Study on crystallization kinetics of plasma sprayed hydroxyapatite coating

Hydroxyapatite (HAp) coatings were deposited using vacuum plasma spraying s ystem. Peak intensities of lattice plane (211), (112), (300) in XRD pattern s were employed to investigate crystallinities of as-received coatings. Hea t 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 o f hydroxyapatite coating decreases greatly, implying that the as-received c oating mainly consists of an amorphous phase. Heat treatment is effective f or the amorphous phase to convert into crystalline in vacuum plasma sprayed hydroxyapatite coating depending on heat treatment time and temperature. T he conversion of hydroxyapatite from amorphous to crystalline is a second o rder 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 r ights reserved.