Synthesis and characterization of hydroxyapatite-wollastonite composite powders by sol-gel processin

Composites of hydroxyapatite-wollastonite were synthesized by a sol-gel route using calcium acetate and triethyl phosphate as precursors of hydroxyapatite and high-purity natural wollastonite added in ratios of 20, 50, and 80wt%. These composites were characterized by thermal analysis, X-ray diffraction, FT-IR and Raman spectroscopy, and scanning and transmission electron microscopic techniques. Formation of hydroxyapatite occurs at a relatively low temperature, about 420°C, accompanied by calcium carbonate; wollastonite remains unreacted. The composites were purified by heat treatment to a higher temperature and washed with hydrochloric acid and distilled water, to produce B-type carbonated hydroxyapatite-wollastonite composites as final products.