INFLUENCE OF Al ON DUCTILITY IMPROVEMENT BY B IN Ni_3Al ALLOYS

The “order-disorder” model was adopted to calculate the lattice vacancies related to the com- position change in Ni_3Al alloys.A great deal of vacancies,i.e.,the non-stoichiometric vacan- cies,may exist in the Ni_3Al alloys containing Al over stoichiometry,i.e.25 at.-%.This was confirmed by the positron annihilation technique.Therefore,the influence of Al content on the enhancing behaviour of B towards the ductility of Ni_3Al alloys can be understood by the interaction of non-stoiehiometric vacancies and B atoms.     

High temperature oxidation of a (Cr2N−Mo2S3)/Cr double-layered coating deposited on steel by D.C. magnetron sputtering

A coating consisting of (Cr₂N−Mo₂S₃) overlay coating and an underlying Cr coating was deposited on a steel substrate by D.C. magnetron sputtering. The oxidation characteristics of the deposited double-layered coating were studied at temperatures ranging from 400 to 900 °C in air. The oxidation product was primarily Cr₂O₃. The unreacted coating beneath the oxide scale had some dissolved oxygen, sulfur, and iron. Oxidation of the coating occurred via complex routes such as the outward diffusion of chromium and nitrogen from Cr₂N and iron from the substrate, and the inward transport of oxygen from air, chromium from Cr₂N, and S from Mo₂S₃. This counter diffusion of various ions occurred easily via fine crystallites that constituted the coating, which had some solubility of S, O, and Fe.     

电沉积法制备Ni-Ti3SiC2复合镀层

以自制纯度超过98%(体积分数,下同)的Ti3SiC2陶瓷粉体为原料,加入分散剂和表面改性剂,制成稳定悬浮液,并加入Watts镀镍电镀液,利用磁力搅拌分散均匀,在阴极电流密度2 A/dm2～5 A/dm2下,在低碳钢基体表面成功得到Ni-Ti3SiC2减摩复合镀层.SEM观察表明,表面改性剂的加入有效地改变了粉体表面电导性质,得到致密平整的复合镀层结构.XRD及EDS分析表明:镀层中Ti3SiC2微粒含量为5%～14%(体积分数,下同).当制备过程中以间歇式搅拌代替连续搅拌时,可得到Ti3SiC2相含量超过30%的复合镀层.复合镀层的显微硬度随微粒含量的升高而增大.     

纳米晶Bi2Se3-Sb2Se3薄膜的SILAR法制备及表征

采用连续离子层吸附反应(SILAR)法,分别用含有Se2-,Bi3+和Sb3+的离子溶液作为独立的阴、阳离子前驱溶液,以载玻片为衬底,在室温下沉积出致密且具有镜面金属光泽的Bi2Se3-Sb2Se3薄膜材料.为了改善薄膜样品的结晶状态,对其进行了退火处理.用AFM观察了薄膜样品的表面形貌,用XRD分析了退火前后薄膜样品的结晶状态.结果表明薄膜样品经200℃较低温度下退火处理4 h以后,薄膜的结晶状态由无定形态转化为多晶态,其平均晶粒尺寸为30 nm～40 nm.     

Defect structure and chemical diffusion in nickel sulfide β-Ni3S2

The chemical composition, defect structure, and diffusion in nickel sulfide -Ni₃S₂ have been investigated in H₂S-H₂ mixtures containing between 1 and 65% H₂S between 560 and 700°C. Gravimetric, density, and X-ray studies were carried out. In the thermodynamically stable compound the ratio of Ni/S varied between 1.3 and 1.75. The X-ray examination showed a step change in the lattice parameter at the Ni/S ratio 1.4. A linear dependence of the density values (between 5.5 and 6.2 g/cm³) on the composition was observed. On the basis of the chemical composition and density measurements the number of nickel and sulfur atoms in 1 cm³ were determined. It has been shown that the Ni₃S₂ phase is defected in both anion and cation sublattices and that its chemical formula may be described as follows: Ni_3±yS_2x, where y 2x. It has been found that in the mixture containing 10% H₂S the process of defect formation is determined by their diffusion in the sulfide. The temperature dependence of the diffusion coefficient is described by the equation D = 13.15 exp(-30,000/RT) cm²/sec. No dependence of D on the sulfur partial pressure was observed, but this may be due to the relatively large uncertainties in the measurement of the diffusion coefficients.     

