Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
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      28 March 1997, Volume 13 Issue 2 Previous Issue    Next Issue
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    Mechanical Properties of Simple s-p Metals, and Defect Energies from Electron Theory and from Interatomic Force Laws
    N.H.March(Oxford University, Oxford, U.K.)
    J. Mater. Sci. Technol., 1997, 13 (2): 81-85. 
    Abstract   HTML   PDF (576KB)
    The cleavage force F(z) needed to separate parallel atomic planes by a distance z is first discussed for simple s-p metals using density functional theory.For the s-p nearly free-electron metals the linearized Thomas-Fermi equation is solved self-consistently in the cases of (a) semi-infinite planes of jellium (i.e. smeared uniform positive ions) and (b) a semi-infinite cylinder of finite radius, cleaved by a plane perpendicular to its axis. In (a), the elastic region has the form F(z)=Az ∝ Zrs-11/2, where rs is the mean interelectronic distance in the jellium model. Size effects are then considered, with possible relevance to atomic force microscopy.Defect energies are treated, using both electron theory and pair force laws.
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    Synthesis and Characterization of Nanocrystalline Ni-Ti and Ni-Cr Powders by Mechanical Alloying
    Shenqi CHEN; Yanchun ZHOU;Yiyi LI (Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)Shouhua HE(Chinese Academy of Science, Beijing 100864, China)
    J. Mater. Sci. Technol., 1997, 13 (2): 86-90. 
    Abstract   HTML   PDF (2084KB)
    Nanocrystalline powders in the Ni-Ti and Ni-Cr systems were prepared by mechanical alloying (MA) of elemental crystalline powders in an inert atmosphere. The microstructure of the mechanically alloyed powders were characterized by XRD and TEM. The ball-milling process results in a drastic decrease of the crystallite size to the nanometer scale. X-ray diffraction analysis reveals that in the Ni-Cr system, no diffraction peaks from NiCr compound were observed even after 20 h of ball milling; while the lattice parameter of Ni increased with the milling time. In the Ni-Ti system, amorphous alloy was formed. Crystalline intermetallic compounds were obtained by post heat treatment of the amorphous alloy.The crystallization temperature of the amorphous NiTi alloy was obtained be DSC measurement.
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    Characteristics of In_(0.52)Al_(0.48)As Grown on InP(100) Substrates by Molecular Beam Epitaxy: Growth Optimisation and Effects of Si Doping
    S.F.Yoon(School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyng Avenue,Singapore 639798, Rep. of Singapore)
    J. Mater. Sci. Technol., 1997, 13 (2): 91-98. 
    Abstract   HTML   PDF (903KB)
    Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at a wide range of substrate tempreatures (470~550℃) and at different Si doping levels has been carried out. Low temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) analyses shaw a strong dependence of the PL and XRD linewidths, XRD intensity ratio (Lepi/Isub), and lattice-mismatch on the substrate temperature. The X-ray diffraction peaks of samples grown at law temperatures show a composition of smaller peaks, indicating the presence of disorder due to alloy clustering. Raman scattering measurements of the same samples show an additional higher energy mode at 273 cm-1 in addition to the InAs-like and AlAs-like longitudinal-optic (LO) phonon modes. Samples doped with Si show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. Supported be observations of a reduction in both the AlAs-like and InAs-like LO phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased, the PL intensity also shows in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.
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    Wear-resisting Oxide Films for 900℃
    M.B.Peterson(Wear Sciences Corporation, Arnold, Maryland, USA)Shizhuo LI(Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)S.F.Murray(Rensselaer Polytechnic Institute, Thoy, New York, USA)
    J. Mater. Sci. Technol., 1997, 13 (2): 99-106. 
    Abstract   HTML   PDF (913KB)
    A study was conducted to develop low-friction, wear-resistant surfaces on high temperature alloys for the temperature range from 26℃ to 900℃. The approach investigated consists of modifying the naturally occurring oxide film in order to improve its tribological properties. Improvement is needed at low temperatures where the oxide film, previously formed at high temperature, spalls due to stresses induced by sliding. Experiments with Ti, W and Ta additions show a beneficial effect when added to Ni and Ni-base alloys. Low friction can be maintained down to 100℃ from 900℃. For unalloyed Ni friction and surface damage increases at 400℃ to 500℃. Two new alloys were perpared based on the beneficial results of binary alloys and ZrO2 diffusion in Ni.Low friction at temperature above 500℃ and reasonable values (0.32~0.42) at low temperature are obtained.
