Crystallization kinetics of a barium-zinc borosilicate glass by a non-isothermal method
authors Lopes, AAS; Monteiro, RCC; Soares, RS; Lima, MMRA; Fernandes, MHV
nationality International
journal JOURNAL OF ALLOYS AND COMPOUNDS
author keywords Differential thermal analysis; Borosilicate glasses; Non-isothermal process; Crystallization kinetics
keywords DIFFERENTIAL THERMAL-ANALYSIS; PHASE-TRANSFORMATION; LOW-TEMPERATURE; MECHANISM; CERAMICS; BEHAVIOR; OXIDE; PLOT
abstract The crystallization kinetics of a glass with a molar composition 40BaO-20ZnO-30B(2)O(3)-10SiO(2) was investigated. The kinetic parameters, activation energy for crystallization (E-c) and Avrami exponent (n), were evaluated under non-isothermal conditions using the results obtained by differential thermal analysis (DTA) performed at different heating rates. DTA curves exhibited two overlapping exothermic peaks associated with the crystallization of the glass. Barium borate (BaB4O7) was the first crystalline phase to be formed and it was followed by the formation of barium zinc silicate (BaZnSiO4), as identified by XRD. For the first exothermic peak, when the fraction of crystallization (v) increased from 0.1 to 0.9, the local activation energy (Ec(v)) decreased from 700 to 500 kJ/mol, while for the second exothermic peak, E-c(chi) slightly increased from 490 to 570 kJ/mol. For the range of 0.1 < chi < 0.9, the local Avrami exponent (n(chi)) increased from similar to 1 to 1.4 for the first exothermic peak and it decreased from similar to 1.7 to 1.4 for the second exothermic peak. Observation by SEM of the microstructure of sintered glass samples revealed that crystallization started at the surface of glass particles, with growth of lamellar crystallites, that together with some quasi-spherical nano-sized crystallites progressed towards the inside of the glass at the highest sintering temperatures. The change of the local activation energy with the fraction of crystallization suggested that a multi-step kinetic reaction took place during sintering and crystallization of the glass. (C) 2013 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE SA
issn 0925-8388
year published 2014
volume 591
beginning page 268
ending page 274
digital object identifier (doi) 10.1016/j.jallcom.2013.12.086
web of science category Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering
subject category Chemistry; Materials Science; Metallurgy & Metallurgical Engineering
unique article identifier WOS:000331066900042
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journal impact factor 3.779
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