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

A simple and scalable approach to fabricate monodispersed Si 3 N 4 hollow microspheres (Si 3 N 4 HMs) with uniform spherical structures is proposed in this study. This approach involves spray drying of Si 3 N 4 precursor, followed by carbothermal reduction nitridation. The homogeneous Si 3 N 4 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 °C for 6 h, while ensuring that the shells of the obtained Si 3 N 4 HMs remained intact. Porous Si 3 N 4 ceramics with different contents of Si 3 N 4 HMs were then prepared using the gel-casting method. It was observed that the densities and dielectric constants of the porous Si 3 N 4 ceramics decreased with an increasing Si 3 N 4 HMs content. Thus, the proposed approach can be used for the synthesis of Si 3 N 4 HMs, that can be further processed into ceramic materials with both low densities and dielectric constants.