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    Study and Application of Mold Filling Simulation of Shaped Castings
    Baicheng LIU;Wei QIU; Houfa SHEN; Zhiqiang GAO (Dept. of Mechanical Engineering, Tsinghua University Beijing 100084, China)
    J. Mater. Sci. Technol., 1997, 13 (2): 107-112. 
    Abstract   HTML   PDF (2137KB)
    In this paper, an algorithm for simulating fluid flow and heat transfer for mold filling of shaped castings is presented. The main features of the algorithm include: 1) a simple but practical technique based on VOF method to determine free surface, 2) an explicit scheme of enthalpy to solve the energy equation more efficiently, and 3) an effective treatment to modify the flux deviation due to pressure iteration. In order to verify these methods, well controlled experiments have been repeatedly done with both water analog and gray iron pouring experiments to record the flow patterns and temperature variations. The calculated results are in accordance with the experimental ones. For the applications, the simulated initial temperature distribution right after mold filling was used to analyse subsequent solidification and to predict shrinkage defects.Actual castings were poured and tested in a foundry plant. The reuslts show that the defects predication with considering fluid flow effects is more precise than that without considering the effects.
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    Synthesis and Properties of Cerium Oxide Nanometer Powders by Pyrolysis of Amorphous Citrate
    Xiangting DONG (Dept. of Materials and Chemical Engineering, Changchun Institute of Optics and Fine Mechanics,Changchun 130022, China)Guangyan HONG, Decai YU; Dashu YU(Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022
    J. Mater. Sci. Technol., 1997, 13 (2): 113-116. 
    Abstract   HTML   PDF (1036KB)
    CeO2 nanometer powders of different sizes were prepared at low temperature by pyrolysis of amorphous citrate. XRD patterns show that CeO2 is cubic in structure, space group Oh5-FM3M·TEM indicates that the prepared CeO2 is spherical in shape, and the particle size distribution is in narrow range. It was found that calcination temperature is a more important factor affecting the crystallite size of CeO2 than calcining time, the smaller the particle. the bigger the crystallattice distortion, the worse the crystal growth. Solubility test of CeO2 in nitric acid reveals that the surface activity of CeO2 decreases with the increasing particle sizes. IR spectra analysis shows that the absorption of Ce-O bond is shifted to higher energy with the decrease of CeO2 particle sizes.
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    Application of the Embedded-atom Method to Liquid Binary Cu-Ni Alloys
    Hongbo LIU; Kuiying CHEN ; Zhuangqi HU (State Key Lab. of RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)Geying AN(School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
    J. Mater. Sci. Technol., 1997, 13 (2): 117-122. 
    Abstract   HTML   PDF (634KB)
    A simple analytic embedded-atom model of monoatoms that includes more than nearest neighbours has been extended to study properties of binary liquid Cu-Ni alloys, here the two-body potential between different species of atoms is taken as a function of the two-body potential for the pure metals with a unique form which yields alloy models with the same invariance to electron density transformations as monoatomic models. Faber-Ziman structure factors have been computed by molecular dynamics simulation on the base of this model. The results are in good agreement with experimental data given by Waseda, thus supporting the overall validity of the approach, especially for cross potential of Cu-Ni pair. Further, a detailed description of structure of binary liquid Cu-Ni alloys with different compositions have been performed using pair analysis and bond orientational order method etc., and then the chemical short range order has also been examined to reveal the structural characterization.
