ABSTRACT Commercially dense pure titanium sheets and porous titanium samples processed by powder metallurgy were treated with a mixture consisting of equal volumes of H2SO4 and H2O2 for 2 or 4 hours. Characterization was performed by scanning electron microscopy, energy dispersive X-ray spectroscopy, confocal scanning optical microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The analyses showed that the chemical patterning approach using a combination of concentrated acid and oxidant was able to generate a nanotexture on dense and porous titanium surfaces. In addition, the treated samples presented an oxide layer consisting predominantly of titanium dioxide with negative charge conferred by the presence of hydroxyl groups, which is an important factor that favors apatite nucleation and protein adsorption. It was also observed that oxide formation was more effective on porous samples than on dense samples, which can be explained by the higher surface area intrinsic to porous media. Finally, the findings indicated that both treatment times promoted similar modifications in surface properties, such as nanotexture and chemical composition, suggesting that the time of 2 hours were enough to induce the surface alterations at the nanoscale.

Porous titanium scaffolds are promising materials for biomedical applications such as prosthetic anchors, fillers and bone reconstruction. This study evaluated the bone/titanium interface of scaffolds with interconnected pores prepared by powder metallurgy, using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Porous scaffolds and dense samples were implanted in the tibia of rabbits, which were subsequently killed 1, 4, and 8 weeks after surgery. Initial bone neoformation was observed one week after implantation. Bone ingrowth in pores and the Ca/P ratio at the interface were remarkably enhanced at 4 and 8 weeks. The results showed that the interconnected pores of the titanium scaffolds promoted bone ingrowth, which increased over time. The powder metallurgy technique thus proved effective in producing porous scaffolds and dense titanium for biomedical applications, allowing for adequate control of pore size and porosity and promoting bone ingrowth.

Titanium/hydroxyapatite (HAP) composites are candidate materials for biomedical applications as implants and hard tissue substitutes since they combine the good mechanical properties and biocompatibility of Ti with the excellent HAP bioactivity and osteointegration. In powder metallurgy processing of these composites, HAP decomposition promoted by Ti during powder sintering is found. In a previous work Ti-50v%HAP greens of 60% theoretical density (dT) were vacuum sintered at 1150 °C and formation of CaO and Ca4O(PO4)2 (TTCP) resulting from the HAP decomposition, as well as Ti4P3 at the Ti/HAP interfaces was obtained. In the present work those composites are compared with similar ones processed from TiH2 as a substitute for Ti which were also vacuum sintered at 1150 °C from greens with 60 to 86%dT. For the lower %dT, the compounds formed were CaO, TTCP and Ti4P3 and for the higher %dT ones, besides those same products, CaTiO3, Ti5P3 and a phase containing Ti, Ca and P were detected.