ALUMINOTHERMIC-CARBOTHERMAL REDUCTION SYNTHESIS OF NANO CRYSTALLINE Al2O3-Ti(C,N) COMPOSITE WITH DIFFERENT BED TYPES

Ceramic-matrix composites containing TiC-TiN have been used in a variety of application because of their superior properties such as high hardness, good wear resistance and high chemical stability. In this research, effect of coke and coke/calcium beds in synthesis of Al2O3-Ti(C, N) composites using alumino-carbothermic reduction of TiO2 has been investigated. Al, TiO2 and active carbon with additives of extra carbon and NaCl and without additives, in separate procedures, have been mixed. Afterwards, mixtures were pressed and synthesized in 1200oC for 4hrs, in coke and coke/calcium beds, separately. Al2O3-Ti(C,N) composite was synthesized in ternary system of Al-TiO2-C with excess carbon and NaCl additives in calcium/coke bed in 1200 . X-ray diffraction patterns (XRD) results showed that existence of calcium in bed resulted in intensification of reduction atmosphere in samples and formation of Ti(C,N) phase enriched from carbon was accelerated. Crystallite sizes of synthesis Ti(C,N) at 1200 °C in reducing conditions were 22-28 nm.