Effect of different amounts of slag on the crystallization behavior of glass-ceramics produced by natural cooling yellow phosphorus slag

Abstract

CaO–Al₂O₃–SiO₂ (CAS) glass-ceramics were prepared by a melting method using different amounts of natural cooling yellow phosphorus slag as the main material, and afterwards the effects of the slag on the crystallization and properties of glass-ceramics were studied by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallization activation energy E of the glass-ceramic samples was calculated by modified Johnson-Mehl-Avrami (JMA) and Ozawa methods, and Avrami indices n of the samples were analyzed with Augis–Bennett equations. The results showed that the crystallization behavior of glass ceramics was surely affected with the addition of different amounts of slag. The crystallization activation energy calculated with the modified Johnson-Mehl-Avrami (JMA) equation ranged from 200.8678 kJ mol⁻¹ (Slag-1) to 380.0184 kJ mol⁻¹ (Slag-3) and from 220.7858 kJ mol⁻¹ (Slag-1) to 400.6569 kJ mol⁻¹ (Slag-3) by the Ozawa method. The crystallization indices increased from 3.20 (Slag-1) to 4.07 (Slag-3). The main crystalline phases were gehlenite (Ca₂Al₂SiO₇) and akermanite (Ca₂MgSi₂O₇) in Slag-1 and Slag-2, while anorthite (CaAl₂Si₂O₈) and akermanite (Ca₂MgSi₂O₇) were the main crystalline phases in Slag-3. The structure of the grains in the samples changed from spherical to columnar. The Slag-3 sample showed stronger acid resistance, alkali resistance and lower water absorption than Slag-1 and Slag-2.