Effect of Reactive Filler Addition for Matrix of SiC Fiber/SiC Composite
Polymer impregnation pyrolysis method (PIP method) has some advantages to fabricate SiC fiber /SiC composite with large or complex form. However polymer derived SiC contains some amount of excess carbon and porosity. In particular the excess carbon is easy to be oxidized in air at high temperature. Therefore reliability of the composite is not sufficient for long term use, because the oxidized matrix makes strong bonding between the fiber and the matrix. In this study, TiO2 as a reactive filler was added into polymer to consume the excess carbon by chemical reaction. Polycarbosilane (PCS) was used as a precursor polymer to synthesize a SiC matrix. It was confirmed that TiO2 was formed TiC on reaction with PCS over 1673 K by preliminary study. SiC fiber, Hi-Nicalon®, was used as reinforcement. Al2O3 powder was coated on surface of SiC fiber as interface layer of fiber/matrix. TiO2 added PCS/hexane solution was compounded with the fiber tow by filament winding. SiC fiber/SiC composite was synthesized at 1673 K for 3.6 ks in Ar. The composite was densified by reinfiltration of TiO2 added PCS solution and pyrolysis at 1673 K. Though densification behavior of the composite with TiO2 is slower than composite without TiO2, it was suggested that composition of synthesized SiC is close to stoichiometric one by apparent density. Fracture behavior of the composite indicated that addition of TiO2 was increase bonding strength between fiber and matrix. Bending strength of composite was increased after oxidation test at 1473 K for 360 ks in air atmosphere.
T. Ohji, T. Sekino and K. Niihara
T. Inoue, M. Suzuki, T. Tanaka, S. Sodeoka, "Effect of Reactive Filler Addition for Matrix of SiC Fiber/SiC Composite", Key Engineering Materials, Vols. 317-318, pp. 487-490, 2006