Research On Crystallization Behavior And Properties Of Red-mud Glass-ceramic

Glass-ceramic is prepared from the original glass via controlled crystallization, and slag glass-ceramic is made from slags. Because of worsing environment situation, it becomes significative to transform slag and some solid wastes into useful materials. This paper reports the glass-ceramics using the most amounts of fly ash and red mud, two kinds of solid wastes. The best nucleation and crystallization temperatures are determined and the kinetics of glass-ceramics are studied by using DTA, then the influences of heat treatments on the crystal phase, the microstructure and the mechanical properties of glass-ceramics are investigated according to the results of the x-ray diffraction and the SEM. Meantime, another three aspects are investigated, which contain the relationship of the micro texture and mechanical property, the influence of different crystal nucleus on red-mud glass-ceramic and the distinctness of red-mud glass-ceramic in melt method and agglomeration method.The results show: the most amounts of red-mud and fly ash are above 90%, and the best heat treatment technics is 697℃, nucleation temperature, for 2h and crystallization temperature 950℃for 2h. For example, taking 5%TiO2 as crystal nucleus, the active energy of glass-ceramics made from fly ash and red mud is 306.37 kJ / mol. n equals 0.7 and nears 1, which shows that the red-mud glass-ceramic is apt to surface crystallization. At the same time, nucleation temperature has a great influence on the crystal-growing mode, but crystallization temperature has a great influence on the crystal state. On the other hand, different crystal phases and different microstructures result in different mechanical properties, so the crystal phase of higher strength and the denser micro texture is beneficial to shaping high strength red-mud glass-ceramics.The results obtained from the investigation of crystal nucleus of red-mud glass-ceramic show: the crystal capability of 5%TiO2 and 5%ZnO is greater than 1%TiO2, and with the increase of TiO2, the main crystal phase change, so crystal nucleus has a influence on the crystal phase and micro structure of red-mud glass-ceramic. In addition, the results obtained from that the red-mud glass-ceramic is made in melt method and agglomeration method show: the micro structure of glass-ceramic made in melt method is denser, and the air hole in it is less than that in agglomeration glass-ceramic, but the micro texture of agglomeration glass-ceramic is evener than melt glass-ceramic. In melt method, the glass-ceramics contain main crystal phase Ca2Al2SiO7 and minor crystal phase Ca(Mg,Fe)Si2O6, and with the increase of crystallization temperature, the main crystal phase and the minor crystal phase has no change, but their proportion changes. However, in agglomeration method, the red-mud glass-ceramic is apt to higher temperature crystallization, when the crystallization temperature increases, the crystal phase changes from Ca2Al2SiO7 to Ca2SiO4.