Papers by Author: R. Gheriani

Abstract: The mainly property of thin solid films technologies is their adhesion to the substrates. Because of its good wear resistance and its low coefficient of friction against steel, TiC is an attractive coating material for wear applications such as bearing components. The adhesion of TiC coatings, however suffers from insufficient reproducibility, which is probably due to uncontrolled process parameters. In our work pure titanium thin films of approximately 0.6 µm in thickness were prepared on 100C6 stainless steel substrates by cathodic sputtering. The samples were subjected to secondary vacuum annealing at a temperature between 400 and 1000°C for 30 min. The reaction between substrates and thin films was characterized using an x-ray diffractometer (XRD). Surface morphology and elements diffusion evaluations were carried out by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The interaction substrates-thin films is accompanied by nucleation and growth of titanium carbide as a function of annealing temperature. By the SEM and EDS results, it appears clearly that the diffusion of manganese to the external layers leads to the destruction of adhesion especially at high temperatures.

Abstract: Titanium dioxide thin films have been prepared by the sol–gel dip-coating method on an ITO substrate. The samples obtained were characterized by different experimental techniques: XRD, Raman, FTIR, spectroscopy of the electrochemical potential and SEM. The X-ray diffraction results showed that the TiO2 thin film obtained for a layer, after a temperature of annealing (400°C) and at the speeds of steeping between 2 and 10 cm∙s-1 was amorphous, and transformed into anatase–brookite at 0.6 cm∙s-1 for 400°C. The data of Raman spectroscopy is in good agreement with the DRX results. Observation by scanning electron microscope shows that the coating was transparent and homogeneous without any visual cracking over a wide area, and the increase in the treatment temperature did not affect the uniformity of the film. The interface of our layers to behaved like a n-type semiconductor.

Abstract: X-ray microanalysis was used in the qualitative and quantitative study of titanium carbides obtained by deposition of thin titanium films on steel substrates using reactive r. f. sputtering of a pure titanium target. The samples are subjected to high vacuum annealing at a temperatures between 200 and 1000°C for 60 min. The morphological analysis by SEM shows that all films exhibited a dense microstructure. The EDS pattern of X-ray microanalysis shows that the non treated samples mainly consist of titanium. The concentration of Ti decreases progressively with the annealing temperature therefore the carbon and iron concentrations increases, this is as result of atomic interdiffusion between the substrate and the thin film. In the highest temperatures of annealing we note the diffusion of the elements of substrate towards outside layers even for those having weak concentrations. The relationship between mechanical properties and the reaction is carried out by Vickers micro-hardness measurements.

Abstract: Titanium carbides are well known materials with great scientific and technological interest. The applications of these materials take advantage of the fact that they are very hard, refractory and that they have metallic properties. In this work, we have studied the influence of the heat treatment temperatures (400-1000°C) on the interaction between the titanium thin films and steel substrates. Steel substrates, 100C6 type (AFNOR norms) containing approximately 1 wt % of carbon were coated at 200°C with titanium thin films by magnetron sputtering. The samples were characterized by X-ray diffraction (XRD) and Auger electron spectroscopy (AES). Vikers micro-hardness measurements carried out on the annealed samples showed that the micro-hardness increases with annealing temperature, reaches a maximum (3500 kg/mm2), then decreases progressively. The growth of micro-hardness is due to the diffusion of the carbon, and to the formation of titanium carbide. However, the decrease of micro-hardness is associated with the diffusion of iron and the formation of iron oxide (Fe2O3). At higher temperatures, we note the formation of titanium dioxide (TiO2).