Composites with titanium dioxide (TiO 2 ) matrix and graphene oxide (GO) or reduce graphene oxide (rGO) filler were recently investigated as Vis-active materials in photocatalytic applications. For self-cleaning photocatalytic coatings, the targeted property is the (super)hydrophilicity. The wettability of a surface can be modified by exposure to radiation. This paper discusses the hydrophilicity variation of the TiO 2 -GO and TiO 2 -rGO composite thin films when exposed to UV or to UV+VIS radiation correlated with the stability of these composites under irradiation. The results outline changes in the surface hydrophilicity under irradiation mainly following the morphology and roughness modifications.

Within the frame of this work, low temperature Ti–Si–C films were deposited on high-speed steel and stainless steel substrates by combined dc/rf magnetron co-sputtering. Composition analysis revealed the existence of two distinct regions: (i) a silicon doped sub-stoichiometric titanium carbide zone and (ii) a titanium rich zone. Structural analysis confirmed the different nature of the prepared films within each of the two zones. The residual stress states (σr) were relatively low, and the hardness values ranged between 11 and 27GPa, with a dependence on the composition as well as on the structural features. The tribological results showed quite similar trends, with both friction coefficients and wear revealing a straight correlation with the composition, and consequently, the different structural arrangements. In general terms, the obtained results showed that the friction coefficient of the samples tended to decrease with increasing CC/CSi atomic ratio, indicating an improvement in tribological behaviour for the samples with the highest carbon contents. In terms of wear resistance, the films with a stoichiometry very close to TiC, Si doped sub-stoichiometric titanium carbide films, presented the best behaviours, revealing that a compromise between the best friction and wear, must be made in order to select the optimum coating.

Ti(C, O, N) thin films were prepared by magnetron sputtering and analysed in terms of their tribological properties. Surface and tribological parameters were analysed and discussed as a function of the films composition and structural features, as well as their thickness. The evolution of friction coefficient values was in concordance with the wear behaviour of the films. According to the atomic composition of the films, an increasing of the carbon percentage and a compound chemical formula closed to the stoichiometric TiC lead to a very good wear behaviour. This aspect is also directly correlated with the friction behaviour.

Magnetron sputtering is a flexible technique and allows producing a significant amount of types of coatings, thus, this method was also used within the frame of this paper in order to obtain dark Ti(CON) coatings. The films, with various compositions, were deposited onto high speed steel (AISI M2) substrates, in a closed field unbalanced reactive d.c. magnetron sputtering system, using a reactive atmosphere composed of acetylene (C source) and a mixture composed of oxygen and nitrogen. The deposition parameters were chosen as a junction of pre-existing knowledge about sputtered Ti-O-N and Ti-C-O films, varying the flow ratio C2H2/(O2+N2). Mechanical properties of the films, namely microhardness and Young's modulus were determined using loading and unloading curves data, obtained with an instrumented nanoindentation equipment using a Berkovitch tip.

The scanning electron microscope uses a focused beam of high-energy electrons to generate a variety of signals at the surface of solid specimens. The signals that derive from electron-sample interactions reveal information about the sample including ;external morphology (texture), chemical composition, and crystalline structure and orientation of materials making zip the sample, In most applications, data are collected over a selected area of the surface of the sample, and a 2-dimensional image is generated that displays spatial variations in these properties. Areas ranging from 1 cm to 5 microns in width can be imaged in a scanning mode using conventional SEM techniques. The SEM is is also capable of performing analyses of selected point locations on the sample; this approach is especially useful in qualitatively, or semi-quantitatively determining chemical compositions, crystalline structure, and crystal orientations.

Within the frame of this work super-hard nanocomposite thin films were deposited using a more recently developed deposition method, namely the magnetron sputtering using a high power generator (HIPIMS) connected to the Ti target and a classical DC pulsed generator connected to the Si target. The films were co-spultered from two metallic targets of Ti and Si (99,99% purity). The silicon content was varied by controlling the DC intensity applied on the silicon target, while HIPIMS discharge parameters were kept constant on the titanium target, The Si enrichment was made by the variation of Si target's intensity between 0.2A and 0.4A. The coatings morphology was observed on brittle-fracture cross sections by scanning electron microscope (SEM). Structure of the layers was achieved via X-Ray Diffraction (XRD). The dynamic friction coefficient and wear rate values (abrasion wear) were estimated using a pin-on-disk tribosystem.

Dark Ti-C-O-N thin films were deposited by dc reactive magnetron sputtering. A titanium target was sputtered while three different gas flows were injected into the deposition chamber: argon (working gas), acetylene and a mixture of oxygen and nitrogen (reactive gases). The films were produced with variation of the gases flow rates, maintaining the remaining parameters constant. Varying the ratio between the reactive gases flow (gas mixture/acetylene) allowed obtaining films with different characteristics. The colour of the films was characterized by spectral reflectance spectroscopy, and expressed in the CIE 1976 L*a*b* colour space. An accurate control of the deposition conditions allowed obtaining intrinsic and stable dark colours for decorative applications. Composition analysis by electron probe microanalysis was done to quantify the elemental concentrations in the films. X-ray diffraction experiments revealed the evolution of the film structure which showed to be essentially amorphous, but with evidences of fee structure.

Ti-Si-C thin-films were prepared by d.c.reactive magneron sputtered on (AISIS M2) steel sample, at 200 degrees C. The depositions were carried out from Ti targets, one with some Si and the other with C pieces incrusted in the erosion zone, working in a simultaneously mode, under the variation of d.c. power applied to the targets. During the deposition process, all the samples were based with a bias voltage of -70V. The atomic composition of a deposited samples was measured by electron probe microanalsis (EPMA) in a Cameca SX-50 apparatus. A tribological characterization for the prepared thin-filims has been done, taking into account the differen measurement of roughness, static friction coefficient and wear. The results revealed that there is no clear correlation between the tribological paramenters, and the general wear behaviour could be explained considering the films composition. Thus, the best results were registered for C/Si ratio (at.%) between 2.2- 5.2, corresponding to a current ration I-Tic/I-TiSi(A) between 1.4-2.9.

The paper analyses the kinetics of the carbide coherence loss and carbide coalescence taking place during tempering of low-alloy steels without molybdenum. For complete and incomplete hardening, the thermo-kinetics parameters of coalescence, the values of the reaction constants and the experimental activation energy values have been calculated. These results have shown that the tempering kinetics for the first stage of tempering (the coherence loss) is different from that for the second stage of tempering (the carbide coalescence), respectively.