| Lightweight alumina bubble ceramic possesses many excellent properties, such as low reheat shrinkage value, high softening point under load, high service temperature, and high compressive strength. Therefore, it can serve as heat insulation layer that can directly contact with flame. It has been believed to be the high temperature insulation material with a great future due to its abundant raw materials and high cost performance. At present, the researches on alumina bubble ceramic mainly focus on its macroscopic properties. However, the results obtained by various researchers showed great differences and the service stability of the products was poor. Consequently, it is necessary to carry out a systematic and thorough research on the preparation, microstructure, and so on, of lightweight alumina bubble ceramic.In this paper, the characteristic and present situation of insulation materials, insulating mechanisms and preparation process of lightweight alumina bubble ceramic have been systematically reviewed. Furthermore, the microstructure of alumina bubble, specialties of binders, properties and actuating mechanism of alumina bubble surface-modified by various binders, microstructure and mechanical properties of lightweight alumina bubble ceramics have been studied, and lightweight alumina bubble ceramics with excellent comprehensive properties has been prepared through optimizing batch and processing technology.The microstructure and properties of lightweight alumina bubble, and basic specialties of various binders have been studied systematically at first. The results showed that lightweight alumina bubble was made up of little -Al2O3 crystal grains, which growed well with average size about 50 m. The grains doesn't combine tightly and there exist flaws such as cracks and pores, which result in great variances of pressure resistance of the bubbles, and the average value was just 15.7N. Alumina sol will decompose to high active -Al2O3 with average particle size of 80~200nm after heat-treatment at 500 . Both ammonium aluminum sulfate and aluminum sulfate will be decomposed to nanometer -Al2O3 with average particle size of 6.2nm and 6.7nm respectively according to BET method after heat-treatment at 900 . After heat-treatment at 900-15 00 , cristobalite-type A1PO4 will form due to the reaction between orthophosphoric acid and -AliOa. Formation phases of the reaction of ammonium aluminum sulfate / orthophosphoric acid composite binder(F3) werehighly related to the heat-treatment temperature. After heat-treatment at 900 , aluminum metaphosphate (A1(PO3)3) formed. When the heat-treatment temperature reaches 1200 , some aluminum metaphosphate will decompose to tridymite form aluminum orthophosphate. When it reached 1700 , the high temperature phase cristobalite-type aluminum orthophosphate will be formed.Wet chemical method has been firstly adopted to introduce various binders for surface-modification of alumina bubble. It has been found that the binder distributed evenly on the bubble and into the pore, and in-situ decomposed to nanometer -Al2O3 or in-situ reacted to form aluminum orthophosphate after heat-treating lightweight alumina bubble at certain temperature, which repaired flaws of the bubble. It showed that varieties of binders, concentration, heat-treatment temprature had obvious effects on the compressive resistance of surface-modified alumina bubble. Among these, compressive resistance of alumina bubble surface-modified by composite binder (F3) showed increasing tendency with the increase of heat-treatment temperature. After heat-treatment at 1700 , it reached 39.7N, which is greatly higher than 15.7N that is average compressive resistance of normal bubble without surface modification.According to the researches on the microstructure and mechanical properties of lightweight alumina bubble ceramics, it has been found that binders introduced for surface-modification of alumina bubble through wet chemical method can effectively promote sintering of lightweight alumina bubble cer...
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