THERMODYNAMIC PROPERTIES OF HOLE TRAPS A AND B IN GaAs

Equilibrium constant K_T and free energy of formation △G°of the reaction(Ga_(As)As_(Ga)+(V_(Ga))(2|-)+(e|-)=As_(Ga)V(G|-)a+Ga_(As)V(G|-)awere deduced as:K_T=(1.088×10~8-1.09×10~(11)·1/T)~2△G°=-2RTln(1.088×10~8-1.09×10~(11)·1/T)These seem to be applicable into practice under certain conditions.     

钒镓合金的阳极氧化

钒镓系除了超导相 V_3Ga(Cr_3Si-类型)之外,还包括一系列金属间相,这些金属间相一部分是纯二元的(例如:V_2Ga_5),但是由于夹杂物,所以部分是三元的(例如:V_5Ga_3Ox 或 V_3GaOx)或者是四元的,(例如:V_5〈Ga,Si〉_3Ox)。为了把显微照片里的不同相彼此区别开来,而且不用其他辅助方法(x 射线显微分析,微硬度测量),     

钒—镓系化合物相分析

关于钒——镓系化合物不少人进行了研究,其结果都有一定的分岐,主要在化合物的化学成分、存在的温度和浓度范围等方面。根据其结构类型及点阵常数的比较和文献(1)中的介绍,钒——镓系化合物大体可以分为富镓相VGa2、V_2Ga_5;含镓量较高相V_5Ga_7、VGa;含镓量较低相V_3Ga_2、V_6Ga_5及富钒相V_3Ga。文献(2)还介绍有     

Fe_(83)Ga_(17)R_(0.6)(R=Ce,Tb,Dy)合金的微结构与磁致伸缩性能

为改善多晶Fe-Ga合金的磁致伸缩性能,在Fe-Ga合金中掺杂稀土Ce、Tb和Dy元素。研究了Fe_(83)Ga_(17)和Fe_(83)Ga_(17)R_(0.6)(R=Ce,Tb,Dy)合金的相结构和磁致伸缩性能。结果表明,Fe_(83)Ga_(17)合金由单一bcc结构Fe(Ga)固溶体相组成,而掺杂稀土后的Fe_(83)Ga_(17)R_(0.6)合金中除保持bcc结构的Fe(Ga)固溶体相外,还出现了R_2Fe_(17)第二相。掺杂稀土后的Fe_(83)Ga_(17)R_(0.6)合金磁致伸缩系数明显大于Fe_(83)Ga_(17)合金。掺杂不同种类的稀土元素对Fe-Ga合金磁致伸缩性能改善的程度不同。在外磁场为557 k A/m时,Fe_(83)Ga_(17)R_(0.6)合金的磁致伸缩系数(206×10~(-6))明显大于Fe_(83)Ga_(17)Tb_(0.6)(165×10~(-6))和FFe_(83)Ga_(17)Dy_(0.6)(161×10~(-6))合金的磁致伸缩系数。     

用元素周期表Ⅲ—Ⅷ族的元素来合金化超导化合物V_3Ga

具有β—W(A15)型晶体结构的金属化合物V_3Ga拥有较高的超导转变温度(根据不同的研究数据为14.5—16.5°K),很高的上临界磁场(210—250KG),和很高的临界电流密度。在一些文献中介绍了V—Ga系相平衡图。事实表明,具有体心立方晶格的镓在钒中的固溶体形成了宽阔的单相区(51%Ga以下,原子百分比),而化合物V_3Ga是呈固态于1350℃生成的。加入各种元素进行合金化,研究其对化合物V_3Ga超导性能的影响,无论从科学方面还是对解决可能的工艺任务来说都是很有意思的。文献中曾经研究过许多元素添加剂对化合物V_3Ga临界温度的影响。文献中指出,在全部的研究工作中合金化都降低了临界温度,並且临界温度的降低照例因添加元素在周期表中的位置不同而不同。然而在文献中发现,添加硅铝稍微提高了临界温度(其值为～0.4°K)。文献的作者们在研究合金化合导致临界温度的变化时:在某些情况下显然没有考虑到合金的结构和相组成。而它们在以各种元素的任何原子组份进行合金化时却可能是完全不同的。本文研究了V_3Ga—Me型合金的结构和相组成的变化,这里Me代表周期表中Ⅲ一Ⅷ族的元素。如同文献一样,在维持比例V:Ga=3:1的情况下,加入其量为5%Me(原子百分比,下同)的合金添加剂。     

