Crystallization of SiO2–CaO–Na2O Glass Using Sugarcane Bagasse Ash as Silica Source
This work reports the feasibility results of recycling sugar cane bagasse ash (SCBA) to produce glass–ceramic. The major component of this solid residue is SiO2 (>89%). A 100 g batch composition containing ash, CaO and Na2O was melted and afterward, poured into water to produce a glass frit. The crystallization kinetic study by nonisothermal method was performed on powder samples (<63 m) at five different heating rates. Wollastonite is the major phase in crystallization at T>970°C, and below this temperature there is a predominance of rankinite. The crystallization activation energies calculated by the Kissinger and Ligero methods are equivalent: 374±10 and 378±13 kJ/mol. The growth morphology parameters have equal values n=m=1.5 indicating that bulk nucleation is the dominant mechanism in this crystallization process, where there is a three-dimensional growth of crystals with polyhedron-like morphology controlled by diffusion from a constant number of nuclei. However, differential thermal analysis (DTA) curves on both monolithic and powder glass samples suggest that crystallization of the powder glass sample occurs through a surface mechanism. The divergence in both results suggests that the early stage of surface crystallization occurs through a three-dimensional growth of crystals, which will then transform to one-dimensional growth.
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Document Type: Research Article
Departamento Física, Química e Biologia, Universidade Estadual Paulista–UNESP, Presidente Prudente, SP 19060-080, Brazil
Department of Building Construction Systems, Eduardo Torroja Institute for Construction Sciences-CSIC, 28033 Madrid, Spain
Publication date: 2010-02-01