Influence of Hydrothermal Processing on the Structuring of Amorphous Strontium Hydroxyapatite

Strontium substituted hydroxyapatite is a biomaterial with high level of biocompatibility with improved cell proliferation from Sr ions in hydroxyapatite. The aim of this research is to study the effect of saturated steam pressure at elevated temperature on the transitions within amorphous strontium hydroxyapatite powder. Processing temperatures and times ranged from 90 to 150∘C for periods of 1, 3 and 6 hours, respectively. Powder was characterized by X-Ray Diffraction and Fourier Transformed Infrared Spectroscopy. The appearance of diffraction peaks in the X-ray diffraction pattern suggested that longer processing times were necessary to transform amorphous strontium hydroxyapatite to a higher crystallinity at lower temperatures. Transition from the amorphous to the crystalline state begins at 150∘C after an hour, at 120∘C after 3 hours, or at 110∘C after 6 hours. Infrared spectroscopy showed the characteristic phosphate absorption band and the presence of carbonate in the powder.     Keywords: hydrothermal processing, biomaterials, hydroxyapatite, material design, biocompatibilit

Thin Bioactive Zn Substituted Hydroxyapatite Coating Deposited on Ultrafine-Grained Titanium Substrate: Structure Analysis

Nanocrystalline Zn-substituted hydroxyapatite coatings were deposited by radiofrequency magnetron sputtering on the surface of ultrafine-grained titanium substrates. Cross-section transmission electron microscopy provided information about the morphology and texture of the thin film while in-column energy dispersive X-ray analysis confirmed the presence of Zn in the coating. The Zn-substituted hydroxyapatite coating was formed by an equiaxed polycrystalline grain structure. Effect of substrate crystallinity on the structure of deposited coating is discussed. An amorphous TiO2 sublayer of 8-nm thickness was detected in the interface between the polycrystalline coating and the Ti substrate. Its appearance in the amorphous state is attributed to prior to deposition etching of the substrate and subsequent condensation of oxygen-containing species sputtered from the target. This layer contributes to the high coating-to-substrate adhesion. The major P–O vibrational modes of high intensity were detected by Raman spectroscopy. The Zn-substituted hydroxyapatite could be a material of choice when antibacterial osteoconductive coating with a possibility of withstanding mechanical stress during implantation and service is needed