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TiO 2 thin films were deposited by DC Sputtering varying the deposit time. These films were characterized by XRD, AFM, photoluminescence, UV–Vis, ellipsometry and XPS. The optical properties of TiO 2 thin films with different thickness, influenced their photocatalytic behavior in two photoinduced process. When TiO 2 thin films were irradiated with a UV light, midgap states were generated and the electrons were placed in lower energies than its band gap, favoring the photocatalytic hydrogen production and CO 2 photoreduction. From PL technique analyses it was observed that electrons occupied midgap states between the bands, with lower energies than the band gap. With these results it was possible to propose an energy diagram in order to correlate with photoinduced processes results. The presence of Ti3+ species was reconfirmed by means of XPS analyses. These species could be found in the midgap states, generated by the interaction between the UV irradiation and the film surface, which contributed to the photocatalytic activity of the films. The hydrogen production was similar for all the thin films studied (33–35 μmol) associated to the presence of similar energy midgap states. In the case of CO 2 photoreduction, all films produced CH 2 O (8951 and 6252 μmol/g) and the films with a thickness of 330 and 420 nm generated CH 3 OH (970 and 292 μmol/g). The extinction coefficient confirmed the XRD results for the film with greatest deposited time, which exhibited the highest crystallinity. All photocatalytic results did not show any dependence with the thin film thickness. Image 1 • Thin films optical properties influenced activity of TiO 2 in photoinduced process. • Ti3+ species, located in midgap states, promoted the generation of 35 μmol of H 2. • Ti3+ species contributed to the photoreduction of CO 2 in formaldehyde and methanol. • Both photoinduced processes performance are independent on the thin film thickness. [ABSTRACT FROM AUTHOR]

Abstract: We describe a duo of experimental methods for determining the transverse dimensions of individual wood fibres using 2D optical microscopy and 3D X-ray tomography. These non-invasive optical sectioning methods, in conjunction with segmentation through image analysis, enables in situ identification of individual fibres in a paper sheet. The relationship between local fibre dimensions, i.e. diameter and fibre wall thickness, are established for kraft (NBSK) pulp fibres and compared to values obtained from wood. For the first time, we propose a criterion for transverse fibre collapse during the papermaking process that is based on both fibre diameter and wall thickness.Graphical abstract: [ABSTRACT FROM AUTHOR]

Highlights • TiO 2 thin films were grown by sputtering method and use as seed layer to grow TiO 2 nanorods by means of hydrothermal method. • TiO 2 nanorods has 3.5 higher activity (132 μmol) than TiO 2 seed layer (38 μmol). • TiO 2 nanorods has the contribution of Ti3+ species, which reduce the band gap value and improve the photocatalytic activity. Abstract TiO 2 nanorods were prepared by hydrothermal method over TiO 2 seed layers deposited by DC Sputtering. From the XRD structural characterization, it has been stated that TiO 2 seed layer present mainly the anatase phase with some contributions of rutile phase, while for TiO 2 nanorods, the rutile phase is present. The thin film thickness were measured using a profilometer, resulting in a thickness of 310 nm for the seed layer and ∼400 nm for TiO 2 nanorods. PL analysis for both films presented an indirect transitions Γ 1b → Χ 2a, as well as oxygen vacancies, defects and surface states. Photocatalytic H 2 production for TiO 2 seed layer film was around 38 μmol, while TiO 2 nanorods produced 132 μmol. This is attributed to the increase to the midgap states present below the conduction band and near to the valence band, which help to improve the photocatalytic activity. [ABSTRACT FROM AUTHOR]

The deposition of decorative coatings is an excellent solution to modify the surface of any material, particularly the aesthetic finishing, without altering the properties of the substrate. Transition metal oxynitride films are interesting for many applications, due the simple and economic way to tune between nitride and oxide bonding. In reactive sputtering, this is done by playing with the flows of N 2 and O 2 , leading to variations of properties (e.g. color) in different directions. In this paper, zirconium is selected as transition metal due to the combination of different characteristics (color, biocompatibility, mechanical properties, corrosion resistance). The literature about Zr-O-N films reveals a confinement of chemical composition. Therefore, the aim of this work is the exploration of the deposition parameter space in order to evaluate the stability of the Zr-O-N system, i.e. verify if the chemical composition of the films still falls in the same range after variation of different deposition parameters. To do that, a series of Zr-O-N films is deposited first at different reactive flows, maintaining the remaining deposition parameters constant. The obtained films can be classified in three different groups, based on their chemical composition, crystalline structure, and film growth. These groups can be successfully explained according to the sputtering characteristics, and correlated with the mechanical properties and color of the films measured by nanoindentation and spectrophotometry respectively. The films deposited by variation of other parameters are introduced afterwards and their characteristics are compared with the reference series. [ABSTRACT FROM AUTHOR]

