Melting Method: The melting method was the earliest and still widely used method for preparing glass ceramics. This method involves uniformly mixing various raw materials and additives, melting them at a high temperature of 1100℃ to 1550℃, homogenizing the glass melt, shaping it, annealing it, and then nucleating and crystallizing it at a specific temperature to obtain glass ceramics with fine, uniform grains and overall crystallization. The biggest advantage of the melting method is that it can utilize any glass forming method, such as pressing, rolling, blowing, drawing, and casting. Compared to conventional ceramic forming processes, this method is suitable for producing products with complex shapes and precise dimensions, facilitating mechanized and automated production, and resulting in glass ceramic products with high density, uniform composition, and no porosity. However, this method requires a high melting temperature, and the amount of crystalline phases in the resulting glass ceramic depends on the overall crystallization ability of the base glass and the heat treatment regime.
Sintering Method: Traditional melting methods for preparing glass ceramics have certain limitations, such as high glass melting temperatures and long heat treatment times. The sintering method overcomes these disadvantages. This method involves water quenching and grinding molten glass to obtain glass powder, which is then sieved and classified to form green bodies. These green bodies are then sintered at a specific temperature, and the samples are cooled in the furnace to obtain the final product. The sintering method is characterized by a lower melting temperature and shorter melting time for the base glass compared to the melting method. Because the glass powder has a higher specific surface area, it crystallizes more easily than glass obtained by the melting method, eliminating the need for nucleating agents. Furthermore, this method does not require a glass-forming stage, making it suitable for preparing glasses melted at extremely high temperatures and glass ceramics that are difficult to form glass. Current research focuses primarily on sintered glass ceramics based on cordierite, enstatite, and lithium aluminum silicon systems.
