Production of Pure, Intimately Mixed Silicon Nitride/SiliconCarbide Powders by a Novel Gas Phase Combustion Synthesis Process

精细、超纯、均匀、松散凝聚的颗粒是高级陶瓷的理想起始材料。氮化硅和碳化硅的混合物特别有价值。在这个项目中，将研究使用硅烷/乙炔/氨火焰生产氮化硅/碳化硅粉末。具体任务包括：(1)实验确定选定的硅烷、氨和乙炔混合物在平焰燃烧器上的火焰稳定性极限与未燃烧气体速度的关系；(2)热力学确定预期火焰温度和产品产量作为输入成分，压力和初始温度的函数；(3)确定操作条件对所生产粉末性能的影响，具体是什么操作条件决定单个颗粒是碳化物和氮化物的混合物，还是氮化物和碳化物是单独的颗粒；(4)产品性质（化学成分、纯度、粒度分布、形貌）的测定；(5)从机制和商业化潜力方面解释研究结果。高质量的超细氮化硅/碳化硅粉体在烧结或热压制备高级陶瓷材料方面具有巨大的潜在市场。先进陶瓷生产的进展目前受到美国制造的高质量粉末的限制。此外，对这一过程中所涉及的机制的理解将对燃烧合成（特别是混合材料）具有广泛的意义。

Fine, ultrapure, uniform, loosely agglomerated particles are desirable starting materials for advanced ceramics. Mixtures of silicon nitride and silicon carbide are particularly valuable. In this program, the use of silane/acetylene/ammonia flames to produce silicon nitride/silicon carbide powders will be studied. Specific tasks include: (1) Experimental determination of flame stability limits on a flat-flame burner for selected mixtures of silane, ammonia, and acetylene as a function of unburned gas velocity; (2) Thermodynamic determination of expected flame temperatures and product yields as functions of input compositions, pressure, and initial temperature; (3) Determination of the effects of operating conditions on the properties of the powder produced, specifically what operating conditions devermine whether the individual particles are a mixture of the carbide and nitride or whether the nitride and carbide are in separate particles; (4) Determination of the product properties (chemical composition, purity, particle size distribution, morphology); and (5) Interpretation of the results in terms of mechanisms and commercialization potential. High quality ultrafine silicon nitride/silicon carbide powders have a large potential market in the preparation of advanced ceramic materials via sintering or hot pressing. Progress in production of advanced ceramics is currently limited by the unavailability of a US-made high quality powder. In addition, an understanding of the mechanisms involved in this process will have broad implications for combustion synthesis (especially of mixed materials) in general.