GaAs基GaSb薄膜的分子束外延生长与发光特性

研究了用分子束外延（MBE）在GaAs衬底上生长GaSb薄膜的工艺。为了减小因晶格失配度较大所引起的位错密度，采用低温GaSb作为缓冲层，有效降低了外延层中的位错密度，提高了晶体质量。通过X射线双晶衍射仪和原子力显微镜测试分析，得到低温GaSb缓冲层的优化生长参数：厚度为20nm，生长速率为1．43μm／h，Ⅴ／Ⅲ束流比为2．0。并在此基础上研究了GaSb薄膜的发光特性：GaSb薄膜的光致发光光谱主要由束缚激子（BE4）和施主-受主对（D-A）辐射复合发光峰组成，在50K时其发光峰强度最强，半峰宽最窄。     

闪锌矿结构AlN、AlP和AlAs的介电和弹性性质的第一性原理研究

采用第一性原理赝势平面波方法对闪锌矿结构AlN、AlP和AlAs的电子结构，介电和弹性性质进行计算，结果表明：基于密度函数扰动理论计算的这些材料的介电和弹性性质与其它第一性原理和分子动力学计算值一致性较好，但与实验值之间有一定的差异：晶格参数的优化、赝势的选取和交换关联项的选择都对计算结果有较大影响。根据计算的弹性常数绘制了这些材料特征平面（101）面的弹性模量图，为这方面材料的力学研究提供参考。     

低温Au-In-Au金属键合及其在VCSELs制作中的应用

研究了Au-In-Au低温金属键合技术,并把它应用到长波长垂直腔面发射激光器(VCSEL)器件结构的制作中.利用该技术不仅有利于提升器件的热学性能,而且有利于提高VCSEL结构中分布Bragg反射腔镜(DBR)的反射率.实验结果表明,InP基外延半腔VCSEL结构成功地在200℃低温下金属键合到Si衬底上,键合强度高,键合质量达到了VCSEL器件工艺制作要求.对键合样品光学特性的分析表明,低温金属键合过程不影响量子阱有源区及DBR的光学性质,这对VCSEL器件结构的制作是有利的.这种低温金属键合技术,有望应用在许多半导体光电器件的制作中.     

NaGd（WO4）2晶体的生长与性能研究

钨酸钆钠是一种新型的激光基质材料。采用提拉法生长出了四方晶系白钨矿结构的钨酸钆钠晶体，分子式为NaGd（WO4）2。通过TG-DTA分析得到晶体的熔点为1253．30℃，从XRD分析得到晶胞参数α=b=0．5248nm，c=1．1257nm。讨论了钨酸钆钠晶体的生长工艺，给出晶体生长的最佳工艺参数为拉速2mm／h，转速为30r／min，冷却速率为15℃／h，最佳的轴向温度梯度为液面上0．7～1℃／mm。测试了钨酸钆钠晶体的Raman光谱，讨论了晶体的振动归属。     

液封直拉半绝缘GaAs中的碳

用高压液封原位合成直拉法生长的半绝缘GaAs单晶是直接离子注入制造场效应晶体管或高速集成电路的理想材料。在单晶生长和器件或电路的制做过程中人们发现，杂质碳在半绝缘GaAs中具有不容忽视的重要地位。它不仅是导致材料呈半绝缘状态的关键杂质，而且岔碳量的多少对晶体质量、器件或电路制做的成败都起着决定性的作用。     

自蔓燃高温合成（SHS）TiC—Al2O3陶瓷

本文采用自蔓燃高温合成（ＳＨＳ）技术结合热压工艺，以ＴｉＯ２粉，Ａｌ粉及石墨粉（Ｃ）为原料制备出了ＴｉＣ－Ａｌ２Ｏ３陶瓷及（ＴｉＣ－Ａｌ２Ｏ３）／Ｎｉ金属陶瓷复合材料，并对其组织结构及性能进行了研究。结果表明，本方法制备的材料性能优于传统方法制备的材料，适于作刀具。     

NiCrBSi-Mo与QSn-Ni/C涂层摩擦副摩擦磨损性能研究*

采用超音速等离子喷涂制备了NiCrBSiMo和QSn-Ni／C涂层，测试了这种摩擦副涂层的常规性能与摩擦磨损性能。结果表明，所获得的涂层孔隙率低，分别为0．82％（NiCrBSi-Mo涂层）、0．76％（QSn-Ni／C涂层），结合强度高，分别为62.2MPa、28．9MPa，两种涂层摩擦副摩擦因数（0．0043）仅为块体材料18Cr2Ni4WA与ZQPb30摩擦副（0．0093）的1／2，相应磨损量（1．1mg／h）也仪为块体材料磨损量（15．6mg／h）的1／15，显示出涂层摩擦副优异的减摩耐磨性能。     

高强度导电性Cu—Cr合金定向凝固微观组织研究

从导电性角度研究了高强度定向凝固Cu—0．8wt％Cr合金的微观组织形态。结果表明；当凝固界面前沿液相中的温度梯度GL=60℃／cm，生长速度V=30μp／s，导电相α（Cu）晶体分校最少；当GL＝30℃／cm时，α枝晶一次问距λ1随V的增大而增大；当GL＝60℃／cm时，α枝晶沿生长方向的长度随V的增大而增大。这些均利于材料导电性的提高。     

Co在Pt（111）面上电结晶的STM及REM研究

采用０．０５ｍｏｌ／Ｌ Ｈ３ＢＯ３＋０．０１ｍｏｌ／Ｌ ＣｏＳＯ４溶液,在Ｐｔ（１１１）面上获得了电结晶Ｃｏ利用电化学扫描隧道显微镜（ＥＣＳＴＭ）及反射电子显微镜（ＲＥＭ）,观察了不同过电位时Ｃｏ的成膜过程,证实了Ｃｏ在Ｐｔ（１１１）面上的电结晶均为三维岛状生长方式。     

Mo-CVD法制备GaAs和CdTe的特种材料研究

用Mo-CVD技术已研制了几种特种半导体材料,(1)注氧GaAs衬底上生长GaAs:根据注氧剂量的不同,已获得各种结晶的GaAs外延层。这种材料将在选择外延中起重要作用;(2)Mo/Si衬底上生长GaAs:由于面积大,价格低和结晶性能较好,GaAs/Mo/Si材料可能成为有前途的太阳电池材料;(3)在GaAs衬底上生长CdTe:CdTe/GaAs是一种复合材料,它有望代替CdTe单晶成为HgCdTe外延的代用衬底。这三种材料的电性和结晶性能已用C-V,I-V,S.E.M和电子衍射以及用X射线能谱进行了研究和测量。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.