Effects of precoating and calcination on microstructure of 3D silica fiber reinforced silicon nitride based composites
(State Key Laboratory of Advanced Ceramic Fibers and Composites,
College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha 410073, China)
College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha 410073, China)
Abstract: Three-dimensional silica fiber reinforced silicon nitride based composites were fabricated by preceramic polymer infiltration and pyrolysis method using perhydropolysilazane as a precursor. The effects of precoating and high temperature calcination on the microstructures of the composites were investigated by scanning electron microscopy. For the composite without a precoating, the fracture surface is plain, and the fiber/matrix interfaces become very unclear after calcination at 1 600 ℃ due to intense interfacial reactions. The composite with a precoating shows tough fracture surface with distinct fiber pull-outs, and the fiber/matrix interfaces are still clear after calcination at 1 600 ℃. It is the appropriate precoating process that contributes to the good interfacial microstructures for the composite.
Key words: silica fiber; precoating; preceramic polymer; silicon nitride based composites; microstructure