L.H. Han
,
J.T. Niu
,
D.M. Jiang
金属学报(英文版)
The superplasticity of AlNp/6061Al composite, fabricated by powder metallurgy method and hot-rolled after extrusion, was investigated. The AlNp/6061Al composite exhibits an m-value of 0.49 and a maximum elongation of 438% in the strain rates ranging from 10-2-10°s-1 and at temperatures from 823K to 893K. Differential scanning calorimeter was used to ascertain the possibility of any partial melting in the vicinity of optimum superplastic temperature. These results suggested that liquid phase existed where maximum elongation was obtained.
关键词:
superplasticity
,
null
,
null
W. Guo
,
J.T. Niu
,
J.F. Zhai
金属学报(英文版)
Non-interlayer liquid phase dissusion welding (China Patent) and laser welding methods for aluminum matrix composite are mainly described in this paper. In the noninterlayer liquid phase dissusion welding, the key processing parameters affecting the strength of joint is welding temperature. When temperature rises beyond solidus tem perature, the bonded line vanishes. The strength of joint reaches the maximum and becomes constant when welding temperature is close to liquid phase temperature. Ox- ide lm in the interface is no longer detected by SEM in the welded joint. With this kind of technique, particle reinforced aluminum matrix composite Al2O3p/6061Al is welded successfully, and the joint strength is about 80% of the strength of composite (as-casted). In the laser welding, results indicate that because of the huge speci c surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement is restrained intensively at certain laser power and pulsed laser beam. The laser pulse frequency directly affects the reinforcement segregation and the rein- forcement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. The maximum strength of the weld can reach 70% of the strength of the parent.
关键词:
non-interlayer liquid phase dissusion welding
,
null
孙银洁
,
胡胜泊
,
李秀涛
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2010.02.027
利用SEM、TEM、XPS、XRD、Raman和元素分析仪分析了M40J和T300的表面化学、物理及微观结构特征.研究发现:M40J含碳量高于T300纤维,而含氮量低于T300纤维,且表面活性基团比T300纤维低;M40J和T300碳纤维表面具有大量沟槽,前者相对长而浅,后者相对短而深;T300纤维端面皮芯结构明显,而M40J端面结构较均匀;M40J的微晶结构及取向性优于T300碳纤维.
关键词:
M40J碳纤维
,
微观结构
,
化学特征
,
物理特征
谢兰清
,
王彩霞
兵器材料科学与工程
基于重整化平均场理论,在二维空穴掺杂t-t′-J-U模型的框架下,用Gutzwiller平均场近似理论研究高温超导体的基态相图,分析了次近邻跃迁电子(t′)对电子平均双重占据数(d)的影响.发现在掺杂浓度δ≠0的掺杂Gossamer超导态,次近邻跃迁的引入使d的数值在欠掺杂浓度区增大,在过掺杂浓度区显著减少.
关键词:
高温超导体
,
相图
,
电子态
,
电子次近邻跃迁
,
双重占据
王昂
,
公茂琼
,
吴剑峰
工程热物理学报
微微型节流制冷器在微小元件和制冷应用中有广阔的前景.本文通过对搭建一微型压缩机驱动的微型混合工质节流制冷器系统,取得初步结果.该微微型J-T节流制冷器采用3D打印技术,通道特征尺寸为0.1 mm,突破了传统机械加工的极限.通道深宽比达到8:1.初步实验表明,微微型J-T节流制冷器达到了230 K温区.由于采用微型压缩机驱动,系统结构紧凑,可在便携生物储存设备、低温医疗以及电子器件冷却等领域应用并能长期运行.
关键词:
微微型节流制冷器
,
混合工质
,
3D打印
Communications in Theoretical Physics
By using strong-field scheme, the complete d(5) energy matrix with D-2d symmetry has been constructed. Then, by diagonalization of this matrix at normal and various pressures, the whole energy spectrum [including the ground-state zero-field splitting (GSZFS)] and its pressure-induced shift (PS) of ZnTe:Mn2+ have uniformly been calculated. The results are in very good agreement with experimental data. According to the eigenfunctions and PS, the assignments of four absorption bands have been given. By taking into account the effect of different deformations of t(2) and e radial wavefunctions on t(2)(3)((4)A(2))e(2)((3)A(2))(4)A(1) and t(2)(3)(E-2)e(2)((3)A(2))E-4, the position of the third absorption band at normal pressure has been estimated. The tetragonal field is important for GSZFS of ZnTe:Mn2+ and its PS, which supports the existence of tetragonal Jahn-Teller distortion in ZnTe:Mn2+. The physical essentials of typical levels, GSZFS and their PS have been revealed.
关键词:
crystal fields;high pressure;optical properties;energy spectrum;Jahn-Teller effect;covalency effect;ZnTe : Mn2+;ligand-field calculation;theoretical calculations;zn1-xmnxte;ruby;epr
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