SHS/PHIP法制备Ti3AlC2可加工陶瓷的塑性特征

研究了用SHS/PHIP技术制备出的Ti3AlC2可加工陶瓷的塑性变形特征。应变速率为1×10^-3/s,从室温到1300℃的压缩实验结果表明,室温到800℃的压缩断裂方式为脆性断裂,但存在显微塑性。主裂纹的偏转与分岔、晶粒的分层与扭折是主要变形机制;1000℃到1300℃,位错运动带来了塑性流变的结果。800℃到1000℃被称为韧脆转变温度区间,在此温度区间以上的应力与应变曲线存在着“硬化区域”,并且随着温度的升高,“塑性区”要大于“硬化区”。     

Surface modification of spherical LiNi1/3Co 1/3 Mn1/3O2 with Al2O3 using heterogeneous nucleation process

To improve the cycle stability at high voltage and high charge/discharge rate, spherical LiNi1/3Co1/3Mn1/3O2 was coated with Al2O3 by using heterogeneous nucleation process, and the physical and electrochemical properties were studied. The SEM images show that there is a uniform coating on the modified spherical LiNi1/3Co1/3Mn1/3O2. The electrochemical tests indicate that the properties of LiNi1/3Co1/3Mn1/3O2 coated with 0.5% aluminum oxide are the best. The initial capacities are 150 and 173 mA.h/g at the rate of I C in the voltage range of 2.7-4.3 V and 2.7-4.6 V, respectively, and the discharge capacities maintain about 99% and 85% after 30 cycles, respectively. While those of the bare LiNi1/3Co1/3Mn1/3O2 are only 90% and 75%, respectively. The CV tests of LiNi1/3Co1/3Mn1/3O2 show that Al203-coating can restrain the oxide-reduction peak currents fading during the charge/discharge course.     

分子自组装制备的掺杂WO3的TiO2光催化薄膜的表征

利用分子自组装技术在载波片上制备了锐钛相TiO2及WO3掺杂的TiO2薄膜。利用原子力显微镜(AFM)和UV-VIS-NIR分光光度计对薄膜进行了表征。利用对罗丹明B的降解评价了所制备薄膜的光催化活性。结果表明：当W／Ti=2at％时，TiO2薄膜的光催化活性得到提高。     

Al3Ti3B中间合金对AZ91D镁合金组织及力学性能的影响

研究了Al3Ti3B中间合金对AZ91D镁合金显微组织及力学性能的影响.通过光学显微镜和扫描电子显微镜观察发现,Al3Ti3B中间合金能显著减小AZ91D合金的二次枝晶臂间距与晶粒尺寸,在加入0.3%Al3Ti3B时晶粒尺寸就由原来的约260 μm减小至约100μm.伴随着合金晶粒尺寸的减小,合金的抗拉强度、屈服强度和延伸率都明显提高,这主要是由于晶粒细化后能阻碍裂纹扩展的有效晶界增多,晶界强化作用显著;同时,Al3Ti3B中间合金的加入促使溶质均匀分布,使共晶体(α Mg17Al12)形貌发生改变,共晶体尺寸减小,这有利于裂纹切过脆性的共晶体传播,提高合金的变形协调能力.     

新型陶瓷刀具的发展与应用

回顾了陶瓷刀具的发展简况及其意义,重点介绍了Si3N4基和TiCN基复合陶瓷刀具的研制、性能和应用.复合Si3N4陶瓷刀具有较高的耐磨性和抗冲击性,特别适合于各类铸铁件的粗精加工,也能进行铣削、刨削等冲击力很大的加工,其切削效率可提高3～10倍;复合TiCN金属陶瓷刀具具有很高的硬度和耐磨性,特别适合于各类高硬高强钢(如淬硬钢等)的加工,可对高硬材料实现"以车代磨"干切削,免除退火工艺和冷却液,大幅度提高生产效率.新型复合陶瓷刀具已经在我国冶金、水泵、矿山机械、轴承、滚珠丝杠、汽车、军工等十几个行业得到应用.