Y.J. Ge
,
G.Q. Zhang
,
Y.M. Liu
金属学报(英文版)
The surface modification of nanometer carbon material has been studied by usingan Induced Dielectric Barrier Discharge Plasma device (IDBD). The experimentalresults show that with different work gases and different discharge conditions, thesurface behaviors of carbon black can be changed according to needs, including theuse of different functional groups and the change of the surface roughness of carbonparticles etc., which increased the grinding and dispersion abilities in binder.
关键词:
surface modification
,
null
,
null
,
null
杨凌霄
,
郭喜平
,
乔彦强
,
潘若冰
金属学报
doi:10.3724/SP.J.1037.2013.00517
为提高Nb-Ti-Si基超高温合金的高温抗氧化性能,采用Si-Ge-Y共渗工艺在其表面制备了Ge-Y改性的硅化物渗层.利用XRD,SEM和EDS分析了渗层的结构和相组成,并对其组织形成机理进行了讨论.结果表明:所制备的渗层具有明显的分层结构,由外至内依次为(Nb,X)(Si,Ge)2 (X代表Ti,Cr和Hf)外层和(Ti,Nb)5(Si,Ge)4内层；Ge在渗层中的含量由外向内逐渐增加.与Y改性硅化物渗层相比,Ge-Y改性硅化物渗层的组织并未发生显著改变,但Ge的添加会在一定程度上减少Si在共渗层表面的吸附和沉积,对渗层的生长有明显的抑制作用.保温不同时间(0-8 h)所制备的渗层具有相似的结构,渗层的生长动力学曲线符合抛物线规律.
关键词:
Nb-Ti-Si基超高温合金
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扩散渗
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硅化物渗层
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Ge-Y改性
,
组织形成
张铁邦
,
付浩
,
陈云贵
,
涂铭旌
,
唐永柏
稀有金属材料与工程
以商业纯Gd为原料,采用非自耗电弧炉氩气保护下熔炼了Gd5Si2Ge2-xSnx(x=0.2,0.5,1)和Gd5Si2-yGe2Sny(y=0.1,0.2,0.5)系列合金,研究Sn合金化对Gd5Si2Ge2晶体结构和磁热性能的影响.粉末XRD结果表明:Sn代Ge样品具有正交Gd5Si4型结构;Sn少量代Si(y=0.1,0.2)的样品具有单斜Gd5Si2Ge2型结构;Gd5Si1.5Ge2Sn0.5则为单斜和正交的混合结构.用超导量子磁强计(SQUID)测定了样品的M-T和不同温度的M-H曲线,结果表明:Gd5Si2Ge2-xSnx(x=0.2,0.5,1)不具有巨磁热效应;Gd5Si1 9Ge2Sn01合金的最大磁熵变达15.3 J/kg·K(0 T～5 T),具有巨磁热效应.
关键词:
Gd5Si2Ge2
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磁热效应
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磁致冷材料
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晶体结构
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磁熵变
Y.G. Cao
,
X.Y. Sun
金属学报(英文版)
J-integral and crack opening displacement δ(COD) were important parameters for characterization of fractures in engineering materials. The relationship between J-integral and COD has been investigated for a long time and was enerally represented as J = m σyδ, where σy is the yield strength and m is a function of specimen geometry and material properties. To determine the value of m, extensive studies and experiments have been performed. The method that used the fracture-surface topography analysis (FRASTA) for determining J-integral from fracture surfaces of materials was introduced. On the basis of the relationship between COD and fracture surface average profile, the relationship between J-integral and COD was deduced and compared with the generally used equation. The method was experimentally confirmed to be able to provide a new way to determine the relationship between J-integral and COD.
关键词:
FRASTA
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null
,
null
Journal of Applied Physics
Magnetic and magnetocaloric effects of (Mn1-xFex)(5)Ge-3 compounds are studied systematically. The maximum of magnetic entropy changes of 8.01 J/kg K under an external field change of 5 T is obtained for (Mn0.9Fe0.1)(5)Ge-3, which is the largest value in Mn5Ge3-based solid solutions. Moreover, the Fe substitution increases the refrigeration capacity (RC) value greatly. The largest RC value of 237 J/kg in (Mn0.8Fe0.2)(5)Ge-3 even compares favorably to that of many well-known magnetic refrigeration materials. Thus the Fe-containing (Mn1-xFex)(5)Ge-3 compounds are much-improved magnetic refrigerants for the application of room-temperature magnetic refrigeration. The increase of the RC value is probably resulted from the formation of magnetic nanostructure. (c) 2007 American Institute of Physics.
关键词:
room-temperature;entropy change;transition;mn5ge3;iron
陈篪
,
姚蘅
,
邓枝生
,
庄韬
,
邓其源
金属学报
<正> 一、引言 J积分和裂纹顶端张开位移δ往弹塑性断裂力学里居很重要的地位。人们假定J=J_c或δ=δ_c是裂纹开始扩展的判据,并试图在J_c与δ_c间互相换算。因此,研究J与δ之间的关系是个有价值的课题。 目前,常被引用的关系呈 J=βσ_yδ (1)的形式。例如:应用无硬化的塑性区窄条模型得到β=1。J=σ_yδ经常被用来做计算。但是,无硬化不符合金属的实际。我们的实验数据表明即使对于σ_(0.2)≈100公斤/毫米~2级高韧性钢(J_(Ⅰc)≈12公斤/毫米)J=σ_yδ所给出的δ已经偏大,对于中、低强度钢
关键词:
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
Physical Review B
The Hamiltonian for a four-sublattice Heisenberg ferrimagnet or ferromagnet with different exchange constants (J(ab) = J(cd) not equal J(bc) = J(da)) was established. An extended Bogoliubov transformation was developed by solving an equation group, consisting of 20 equations and 20 unknowns. The procedure for solving the equation group was carried out by introducing a simple way of reducing the numbers of the equations and the unknowns. The spin-wave spectra in the present system have been determined by performing the standard Holstein-Primakoff transformation and the Bogoliubov one. It has been found that the spin-wave spectra of the present system depend on the exchange constants and that the degeneracy of the spin-wave spectra remains. The results for a special case (J(ab) = J(bc)) i.e., an antiferromagnet are discussed briefly. The spin-wave spectra of the four-sublattice Heisenberg antiferromagnet are found to be degenerative also and they are linear in k for small k.
关键词:
model
廖凌宏
,
周志文
,
李成
,
陈松岩
,
赖虹凯
,
余金中
,
王启明
材料科学与工程学报
由于Si/SiGe异质结构的带阶差主要发生在价带,为实现高效率的发光,本文从理论上设计了在硅基Si1-x Gex虚衬底上外延应变补偿的Si/S1-y Ge,(y>x)量子阱的能带结构,将量子阱对电子的限制势垒提高到100meV以上.在实验上,采用300℃生长的Ge量子点插入层,制备出薄的SiGe驰豫缓冲层(虚衬底),表面Ge组份达到0.25,表面粗糙度小于2nm,驰豫度接近100%.在我们制备的SiGe缓冲层上外延了应变补偿SiGe/Si多量子阱结构,并初步研究了其发光特性.
关键词:
低维无机非金属材料
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量子阱
,
光致发光谱
,
弛豫缓冲层
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
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null
,
null
