Design, preparation, and structure of particle preforms for Si₃N_4(p)/Si₃N₄ radome composites prepared using chemical vapor infiltration process

A particle preform was designed and prepared by conglomerating and cold-pressed process, which was condensed by chemical vapor infiltration (CVI) process to fabricate silicon nitride particles reinforced silicon nitride composites. The conglomerations are of almost sphericity after conglomerated. There are large pores among the conglomerations and small pores within themselves in the preform according to the design and the test of pore size distribution. The pore size of the preform is characterized by a double-peak distribution. The pore size distribution is influenced by conglomeration size. Large pores among the conglomerations still exist after infiltrated Si₃N₄ matrix. The conglomerations, however, are very compact. The CVI Si₃N₄ looks like cauliflower-shaped structure.