The effect of Al content on the processing of reaction-bonded Al2O3 (RBAO) ceramics using 40v/o ~ 80v/o Al- Zn-Mg alloy powder was studied in order to improve traditional RBAO ceramic processes that use ~ 40v/o pure Al powder. The influence of high Al content in starting Al2O3-Al alloy powder mixtures on its particulate characteristics, reaction-bonding, microstructure, physical and mechanical properties was revealed. Starting Al2O3-Al alloy powder mixtures with 40v/o ~ 80v/o Al alloy powder were milled, reaction-bonded, post-sintered, and characterized. With an increasing Al alloy content, the milling efficiency of Al alloy powder was lowered, resulting in a larger particle size after milling. However, in spite of the larger particle size of Al alloy powder, the oxidation, i.e., reaction-bonding, of the Al alloy was successfully completed via solid and liquid state oxidation, in which the activation energy of the oxidation was nearly the same regardless of Al alloy content. After reaction-bonding and post-sintering at 1600 oC, RBAO ceramics from 80v/o Al alloy content showed a relative density of ~97% and a flexural strength of 251 MPa compared to ~ 96% and 353 MPa for RBAO ceramics from 40v/o Al alloy content, respectively. The lower flexural strength at 80v/o Al alloy content was due to the weak spinel phase that formed from Zn, Mg alloying elements in Al.

Fabrication of reaction-bonded Al2O3 (RBAO) ceramics using Al-Zn-Mg alloy powder was studied in order to improve traditional RBAO ceramic processing using Al powder. The influence on reaction-bonding and microstructure, as well as on physical and mechanical properties, of the particulate characteristics of the Al2O3-Al alloy powder mixtures after milling, was revealed. Variation of the particulate characteristics of this Al2O3-Al alloy powder mixture with milling time was reported previously. To start, the Al2O3-Al alloy powder mixture was milled, reaction-bonded, post-sintered, and characterized. During reaction-bonding of the Al2O3-Al alloy powder mixture compacts, oxidation of the Al alloy took place in two stages, that is, there was solid- and liquid-state oxidation of the Al alloy. The solid-state oxidation exhibited strong dependence on the density of surface defects on the Al-alloy particles formed during milling. Higher milling efficiency resulted in less participation of the Al alloy in reaction-bonding. This was because of its consumption by chemical reactions during milling, and subsequent powder handling, and could be rather harmful in the case of over-milling. In contrast to very little dependence of oxidation of the Al alloy on its particle size after milling, the relative density, microstructure, and flexural strength were strongly dependent on particle size after milling (i.e., on milling efficiency). The relative density and 4-point flexural strength of the RBAO ceramics in this study were ~98% and ~365 MPa, respectively, after post-sintering at 1,600˚C.

본 연구에서는 Cu-Cu2O의 공정반응에 의한 구리와 알루미나의 직접접합에 대하여 연구 하였다. 1.5×10-1torr, 1015˚C에서 산화시킨 후 10-3torr, 1075˚C에서 접합시킨 시편의 접합력과 계면특성을 인장시험, SEM, EDS 및 XRD를 통하여 분석하였다. 3분 산화시켜 접합하면 우수한 접합강도를 보이며 산화시간이 이보다 짧거나 길면 결합력은 저하하였다. 과단은 알루미나 공정조직 계면에서 발생하였으며 파단후 Al2O3표면에는 Cu쪽에서 빠져나간 Cu2O nodule의 존재하였는 바 접합력은 Cu2O-Al2O3계면보다는 Cu-Cu2O계면에 좌우됨을 보여주고 있다. 접합력은 접합시간에 따라 완만한 증가를 보였으며 CuAl2O4및 CuAlO2의 반응생성물이 접합중 형성되었다.