采用粉末冶金技术制备的空心微珠分散钛基复合材料的表征及磨损性能(英文)

采用粉末冶金技术制备空心微珠分散的钛基复合材料,并对其磨损和腐蚀行为进行研究。结果表明,所制备的复合材料组织中在α-Ti基体中分散有平均孔径为50~150μm的空心微珠。复合材料的多孔性归因于压制过程中载荷对空心微珠颗粒的破坏及空心微珠本身的空心特性。X射线衍射分析表明复合材料由Al2O3、SiO2、TiO2和α-Ti相组成。基体钛合金的显微硬度为HV 240,而复合材料的显微硬度在HV 1100~HV 1800范围内变化。磨损实验表明,相对于商用Ti-6Al-4V合金,复合材料对硬化钢球和WC球的抗磨损性能得到显著增强。复合材料在3.56%NaCl(质量分数)溶液中的腐蚀行为表明,其耐点蚀性能改善,腐蚀电位向正(更高)方向移动。然而,与商用Ti-6Al-4V合金相比,空心微珠分散钛合金的腐蚀速率增大。     

Efficiency of a gyrotron operating in modes with axial index equal to two

The efficiency of a gyrotron operating in circular TE modes with axial index equal to two is presented as a function of the generalized parameters µ, F, and ?. The numerical results are valid for a wide range of operating conditions, including voltage, current, beam radius, cavity geometry and operating mode.     

Studies on Processing of Nickeliferrous Sources in India

Nickel requirement in India is met through imports although there are known deposits of nickel laterites. In addition, there are secondary sources such as nickel sulphide in multimetal sulphides associated with uranium ore, low grade nickel bearing lateritic overburden of chromite mining and industrial wastes, such as spent catalyst and grinding waste of alnico. The primary deposits are extensive but the grade is low. All the other sources are small and some of them are quite complex. Recovery of metal values from such sources is important on account of resource conservation. The paper reviews the studies carried out in different laboratories in India.     

Thermal Expansion of CeO2, Ho2O3, and Lu2O3 from 100° to 300°K by an X-Ray Method

Thermal expansion of CeO₂, Ho₂O₈, and Lu₂O₃ was determined from 100° to 300°K by a back-reflection X-ray technique. The variation of thermal expansion with temperature is the same as that of specific heat for CeO₂ and Ho₂O₃; these oxides obey the Grueneisen model of thermal expansion in the temperature range studied.     

Diffusion-Controlled Redox Kinetics in a Glassmelt

A diffusion model was developed to analyze the rate at which Fe²⁺/Fe³⁺ equilibration occurs in a Ca-Al-borosilicate melt in an air atmosphere at 1260°C. The resulting diffusion coefficient of oxygen determined from the model of 3.7 × 10⁻⁷ cm²/s is in agreement with the range of values reported for other glass-melts at this temperature and with the value determined from the viscosity of the melt using the Eyring model. The results support the general interpretation of the multivalent ion oxidation equilibrium as a diffusion-controlled process. The model thus provides a means to determine the diffusivity of oxygen in glassmelts from the kinetics of the oxidation reaction for a variety of redox ions.     

Effect of rabadi fermentation of barley on HCl-extractability of minerals

Rabadi fermentation of raw (freshly ground) as well as autoclaved barley flour at 30, 35, and 40°C for 6, 12, 18, 24, and 48 h brought about a significant increase in HCl-extractability of iron, copper, zinc, manganese, calcium, and phosphorus; longer periods and higher fermentation temperatures increased HCl-extractability. Increased non-phytate phosphorus and inorganic phosphorus in the fermented product, with a corresponding decrease in phytate phosphorus, was maximum at 40°C for 48 h and minimum at 30°C for 6 h. The level of phytic acid was significantly negatively correlated with HCl-extractability of minerals in the fermented products.