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Suppression of Surface Crystallization of CaO-Al2O3-SiO2 Glass via Hydrothermal Treatment under Acidic Conditions
Langmuir ( IF 3.7 ) Pub Date : 2024-01-09 , DOI: 10.1021/acs.langmuir.3c03268
Shingo Machida 1
Affiliation  

This study demonstrates bulk crystallization of CaO-Al2O3-SiO2 (CAS) glass with suppression of surface crystallization via hydrothermal treatment under acidic conditions. It focuses on CAS glass-ceramics (GCs) with precipitated metastable CaAl2Si2O8, a layered calcium aluminosilicate, because it features a single bulk crystallization phase with a relatively lower volume fraction. After hydrothermal treatment under nitric acid, the resultant glasses possessed silica-rich surface layers. When the obtained glass with the surface layer was heat-treated at 1100 °C for 6 h, the resultant surface layer was easily peeled off by hand, and the cross section of both the edge and interior of the specimen showed precipitation of only metastable CaAl2Si2O8. The volume fraction of this crystalline phase was ∼50%, which was 20% larger than those reported for CAS GCs heat-treated at 1050 °C. By contrast, anorthite, the stable phase of CaAl2Si2O8, grew and invaded from the surface to the interior of the glass specimen heat-treated at 1100 °C for 6 h but not subjected to the hydrothermal treatment. These results indicate that the presence of a silica-rich layer on the glass surface suppressed surface crystallization even at the temperature that promotes surface crystallization, suggesting that the range of heat treatment conditions for glass crystallization can be expanded, enabling microstructural control of CAS GCs.

中文翻译:


酸性条件下水热处理抑制CaO-Al2O3-SiO2玻璃表面结晶



本研究证明了 CaO-Al 2 O 3 -SiO 2 (CAS) 玻璃的块体结晶,并通过酸性条件下的水热处理抑制了表面结晶。它专注于具有沉淀亚稳态CaAl 2 Si 2 O 8 (一种层状铝硅酸钙)的CAS 玻璃陶瓷(GC),因为它具有体积分数相对较低的单一块体结晶相。在硝酸下水热处理后,所得玻璃具有富含二氧化硅的表面层。当得到的带有表层的玻璃在1100℃下热处理6小时时,所得表层很容易用手剥离,并且样品边缘和内部的横截面仅显示出亚稳态CaAl的析出。 2 Si 2 O 8 。该结晶相的体积分数约为 50%,比报道的在 1050 °C 下热处理的 CAS GC 的体积分数大 20%。相比之下,在1100℃下热处理6小时但未进行水热处理的玻璃样品中,CaAl 2 Si 2 O 8的稳定相钙长石生长并从表面侵入到内部。这些结果表明,即使在促进表面结晶的温度下,玻璃表面富二氧化硅层的存在也会抑制表面结晶,这表明玻璃结晶的热处理条件范围可以扩大,从而能够控制 CAS GC 的微观结构。
更新日期:2024-01-09
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