Maxime Gauthier

Surface and Corrosion Electrochemical Characterization of Titanium Foams for Implant Applications

Electrochemical impedance spectroscopy has been revealed to be a useful tool to evaluate the exposed surface area and consequently to evaluate the corrosion behavior of titanium foams intended for biomedical applications.In order to find the most accurate corrosion assessment, a new equivalent circuit involving a porous model in series with a double TiO 2 layer model was proposed to fit the experimental data. Although seldom used in the literature, such technique could be useful for the characterization of porous media. Determining corrosion potentials and current densities, the titanium foams have revealed to be slightly more resistant to corrosion in simulated body fluid solutions at 37°C under static mode (no stress applied to the samples) compared to dense and polished titanium. The best titanium foams exibited penetration rates around 0.07 μm yr - 1 . Cyclic voltammetry experiments have shown that the titanium oxide layer stability was not affected by the fabrication process of the foams.

Production of Metallic Foams Having Open Porosity Using a Powder Metallurgy Approach

Abstract A technique has been recently developed to produce foamed metallic structures from dry powder blends containing a metallic powder, a polymeric binder, and a foaming agent. The blend is molded and heat-treated to foam and consolidate the material. The final properties may be tailored by varying the sintering temperature. Microstructure, chemical composition, and properties of nickel (Ni) foams sintered at different temperature are presented and discussed. The resulting material has an open cell microstructure with three levels of porosity. This structure leads to materials having low density (∼ 90% porosity) and high specific surface area. The specific surface area is reduced and the mechanical strength is increased when the sintering temperature increases.

Mechanical Properties of Thermomechanically-Processed Metastable Beta Ti-Nb-Zr Alloys for Biomedical Applications

Metastable beta-titanium alloys combine exceptionally low Youngs modulus and high biocompatibility, thus attracting special interest in the prospect of their application as biomedical implant material. In this work, Ti-21.8Nb-6Zr (at.%) ingots were manufactured by vacuum argon melting followed by hot isothermal pressing. The obtained ingots were thermomechanically processed using the following TMP sequence: a) cold rolling (CR) from e=0.37 to 2 of the logarithmic thickness reduction; and b) post-deformation annealing (PDA) of between 450 and 700°C (10’…5 h for 600°C and 1 h for other temperatures). The influence of the TMP on the alloy’s mechanical properties under static and cyclic loading was studied.

Sub-fragmentation of structural reactive material casings under explosion

A concept of reactive hot spots intruded in a thick, structural reactive material casing was investigated to generate fine fragments for efficient energy release from casing material under explosive loading. This was achieved through distributing micro MoO3 particles into a granular Al casing, made by hot isostatic pressing, in a fuel-rich ratio of 10Al+MoO3. Reaction of Al and MoO3 during casing primary or secondary fragmentation creates heat and gas products to form micro-scale hot spots, whose expansion initiates local fractures leading to fine fragments of the rest of Al. Explosion experiments, using a 4.4 cm diameter cased charge with a casing-to-explosive mass ratio of 1.78 in a 2.1 m3 cylindrical chamber, demonstrated the presence of fine fragments and more efficient fragment combustion to augment air blast, as compared to a baseline pure Al-cased charge, thus indicating the feasibility of the concept.