Duke D A, Chase G A
Appl Opt. 1968 May 1;7(5):813-8. doi: 10.1364/AO.7.000813.
Titania- and zirconia-nucleated glasses in the basic Li(2)Al(2)O(4)-SiO(2) system were found suitable for casting relatively large mirror blanks. Upon heat treatment, these glasses crystallized uniformly to yield transparent, very low expansion beta quartz solid solution glass-ceramics. Special care was required in processing large diameter blanks, owing to localized temperature increases resulting from the exothermic heat of crystallization. Glass-ceramics with a wide range of beta quartz solid solution stability resulted in a uniform product. Transparent glass-ceramic mirror blanks were obtained with average expansion coefficients from 5 degrees C to 50 degrees C of 0 +/- 0.3 x 10(-7)/ degrees C. Ware up to 15 cm thick was processed to less than 10 micro/cm strain, with no change in expansion or transparency through the blank. Work with thick ware provided additional insight into the problems that might be encountered in the fabrication of very large castings.
在碱性Li₂Al₂O₄ - SiO₂体系中发现，以二氧化钛和氧化锆为晶核的玻璃适合铸造相对较大的镜坯。经过热处理，这些玻璃均匀结晶，形成透明的、极低膨胀率的β - 石英固溶体微晶玻璃。由于结晶放热导致局部温度升高，加工大直径坯料时需要特别小心。具有广泛β - 石英固溶体稳定性的微晶玻璃可得到均匀的产品。获得了平均膨胀系数在5℃至50℃范围内为0 ± 0.3×10⁻⁷ /℃的透明微晶玻璃镜坯。加工厚度达15厘米的制品时，应变小于10微应变/厘米，整个坯体的膨胀和透明度均无变化。对厚制品的研究为制造非常大的铸件时可能遇到的问题提供了更多见解。
