Sintering behavior and growth mechanism of β-TCP in nanocrystalline hydroxyapatite synthesized by mechanical alloying

Nanocrystalline carbonated HAp powder has been synthesized successfully within 2 h by mechanical alloying the stoichiometric mixture of CaCO3, CaHPO4 center dot 2H(2)O at room temperature under open air. To observe the sintering behavior of HAp the as-milled sample is sintered at different temperatures. The amorphous HAp phase (-14 vol%) in as-synthesized sample transforms completely to crystalline HAp after sintering at 700 degrees C and after sintering the sample at 800 degrees C, the crystalline HAp partially transforms to beta-TCP phase. Presence of low content of beta-TCP phase in HAp powder could be useful in artificial hard tissue applications. Increase in sintering temperature up to 1000 degrees C results in enhancement of decomposition rate of HAp into beta-TCP phase. Microstructure characterization in terms of lattice imperfections and relative phase abundances in non-sintered and all sintered samples are made both by analyzing the respective XRD patterns using Rietveld's structure refinement method as well as TEM images. The growth mechanism of beta-TCP from crystalline HAp phase has been proposed based on structure and microstructure characterizations of sintered samples. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.