This work focuses on the improvement of the mechanical properties of hydroxyapatite (HA) through the addition of 3 mol% yttria partially stabilized zirconia (PSZ). Enamel‐derived HA (EHA) from freshly extracted human teeth and commercial HA (CHA) were chosen as the matrix. The effects of addition up to 10 wt% of PSZ and of sintering temperature (1000°–1300°C) on the density, microhardness, and compression strength were evaluated. For EHA–PSZ composites, the density and mechanical properties were generally enhanced by adding 5 wt% PSZ, especially after sintering at 1200°C, whereas CHA–PSZ composites showed lower strength values at sintering temperatures of 1200° and 1300°C with respect to EHA–PSZ composites. This may be due to the lower stability of CHA–PSZ composites with higher amounts of calcium zirconate formed over 1100°C when compared with EHA–PSZ composites.

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In this study, the morphology of the Hydroxyapatite (HA) coatings sprayed on Ti alloy samples by Detonation Gun Spray (D-Gun) and the effect of aging before and after heat treatment in physiological solution were observed. Cross-sectional porosity and percentages of amorphous and crystal phase were measured using optical, electron microscopy, and X-ray diffraction analysis. Differential Thermogravimetric Analysis (DTA) was performed to estimate the glass-crystalline phase transformation temperatures. Heat-treatment at 300, 500, 700, 800 and 1200 degrees C were carried out to confirm DTA results. As a final analysis, the aging effect using Ringer's solution for 1 week on heat-treated and non-heat-treated samples was measured. It was observed that, in D-Gun sprayed samples, the cross-sectional porosity stayed in the accepted 5% range as reported for other spraying techniques.(1-5) On the other hand, surface porosity measured using the water immersion method remained in the conventional porosity limit of 15% for non-heat-treated samples. Heat-treatment had a small influence on the porosity while the crystallinity increased considerably; in addition, aging had little effect on HA crystallinity for heat treated samples. This work showed that D-gun sprayed HA coatings had lower porosity and better integrity than other coatings, due to which we can expect better performance during in vivo applications.

Hydroxyapatite (HA) is one of the most widely used biomaterials for orthopedic and dental applications. However, HA is a brittle and weak material and this constrains its orthopedic applications. There are several methods for the improvement of mechanical properties of the HA. One of these methods is to strengthen the HA material by a secondary phase (i.e polymer, metal or ceramics), to make a stronger composite material. Alumina (Al2O3) is a bioinert material, which has been widely investigated as a reinforcing agent for HA. The aim of this study is to compare the microstructural and mechanical properties of HA-Al2O3 composites with the addition of 5 and 10 wt.% of commercial inert glass (CIG). The grain samples were produced according to BS 7253 at 350 MPa. Then, they were sintered at temperatures between 10001300• C for 4 hours. The samples were also analyzed by SEM + EDS to determine microstructural properties, phase analysis was done by X-ray diractometer (XRD), mechanical properties were measured by compression and hardness tests. Results show that HA-Al2O3 composites with addition of 5 and 10 wt.% CIG have reached high density values and high mechanical properties, such as compression strength and hardness at 1300• C. The compression strength and hardness of composites has increased with the increasing CIG content.