Hydrothermal Synthesis of Single-Phase Hydroxyapatite Whiskers
and Crystal Structure Characterisation by HRTEM and Image Simulation
Z.L. Dong
and T.J.White
Centre for Advance
Research of Ecomaterials, Institute of Environmental Science and Engineering,
Innovation Centre, Blk 2, Unit 237, Nanyang Technological University, Singapore
637723 (zldong@ntu.edu.sg)
This study reports
the crystallographic characterisation of synthetic hydroxyapatite (HA) whiskers
suitable for both environmental (e.g. toxic metal capture) and biomedical (e.g.
hard tissue replacement) applications.
In both cases, an excellent understanding of HA crystal structure and
microstructure is critical to ensure good chemical durability. In this study, hydroxyapatite whiskers
were synthesised through soft chemical reaction followed by hydrothermal and
heat treatments. Powder X-Ray
diffraction (XRD) and high resolution transmission electron microscopy (HRTEM)
confirmed that either HA or HA plus tricalcium phosphate (TCP) composite were
obtained, depending on the treatment conditions. Pure HA crystallised after hydrothermal reaction at 200¡C. Rietveld refinement was used to determine the hexagonal
lattice parameters and atom positions of P63/m HA. Microstructures were investigated by
HRTEM (with cooling holder) and interpreted via multislice image simulation
(with JEMS). Further study is
needed to control the particle size, morphologies and HA/TCP ratios, which will
subsequently influence the properties of fabricated HA coatings or bulk
materials, as well as their capacity for heavy metal removal from waste
effluents and in vivo longevity.