硅灰石玻璃陶瓷的析晶特性及其析晶热力学和动力学

摘要

Wollastonite glass ceramics were prepared using the reactive crystallization sintering method by mixing waste glass powders with gehlenite. The crystallization property, thermodynamics, and kinetics of the prepared wollastonite glass ceramics were determined by X-ray diffraction analysis, scanning electron microscopy, energy-dispersive spectroscopy, high-resolution transmission electron microscopy, and differential thermal analysis. Results showed that crystals of wollastonite and alumina could be found in the gehlenite through its reaction with silicon dioxide. The wollastonite crystals showed a lath shape with a certain length-to-diameter ratio. The crystals exhibited excellent bridging and reinforcing effects. In the crystallization process, the aluminum ions in gehlenite diffused into the glass and the silicon ions in the glass diffused into gehlenite. Consequently, the three-dimensional frame structure of gehlenitewas partially damaged to form a chain-like wollastonite. The results of crystallization thermodynamics and kinetics indicated that crystallization reaction could occur spontaneously under a low temperature (1173 K), with 20 wt％ gehlenite added as the reactive crystallization promoter. The crystallization activation energy was evaluated as 261.99 kJ/molby using the Kissinger method. The compression strength of the wollastonite glass ceramic samples (7.5 cm×7.5 cm) reached 251 MPa.%将废玻璃粉与钙铝黄长石混合,使用反应析晶烧结法制备了硅灰石玻璃陶瓷.采用X射线衍射分析、扫描电镜、能谱、高分辨透射电镜和热分析等方法,研究了硅灰石玻璃陶瓷的析晶特性及其析晶热力学与动力学.结果表明,钙铝黄长石与二氧化硅发生反应,析出硅灰石及氧化铝.该硅灰石晶体为一定长径比的板条状,能起到很好的桥联与补强作用.反应析晶过程中钙铝黄长石的铝离子向玻璃中扩散,玻璃的硅离子向钙铝黄长石中扩散,使具有三维架状结构的钙铝黄长石遭到部分破坏,形成链状结构的硅灰石.析晶热力学及动力学研究结果表明,在较低温度(1173 K)下,添加20 wt％钙铝黄长石作为反应析晶促进剂,该析晶反应可自发进行.使用Kissinger法计算析晶活化能为261.99 kJ/mol.制备的大块硅灰石玻璃陶瓷(7.5 cm×7.5 cm)抗压强度可达251 MPa.