Preparation of porous silicon nitride ceramics by freeze drying

Silicon nitride ceramics have excellent mechanical properties, good thermal and chemical stability, low dielectric constant and dielectric loss. It is an ideal choice for high-speed aircraft electromagnetic wave transmission materials. In this paper, the preparation methods of porous silicon nitride materials with controllable dielectric constant and pore structure were systematically studied. Porous silicon nitride materials with controllable pore structure and directional growth were prepared by freeze-drying process and adjusting the solid content of slurry. (C) 2019 The Authors. Published by Elsevier B.V.