Preparation And Performance Research Of Gangue Glass-ceramic

In recent years, with the fact that coal keeps accounting for a large proportion in our country's energy structure, the gangue, a solid waste which separated in process of coal production, is increasing. Till date, the utilization of such waste is mainly through rough machine, which is, however, low value added. This study is trying to solve the problem by using gangue as main raw material to prepare glass-ceramic. It researches the whole preparation by studying the founding process and properties of different composition base glass. It studies crystallization and sintering behavior of different composition glass-ceramic under different heat treatment, investigates the internal structure of glass-ceramic under different heat treatment to get the construction regulation of glass-ceramic. The macro performances of these glass-ceramics are tested respectively after preparation. As result, a new type coloring process raised. According to experimental studies, this study reaches conclusions as follows:1 The process of using gangue and other material to prepare base glass: When heated, the organic carbon of gangue combustion, the kaolin dehydrate and react with other compositions and come out silicate. The silicate melt, clarify and homogenize to clear glass liquid with lower viscocity under high temperature. The base glass melting process become faster with the temperature raises.Gangue base glass with high Na₂O content and high proportion of SiO₂/Al₂O₃ melt easily: Glass contained with 25% Na₂O melts at 1300?. While base glass with proportion 3.0 of SiO₂/Al₂O₃ melts at 1350?. Glass containing 12% MgO melts at 1400?, the melt temperature increased no matter the MgO containing higer or lower than this rate.2 With the increasing of Na₂O from 10% to 25%, the main crystalline phase in the glass-ceramics is changed over from forsterite to nepheline, and eventually to sodium aluminium silicate. The crystal size grew gradually and the number of crystal follows a rule of increase fast at fist and then decrease slowly. Glass with high MgO content is tend to get forsterite and when MgO content as 19%, crystallization goes well. While the proportion SiO₂/Al₂O₃?2.0, the crystal size increase gradually, the main crystalline phase in the glass-ceramics is changed over from nepheline to forsterite because of remelted of nepheline.3 Sintering of gangue glass-ceramic belongs to liquid phase sintering, which is effected by viscosity and crystallization of glass-ceramic. Sintering of glass-ceramic is faster when the glass liquid with lower viscocity under high temperature, with high Na₂O content, and high proportion of SiO₂/Al₂O₃. For glass with high MgO content, sintering of glass-ceramic is decreased because of a large amount of MgO participation in the crystallization.4 During heat treatment of glass-ceramic, crystallization firstly happen on the surface of glass base when temperature is low, with temperature increasing, both size and quantity of crystal increased. Gangue glass-ceramic began sintering at a certain temperature point, the samples densification gradually with increase of crystal size and quantity. However, when temperature too high, the lower-melting-point crystal remelt, crystal quantity decrease and the melted liquid would cover the gas between granules, which is not good for samples densification. The changes in construction shalll finally lead to the changes of glass-ceramic performances.5 In moulding process, gangue glass-ceramic is colored blue when add with 1% Co₂O₃ and purple with 3% NiO. However, when adding 1% K₂Cr₂O₇, it shows yellow stripe on the sample surface.