A smart processing of silicon oxynitride ceramic powders with variable morphology controlled by hard template assistance

Spherical and rod-like Si₂N₂O ceramic powders were successfully prepared using a hard template strategy to meet different application background. The mesoporous silica spheres and rod-like silica (SBA-15) particles were selected as hard templates and also served as reactants. Highly active mesoporous silica is reacted through a combination of sucrose-nano-casting and carbothermal reduction nitridation (CRN) to successfully synthesize spherical and rod-like powders. Temperature and holding time of calcination are found to be significant factors for the formation of pure and well-crystallized powders. Insufficient temperature and holding time cause an incomplete reaction between silica, carbon and nitrogen, and also lead to the formation of amorphous phase. In the processing, sucrose was used as carbon source to incorporate evenly into mesopores of templates to assist CRN reaction. Big surface areas and high porosity of mesopores in SiO₂ provide an additional driving force to decrease the formation temperature of Si₂N₂O phase to 1280 °C. As-synthesized powders inherit same morphology as their parental mesoporous templates, which indicate that two mesoporous templates play an important role in guiding the growth of ceramic particles. In the research, we develop a smart processing for synthesis of oxynitride powders with variable morphology controlled by template.