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    High Resolution Electron Microscopy Observations of Structural Changes in Iron Nitride Films Annealed in Vacuum
    Shengkai GONG ; Huibin XU (Dept. of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China)
    J. Mater. Sci. Technol., 1997, 13 (2): 123-126. 
    Abstract   HTML   PDF (3920KB)
    Iron-nitride films were prepared by reactive sputtering, and the effect of annealing treatment on the structures was investigated by means of in-situ electron microscopy and high resolution electron microscopy (HREM). As-deposited films were observed to be a mixed structure of a few ultrafine ε-Fe2-3N particles existing in the amorphous matrix. lt was found that the structurerelaxation in the amorphous occurred at 473 K, and the ultrafine grains began to grow at the higher annealing temperatures. The transition of the amorphous to ε-Fe2-3N was almost completed at 673 K. It is considered that the formation of the ideal ε-Fe3N is originated from the ordering of the nitrogen atoms during the annealing in vacuum. On the other hand, γ'-phase (Fe4N) was seen to precipitation of ε-phase at 723 K. Two possible modes are proposed in the precipitation of γ'-phase, depending on the heating rate and crystallographic orientation relationships. i.e. [121]ε [001]γ, (210)ε(110)γ and [100]ε[110]γ, (001)ε(111)γ. In addition,α-Fe particles were observed to form from the γ'-phase at high temperatures. We assumed that these structural changes are due to the diffusion of nitrogen and iron atoms during the annealing,except for the case of the precipitation of the γ'-phase as depicted above. The results obtained in this work are in a good agreement with the assumption.
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    Pack Aluminizing of Copper
    M.E.Abd El-Azim ; H.M.Soliman (Metallurgy Dept., Atomic Energy Authority Cairo, Egypt)
    J. Mater. Sci. Technol., 1997, 13 (2): 127-132. 
    Abstract   HTML   PDF (3172KB)
    Aluminizing of Cu by a pack cementation process was performed to improve its surface properties.The effect of variation of pack aluminizing temperature from 800 to 900℃ and aluminizing time from 1 to 6 h on the microstructure and the thickness of the aluminide coating of Cu was investigated. Pack aluminizing of Cu significantly improved the microhardness and the oxidation resistance. The microhardness was increased about seven times and the oxidation resistance,after 96 h exposure in air at 900℃, was extremely increased ten times by aluminizing Cu at 900℃ for 3 h.
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    A Continuum Model for Heavy-electron Metal
    Wuming LIU (Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100080, China)Zhu YU (Dept. of Physics, Yunnan Normal University, Kunming 650092, China)Fucho PU(Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China)
    J. Mater. Sci. Technol., 1997, 13 (2): 133-136. 
    Abstract   HTML   PDF (281KB)
    The exact eigenstates of the Hamiltonian of a continuum model for heavy-electron metal are constructed by using the Bethe ansatz. The Bethe ansatz equations are obtained from the periodic boundary conditions. The results show that this system is also completely integrable.
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    Effects of the Composition of Electrodeposited Fe-Ni-P Alloy on the Thermostability and Magnetic Properties
    Chenghui GAO ; Baiyang ZHOU (Institute for Materials Research, Fuzhou University, Fuzhou 350002, China)(Manuscript received February 22, 1996, in revised form June 3, 1996)
    J. Mater. Sci. Technol., 1997, 13 (2): 137-140. 
    Abstract   HTML   PDF (408KB)
    The magnetic properties, structure defects of electrodeposited Fe-Ni-P alloys with various compositions and the thermostability at amorphous state have been studied by DSC, positron annihilation and electronic integrating instrument methods. The results show that the thermostability of amorphous Fe-Ni-P alloys increases with Fe content. Emergence and recrystallization of stable phases defer as the P content of the coating increases. The minimum Hc, Br and Ph occur at 9.4 P (wt pct) content. Maximum Hc, Br and Ph occur at the weight ratio of Fe to Ni equaling to 1/9.
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    A Near-bulk Quasicrystal Alloy Formed in Zn-Mg-Y System
    Yali TANG; Ningfu SHEN ; Xiaofang LIU(Research Center for Materials, ZhengZhou University of Technology, Zhengzhou 450002, China)Zhiping LUO(Institute of Aeronautical Materials, Beijng 100095, China)Baicheng LIU(Tsinghua University, Beijing 100084, China)
    J. Mater. Sci. Technol., 1997, 13 (2): 141-144. 
    Abstract   HTML   PDF (1843KB)
    Zn-Mg-Y and Mg-Zn-Y-Zr ingots with different chemical compositions were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The icosahedral phases were found in all alloys studied in present work under the as-cast conditions. There are nearly all quasicrystal phases with some MgZn2 Laves phase in a Zn-28.31Mg-13.80Y alloy (wt pct).After annealing at 400℃ for 8 h, the quasicrystal phases transformed to an fcc "W" phase in an Mg-5.57Zn-1.08Y-0.60Zr alloy (wt pct).
