SiC晶须对Al2O3／TiB2／SiCw陶瓷刀具材料高温断裂韧性的影响

研究了不同ＳｉＣ晶须含量的Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ陶瓷刀具材料的断裂韧性随温度的变化规律。结果表明：Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ陶瓷材料的Ｋ１Ｃ在１０００℃内随温度的升高而增大；晶须含量越大，通过计算分析表明，随温度的升高粘裂时拔出的晶须大大增多，当晶须体积含量（下同）为２０％时，Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ陶瓷在室温时只有长径比小于２．８７的晶须在断裂时才有可能产生拔出，而在９００℃时     

Al2O3／SiCW陶瓷刀具材料中晶须的取向对其力学和切削性能的影响

Ａｌ２Ｏ３／ＳｉＣＷ陶瓷刀具材料由于热压过程的影响，造成晶须在基体中定向排布于垂直热压方向的平面上，因此不同方向的补强、增韧效果有所差异。本工作测量了Ａｌ２Ｏ３／ＳｉＣＷ陶瓷刀具材料不同方向上的断裂韧性和抗弯强度，分析了晶须的取向对该陶瓷刀具材料力学性能的影响。切削试验表明晶须的取向对晶须增韧陶瓷刀具材料的磨损和破损性能有较好的影响。根据切削加工过程中刀具的受力特点，提出了有利于切削加工的刀具前、     

氧化硅陶瓷高温摩擦学性能

本文研究热压氮化硅陶瓷与３Ｃｒ２Ｗ８Ｖ钢组成的销－盘摩擦副，在空气中非润滑条件下，４００￣８００℃不同载荷（４９￣３４３Ｎ）的摩擦磨损性能；测定了磨擦系数的Ｓｉ３Ｎ４销的磨损因子；通过对Ｓｉ３Ｎ４磨损面的ＳＥＭ形貌观察、Ｘ射线相结构分析，探讨了陶瓷销的磨损机理。     

新型复相陶瓷刀具材料Jx-2-I协同增韧补强机理的研究

本文研制成功的新型陶瓷刀具材料—ＳｉＣ晶须（ＳｉＣｗ）增韧和ＳｉＣ颗粒弥散增韧Ａｌ２Ｏ３陶瓷刀具Ｊｘ－２－Ｉ,该刀具材料具有高的抗弯强度和断裂韧性等优点;对比Ａ（Ａｌ２Ｏ３）、ＡＰ（Ａｌ２Ｏ３／ＳｉＣｐ）、ＡＷ（Ａｌ２Ｏ３／ＳｉＣｗ）、Ｊｘ－１（Ａｌ２Ｏ３／ＳｉＣｗ）和Ｊｘ－２－１（Ａｌ２Ｏ３／ＳｉＣｐ／ＳｉＣｗ）等陶瓷材料的力学性能可以看出,在Ｊｘ－２－Ｉ材料中具有明显的增韧补强叠加效应;本文在热失配分析和微观结构观察的基础上详细研究了Ｊｘ－２－Ｉ刀具材料的增韧补强机理,系统研究了Ｊｘ－２－Ｉ中各种增韧补强机理之间的协同效应。     

晶须的取向对Al2O3／TiB2／SiCW陶瓷复合材料高温耐磨性能的影响

研究了晶须的取向对Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ陶瓷复合材料在下空气和氮气氢气中与硬质合金摩副往复滑动摩擦时的耐磨性能的影响。结果表明：该材料表面的耐磨性能随θ角的不同而变化，随θ角的增大，材料表面的耐磨性能提高。在高温空气氢气中摩擦时，由于ＳｉＣ晶面的氧化使得材料表面晶须的增韧补强作用削弱，加速了材料的磨损。通入氮气有利于减轻ＳｉＣ晶须的氧化，可提高瓣耐磨性能。     

几类典型结构陶瓷材料的冲蚀磨损行为研究

研究了几类典型结构陶瓷材料，如Ａｌ２Ｏ３，ＳｉＣ，Ｓｉ３Ｎ４陶瓷，Ａｌ２Ｏ３－ＺｒＯ２系相变增韧陶瓷（ＺＴＡ，ＴＺＰ）和ＳｉＣｗ／Ｓｉ３Ｎ４系晶须补强陶瓷（ＷＲＳＮ）有９０ｍ／ｓ下的冲蚀磨损性能，以及其与材料性能（硬度，断裂韧性）和冲蚀条件（粒子硬度，冲击角度）之间的关系，分析了冲蚀磨损机制。陶瓷材料的低角冲蚀磨损机制主要包括：研磨状损伤，犁沟状微切削损伤和晶粒剥落。低角冲蚀磨损率随材料硬度的增加     

