| Title |
Effect of In Situ YAG on Microstructure and Properties of the Pressureless-Sintered SiC-ZrB_2 Electroconductive Ceramic Composites |
| Authors |
신용덕(Shin, Yong-Deok) ; 주진영(Ju, Jin-Young) |
| Keywords |
Electroconductive ceramic composites ; Pressureless-sintered ; Al_2O_3+Y_2O_3 sintering additives ; PTCR ; In Situ YAG(Al_5Y_3O_{12}) |
| Abstract |
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-sintered SiC-ZrB_2 electroconductive ceramic composites. Phase analysis of composites by XRD revealed mostly of {α}-SiC(4H), ZrB_2, {β}-SiC(15R) and In Situ YAG(Al_5Y_3O_{12}). The relative density and the flexural strength showed the highest value of 86.8[%] and 203[Mpa] for SiC-ZrB_2 composite with an addition of 8[wt%] Al_2O_3+Y_2O_3 as a sintering aid at room temperature respectively. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed 3.7 and 3.6[MPa·m^{1/2}] for SiC-ZrB_2 composites with an addition of 8 and 12[wt%] Al_2O_3+Y_2O_3 as a sintering aid at room temperature respectively. 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 additives during sintering. The electrical resistivity showed the lowest value of 6.5×10^{-3}[({Ω}·cm] for the SiC-ZrB_2 composite with an addition of 8[wt%] Al_2O_3+Y_2O_3 as a sintering aid at room temperature. The electrical resistivity of the SiC-ZrB_2 composites was all positive temperature coefficient(PTCR) in the temperature ranges from 25[°C] to 700[°C]. The resistance temperature coefficient showed the highest value of 3.53×10^{-3}/[°C] for SiC-ZrB_2 composite with an addition of 8[wt%] Al_2O_3+Y_2O_3 as a sintering aid in the temperature ranges from 25[°C] to 700[°C]. In this paper, it is convinced that {β}-SiC based electroconductive ceramic composites for heaters or ignitors can be manufactured by pressureless sintering. |