Effects of processing parameters on the fabrication of near-net-shape fibre reinforced oxide ceramic matrix composites via sol–gel route

Abstract

The sol infiltration technique was found to be very effective for the fabrication of near-net-shape mullite fibre reinforced ceramic matrix composites (CMCs). The infiltrated sol, in single- and bi-component oxide systems with equivalent molar compositions of Al 2O 3 (A), 60 Al 2O 3:40 SiO 2 (AS), 87 Al 2O 3: 13 ZrO 2 (AZ), and 94 ZrO 2:06 Y 2O 3 (ZY), after drying and calcination, formed the matrix. The discontinuous mullite fibres (as preforms with 15 vol.% fibre content) acted as the reinforcement agents. The characteristics of the CMCs were found to be strongly dependent on the type of the sols (infiltrates) and their viscosity, presence of non-reactive fillers in the sol, number of infiltrations, intermediate and final sintering temperatures and in-situ deposition of carbon in the fabricated materials. The CMCs were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and the three point bend test. SEM indicated fibre pull-out in the fracture surface of the CMCs. The pseudo-ductile character, developed in the CMCs, was evident from the load–elongation curve of the three-point bend test. The carbon-containing CMCs exhibited a modulus value of almost 51 GPa.