Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 732, Issue -, Pages 141-148Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2017.10.166
Keywords
Glass ceramic fillers; Crystallization kinetics; Microstructure; Microhardness; Coefficient of thermal expansion; Softening temperature
Categories
Funding
- National Natural Science Foundation of China [51605042]
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The effects of TiO2 content on the crystallization behavior, microstructure, microhardness, coefficient of thermal expansion (CTE) and softening temperature of CaO-Al2O3-SiO2 glass ceramic fillers were investigated. The results show that the crystallization activation energy (E) firstly decreases and then increases with the TiO2 addition from 10 wt% to 20 wt%. The microstructure and phase composition of glass ceramics importantly depend on the content of TiO2. Low TiO2 content results in formation of Ti-contained crystals (CaTiSiO5) due to phase separation. In contrast, high TiO2 concentrations lead to precipitation of small titanium oxide crystals that act as nuclei, facilitating the development of CaAl2-Si2O8. Furthermore, the formation of crystalline phases is beneficial for improving the microhardness and refractoriness of glass ceramics. The CaO-Al2O3-SiO2 glass with 15 wt% TiO2 addition exhibits the highest crystalline volume fraction possibly due to the lowest activation energy of crystallization. As a result, its microhardness and softening temperature can reach as high as 898.2 HV and 1027 degrees C, respectively. However, its CTE slightly decreases from 7.44 x 10(-6)/degrees C to 6.35 x 10(-6)/degrees C after crystallization treatment because of the formation of CaTiSiO5. (C) 2017 Elsevier B.V. All rights reserved.
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