Performance of Si₃N₄ hollow microspheres prepared by spray drying and carbothermal reduction nitridation

A simple and scalable approach to fabricate monodispersed Si3N4 hollow microspheres (Si3N4 HMs) with uniform spherical structures is proposed in this study. This approach involves spray drying of Si3N4 precursor, followed by carbothermal reduction nitridation. The homogeneous Si3N4 precursor was first obtained by mixing phenolic resins and silicon resins, which are carbon and silicon sources, respectively. The spray drying process was then tuned by regulating the viscosity of the precursor by adding polyvinyl butyral in an appropriate ratio. Next, the hollow precursor microspheres were pyrolyzed at 1500 degrees C for 6 h, while ensuring that the shells of the obtained Si3N4 HMs remained intact. Porous Si3N4 ceramics with different contents of Si3N4 HMs were then prepared using the gel-casting method. It was observed that the densities and dielectric constants of the porous Si3N4 ceramics decreased with an increasing Si3N4 HMs content. Thus, the proposed approach can be used for the synthesis of Si3N4 HMs, that can be further processed into ceramic materials with both low densities and dielectric constants.