale University PO Box 208114 New Haven CT 06520-8114 United States Dept. of Mechanical Engineering and Materials Science Yale University PO Box 208286 New Haven CT 06520-8286 United States Dept. of Physics Yale University PO Box 208120 New Haven CT 06520-8120 United States

Unstructured proteins are biologically important, but challenging to characterize by traditional biophysical methods. We describe how single-molecule fluorescence can probe the conformations of disease-related unstruc... 详细信息

ISBN: (纸本)9781557529176

关键词： Proteins

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Potential Bone Replacement materials Prepared by Two Methods

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MRS Online Proceedings Library 2011年第1期1418卷 177-188页

作者： Lee, Steve Porter, Michael Wasko, Scott Lau, Grace Chen, Po-Yu Novitskaya, Ekaterina E. Tomsia, Antoni P. Almutairi, Adah Meyers, Marc A. McKittrick, Joanna Materials Science and Engineering Program University of California San Diego La Jolla USA Skaggs School of Pharmacy University of California San Diego La Jolla USA Lawrence Berkeley National Laboratory Berkeley USA Department of Materials Science and Engineering National Tsing Hua University Hsinchu Taiwan Republic of China Dept. of Mechanical and Aerospace Engineering University of California San Diego La Jolla USA

Natural and synthetic hydroxyapatite (HA) scaffolds for potential load-bearing bone implants were fabricated by two methods. The natural scaffolds were formed by heating bovine cancellous bone at 1325°C, which removed the organic and sintered the HA. The synthetic scaffolds were prepared by freeze-casting HA powders, using different solid loadings (20–35 vol.%) and cooling rates (1–10°C/min). Both types of scaffolds were infiltrated with polymethylmethacrylate (PMMA). The porosity, pore size, and compressive mechanical properties of the natural and synthetic scaffolds were investigated and compared to that of natural cortical and cancellous bone. Prior to infiltration, the sintered cancellous scaffolds exhibited pore sizes of 100–300 μm, a strength of 0.4–9.7 MPa, and a Young’s modulus of 0.1–1.2 GPa. The freeze-casted scaffolds had pore sizes of 10–50 μm, strengths of 0.7–95.1 MPa, and Young’s moduli of 0.1–19.2 GPa. When infiltrated with PMMA, the cancellous bone- PMMA composite showed a strength of 55 MPa and a Young’s modulus of 4.5 GPa. Preliminary data for the synthetic HA-PMMA composite showed a strength of 42 MPa and a modulus of 0.8 GPa.

关键词： bone composite ceramic

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Halide Vapor Phase Epitaxy of Gallium Nitride Films on Sapphire and Silicon Substrates

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MRS Online Proceedings Library 2011年第1期395卷 243-248页

作者： N.R. Perkins M.N. Horton Z.Z. Bandic T.C. McGill T.F. Kuech University of Wisconsin Materials Science Program Madison USA Department of Applied Physics California Institute of Technology Pasadena USA Dept. of Chemical Engineering University of Wisconsin Madison USA

A major limitation of the current technology for GaN epitaxy is the availability of suitable substrates matched in both lattice constant and thermal expansion coefficient. One alternative for the development of GaN substrates rests in the application of halide vapor phase epitaxy (HVPE) to produce GaN films at high growth rates. In this paper, we describe the growth of thick GaN films via the HVPE technique on (0001) sapphire and (111) Si substrates. At a temperature of 1030°C, films are grown at rates between 70 and 90 μm/hr, yielding total thicknesses exceeding 200 μm on sapphire. DCXRD measurements of GaN/sapphire indicate FWHM values less than 220 arcsec on 180 μm thick films. Room temperature PL measurements of GaN/sapphire indicate strong emission at 3.41 eV, with a FWHM value of 65 meV. Moreover, no detectable deep level emission was found in room temperature PL measurement. Under optimized conditions, films are morphologically smooth and optically clear. The GaN morphology appears to be a strong function of the initial nucleation conditions, which in turn are strongly affected by the partial pressure of GaCl. HVPE growth on (111) Si substrates is accomplished using an AlN MOVPE buffer layer.

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Nanothick Layer Transfer of Hydrogen-Implanted Wafer Using Polysilicon Sacrificial Layer

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MRS Online Proceedings Library 2011年第1期921卷 1-6页

作者： C. H. Huang C. L. Chang Y. Y. Yang T. Suryasindhu W. C. Liao Y. H. Su P. W. Li C. Y. Liu C. S. Lai J. H. Ting C. S. Chu C. S Lee T. H. Lee Dept. of Mechanical Engineering National Central University Chung-Li Taiwan Dept. of Electrical Engineering National Central University Chung-Li Taiwan Dept. of Chemical and Materials Engineering National Central University Chung-Li Taiwan Department and Graduate Institute of Electrical Engineering Chang Gung University Kwei-Shan Taiwan National Nano Device Laboratories Hsinchu Taiwan United SOI Corporation Berkeley USA Dept. of Physics National Central University Chungli Taiwan Inst. of Materials Science and Engineering National Central University Chung-Li Taiwan

A fabrication method of 2-D nanostructure materials applied for forming nanothick SOI materials without using post-thinning processes is presented in this paper. The thickness of SOI layer is precisely controlled by a polysilicon layer as a sacrificial layer in the implantation step to acquire a desirable implant dept.. Polysilicon layer was initially deposited on the thermal oxidized surface of silicon wafer prior to the ion implantation step with 4×1016 /cm−2, 160KeV, H2+ ions. The as-implanted wafer was contained a hydrogen-rich buried layer which dept. from the top surface is less than 100 nm. Before this as-implanted wafer being bonded with a handle wafer, the polysilicon layer was removed by a wet etching method. A nanothick silicon layer was then successfully transferred onto a handle wafer under 10-minute microwave irradiation after the bonding step. The thickness of the final transferred silicon layer was 100 nm measured by transmission electron microscopy (TEM).

关键词： nanostructure nanoscale ion-implantation

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