绿色/红色长余辉材料γ-Zn3（PO4）2:Mn2+,Ga3+,Ho3+的合成及光谱性质

采用高温固相法合成了Mn2+单掺杂、Mn2+,Ga3+(Ho3+)共掺杂以及Mn2+,Ga3+,Ho3+三掺杂的γ-Zn3(PO4)2。在Mn2+单掺杂的样品中,发射峰位于620nm,该样品在紫外光照射样品后,发现存在红色余辉,余辉中心与荧光中心相同。当Mn2+,Ga3+(Ho3+)共掺杂时,样品同时存在峰值位于620nm的红光发射和峰值位于507nm的绿光发射,紫外光照射样品后,样品存在红色余辉及绿色余辉。Ga3+和Ho3+在基质中自身是不发光,作为共掺杂离子,不仅可以起到调节发光中心的作用,还形成了新的深度适合的陷阱,使得绿色余辉及红色余辉性能有了很大的提高。掺杂双陷阱离子Ga3+和Ho3+,样品余辉性能最佳。     

Improved magnetostriction of Fe_(83)Ga_(17) ribbons doped with Sm

In order to demonstrate that light rare-earth(RE)dopants with strong magnetocrystalline anisotropy, whose net moment couples are antiparallel to those of iron, can also induce giant magnetostriction in Gafenol, a light RE element Sm was selected as the third element to dope into Fe_(83)Ga_(17) alloy.(Fe_(83)Ga_(0.17))_(100-x) Sm_x(0≤x≤0.42) ribbons were prepared by melt spinning. The increase of the lattice parameters and saturation magnetization indicates that some Sm atoms enter the A2 matrix substitutionally. Doping the Fe_(83)Ga_(17) ribbons with the light RE Sm element drastically improves the magnetostriction. Perpendicular magnetostriction value of λ_⊥=-5*10~(-4)is achieved in(Fe_(83)Ga_(0.17))_(99.75)Sm_(0.25). It is confirmed that the stronger local magnetocrystalline anisotropy induces larger enhanced magnetostrictions. The greatly enhanced magnetostriction is somehow related to the local microstrains induced by the RE dopants. It is likely that the RE-induced defects in the(Fe_(83)Ga_(0.17))_(100-x)RE_x ribbons function in the similar way as the Ga–Ga pair defects in the undoped Fe–Ga alloys.     

Cu、Ga和C掺杂对MnAl合金相结构及磁性能的影响

研究Cu、Ga、C元素掺杂的MnAl合金的相结构和磁性能。结果表明:在Cu或者Ga掺杂的MnAl合金中加入C元素,有助于磁性相τ-MnAl的形成。Mn_(50)Al_(47)Ga_3C_3粉末的饱和磁化强度(M_s)随着球磨时间的增加而减小,矫顽力(H_c)随着球磨时间的增加先增大后减小。球磨前Mn_(50)Al_(47)Ga_3C_3合金(1000℃×20 h)样品的饱和磁化强度为89.98 Am~2/kg,约为其理论饱和磁化强度值144 Am~2/kg的62.5%;获得最好磁性能是在粉末球磨1h后,Ms=51.91Am~2/kg,Hc=155.2 kA/m。     

用复合加工法制作的V_3Ga超导线材

作为以Cu—Ga合金和V芯复合加工法制取V_3Ga化合物多芯线的基础研究;介绍了复合带材、35芯多芯线材Cu—Ga合金的组织、复合材料的加工性以及V_3Ga的扩散生成研究。通过Cu—Ga固溶合金与V芯的复合材料的加工及热处理认为V_3Ga超导线材是很容易获得的。Cu—Ga固溶合金的加工性是良好的,但当Ga浓度超过20%原子比时,则有走相析出使其合金硬度增加,故冷加工很困难。Cu—Ga合金熔体与V芯适于     

Fe_(83)Ga_(17)合金的显微结构及磁致伸缩性能

为了提高Fe_(83)Ga_(17)合金的磁致伸缩性能,对铸态合金进行1100℃×1 h的均匀化处理后,再分别进行650、700、750、800和850℃×3 h退火处理。通过物相、显微组织、DSC、硬度及磁致伸缩性能分析,结果表明,Ga原子固溶进Fe晶格后,晶格常数增大;经过热处理后,晶粒内的亚晶界消失,并析出了大量的富Ga相,硬度下降;在退火温度为800℃时,100方向的晶粒数目增多,磁致伸缩系数达到95×10~(-6),是铸态下的3.8倍。均匀化及退火处理对Fe_(83)Ga_(17)合金的磁致伸缩性能有明显提升。     

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.     

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。     

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.     

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.     

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).     

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.