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.