Abstract
The crystallization process of some glasses in the ternary Na2O–SiO2–PbO system with good chemical stability that can be used for waste inertization was studied using X-ray diffraction (XRD), infrared spectroscopy (FT-IR), differential thermal analysis (DTA) and scanning electron microscopy. The parent glasses were characterized by XRD and FT-IR, and their vitreous state was determined. DTA measurements evidenced glass transition (T g) and crystallization temperatures (T c). The thermal treatments were conducted at vitreous transition temperature (400 °C) and at highest effect of crystallization (650 °C). XRD evidenced the lead and sodium silicate crystalline phases in samples treated at 650 °C for 12 h. Micrometer crystallites dispersed in the glass matrices have affected the transparence of glasses and made them opaque after treatment at 650 °C. The influence of oxide quantities in compositions on the crystallization tendency was revealed. A PbO higher content than that of SiO2 as well as lower Na2O content decreased the tendency of crystallization.
Highlights
Many authors have intensively studied the crystallization process of glasses to apply the results in industrial processes [1,2,3,4,5,6,7,8,9,10,11,12]
The crystallization process of some glasses in the ternary Na2O–SiO2–PbO system with good chemical stability that can be used for waste inertization was studied using X-ray diffraction (XRD), infrared spectroscopy (FTIR), differential thermal analysis (DTA) and scanning electron microscopy
The properties of glass–ceramics are determined by the crystallization phases precipitated from the glasses and their microstructures, which depended on composition of the parent glasses as well as thermal treatment [13,14,15,16]
Summary
Many authors have intensively studied the crystallization process of glasses to apply the results in industrial processes [1,2,3,4,5,6,7,8,9,10,11,12]. The crystallization of glasses can be homogeneous when this phenomenon begins from critical nuclei formation on surface or in volume or heterogeneous when nucleation of foreign solid particles or phase boundaries occurs [18, 19]. Glasses that are obtained by cooling homogeneous (single phase) liquids are generally transparent, but many of them have a heterogeneous structure on a submicroscopic scale [16]. This ‘‘microphase separation’’ is found in numerous binary and ternary silicate and borate systems (e.g. Na2O–SiO2, Li2O–SiO2, Na2O–CaO–SiO2, etc.) [3, 6, 8]. The authors found that phase separation increases the crystal nucleation and growth rates
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