Combustion Synthesis of Powders for Advanced Ceramic Materials

细小、超纯、球形颗粒是生产高性能高级陶瓷制品的理想原料。AeroChem拥有独特的火焰合成工艺来制备包括氮化硅在内的高质量粉末。这一过程与通常的燃烧合成不同，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、肼和氮气在平焰燃烧器上燃烧。在不添加添加剂的情况下，成功地对样品进行了热等静压，制得了高质量的粉末。然而，由于联氨的成本、爆炸性和毒性，联氨的使用使该过程在商业上不可接受。虽然热力学和其他方面的考虑表明，氨应该支持没有联氨的火焰，但我们一直无法在没有联氨的情况下运行。提出了一种计算机模拟研究，以了解为什么氨/硅烷系统在已采用的条件下不支持火焰，并确定在什么条件下可以支持火焰。然后将进行实验，以确定在所定义的条件下操作的实际可行性。这一计划的成功完成将使先进陶瓷生产能够获得比目前可用的更高质量的粉末。拟议研究的最终产品将是一种经济的工艺，用于制备用于先进陶瓷的高质量氮化硅粉末。目前先进陶瓷的进展受到美国制造的高质量粉末供应不足的限制。

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.