| 초록 |
Preparation of electrical conductive ceramics was investigated in order to determine the possibility of its advanced ceramic application. As you know, nonoxide ceramics, boride material has excellent properties of high hardness, high melting point, and good electrical conductivity, etc. Titanium diboride (TiB2) has excellent electrical conductivity equivalent to pure iron such as 107S/m (10-5Ωcm) at room temperature like steel. In this study, the effect of sintering aids addition on the pressureless sintering process of TiB2 ceramic as a good electrical conductivity was investigated and discussed from microstructual and compositional viewpoints. The addition of both Cr and C as the sintering aids accelerated the densification of TiB2 significantly. Simultaneous addition of approximately 7mass% Cr and 1mass% C resulted in high density (pore free), high bending strength (400MPa), and high Vickers hardness (23GPa). According to the X-ray diffraction data of TiB2 composites fired at 900 to 1900˚C showed that Cr and C reacted with TiB2 to from CrB and TiC during the sintering process. Both CrB and TiC were formed at the grain boundaries of TiB2 matrix. Also, the solid solution between TiB2 and sintering aids was recognized by EPMA. The SEM micrograph observation supported that a liquid phase was significantly concerned in the TiB2 sintered body. The fracture surface of TiB2 sintered body showed both transgranular and intergranular fracture mode. It is considered that the addition of both Cr powder and C powder was effective in promoting the bonding between grains without abnormal grain growth and removing pores with absorbed oxygen by reduction reaction to achieve high density. The electrical conductivity of the sample was 107S/m and 106S/m at room temperature and 800˚C, respectively. The wire electrical discharge machining conditions on the surface roughness was discussed. The surface roughness of the sample increased with increasing cutting speed (5 to 40mm2/min). |
