材料期刊网

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

Theoretical elastic stiffness, structural stability and thermal conductivity of La(2)T(2)O(7) (T = Ge, Ti, Sn, Zr, Hf) pyrochlore

Acta Materialia

In order to achieve better understanding of the structural/property relationships of La(2)T(2)O(7) (T = Ge, Ti, Sn, Zr, Hf) pyrochlore, first-principles calculations were conducted to investigate the bonding characteristics, elastic stiffness, structural stability and minimum thermal conductivity. The results show that the relatively weak La-O bonds play a predominant role in determining the structural stability, mechanical and thermal properties of these compounds. In addition, the elastic and thermal properties are influenced when the T atom changes from Ge to Hf. When the bonding strength is enhanced by applying hydrostatic pressure, apart from c(11), c(12), and B, which normally increase at high pressures, it is found that the shear elastic moduli, c(44) and G, which relate to the shear deformation resistance, abnormally remain almost constant. The underlying mechanism may help to explain the damage tolerance of pyrochlore compounds. After comprehensive consideration of the elastic anisotropy, a modified David Clarke-type equation is used to calculate the minimum thermal conductivity of the studied pyrochlore materials, which display an extraordinary low thermal conductivity. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词: Non-binary oxides;Mechanical properties;Thermal conductivity;Density;functional theory;Local density approximations (LDA);oxide pyrochlores;a(2)b(2)o(7);simulation;disorder

B元素的添加对Gd5.1Si2Ge2合金磁热性能的影响

张岸 , 侯雪玲 , 张鹏 , 胡星浩 , 徐晖 , 倪健森 , 周邦新 , 赵彤

稀有金属材料与工程

研究了B元素的添加对Gd5.1Si2Ge2合金的晶体结构和磁热效应的影响.XRD表明:对于Gd5 lSi2Ge2-xBx系列合金,少量的B(x=0.01)替代Ge的样品具有单斜Gd5Si2Ge2结构.随着B含量的增加.合金中开始出现正交结构的Gd5Si4相,居里温度也从285 K(x=0.01)提高到303 K(x=0.15),增加幅度为18 K;相应地绝热温变从2.4 K下降到2 K(1.2 T),仍然保持着较大的绝热温变.对于Gd5.1Si2-yGe2By系列合金,少量的B替代Si的样品具有Gd5Si2Ge2型的单斜结构.随着B含量的增加,合金中出现了低温反铁磁性Gd5Ge3相,居里温度和绝热温变呈现下降趋势.

关键词: 室温磁制冷 , Gd5.1Si2Ge2合金 , B合金化 , 晶体结构 , 绝热温变 , 磁热效应

Gd5Si1.975Ge1.975T0.05(T=Ni,Fe,Cr,Mn,Co)合金的结构及磁热效应

张恩耀 , 陈云贵 , 李采临 , 唐永柏 , 谭缙 , 涂铭旌

稀有金属材料与工程

研究了Gd5Si1.975Ge1.975T0.05(T为Ni、Mn、Cr、Co、Fe)合金的结构及磁热效应.XRD结果显示:当T元素的原子序数为偶数时,合金形成了单一的Gd5Si2Ge2单斜结构;而当原子序数为奇数时,则为Gd5Si2Ge2单斜结构和正交结构的混合相.在拥有单一相的合金中均发现了巨磁热效应,然而在具有混合相的合金中由于未能发生一级结构相变而导致了低的磁熵变.此外,Gd5Si1.975Ge1.975Cr0.05合金的磁制冷量达到了112 J/kg,相对于Gd5Si2Ge2合金提高了50%.

关键词: Gd5Si2Ge2合金 , 合金化 , 磁热效应 , 热滞后

S-T-B流型判别方法

孙长征 , 宇波 , 魏进家

工程热物理学报

通过分析气相、液相、管壁之间的关系,将气液混输管道中的流型划分为五种,并总结了各流型的特点及气液相和管壁间的几何关系;在对Baker、Brill、Beggs-Brill、Taitel、段塞特征分析(SCA)等流型判别方法进行分析的基础上,提出了一种综合使用SCA、Taitel和Brill三种方法的流型判别方法 S-T-B法.经算例验证,该方法对气液两相混输的流型判断准确性较高,可以作为气液混输工艺计算过程中确定流型的方法.

关键词: 气液混输 , 流型 , 段塞特征分析法 , S-T-B

B掺杂Si80Ge20合金的快速制备及热电性能

罗文辉 , 李涵 , 郝文 , 胡小龙 , 唐新峰

功能材料

采用电弧熔炼、快速球磨结合放电等离子烧结快速制备了单相Si80Ge20Bx(x=0.5、1、1.5、2)热电材料,对烧结后试样进行了物相结构分析和热电性能表征.结果表明,B的引入导致样品载流子浓度增加,电导率随着B掺量增加而大幅增加,而Seebeck系数反之下降.B的固溶增加试样中点缺陷浓度而导致声子散射增加,热导率下降明显.当x=1时,样品在1000K获得最大ZT值0.78.

