Combustion of silicon powders containing organic additives in nitrogen gas under pressure: 2. Composition of combustion products

Combustion of silicon powders containing organic dopants in nitrogen gas under pressure was found to yield a mixture of α-Si₃N₄, β-Si₃N₄, SiC, and Si₂N₂O. Relative amount of these compounds in combustion product was found to depend on the pressure of nitrogen gas, type and concentration of dopants, combustion geometry, and cooling rate. The formation of α-Si₃N₄ was found to occur in the presence of oxygen-containing dopants. The type of dopant was also found to affect the morphology of product particles.      

Some New Perspectives on Oxidation of Silicon Carbide and Silicon Nitride

This study provides new perspectives on why the oxidation rates of silicon carbide and silicon nitride are lower than those of silicon and on the conditions under which gas bubbles can form on them. The effects on oxidation of various rate-limiting steps are evaluated by considering the partial pressure gradients of various species, such as O₂, CO, and N₂. Also calculated are the parabolic rate constants for the situations when the rates are controlled by oxygen and/or carbon monoxide (or nitrogen) diffusion. These considerations indicate that the oxidation of silicon carbide and silicon nitride should be mixed controlled, influenced both by an interface reaction and diffusion.     

有机聚硅氧烷在医药中的应用进展

总结了硅橡胶、硅油、硅树脂在医药中的应用,并介绍了硅烷化技术在药物合成、蛋白质分析检测等生物工程方面的应用和一些新型抗肿瘤、抗癌的含硅药物及多孔硅膜的药物缓释体系的发展。     

Nitridation behavior of silicon powder compacts of various thicknesses with Y2O3 and MgO as sintering additives

The effects of the nitriding temperature (1300 and 1350°C), holding time (0‐4 hours), and thickness of Si powder compacts on the nitridation behavior of silicon were investigated by examining the nitridation rates, analyzing phase compositions, and observing the microstructures of nitrided compacts. Si powder compacts doped with Y₂O₃ and MgO as sintering additives were prepared with thicknesses of 3, 6, and 9 mm. The phases of nitrided compacts were transformed from Si to α‐Si₃N₄ and β‐Si₃N₄ with an increase in the nitriding temperature and holding time. The degree of nitridation increased with the nitriding temperature and holding time. The β/(α+β) ratio increased with the nitriding temperature and holding time, and with a decrease in the thickness of the Si powder compacts. However, all compacts exhibited the same tendency for a higher β/(α+β) ratio at the compact surface than in the bulk of the compact. The variation in the β/(α+β) ratio for each compact decreased with an increase in the nitriding temperature and holding time.     

Oxidation of Silicon and Silicon Carbide in Ozone-Containing Atmospheres at 973 K

The oxidation behavior of a silicon wafer, chemically vapor-deposited SiC, and single-crystal SiC was investigated in an oxygen—2%–7% ozone gas mixture at 973 K. The thickness of the oxide film that formed during oxidation was measured by ellipsometry. The oxidation rates in the ozone-containing atmosphere were much higher than those in a pure oxygen atmosphere. The parabolic oxidation kinetics were observed for both silicon and SiC. The parabolic rate constants varied linearly with the ozone-gas partial pressure. Inward diffusion of atomic oxygen formed by the dissociation of ozone gas through the SiO₂ film apparently was the rate-controlling process.     

Volatility Diagrams for Silica, Silicon Nitride, and Silicon Carbide and Their Application to High-Temperature Decomposition and Oxidation

Volatility diagrams—isothermal plots showing the partial pressures of two gaseous species in equilibrium with the several condensed phases possible in a system—are discussed for the Si-O and Si-N systems, and extended to the Si-N-O and Si-C-O systems, in which the important ceramic constituents SiO₂, Si₃N₄, Si₂N₂O, and SiC appear as stable phases. Their use in understanding the passiveactive oxidation transitions for Si, Si₃N₄, and SiC are demonstrated.     

Mössbauer Study of the Influence of Fe-Si-N Liquid in the Synthesis of β-Si3N4 from Silica

Mössbauer spectra of the products obtained by carbothermal reduction and distribution of silica in the presence of iron in the temperatures range 1200^o to 1540^o were studied. The preponderance of β- Si₃N₄ over the α form at a higher reaction temperature were assumed to be related to the formation of an Fe-Si-N liquid. The liquid did not alter its composition with the variation of reduction-temprature, Iron had no effect on the reaction mechanism below 1300^oC.     

化妆品中用硅粉、硅悬浮液的最新技术(日)

硅是化妆品生产不可缺少的原料之一。介绍了硅粉、硅悬浮液用于化妆品生产的最新技术, 特别是毛发调理产品中的应用。硅粉作为固体原料有望成为化妆品中新产品的生产原料。     

Improved Resistance to Damage of Silicon Carbide-Whisker-Reinforced Silicon Nitride-Matrix Composites by Whisker-Oriented Alignment

The effects of whisker-oriented alignment on resistance to damage of SiC( w )/Si₃N₄ composites have been investigated by the Vickers indentation method and R -curve behavior. It is shown that increasing the degree of whisker-oriented alignment decreases the lengths of Vickers impressions and indentation cracks. The results exhibit rising R -curve behaviors for the SiC( w )/Si₃N₄ composites with different degree of whisker-oriented alignment. Moreover, the initial crack length c _i, the threshold of crack growth resistance K _i, and the upper bound of crack growth resistance K _∞ change regularly with increasing degree of whisker-oriented alignment. All results suggest that the whisker-oriented alignment improves the resistance to damage of the composites, resulting in a more reliable and usable composite.     

硅整流改为可控硅整流技术总结

介绍了硅整流改为可控制硅整流的技术改造过程及应注意的问题，改造后的整流技术具有操作简单，提高经济效益的特点。