Effects of additives and sintering temperature on phase evolution and properties of carbon-clay ceramic composites

Effects of additives on phase development and physico-mechanical properties of mullite-carbon was investigated. Powdered clay, kaolinite and graphite of predetermined compositions were blended with additives using ball mill for 3 hrs at 60 rev/min. Samples were produced by uniaxial compression and sintered between 1400 degrees C and 1600 degrees C for one hr. They were characterized for various properties, developed phases and microstructural features. It was observed that the properties and phase developments in the samples were influenced by the additives. 10 wt % SiC served as nucleating point for SiC around 1400 degrees C. 10 wt % TiO2 lead to development of 2.5 wt % TiC at 1500 degrees C which increased to 6.8 wt % at 1600 degrees C. Ifon clay in the sample leads to development of anorthite and microcline in the samples. 10 wt % TiO2 is effective as anti-oxidant for graphite up to 1500 degrees C. Base on strength and absorbed energy, sample C (with 10 wt % TiO2) sintered at 1500 degrees C is considered to be optimum.