Journal
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
Volume 7, Issue 4, Pages 479-486Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jmrt.2018.02.002
Keywords
Hydroxyapatite; Conversion kinetics; Activation energy; Avrami equation
Funding
- FAPERJ [2015005263]
- CNPq [140144/2012-9]
- CAPES [10.980/13-0]
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This work describes the kinetics of conversion of brushite coatings, produced by chemical deposition, to hydroxyapatite. The conversion was performed in alkaline solution at three temperatures: 50 degrees C, 55 degrees C, and 60 degrees C. The evolution of the transformation was assessed by X-ray diffraction, and the phase fractions were determined by Rietveld refinement. The Johnson-Mehl-Avrami equation was applied to the data in order to describe the conversion mechanisms. The value of 42 kJ/mol obtained for the conversion activation energy is of the same order as found in similar surface-controlled dissolution processes. The Avrami exponent was n=3.5, which is consistent with an interface-controlled growth of three-dimensional HA crystals with decreasing nucleation rate. (C) 2018 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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