The kinetic Monte Carlo (KMC) method is a powerful and simple tool to simulate the growth of thin films by deposition. However, one of its major drawbacks is the artificial order induced by the use of regular lattices. An algorithm that mimics the crystallization processes in bi-component thin film depositions via a novel KMC approach is presented in this work. This new algorithm, named GEM-CA (Geometrical Energy Modification-Crystallization Algorithm), modifies the hopping energy barrier depending on the geometrical configuration of the atoms surrounding one particular position. The novel approach allows obtaining amorphous, crystalline and mixed structures (i.e. nanocomposites), depending solely on the synthesis parameters. In addition, we have developed a method for the analysis of deposited structures based on their degree of order. The influence of different deposition parameters such as temperature or composition is discussed in detail. GEM-CA reproduces experimentally observed trends of bi-component film deposition. [ABSTRACT FROM AUTHOR]

In this paper, we present a statistical method that allows evaluating the degree of a transparency of a thin film. To do so, the color coordinates are measured on different substrates, and the standard deviation is evaluated. In case of low values, the color depends on the film and not on the substrate, and intrinsic colors are obtained. In contrast, transparent films lead to high values of standard deviation, since the value of the color coordinates depends on the substrate. Between both extremes, colored films with a certain degree of transparency can be found. This method allows an objective and simple evaluation of the transparency of any film, improving the subjective visual inspection and avoiding the thickness problems related to optical spectroscopy evaluation. Zirconium oxynitride films deposited on three different substrates (Si, steel and glass) are used for testing the validity of this method, whose results have been validated with optical spectroscopy, and agree with the visual impression of the samples. [ABSTRACT FROM AUTHOR]

Abstract: In this paper the tribological and adhesive performance of DLC films prepared by plasma assisted chemical vapor deposition on acrylic rubber (ACM) are studied. The effect of applied load and sliding velocity on the coefficient of friction and wear rate has been investigated. Effects of the rubber substrate and of ageing of the coated samples have also been explored. In addition, the adhesion of the DLC films to the rubber substrates is evaluated via stretch tests and the measured adhesion strength is larger than 40MPa, indicating a superb adhesion to the substrate. It is shown that the tribological performance is greatly influenced by the viscoelastic properties of the substrate, and higher coefficients of friction are obtained at higher loads and velocities. The wear followed a similar trend, although very low in all the cases. [Copyright &y& Elsevier]

We study buoyant displacement flows with two miscible fluids of equal viscosity in ducts that are inclined at angles close to horizontal (β≈90°). As the imposed velocity (V⁁0) is increased from zero, we change from an exchange flow dominated regime to a regime in which the front velocity (V⁁f) increases linearly with V⁁0. During this transition, we observed an interesting phenomenon in which the layer of displaced fluid remained at the top of the pipe (diameter D⁁) during the entire duration of the experiment, apparently stationary for times t⁁>=103D⁁/V⁁0 (the stationary residual layer). Our investigation revealed that this flow marks the transition between flows with a back flow, counter to the imposed flow, and those that displace instantaneously. The same phenomena are observed in pipes (experiments) and in plane channels (two-dimensional numerical computations). A lubrication/thin-film model of the flows also shows the transition from back flow to instantaneous displacement. At long times, this model has a stationary residual layer solution of the type observed, which is found at a unique ratio χ of the axial viscous velocity to the imposed velocity. The prediction of the stationary residual layer from the lubrication model is compared with the transition in observed behavior in our pipe flow experiments and our 2D numerical displacements in the channel. Reasonable agreement is found for the pipe and excellent agreement for the channel. Physically, in either geometry at transition, the upper layer of the fluid is in a countercurrent motion with zero net volumetric flux; the velocity at the interface is positive, but the velocity of the interface is zero. This results from a delicate balance between buoyancy forces against the mean flow and viscous forces in the direction of the mean flow. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we concentrate on the microstructure of diamond-like carbon films prepared by plasma assisted chemical vapor deposition on acrylic rubber. The temperature variation produced by the ion impingement during plasma cleaning and subsequent film deposition was monitored and controlled as a function of bias voltage and treatment time. Its influence during film growth on the appearance of patterns of cracks and wrinkles, caused by the thermal stresses is evaluated. Different growth modes are proposed in order to explain the smaller patch sizes observed at negative variations of temperature. The coefficient of friction (CoF) of the samples is measured using a pin-on-disk tribometer in non-lubricated conditions. Much lower CoF values than unprotected rubber are seen, which can be correlated with the observed patch size. [ABSTRACT FROM AUTHOR]

