| Title |
Effects of In Situ YAG on Properties of the Pressurless Annealed Sic-TiB_2 Electroconductive Ceramic Composites |
| Authors |
신용덕(Shin, Yong-Deok) ; 주진영(Ju, Jin-Young) ; 고태헌(Ko, Tae-Hun) |
| Keywords |
YAG(Al_5Y_3O_{12} ; ) ; Liquid-Phase-Sintered(LPS) ; Electroconductive ceramic composite ; PTCR ; Transition metal TiB_2ZrB_2 |
| Abstract |
The composites were fabricated 61[vol.%] {β}-SiC and 39[vol.%] TiB_2 powders with the liquid forming additives of 8, 12, 16[wt%] Al_2O_3+Y_2O_3 as a sintering aid by pressureless annealing at 1650[°C] for 4 hours. The present study investigated the influence of the content of Al_2O_3+Y_2O_3 sintering additives on the microstructure, mechanical and electrical properties of the pressureless annealed SiC-TiB_2 electroconductive ceramic composites. Reactions between SiC and transition metal TiB_2 were not observed in the microstructure and the phase analysis of the pressureless annealed SiC-TiB_2 electroconductive ceramic composites. Phase analysis of SiC-TiB_2 composites by XRD revealed mostly of {α}-SiC(6H), {β}-SiC(3C), TiB_2, and In Situ YAG(Al_2Y_3O_{12}). The relative density of SiC-TiB_2 composites was lowered due to gaseous products of the result of reaction between SiC and Al_2O_3+Y_2O_3. There is another reason which pressureless annealed temperature 1650[°C] is lower 300~450[°C] than applied pressure sintering temperature 1950~2100[°C]. The relative density, the flexural strength, the Young's modulus and the Vicker's hardness showed the highest value of 82.29[%], 189.5[Mpa], 54.60[Gpa] and 2.84[Gpa] for SiC-TiB_2 composites added with 16[wt%] Al_2O_3+Y_2O_3 additives at room temperature. Abnormal grain growth takes place during phase transformation from {β}-SiC into {α}-SiC was correlated with In Situ YAG phase by reaction between Al_2O_3 and Y_2O_3 additive during sintering. The electrical resistivity showed the lowest value of 0.0117[{Ω}·cm] for 16[wt%] Al_2O_3+Y_2O_3 additives at 25[°C]. The electrical resistivity was all negative temperature coefficient resistance (NTCR) in the temperature ranges from 25°C to 700[°C]. The resistance temperature coefficient of composite showed the lowest value of -2.3×10^{-3}[°C]^{-1} for 16[wt%] additives in the temperature ranges from 25[°C] to 100[°C]. |