Combustion Synthesis of Powders for Advanced Ceramic Materials

精细、超纯、球形颗粒是生产高性能高级陶瓷产品的理想原料。AeroChem拥有独特的火焰合成工艺来制备高质量的粉末，包括氮化硅。这个过程不同于通常的燃烧合成，因为不使用氧气：产生颗粒的反应物也支持火焰。对于氮化硅，硅烷、氨、肼和氮在平焰燃烧器上燃烧。一种高质量的粉末，其样品，无添加剂，成功地进行热等静压。然而，由于肼的成本、爆炸性和毒性，使用联氨使得该工艺在商业上不可接受。虽然热力学和其他方面的考虑表明，氨应该支持没有肼存在的火焰，但我们无法在没有肼的情况下运行。提出了一种计算机模拟研究，以理解为什么氨/硅烷系统在所采用的条件下不支持火焰，并确定可以支持火焰的条件。然后将进行实验，以确定在规定条件下操作的实际可行性。该计划的成功完成将为先进的陶瓷制造提供比目前更高质量的粉末。该研究的最终产物将是制备用于高级陶瓷的高质量氮化硅粉末的经济方法。由于无法获得美国制造的高质量粉末，目前先进陶瓷的进展受到限制。

Fine, ultrapure, spherical particles are desirable starting materials for producing high performance afvanced ceramic products. AeroChem has a unique flame synthesis process for preparing such high quality powders, including silicon nitride. This process differs from the usual combustion synthesis in that no oxygen is used: the particle-producing reactants also support the flame. For silicon nitride, silane, ammonia, hydrazine, and nitrogen are burned on a flat flame burner. A high quality powder is produced of which a sample, without additives, was successfully subjected to hot isostatic pressing. However, the use of hydrazine makes the process commercially unacceptable because of the cost, explosive nature, and toxicity of hydrazine. While thermodynamic and other considerations indicate that ammonia should support a flame without hydrazine present, we have not been able to operate without some hydrazine. A computer modeling study is proposed to understand why the ammonia/silane system does not support a flame under the conditions which have been employed, and to define the conditions under which a flame could be supported. Experiments will then be performed to determine the practical feasibility of operating under the defined conditions. Successful completion of this program would make available for advanced ceramic manufacture a higher quality powder than is currently available. The final product of the proposed research would be an economical process for the preparation of a high quality silicon nitride powder for use in advanced ceramics. Present progress in advanced ceramics is limited by the unavailability of a US made high quality powder.