{'fraction_non_alphanumeric': 0.03171641791044776, 'fraction_numerical': 0.014303482587064677, 'mean_word_length': 5.28515625, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Characterization of Novel Bioactive Hydroxyapatite-TiO2 Coatings Obtained by High Velocity Oxy-Fuel


 Hydroxyapatite (HAp: Ca10(PO4)6OH2) is a biocompatible and bioactive ceramic material widely used as a coating on metal surfaces (dental implants, hip replacements ...), but the low adhesion between HAp and the substrate due to the differences in thermal expansion coefficients of both, and the degradation of HAp, is being improved through the addition of TiO2 to reach a good combination of mechanical properties. Therefore, the objective of this project is to produce 80%HAp-20%TiO2 (by weight) coatings on Ti6Al4V by High-Velocity Oxy Fuel (HVOF). The microstructure study has been carried out using scanning electron microscopy, and the characterization of the present phases, hydroxyapatite and rutile mainly, using X-ray diffraction and Raman spectroscopy (the last one to find out which are the minority phases, such as anatase and tricalcium phosphates). Also Rietveld method has been used to quantify the amount of amorphous phase, lower than in the case of plasma-sprayed coatings. The coatings adhesion has been measured by tensile tests according to ASTM C633-01(2008), finding an improvement over the adhesion of plasma sprayed coatings, and also of hydroxyapatite coatings; also their bioactivity has been evaluated through its immersion in simulated body fluid (SBF), and through in vitro tests to study osteoblast behaviour on the coatings surfaces, with positive results. To conclude, a discussion about the results is made to analyze the industrial viability of these kinds of coatings.