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    X-ray Powder Diffraction Pattern of Bi_4(SiO_4)_3
    Hongchao LIU ; Changlin KUO (Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China)
    J. Mater. Sci. Technol., 1997, 13 (2): 145-148. 
    Abstract   HTML   PDF (395KB)
    In cooperation with figure-of-merits the Rietveld analysis can appraise both angular and intensity data of powder diffraction. In this work, X-ray diffraction pattern of Bi4(SiO4)3 was redetermined with intensity figure-of-merits, which qualify agreement between observed and calculated relative intensities. F30 is 158.90 (0.0059, 32), intensity figure of merit Rint is 8.7, I20(17), 8.0. The values of figure-of-merits show that the data of JCPDS cards are distorted. Both the experimental and calculated peak positions and heights are listed in detail.
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    Characteristics of Amorphous Mn_3AlC Phases Formed by Mechanical Milling
    Fuxing YIN ; Nanju GU (Hebei Institute of Technology, Tianin 300132, China)T.Shigematsu ; N.Nakanishi(Faculty of Science, Konan University Kobe 658, Japan)Y.Osawa ; A.Sato(National Research Institute of Metals, Tsukuba 305, Japan)
    J. Mater. Sci. Technol., 1997, 13 (2): 149-153. 
    Abstract   HTML   PDF (498KB)
    Amorphization of Mn carbides by rapid quenching method has been proved to be unsuccessful.By mechanical milling in the present work, amorphous phases have been formed in the perovskitetype Mn3AlC compound. The transformation process from crystalline to amorphous phase was found to be milling time controlled, and 10 h is a critical period for the macroscopically single amorphous phase to form. It has been clarified that the redistribution of C atoms is an instinctive factor for amorphous phase to nucleate, and the atomic configuration in the amorphous phase is changed much in longer milling that different crystallizing behaviours have been caused. With X-ray diffraction and differential scanning calorimetry (DSC) results, an atomic configuration transition model is considered for the structures of the amorphous phases changed during milling.
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    Influence of Experimental Parameters on Reactive Magnetron Sputtering CN_x Thin Films
    Weitao ZHENG ; Tao DING (Dept. of Materials Science, Jilin University, Changchun 130023, China)I.Ivanov ; J.-E Sundgren (Dept. of Physics, Linkoping University, S-581 83 Linkoping, Sweden)
    J. Mater. Sci. Technol., 1997, 13 (2): 154-156. 
    Abstract   HTML   PDF (289KB)
    Carbon nitride thin films were deposited on Si(001) using unbalanced magnetron sputtering at different experimental parameters. The effects of nitrogen partial pressure, substrate temperature and substrate bias on the deposition rate and nitrogen content are discussed.
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    Synthesis and Properties of Laβ-Al_2O_3
    Congjin JIN ; Yanruo HONG (State Support Lab. on Solid Electrolytes and Testing Techniques, University of Science & Technology Beijing,Beijing 100083, China)
    J. Mater. Sci. Technol., 1997, 13 (2): 157-160. 
    Abstract   HTML   PDF (420KB)
    Laβ-Al2O3 solid electrolytes were synthesized directly and their conductivities were measured in terms of ac impedance spectroscopy.The magnitude of conductivities is 10-6 to 10-2 S·cm-1.Based on these data, the dependence of the conductivity of Laβ-Al2O3 upon the temperature and the dopant concentration in the electrolytes was studied, and the activation energy for conduction was calculated, which is 0.89 eV to 1.02 eV from 450℃ to 1000℃. The ion transference numbers were also determined.
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ISSN: 1005-0302
CN: 21-1315/TG
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