| 가압-진공 하이브리드 주입 성형에 의한 알루미나의 성형에 미치는 다단 가압의 영향 |
| 조경식, 이현권, 우병준 |
| 금오공과대학교 신소재시스템공학부 |
| Effect of Step Pressure on Shape Forming of Alumina by Pressure-Vacuum Hybrid Slip Casting |
| Kyeong-Sik Cho, Hyun-Kwuon Lee, Byeong-Joon Woo |
| School of Advanced Materials & System Engineering, Kumoh National Institute of Technology |
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| ABSTRACT |
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Conventional cold isostatic pressing, slip casting, and filter pressing are not completely suitable for fabricating large plates because of disadvantages such as the high cost of equipment and formation of density gradient. These problems could be avoided by employing pressure-vacuum hybrid slip casting (PVHSC). In the PVHSC, the consolidation occurs not only by the compression of the slip in casting room, but also by vacuum sucking of the dispersion medium around the mold. We prepared the alumina bodies by the PVHSC in a static- or stepwise-pressure manner for loading up to 0.5 MPa using an aqueous slip. The green bodies were dried at $30^{circ}C$ with 40 ~ 80% relative humidity. Under static pressure, casting induced a density gradient in the formed body, resulting in cracking and distortion after the firing. However, the stepwise pressure loading resulted in green bodies with homogeneous density, and the minimization of the appearance of those defects in final products. Desirable drying results were obtained from the cast bodies dried with 80% RH environment humidity. When sintered at $1650^{circ}C$ for 4 h, the alumina plate made by stepwise-pressure casting reached full density (> 99.7% relative density). |
| Key words:
Alumina, Slip casting, Shape forming, Pressure slip casting, Vacuum slip casting |
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