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Exploring on Densification of Ceramic Fabricating at Ultra-temperature

Author: BaoZuo
Tutor: FuZhengYi；ZhangJinYong
School: Wuhan University of Technology
Course: Materials Science
Keywords: Al2O3/YAG SHS eutectic ceramic microstructure
CLC: TQ174.1
Type: Master's thesis
Year: 2011
Downloads: 27
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Abstract

Al2O3/YAG oxide eutectic was considered as one of candidates always exists in the heat and oxidizing environments, due to the excellent heat-resistant properties. In this paper, Al2O3/YAG oxide eutectic was studied combine with the self-propagating high-temperature synthesis (SHS) which have some advantages as the reaction can reach to very ultra temperature and finished in few seconds, and we researched the possibility of fabricating densification ceramics on ultra high temperature, then compared the microstructure of this ceramic making in different methods.The SHS reaction was used as a heat resource and the raw powder which mixed in the eutectic point was pressed into a cylindrical and bodied in the center of it. The most applicable systems was chosen after tested and analyzed the different SHS systems temperature curves, and compared the bulks which was obtained from different SHS systems; the effects of microstructure relative with adding weigh of SHS reaction and changing size of raw powders was analyzed. The result declared that the Al2O3/YAG eutectic ceramics was obtained by using self-propagating high-temperature synthesis (SHS) method; the perfect bulk was produced when 160g Ti-C reaction was used in this research; and the uniform sample was obtained when the raw powder size was almost in the same scale. The phase and microstructure researches illustrated that there were only two phase Al2O3 and YAG was existed and this two phase was coupling growth. The component phases form an interpenetrating and interconnecting complex three-dimensional network known as Chinese script (CS) structure and some kinds of new microstructures with regular growth morphology are surveyed in the eutectics prepared by this technique which are never found in the Al2O3/YAG binary eutectic in previous reports. No amorphous phases are observed at the interfaces the Al2O3 and YAG phases and relatively compatible interfaces are formed throw the HRTEM testing.In this study, we also used other two methods like Hot Press (HP) and Electric Beam Melting (EBM) to fabricate the Al2O3/YAG eutectic ceramic. The phase and microstructure was analysis to compare different method. The density and hardness was measured, and the fracture toughness was accounted from hardness testing. The density and hardness of HP sample was less, and the microstructure was not form like the other two samples which was interconnecting complex three-dimensional network. The EBM sample had fine texture and higher density, but it was too small and hardly to measured mechanical properties like hardness and fracture. Contrast with HP and EBM method, the SHS method not only could produce a bulk with fine microstructure and good properties, but also was a cheaper way to fabricate Al2O3/YAG eutectic ceramic.

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