Microstructure development in clays upon heat treatment: Kinetics and equilibrium
authors Santana, LNL; Gomes, J; Menezes, RR; Neves, GA; Lira, HL; Segadaes, AM
nationality International
journal APPLIED CLAY SCIENCE
author keywords Clays; Heating parameters; Phase transformations; Mullite
keywords MULLITE FORMATION; THERMAL-TREATMENT; RAW-MATERIAL; PORCELAIN; CERAMICS; KAOLINITE; MONTMORILLONITE; BENTONITES; MICROWAVE; EVOLUTION
abstract Knowledge about the relationships between mineralogical and microstructural characteristics of clays and the transformations that occur during firing is of fundamental importance for various industries, enabling the manufacture of better quality products and widespread use of those raw materials. The aim of this study was to interpret phase development and morphological transformations in clays subjected to different heat treatments, with emphasis on the effect of impurities (iron and alkalis), temperature and heating rate. The experiments were carried out using conventional and microwave heating, with characterization by X-ray diffraction and scanning electron microscopy. The interpretation of the results based on the mullite-silica-leucite phase diagram showed that crystallization and grain growth are closely related to the amount and viscosity of the liquid phase present at the firing temperature, which vary with the composition and can be predicted by the phase diagram. Faster heating rates tend to slightly delay the establishment of equilibrium, which appears to have special bearing on the liquid phase viscosity, hence, on grain growth. As a consequence, the resulting microstructure contains mullite needles that are shorter and more uniform in size. (C) 2016 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE BV
issn 0169-1317
year published 2017
volume 135
beginning page 325
ending page 332
digital object identifier (doi) 10.1016/j.clay.2016.10.014
web of science category Chemistry, Physical; Materials Science, Multidisciplinary; Mineralogy
subject category Chemistry; Materials Science; Mineralogy
unique article identifier WOS:000390621800035
  ciceco authors
  impact metrics
times cited (wos core): 0
journal impact factor (jcr 2016): 3.101
5 year journal impact factor (jcr 2016): 3.391
category normalized journal impact factor percentile (jcr 2016): 74.807
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