材料期刊网，材料期刊，材料类期刊，材料期刊投稿

基于Eulerian-Eulerian方法, 阐述了简化枝晶状等轴晶、柱状晶以及金属液三相完全混合的凝固模型. 模型考虑了等轴晶的移动及柱状晶对等轴晶的捕获, 跟踪了柱状晶尖端的位置并考虑了等轴晶和柱状晶的相互竞争生长, 因此该模型具备了预测柱状晶向等轴晶转变(CET)的能力; 为了在不过量增加计算量的前提下提高模型的精度, 模型对等轴晶采取了简单的枝晶化处理, 即采用简化方法描述等轴晶包络线内固相分数. 分别模拟了3.25和25 t钢锭的凝固过程, 成功预测了大型钢锭凝固过程所形成的底部锥形负偏析、“类-A型”偏析以及CET等现象. 分析认为长细形状铸锭中出现的顶部负偏析区, 是由于凝固后期所形成的局部小钢锭及等轴晶在其内部的沉积聚集而成.

关键词: 数值模拟 , 宏观偏析 , 钢锭 , 晶粒运动 , CET

LIQUIDUS OF SYSTEM Ag-Cu-Ge

LIU Shuqi , YI Tao , Peking University , Beijing , China

金属学报(英文版)

The diagram of Ag-Cu-Ge system was constructed from the investigation of 13 internal sec- tions by DTA heating as well as cooling curves in an atomsphere of dry N_2 . The phase dia- gram is subdivided into two pseudo-ternary systems shown as Ag-Cu-Cu_3Ge and Ag-Cu_3Ge-Ge. Both systems belong to simple eutectic type. The ternary eutectic points lie in." E_1, Ag(22.0)-Cu(58.8)-Ge(19.2), 632℃ and E_2 , Ag(44.3)-Cu(29.5)-Ge(26.2), 533℃. The three side binary systems were redetermined.

关键词: phase diagram , null , null

Crystal structures of compounds in the pseudobinary system Gd5Ge4-La5Ge4

Journal of Alloys and Compounds

Crystal structures of compounds at ambient temperature in the pseudobinary system Gd5Ge4-La5Ge4 were studied by X-ray powder diffraction (XRD). There exist three single-phase regions in this system. The crystal structure of Gd5Ge4, La5Ge4 and Gd3La2Ge4, which are prototype compounds in three phase regions, respectively, were reported. The Gd5Ge4 and La5Ge4 crystallize in the orthorhombic Sm5Ge4-type structure with space group Pnma. The ternary intermediate compound Gd3La2Ge4, which is determined for the first time, crystallizes in the monoclinic Gd5Si2Ge2-type structure with space group P112(1)/a. The Rietveld powder diffraction profile fitting technique was used for the refinement of crystal structure. The lattice parameters, atomic occupations, interatomic distances of the Gd5Ge4, La5Ge4 and Gd3La2Ge4 compounds were derived. (C) 2003 Elsevier B.V. All rights reserved.

关键词: rare earth compounds;crystal structure;X-ray diffraction;phase-relationships;gd-5(si2ge2);transition;silicon

Thermodynamic Analysis of Ag_3Ge Phase Formation

O.P.Pandey(School of Basic and Applied Sciences , Thapar Institute of Engineering and Technology Patiala-147 001 , India )S.N.Ojha and S.Lele(Dept. of Metallurgical Engineering , Banaras Hindu University , Varanasi-221 005 , India)

材料科学技术（英文）

In the present work a thermodynamic model is presented for the nucleation of metastable Ag3Ge phase from the undercooled melt in Ag-Ge alloy system. It is shown that under kinetically induced favourable condition, nucleation of a single phase compound with an approximate stoichiometry Ag3Ge has greater affinity for nucleation over Ag and Ge based phases requiring diffusion in the liquid.

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THE EVOLUTION OF TECHNOLOGY DEVELOPMENT AT GE CORPORATE R & D

T.B.Cox(GE Corporate Research & Development , Niskayuna , NY 12309 , USA Manuscript received 26 August 1996)

金属学报(英文版)

A brief review of the nearly 100 year history of Corporate Researeh and Development at GE is presented. Observations on the changing nature and relevance of industrial research are discussed. Examples of current technology projects for aircraft engine materials are reviewed. Emphasis of these projects is placed on high performance,low cost and high quality.

