Study on crystallization kinetics of plasma sprayed hydroxyapatite coating

Hydroxyapatite (HAp) coatings were deposited using vacuum plasma spraying system. Peak intensities of lattice plane (211), (112), (300) in XRD patterns were employed to investigate crystallinities of as-received coatings. Heat treatments at temperatures 600, 650, 700 and 800 degrees C were proceeded to reveal crystallization kinetics of vacuum plasma sprayed hydroxyapatite coating. Computer software was used to deal with the data processing. The results obtained showed that, after vacuum plasma spraying, crystallinity of hydroxyapatite coating decreases greatly, implying that the as-received coating mainly consists of an amorphous phase. Heat treatment is effective for the amorphous phase to convert into crystalline in vacuum plasma sprayed hydroxyapatite coating depending on heat treatment time and temperature. The conversion of hydroxyapatite from amorphous to crystalline is a second order reaction, and the activation energy is calculated to be 11.31x10(4)kJ/mol. (C) 1999 Published by Elsevier Science Limited and Techna s.r.l. All rights reserved.