Ti–6Al–4V spherical particles (22–45 μm) injected in a dc plasma jet using N₂ as plasma forming gas, and collected in a controlled atmosphere chamber filled with nitrogen at 10⁵ Pa are directly nitrided from their surface to their core without any apparent nitrogen gradient. Particles are composed of small grains of the δ-TiN phase, with a uniform composition of TiN_0.55, strongly linked together by a secondary phase (Al–Ti–V–O). This result is achieved in very short times (∼ms) and nitrogen reacts only with titanium. The other elements (Al, V) play the role of oxygen getters, particularly aluminum which evolves probably as the volatile suboxide AlO. The mean composition of the particles is TiN_0.43O_0.05V_0.05Al_0.03. The nitridation occurs inside the plasma jet core by the convective movement induced within the droplets by the high velocity plasma jet. The conditions for this convective movement (Reynolds number of the particles relatively to the plasma flow higher than 20, and the ratio of kinematic viscosities of the plasma to that of the alloy over 50) are fulfilled in the nitrogen dc plasma jet core. This convective movement continuously renews fresh alloy at the surface and entrains δ-TiN grains formed at the surface inside droplets, as well as dissolved nitrogen. Nitrided grains finally grow thanks to the nitrogen dissolution and diffusion within the liquid. The interest of this process, compared to classical furnace nitridation of the alloy, is its rapidity, the lack of nitrogen gradient, and the favourable role of the secondary phase for some mechanical properties.

In this paper, the influence of Ti-TiC satellite powder obtained in situ by the CVD method on the microstructure, properties, and residual stress of titanium cold-sprayed coatings was studied. A commercially available titanium powder was subjected to a satelliting process using the CVD process, where TiC particles were in situ formed on titanium granules. Then, a powder mixture of pure Ti and 20 wt.% of Ti-TiC satellite powder was obtained. Cold spray coatings of Ti-(Ti-TiC)_sat powder mixtures were applied to Ti6Al4V substrates with carrier gas temperatures of 900 °C and 1100 °C. The coating characterization included microstructural analyses by SEM, hardness measurements, determination of Young’s modulus, phase composition by XRD, and residual stress measurements. Cross-sectional analysis revealed good cohesion between Ti and TiC during the satelliting process, which survives coating deposition. Moreover, the higher spraying temperature resulted in TiC crystallite size reduction, higher hardness, and Young’s modulus, decreasing linear and shear stresses.

Since the COVID-19 pandemic, efforts in the field of surface decontamination have been redoubled. Finding innovative self-cleaning devices has become a challenge, and several solutions have been proposed in the market in recent years. In this work, an optimized powder/suspension plasma spray process at atmospheric pressure, using a Triplex Pro 210^TM torch, is implemented to produce Cu-TiO₂ surface coatings on stainless steel. The purpose is to investigate the potential improvement of antibacterial efficacy by the reactive surface species generated from TiO₂ photoactivity under irradiation. A water-based suspension, prepared with AnalaR NORMAPUR^TM TiO₂, is used as a precursor to incorporate the photocatalyst into an antibacterial copper matrix. Surface antibacterial tests according to ASTM 2180 standards were performed, and experiments were performed in treated contaminated water. Sub-stoichiometric blue TiO₂ coatings showed complete bacterial elimination after 90 min of visible light irradiation, and Cu-TiO₂ surface coatings were even able to disinfect the surfaces under white light, making the application interesting for bacterial destruction under natural illumination. These materials are also intended for application in water treatment, including both pathogens and chemical micropollutants, which is a pressing issue facing many countries today.

Suite à la pandémie de la Covid-19, un effort considérable est actuellement déployé, tant dans la recherche académique que dans le secteur industriel, pour élaborer des revêtements capables de protéger les surfaces contre les microorganismes et ainsi limiter leur temps de résidence, leur développement et par suite leur transmission. Dans le cadre d’une collaboration interdisciplinaire IRCER, E2Lim et Sanodev, ce travail s’intéresse à la fonctionnalisation d’une surface par le biais d’un revêtement biocide non toxique et photocatalytique capable d’inhiber la croissance des microorganismes. Dans ce but, les potentielles propriétés bactéricides vis-à-vis de Escherichia coli de différents revêtements élaborés par projection plasma (photocatalytiques et non photocatalytiques) ont été évaluées.