The influence of precursor concentration, pressure, temperature and time of hydrothermal synthesis on the development of calcium hydroxyapatite structure has been analyzed. The obtained results show that it is possible to adjust the conditions of hydrothermal synthesis from solutions of relatively high concentrations to obtain calcium hydroxyapatite nanopowders of well-defined structure. The relationship between the synthesis and the lattice parameters, as well as the crystallite size and the microstructure of synthesized hydroxyapatite has been established. The synthesized powders are preferentially carbonated hydroxyapatite of the B type in the form of agglomerates that accommodate two-modal size pores of 1.5-10 and 50-200 nm. The structure of calcium hydroxyapatite particles consists of crystallites 8-22 nm in size, bound within prime particles, which size is between 10 and 63 nm, that in turn form bigger agglomerates 200 nm in size, which further cluster building up agglomerates 5-20 microm in size.

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Wet spray pyrolysis of fine, well-dispersed a SiO2 sol was used for the deposition of thin films of silicon dioxide. The sol was obtained by hydrothermal precipitation of silicon acid from a solution at pH = 10. The morphology, roughness, phase composition, chemical homogeneity and the mechanism of the films were investigated by SEM, EDS and IR spectroscopy. The obtained results show a complete covering of the titanium substrate with SiO2 after 3 h of deposition. It was observed that the film thickness increased from 3 to 19 microm, the roughness of the film decreased from 12 to 3 microm, while the morphology of the deposit changed considerably. A hydroxyapatite film was prepared on the so-obtained SiO2 thin film by spray pyrolysis deposition and its morphology and phase composition were investigated.

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