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정광철,주경,전윤석,오근호,김의훈,이석근,Chung, K.C.,Joo, K.,Chun, Y.S.,Orr, K.K.,Kim, E.H.,Lee, S.K. 한국세라믹학회 1989 한국세라믹학회지 Vol.26 No.2
Al2O3/SiC composite-material was synthesized by the birth-spread mechanism through the carbothermal reduction reaction of SiO2 in Ha-Dong Kaolin with carbon powder under H2 gas atmosphere at 1300~140$0^{\circ}C$. Average diameter of synthesized SiC whiskers were 1${\mu}{\textrm}{m}$ and aspect ratio (c/a) was 10~100. Al2O3 particles and SiC whiskers were mixed homogeneously in the reacted pellet.
이중조직을 갖는 Y-TZP/Y-TZP-$Al_2O_3$ 복합체의 열충격 거동
황규홍,김의훈,김환,Hwang, K.H.,Kim, E.H.,Kim, Hwan 한국세라믹학회 1992 한국세라믹학회지 Vol.29 No.4
Duplex composites such as Y-TZP/Y-TZP-20 wt.% Al2O3 and Y-TZP/Y-TZP- 40 wt.% Al2O3 were made by mixing the sieve-shaked granules followed by isostatic pressing and sintering at 150$0^{\circ}C$ for 1 hour. So Y-TZP became matrix region and Y-TZP-20 wt.% Al2O3 or Y-TZP-40 wt.% Al2O3 became dispersed regions. In these composites, propagating cracks due to thermal shock always run into the dispersed region because these regions act as compressive zone due to low thermal expansion than matrix region. So duplexes having dispersed regions of Y-TZP-40 wt.% Al2O3 showed higher retained strength after thermal shock than matrix only composites because crack propagations were stopped more or less in the dispersed region. But when crack propagations were much more easy than matrix like Y-TZP-20 wt.% Al2O3 region, retained strength was decreased than the matrix only composites despite of the low initial strength.
황규홍,박정환,윤태경,김의훈 국립경상대학교 공과대학 부설 첨단소재연구소 1993 尖端素材 Vol.3 No.-
The reaction-sintered alumina ceramics were fabricated using the oxidation of Al, and their properties were measured. Alumina ceramics of low dimensional changes were prepared from the Al₂O₃/Al powder mixtures using the volume expansion due to the oxidation of Al. Intensive milling process such as attrition milling was beneficial for homogeneous oxidation of Al. After isopressing at 50 to 400 MPa the specimens were oxidated at 800∼1200℃ for 8 hrs. During this process fine alumina grain was formed at the surface of Al and volume expansion was occured. Sintering was carried out at 1450 to 1600℃ for 3 hrs. The sintered density of 97% theoretical was achieved, but low contents of Al leads to relatively high shrinkage of about 8%. On the other hand Al₂O₃/AlMg powder compacts were easily densified at the relatively low sintering temperature of 1450℃. But relatively high shrinkage was obtained due to the spinel formation. So SiC was added to compensate the large shrinkage because the volume of SiC was much increased during the oxidation that near net shape product could be fabricated. But in the contrary to the Al₂O₃/Al composites, the sintered body of Al₂O₃/Al-Mg/SiC was consisted of alumina and spinel phases. And mullite was formed at the higher SiC contents.