PROCESSING OF TRANSPARENT GLASS-CERAMIC

摘要

A transparent glass-ceramic armour known as TRANSPLY<TM> is made from a lithium disilicate based material and includes silica as a majority constituent, lithium oxide as a next major constituent and nucleating agents comprising zirconium dioxide in major part and phosphorus pentoxide in minor part. Improved visual clarity is obtained by the addition of certain refining agents to the initial melt. Improved manufacture involves heat-treatment of a vitreous precursor material, including the steps of: (a) performing a nucleation heat treatment step to produce a nucleus population density in excess of 10<20> per cubic metre, preferably by heating the vitreous material to a nucleation temperature in the range 520 DEG C to 580 DEG C, more preferably 530 DEG C - 570 DEG C, most preferably approximately 550 DEG C, and maintaining said nucleation temperature for a time period in the range 10 to 170 hours, preferably 50-170 hours, most preferably 100 hours; (b) performing a crystallization heat treatment step (optionally time-separated from the nucleation heat treatment step) by further heating the vitreous material to a crystallization temperature, preferably in the range 710 DEG C to 770 DEG C, most preferably approximately 750 DEG C, and maintaining the crystallization temperature for a time sufficient to achieve a desired degree of crystallization, preferably about 15 minutes to two hours; and (c) cooling the material to room temperature at a rate such as to avoid differential temperature damage. The armour may be used in protective visors, buildings, vehicle observation ports and windscreens for the automotive and aircraft industries.