Jamal Bougdira

In this work we report on the investigation of the transport behavior of Ti neutral atoms sputtered in a reactive high power impulse magnetron sputtering device used for TiN coating deposition. The time-resolved tunable diode laser induced fluorescence (TR-TDLIF), previously developed to study the transport of tungsten atoms, was improved to measure Ti neutral atom velocity distribution functions. We find that the TR-TDLIF signal has to be fitted using three Gaussian distributions, corresponding to the energetic, thermalized, and quasi-thermalized (atoms with non-zero mean velocity) atom populations. The ability to distinguish populations of atoms and to determine their corresponding deposited flux and energy may be of great interest to control film properties as desired for targeted applications. From the fitting, the vapor transport parameters (flux and energy) are calculated and studied as a function of distance from the target, pressure, and percentage of nitrogen in an Ar/N ₂ gas mixture. The study focuses on the effect of added nitrogen on the transport of sputtered atoms.

A time-resolved tunable diode-laser (DL) induced fluorescence (TR-TDLIF) technique has been used to identify different populations of atoms (on different stages of transport) to determine their corresponding deposited energy and flux. The temporal dimension permits the splitting of the processes of sputtering during the discharge and particles transport in the post-discharge where atoms and flux velocity distribution functions (AVDF, FVDF) of each population were measured varying the discharge parameters (power, voltage, pressure, and distance from target). Tungsten (W) was chosen, being an interesting case in terms of sputtered atom transport, considering its weight which implies weak changes of directivity or energy transfer after collisions with the buffer gas. The high temporal and spectral resolutions of TR-TDLIF are the keys for the distinction of the atoms populations and the stage corresponding to the transition from the ballistic to diffusive regime of transport was observed for the first time and named quasi-diffusive regime. Thus, the ability to dissociate populations of atoms and to determine their deposited flux and energy may be of great interest to adjust film properties as desired for applications.

Ceramics titanium silicon carbide Ti 3 SiC 2 Max phase was rapidly synthesised and simultaneously consolidated by spark plasma sintering at which the extensive volume expansion occurred as a function of the temperature from ball milled SiC/Ti/C powders with Ti/SiC ratio of 3:1:2. The XRD patterns results were confirmed by FESEM observations and the EDAX analyses. The reinforced and unreinforced 3Ti+1.2SiC+0.8C, 3Ti+1.2SiC+0.8C/SWCNTs powders were processed by using spark plasma sintering (SPS) at temperatures of 1100, 1200 and 1300 o C with diting of SWCNTs from 0.0 to 1.0 wt% SWCNTs/Ti 3 SiC 2 nanocomposite. The effects of SWCNTs addition on phases, microstructure and hardness of the nanocomposite were investigated. The best product contained 1.0 wt% CNTs/ Ti 3 SiC 2 /TiC which was sintered at 1300 °C, 60 MPa for 10 min The phase composition of the product could be tailored by adjusting the process parameters. The anisotropic hardness was observed in respect to the textured product.

A new graphite crystal morphology has been recently reported, namely the graphite hexagonal pyramids (GHPs). They are hexagonally-shaped crystals with diameters ranging from 50 to 800 nm and a constant apex angle of 40°. These nanostructures are formed from graphite substrates (flexible graphite and highly ordered pyrolytic graphite) in low pressure helicon coupling radiofrequency argon plasma at 25 eV ion energy and, purportedly, due to a physical etching process. In this paper, the occurrence of peculiar crystals is shown, presenting two hexagonal orientations obtained on both types of samples, which confirms such a formation mechanism. Moreover, by applying a pretreatment step with different time durations of inductive coupling radiofrequency argon plasma, for which the incident ion energy decreases at 12 eV, uniform coverage of the surface can be achieved with an influence on the density and size of the GHPs.