Freeze-Drying Defect Control of Alumina-Based Ceramic Body Prepared with Gel Casting Technology[J]. 2014, 48(1): 123-126+132.DOI: 10.7652/xjtuxb201401021.
In producing precision ceramic casting mould of complex components by gel casting technology
the internal cracks generated in the freeze-drying process affect the mould quality seriously. In this study
computer tomography(CT)was employed to track the crack generation. The results show that internal cracks occur when water loss rate is within 20%-60%. According to the freeze-drying theory
the internal crack generation mechanism in gel casting ceramic body is analyzed. When the temperature of the subsurface gets higher than the eutectic temperature of the green body(-3.6 ℃)in the rapid ice sublimation stage(in which the water loss rate is about 20%-60%)
the frozen layer melts to result in a dramatic drop in strength and an increase in drying stress
leading to cracks generation. Lowering the drying temperature(from 15 ℃ to -5 ℃)and setting through holes of 0.8 mm in diameter in the green body can keep the subsurface temperature lower than the eutectic temperature in the rapid ice sublimation stage to prevent the crack generation effectively.
关键词
Keywords
references
JANNEY M A. Method for molding ceramic powders: US, 4894194[P]. 1990-01-16.
JANNEY M A, NUNN S D, WALLS C A, et al. The handbook of ceramic engineering[M]. New York, USA: Marcel Dekker, 1998: 13-15.
JANNEY M A, OMATETE O O. Method for molding ceramic powders using a water-based gelcasting: US, 5028362[P]. 1991-06-02.
KRAUSE C. ORNL's gelcasting: molding the future of ceramic forming?[EB/OL].[2013-04-21]. http:∥www.ornl.gov/info/ornlreview/rev28-4/text/gelcast.htm.
SU Shuqiang, DING Zhihua, HUA Zezhao. Study on the measurement of the product temperature at the moving sublimation interface during the freeze drying process[J]. Journal of Engineering Thermophysics, 2004, 25(5): 852-854.