Crystallization of SiO2–CaO–Na2O Glass Using Sugarcane Bagasse Ash as Silica Source
Abstract: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.
Document Type: Research Article
Affiliations: 1: Departamento Física, Química e Biologia, Universidade Estadual Paulista–UNESP, Presidente Prudente, SP 19060-080, Brazil 2: Department of Building Construction Systems, Eduardo Torroja Institute for Construction Sciences-CSIC, 28033 Madrid, Spain
Publication date: February 1, 2010