Ti6Al4V alloy is still attracting great interest because of its application as an implant material for hard tissue repair. This research aims to produce and investigate in-situ chitosan/hydroxyapatite (CS/HA) nanocomposite coatings based on different amounts of HA (10, 50 and 60 wt.%) on alkali-treated Ti6Al4V substrate through the sol-gel process to enhance in vitro bioactivity. The influence of different contents of HA on the morphology, contact angle, roughness, adhesion strength, and in vitro bioactivity of the CS/HA coatings was studied. Results confirmed that, with increasing the HA content, the surface morphology of crack-free CS/HA coatings changed for nucleation modification and HA nanocrystals growth, and consequently, the surface roughness of the coatings increased. Furthermore, the bioactivity of the CS/HA nanocomposite coatings enhanced bone-like apatite layer formation on the material surface with increasing HA content. Moreover, CS/HA nanocomposite coatings were biocompatible and, in particular, CS/10 wt.% HA composition significantly promoted human mesenchymal stem cells (hMSCs) proliferation. In particular, these results demonstrate that the treatment strategy used during the bioprocess was able to improve in vitro properties enough to meet the clinical performance. Indeed, it is predicted that the dense and crack-free CS/HA nanocomposite coatings suggest good potential application as dental implants.

Composites including silicide of tungsten and boride of tungsten intermetallic compound as reinforced agents in alumina matrix have a good mechanical properties in low and high temperature (high friction resistance, strength, resin stance to creep and relatively high thermal shock resistance), moreover, they have chemical neutral with a high corrosion resistance in a high corrosive and high temperature environment. The purpose of this study is to investigate thermal analysis, phase and microstructural evaluation during synthesis of above mentioned composite by combustion aluminothermic processing in three systems 1-Al+Si+WO3, 2-Al+B2O3+WO3 and 3-Al+B2O3+Si+WO3. A Ball-milled starting material according to stoichiometric ratio was thermal analyzed (DTA-TGA) for each of above mentioned system. The XRD results never show any new phase during ball-milling even up to 10 hours. The forming of tungsten silicide (WxSiy) is in lower temperature in comparison with tungsten boride (WxBy) during the thermal analysis experiments. The presence of Si in the Al+B2O3+WO3 system facilitates the formation of tungsten borides. The microstructural observations show a uniform and dense distribution of silicide and boride of tungsten in the alumina matrix. Silicide phases are small grain with spherical morphology whereas; the boride phases are coarser and relatively elongated with irregular morphology.