Formation of carbon fiber-reinforced ceramic matrix composites with polysiloxane/silicon derived matrix

A ceramic matrix for carbon fiber-reinforced ceramic matrix composites (CMCs) has been developed from poly(methylsilsesquioxane)/silicon mixtures, using a low-cost process. In this process the space in two-dimensional carbon fiber preform was filled with a slurry composed by Si powder dispersed into poly(methylsilsesquioxane)/trietoxysilane solutions. Three different volume ratio of Si:polymer were used to stack eight-harness plain weave of carbon fiber, forming laminates composites, which were pressed and cured up to 200 °C. The compact bodies were first pre-pyrolyzed at 1000 °C and then pyrolyzed at 1450 °C/2 h and 1500 °C/1 h. On pyrolysis, the polymer-filler mixture was converted to a multiphase ceramic matrix through reactions between Si, gaseous and solids products from the polymer degradation and the N2 atmosphere. Pyrolysis led to conversion of the initial matrix into silicon oxide (SiO2), silicon carbide (SiC) and silicon oxinitride (Si2ON2), though after pyrolysis at 1450 °C metallic silicon was still detected. With one cycle of infiltration the composite characteristics were followed by bulk density and open porosity measurements, X-ray diffraction, microscopy and mechanical testing.