Preparation of silica fiber reinforced silicon nitride composites using two precursors pyrolyzed at low temperature

Perhydropolysilazane(PHPS) and polyhydridomethylsilazane(PHMS) were used as preceramic polymers,respectively,to prepare three-dimensional silica fiber reinforced silicon nitride composites through repeated infiltration and pyrolysis at a low temperature(600℃),and the mechanical properties and microstructures of the composites were investigated through comparison.The composite prepared with PHPS,with density of 1.83g/cm~3,porosity of 10%,and flexural strength of 45.4MPa,shows a smooth fracture surface and strong fiber/matrix bonding,while the composite prepared with PHMS exhibits a rough fracture surface and moderate interfacial(adhesion),lower density of 1.66g/cm~3,higher porosity of 16%,but higher flexural strength of 56.3MPa.The(different) activities of the precursors result in different interfacial microstructures and mechanical properties of the composites.