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

Abstract

Nanocrystalline carbonated HAp powder has been synthesized successfully within 2h by mechanical alloying the stoichiometric mixture of CaCO3, CaHPO4·2H2O 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 (~14vol%) in as-synthesized sample transforms completely to crystalline HAp after sintering at 700°C and after sintering the sample at 800°C, the crystalline HAp partially transforms to β-TCP phase. Presence of low content of β-TCP phase in HAp powder could be useful in artificial hard tissue applications. Increase in sintering temperature up to 1000°C results in enhancement of decomposition rate of HAp into β-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 β-TCP from crystalline HAp phase has been proposed based on structure and microstructure characterizations of sintered samples.