一次低烧SrTiO3基晶界层电容器的研究

研究了以Ｌｉ２ＣＯ３为助烧结剂、Ｓｒ（Ｌｉ１／４Ｎｂ３／４）Ｏ３为施主掺杂剂、Ｂｉ２Ｏ３和ＳｉＯ２为晶界绝缘剂的ＳｒＴｉＯ３基晶界层电容器的一次低温烧成技术。初步探索了Ｔｉ／Ｓｒ比值、施主掺杂剂、绝缘剂对显微结构及介电性能的影响。在１１５０℃烧成温度下，获得了εａｐｐ〉３．５×１０＾４；ｐ〉１．０×１０＾１１Ω·ｃｍ；ｔｇδ〈１．０％；ΔＣ／Ｃ〈±５．０％（－２５￣＋８５℃）的ＳｒＴｉＯ３基晶界层     

新型高效催化剂气相聚合制备聚乙烯

综合报道了新型乙烯气相聚合ＭＧ型催化剂的制备及其聚合反应性能。研究了采用浸渍反应法制备含ＴｉＣｌ４／ＭｇＣｌ２／ＺｎＣｌ２／ＳｉＯ２醇／Ａｌ（ｉ－Ｂｕ）３的ＭＧ－４型高效催化剂。在压力１．０ＭＰａ下,乙烯聚合催化效率高达４４５￣８８４ｋｇＰＥ／ｇＴｉ,制得了表观密度≥ｇ／０．３７／ｃｍ＾３、重均颗粒分布（２０￣２００目）≥９７．７％、颗粒状态良好的聚乙烯。用ＤＳＣ、ＳＥＭ、ＷＡＸＤ对聚合产物进行了     

混炼胶在圆锥口型挤出膨胀行为的研究

分析了混炼胶在收敛流变中的粘弹特性，应用张量分析方法，在高聚物熔体入口收敛流动中，引入纯拉伸流变概念，导出了描述胶料在圆锥口型挤出膨胀的方程：Ｂ￣２＝３［１＋（ＫＳ＿Ｒ）￣２］￣（－２／３／７）．实验结果表明，当圆锥口型入口角较大时，对混炼胶挤出膨胀的影响，是拉伸流变效应起主导作用。     

氮化硅超细粉原位生长“无缺陷”a—氮化硅晶须

研究了用加压氮化法（ｉｎｃｒｅａｓｉｎｇ ｐｒｅｓｓｕｒｅ ｎｉｔｒｉｄａｔｉｏｎ，简称ＩＰＮ法）制备高活性、高纯度的氮化硅超细粉。用这种超细粉在一定温度范围内原位生长出“无缺陷”的ａ－Ｓｉ３Ｎ４晶须，其截面直径×长的尺寸分别为（０．１￣０．３ｕｍ）×（１０￣３０ｕｍ）。在氮化硅基体中加入“无缺陷”ａ－ＳｉＮ４晶须后，材料的断裂韧性ＫＩｃ达１０．５±０．９ＭＰａ·ｍ＾１／２；室温强度ａｆＲＴ达９２     

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.     

Superplastic Deformation in Silicon Nitride–Silicon Oxynitride In Situ Composites

Starting with a mixture of ultrafine β-Si₃N₄ and a SiO₂-containing additive, a superplastic Si₃N₄-based composite was developed, using the concept of a transient liquid phase. Significant deformation-induced phase and microstructure evolutions occurred in the nonequilibrium, fine-grained Si₃N₄ material, which led to the in situ development of a Si₃N₄–22-vol%-Si₂N₂O composite and strong texture formation. The unusual ductility of the composites with elongated Si₂N₂O grains was attributed to the fine-grained microstructure, the presence of a transient liquid phase, and the alignment of the elongated Si₂N₂O grains. The mechanical properties of the resultant composite were enhanced rather than impaired by superplastic deformation and subsequent heat treatment; the resultant composite exhibited both high strength (957 MPa) and high fracture toughness (4.8 MPa·m^1/2).     

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.