Synthesis of Al2O3-TiC Composites by SHS and Hot-pressing of the Synthesized Powders

초록

In general, Al2O3-TiC composites consist of fine titanium carbide grains which were dispersed in alumina matrix and TiC hardens alumina matrix to cause the limit of grain growth and to give a great improvement in toughness. In this study, differently from conventional method with commercial Al2O3 and TiC powders as starting materials, Al2O3-TiC composites were synthesized from two elements and an oxide (TiO2-Al-C system) by SHS technique, a spontaneous exothermic reaction of elements, and then compared physical properties of two hot-pressed bodies for synthesized powders and commercial powders of Al2O3 and TiC. Those specimens were hot-pressed at 1800℃, 1850℃ and 1900℃, under a pressure of 30MPa for 1hour, respectively. As a result of checking the effect of various carbon sources through SHS method, carbon black was better in reactivity rather than activated carbon and graphite. According to results of thermal analysis and XRD, Al phase reacted with TiO2 at about 1000℃ to form Al2O3 and remaining Ti. And coinstantaneously Ti reacted with the carbon black to produce TiC, accordingly Al2O3-TiC composites were formed. Relative density, flexural strength and hardness in properties of two hot-pressed bodies with different starting materials were similar to each other. However, hot-pressed bodies of SHS synthesized powders had a superior fracture toughness. This is considered because Al2O3 and TiC phases were complicatedly connected together at the beginning of the formations.