关键词: B掺杂SiGe合金 , 电弧熔炼 , 快速球磨 , 放电等离子烧结 , 热电性能

放电等离子烧结制备Si80Ge20B0.6合金及其热电性能

赵然 , 沈丽 , 张忻 , 路清梅 , 郭福

功能材料

采用高能球磨与放电等离子烧结相结合的方法制备出了单相Si80Ge20B0.6合金块体热电材料.在400～900K 温度范围内对其进行了热电性能测试.粉末冶金法制备的合金内的晶界对载流子形成散射,保温时间较长的试样的电导率明显高于保温时间较短的试样.所有试样的热导率处于2.7～4.5W/(mK)范围.保温9min的试样在900K时ZT值最高,达到0.47.

关键词: SiGe合金 , 机械合金化 , 放电等离子烧结 , 热电性能

Theoretical studies of the spin Hamiltonian parameters and local structures for Cs3CoX5 (X = Cl, Br)

Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy

The spin Hamiltonian (SH) parameters (zero-field splitting D and anisotropic g factors g(parallel to) and g(perpendicular to)) and local structures for Cs3COX5 (X = Cl, Br) are theoretically studied from the perturbation formulas of the SH parameters for a 3d(7) ion in tetragonally distorted tetrahedra based on the cluster approach. In these formulas, both the contributions from the crystal-field (CF) mechanism and those from the charge-transfer (CT) mechanism are taken into account. It is found that the [COX4](2-) clusters are slightly elongated and the tetragonal distortion angles Delta theta(=theta-theta(0), where theta(0) approximate to 54.74 degrees is the bonding angle related to the C-4-axis in regular tetrahedra) are about -1.68 degrees and -1.71 degrees for X = Cl and Br, respectively. The calculated SH parameters as well as the effective magnetic moments based on the above angles are in reasonable agreement with the observed values. From the studies, the importance of the contributions to the SH parameters from the CT mechanism increases with increasing the spin-orbit coupling coefficient of the ligand, i.e., Cl- < Br-. The results are compared with those obtained from the conventional crystal-field model in the previous works. (c) 2005 Elsevier B.V. All rights reserved.

关键词: crystal-fields and spin hamiltonians;electron paramagnetic resonance;(EPR);Co2+;Cs3CoX5 (X = Cl, Br);polarized neutron-diffraction;ensemble-representable densities;atomic;screening constants;magnetic-structure factors;superposition model;crystal-structure;optical spectra;ground-states;scf functions;cocl42;ion

P型Si80Ge20B0.6-SiC纳米复合材料的微观结构与热电性能研究

杨小燕 , 吴洁华 , 任都迪 , 张天松 , 陈立东

无机材料学报 doi:10.15541/jim20160060

采用感应熔炼、球磨与放电等离子烧结的方法制备了SiC第二相均匀分布的Si80Ge20B0.6-SiC纳米复合热电材料.系统研究了细化Si80Ge20B0.6晶粒尺寸与复合SiC纳米颗粒对材料热电性能的影响.球磨导致的Si80Ge20B0.6晶粒尺寸的降低显著增加了材料的晶界数量,进而增强了晶界对中长波声子的散射,能够有效降低材料的晶格热导.Si80Ge20B0.6基体中均匀分布的纳米SiC颗粒提供了额外的散射中心和界面,可进一步增强声子散射,降低材料的晶格热导.在纳米结构化与SiC纳米复合的共同作用下,材料在1000 K时热电优值ZT达到了0.62,较基体提高了17％.证明纳米结构化与纳米复合方法能够共同作用于硅锗合金,提高其热电性能.

关键词: 硅锗合金 , SiC纳米颗粒 , 热电材料 , 纳米复合 , 纳米结构

Magnetic properties and magnetocaloric effect of Nd(Mn(1-x)Fe(x))(2)Ge(2) compounds

Journal of Alloys and Compounds

Polycrystalline Nd(Mn(1-x)Fe(x))(2)Ge(2) (0 <= x <= 1) compounds have been prepared by arc-melting. X-ray powder diffraction analysis shows that all samples crystallize in the ThCr(2)Si(2)-type structure with the space group 14/mmm. The substitution of Fe for Mn results in decreases of the lattice constants a, c and the unit-cell volume V. Magnetic properties and magnetocaloric effect of the compounds Nd(Mn(0.9)Fe(0.1))(2)Ge(2) and Nd(Mn(0.8)Fe(0.2))(2)Ge(2) have been studied by magnetic measurements. A spin reorientation transition at about 188 K is observed for Nd(Mn(0.9)Fe(0.1))(2)Ge(2). The Nd(Mn(0.8)Fe(0.2))(2)Ge(2) compound shows more complicated magnetic behavior, which is characterized by four magnetic ordering states below room temperature. The maximum values of the magnetic entropy change are 2.35 and 1.84 J kg(-1) K(-1) for x = 0.1 and 0.2, respectively, under the applied field changing from 0 to 5T. The relative cooling powers of Nd(Mn(0.9)Fe(0.1))(2)Ge(2) and Nd(Mn(0.8)Fe(0.2))(2)Ge(2) are 145.9 and 133.8 J kg(-1) under an applied field change of 5T. (C) 2009 Elsevier B.V. All rights reserved.

关键词: Metals and alloys;Magnetocaloric;X-ray diffraction;room-temperature applications;neutron-diffraction;phase-transitions;crystal-structure;solid-solution;refrigeration;silicides;mn;0-less-than-or-equal-to-x-less-than-or-equal-to-1;mnas1-xsbx