Research Of CaO/SiO₂ Ration On The Structure And Performance Of CAS Glass-ceramics

In recent years, with the development of the glass-ceramics industry of CaO-Al₂O₃-SiO₂ system and the main crystal phase of the β-wollastonite, lots of research papers were published which included crystallization, composition, techniques, properties and so forth. CaO content is the fundamental and important composition of the CAS glass-ceramics, it directly affect the heat treatment of the sintering and crystallization and physiochemical performance such as the coefficient of thermal expansion, transition temperature, mechanical properties, microstructure, but the former researches were only on some aspects instead of a whole view, so it is necessary to do a total research of the influence of the CaO content.In this paper, the subject takes the CaO-Al₂O₃-SiO₂ system glass-ceramics of whose main crystallization phase is β-wollastonite as the research object, prepares the glass-ceramics by sintering. The kinds, sizes and contents of the crystallization are controlled by adjusting the content of the basic glass components- CaO. The relationship between the content of component and the heat treatment and physiochemical performance is studied, such as microstructure, thermal expand coefficient, hardness, etc. Also some national and industry standards of the natural facing stones and building decorative glass-ceramics are used to test the sample glass-ceramics as well, such as GB/T 9966.1-9966.6 2001 and JC/T872-2000.The Kissinger equation and sintering kinetics equation are first used to calculate the crystallization and sintering activation energy, respectively. The initiative time of the sintering and crystallization are obtained by grads stove and polarized microscope, analyzed the influence of the CaO content on the processing of the glass-ceramics, then the hardness, bulk density, true porosity, water absorption and acid resistance are tested.The experimental results show that the increase of CaO promotes the crystallization and sintering of glass-ceramics and decrease the activation energies, the initiative time of the sintering and crystallization are decreased also, it is good for crystallization, but the range of the sintering is decreased, and have negative effect on sintering especially when CaO content is more than 20wt%, this is bad for leveling and compacting process. With the increase of CaO content, the compressive strength, flexural strength, density, abrasion resistance, acid resistance are increased also due to the increase of the β-wollastonite. But with the sintering processing is hard to continue, the porosityand water absorption ratio are increased, this is because the glass-ceramics can not be compacted thoroughly, and the surface is not leveling.The results can be got as the best synthesis performances of the glass-ceramics can be got when the CaO/ SiO2content is between 0.24—0.34.