A novel technique for fabrication of near-net-shape CMCs

A sol-gel vacuum infiltration technique has been developed for the fabrication of near-net-shape ceramic matrix composites (CMCs) using discontinuous mullite fibre preform with 15 vol.% of fibre content and ZrO(2)(.)10 Wt-% Y2O3 sol as the infiltrant. Effect of sol viscosity, number of infiltration and calcination temperature on physico-mechanical properties of fabricated CMCs were examined. Characterization of the fibre preform, matrix material (in the form of ceramic specimen without fibre) and the developed CMCs were performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD indicated the presence of cubic (c) and tetragonal (t) zirconia in both the CMCs and the ceramic specimens calcined even at 1400degreesC. Flexural strength of the CMCs and the ceramic specimens (calcined at 1400degreesC), determined by the three-point bending test, was found to be about 14 mPa and 1(.)40 mPa, respectively. SEM indicated multiple fracture of the matrix which gave rise to pseudo elasticity. This is also evident from the load-displacement curve of the three-point bend test. SEM studies also indicated fibre pull-out in the fracture surface of the CMCs