Commercially dense pure titanium sheets and porous titanium samples processed by powder metallurgy were treated with a mixture consisting of equal volumes of H 2 SO 4 and H 2 O 2 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.
The present work is a continuation of the research carried out in a previous work, with the aim of improving the production of Ti35Nb alloy by reducing the particle size of Ti (from 50-149 Μm to < 53 Μm) and Nb (from 31-500 Μm to < 62 Μm) powders. Micro (MI) and Macroporous (MA) Ti35Nb alloy samples were processed by powder metallurgy. Ammonium bicarbonate (AB) was utilized as pore former additive for processing MA samples. The powders were mixed, uniaxially pressed and then sintered at 1300 ºC for 2 hours under argon atmosphere. The samples were characterized by SEM/EDS, XRD, profilometry, and Vickers hardness test. The porosity levels were determined by geometric method, Archimedes' principle and quantitative metallographic analysis. The results showed that the processing parameters used in this work successfully produced porous Ti35Nb alloys with completely stabilized β-Ti phase, indicating an enhancement in the methodology when compared with those reported in previous work. Smaller particle sizes influenced positively on the chemicalphysical properties of MI and MA samples, since they demonstrated an improvement in the their characteristics, such as: more homogeneous microstructure; better particle consolidation; homogeneous elemental distribution with no relevant chemical contamination; porosity values in accordance with literature; presence of low amounts of titanium oxides on the surfaces which can improve the biocompatibility features; suitable surface roughness parameters for bone implant applications and favouring adhesion of bioceramic coatings; more uniform microhardness values for both samples which make the material with a further predictable mechanical behavior.
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