• CuO thin films were studied as photocatalyst in two photoinduced process. • The highest hydrogen production of these films was 24 μmol under sunlight simulated. • The highest activity of CO 2 photoreduction by CuO films produced CH 2 O (6816 μmol/g). CuO thin films were obtained by DC Sputtering varying the deposit time: 10, 20 and 30 min with the thickness of 60, 120 and 180 nm, respectively. These films were used photocatalysts in two different photocatalytic processes: hydrogen production and CO 2 photoreduction under simulated sunlight. The film with 120 nm of thickness generated the highest amount of hydrogen (24 μmol) of the films tested. Furthermore, the ellipsometry results showed that this film absorbs the simulated light in the UV-to-IR region, which facilitates their photocatalytic performance. In the CO 2 photoreduction process, the CuO film with the lowest thickness exhibited the best performance, yielding 6816 μmol/g CH 2 O, while the film of 120 nm in thickness generated a mixture of CH 3 OH (1536 μmol/g) and CH 2 O (450 μmol/g). It is assumed that the optical properties, such as absorption coefficient, refractive index, and extinction coefficient, of the film favored the production of formaldehyde and methanol. [ABSTRACT FROM AUTHOR]

Modulated Infrared Radiometry is a photothermal technique which allows thermal characterization of coatings, whose properties are determined by applying the "Extremum Method". The objective of this work is to apply this method on a set of films where all the parameters influencing the model are adjusted systematically in a matrix of 36 different samples. Thus, Zr-O-N films were deposited by sputtering varying three factors: i) composition/bonding of the film: metallic Zr, crystalline metallic-type Zr-O-N and disordered Zr-O-N (films deposited in the metallic, reactive and poisoned regimes of the hysteresis curve, respectively); ii) each film was deposited simultaneously on three different substrates: steel, glass and silicon; iii) in each batch, four different thicknesses were grown. Each type of film was deposited with 4 different thicknesses, on top of 3 different substrates, in the same batch, maximizing their similarity. In general, the results allow to discriminate among films and are consistent regardless the type of substrate, although some dispersion of data is observed. The trends of the thermal parameters depending on the thickness were explained in terms of the films' microstructural/chemical characteristics, and the influence of each substrate. The values of the thermal parameters agree with those found in literature, reflecting the nature of the films. • Determination of thermal properties of Zr-O-N thin films using Modulated Infrared Radiometry and Extremum Method. • Validation of the method for different types of Zr-O-N films, deposited on different substrates with different thicknesses. • Lower dispersion of values of the thermal parameters for the disordered ceramic Zr-O-N films. • Thermal parameters are in agreement with results from literature, and in line with the chemical nature of the films. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure and chemical bonding of DLC films prepared by plasma assisted chemical vapor deposition on acrylic rubber (ACM) are studied in this paper. The temperature variation produced by the ion impingement during plasma cleaning and subsequent film deposition was used to modify the film microstructure by controlling the different degrees of strain applied to the substrate. The film microstructure is studied by top view and cross sectional SEM. The observed patch sizes are correlated with the variation of temperature that occurred during deposition. Finally, the chemical bonding of the samples is studied by Raman spectroscopy. All the samples show similar spectra regardless the bias voltage used. [Copyright &y& Elsevier]