关键词: :spray forming , null , null

ELECTRONIC-STRUCTURE AND MAGNETISM OF FE-GE INTERFACES

Journal of Physics-Condensed Matter

The local electronic density of states (LDOS) has been calculated for Fe-Ge(110), Fe-Ge(111) and Fe-Ge(100) interfaces and neighbouring atomic planes using the recursion method. Interface states are found to exist within the mutual gaps of the constituent atoms and strongly depending on the local atomic environments. The most excess LDOSS are found for Fe-Ge(111) interface and the least for Fe-Ge(110). The magnetic moments for Fe atoms are found to decrease when the Fe layer approaches the interface boundary, which is in accord with the experiments. The electron spin polarization parameters evaluated from the LDOS are qualitatively consistent with experimental measurements.

关键词: spin polarization;surface magnetization;recursion method;states;iron;films;ni

Fabrication of uniform Ge-nanocrystals embedded in amorphous SiO(2) films using Ge-ion implantation and neutron irradiation methods

Applied Physics Letters

Uniform Ge-nanocrystals (Ge-ncs) embedded in amorphous SiO(2) film were formed by using (74)Ge(+) ion implantation and neutron transmutation doping (NTD) method. Both experimental and theoretical results indicate that the existence of As dopants transmuted from (74)Ge by NTD tunes the already stabilized (crystallized) system back to a metastable state and then activates the mass transfer processes during the transition form this metastable state back to the stable (crystallized) state, and hence the nanocrystal size uniformity and higher volume density of Ge-ncs. This method has the potential to open a route in the three-dimensional nanofabrication. (C) 2011 American Institute of Physics. [doi:10.1063/1.3553770]

关键词: transmutation-doped gaas;electrical-properties;misfit dislocations;lasers go;silicon;films

Photoluminescence study of Ge nanocrystals irradiated by reactor neutron flux

Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms

Samples of Ge nanocrystals (Ge-ncs) embedded in amorphous SiO2 film were prepared by Ge ion implantation and subsequent primary thermal annealing. These samples were irradiated by neutron flux in a nuclear reactor followed by the second annealing. Irradiation with thermal neutrons leads to doping of nanocrystals with Ga, As and Se impurities due to nuclear transmutation of isotope Ge-70 into Ga-71, isotope 74 Ge into 75 As, isotope 76 Ge into 77 Se, respectively (neutron transmutation doping, NTD). Irradiation with fast neutrons leads to appearance of radiation damages, which are expected to be removed after the second annealing. Photoluminescence (PL) measurements show that PL is quenched after neutron irradiation, and restored after annealing higher than 500 degrees C. The PL spectra of doped Ge-nes samples show more intense exciton radiative luminescence than of undoped Ge-ncs sample, which is related to that the donor and acceptor impurities recombine the nonradiative centers in the interface of Ge-ncs and SiO2 matrix, and enhance the probability of exciton recombination. (c) 2007 Elsevier B.V. All rights reserved.

关键词: Ge nanocrystals;neutron transmutation doping;photoluminescence;Raman;scattering;doped si nanocrystals;electron-spin-resonance;semiconductor;nanocrystals;n-type;implanted sio2-films;silicon nanocrystals;porous;silicon;raman;luminescence;temperature

OPTICAL PROPERTIES OF GeO 2 AND Ge NANOCRYSTALS

Y.H.Zhou 1) , Y.Y.Feng 2) and H.Y.Lu 2) 1)Department of Physics Nanjing Normal University , Nanjing 210097 , China 2)Physics and Ch寁O P T I C A L P R O P E R T I E S O F Ge O2 A N D Ge N A N O C R Y S T A L S Y. H. Zhou1) , Y. Y. Feng2) and H. Y. Lu2)1) Department of Physics Nanjing Normal University , Nanjing 210097 , China2) Physics and Chemical Centralab Nanjing Normal University , Nanjing 210097 , China

金属学报(英文版)

he co m pound m aterial of n m size particles Ge O2 Si O2 w as synthesied through hydrolysis of Si( O C2 H4) and Ge Cl4 . A heat treatm ent w as carried out for the sa m ples at 100 ～1200 ℃in air . Its optical property w as deter mined by U V Vis spectur m . We have found that theabsorption edge of spectru m shifted progressively to longer w avelengths . The quantu m size ef fect of nanocrystals appears because crystals gro w and energy of optical band gap reduces d ueto the influence of te m perature . By the analysis of X ray diffraction w e have observed theprocess in w hich the structure of particles changed fro m disorder into order .

关键词: nano m aterial , null