GLASS CERAMIC MATERIAL

摘要

The invention relates to a method of manufacturing a fine-grained glass ceramic material from a thermally crystallisable vitreous material, which may be a composition of the SiO2-Al2O3-Li2O or SiO2-Al2O3-BaO or SiO2-Al2O3-MgO systems containing a nucleating agent such as P2O5, ZrO2 or TiO2, in which method the material is melted, shaped to a desired form and thereafter supported throughout the subsequent thermal processing, which comprises rapidly cooling the shaped material to a temperature in the range which is conducive to fine-grained crystal growth in the material and regulating heat extraction from the material while in that range to induce the required degree of crystal growth, and then continuing cooling of the glass ceramic so produced. In some cases it is preferred to hold the temperature at a substantially constant value in that range for a time, generally not more than 30 minutes. In other cases heat extraction may be continued without interruption during crystallisation.