Study On Synthesis Of Porous Calcium Hexaluminate

Energy shortage has been become one of the main factors which prevent the developing speed of the world economy in 21 century. Developing the energy savings engineering rapidly and using the high quality insulating materials widely are very important to the construction of the national economy. As a new, environmental and excellent insulating material, calcium hexaluminate with porous microstructure has been noticed by some overseas scientists. This porous material can substitute for the conventional insulating materials, such as refractory fiber materials, and its application prospect is very extensive.The influence of a series factors on phases evolution, microstructure and physical properties of the porous calcium hexaluminate has been investigated by means of TG-DSC, XRD and SEM in this paper. The main results are as follows:1).The optimal synthesis temperature of calcium hexaluminate is above 1500 C and no planar grain form in the material using pseudo-boehmite as raw material. Correspondingly, the optimal synthesis temperature is about 1500'C and the morphology of calcium hexaluminate grains is all planar using industrial y-alumina, active a-alumina and aluminium hydroxide as raw materials.2). The physical properties, optimal synthesis temperature and microstructure of porous calcium hexaluminate are influenced distinctly by the particle size distribution of industrial y-alumina. With increasing of average particle size of industrial y-alumina, the thickness of the planar grain decreases gradually, the pore size enlarges, the apparent porosity adds and the cold rushing strength descends sharply. The largest amount of calcium hexaluminate appears when the particle sizes of industrial y-alumina and lightweight calcium carbonate are close each other.3). Compared with the temperature factor, the influences of moulding pressure, heating time and mechanical milling time on physical properties of the porous material is on the small side.4). Introducing carbon black into the material can decrease the thickness of the planar grain , increase the apparent porosity and descend the cold rushing strength correspondingly.5). The influence of Mg(CH3COO)2 content on apparent porosity is insignificant, but on cold rushing strength and microstructure is distinct. With increasing of content of Mg(CH3COO)2, the grain size minishes and the cold rushing strength enhances. The grain size enlarges reversely when the content of Mg(CH3COO)2 exceeds 4%.6). The influence of uf-SiO2 content on apparent porosity, cold rushing strength and microstructure is significant. With increasing of content of uf-SiO2, the size of planar grain decreases. No planar grain with edge forms when the content of SiO2 exeeds 1%.