Search results for "thin film"
showing 10 items of 1200 documents
Evaluation of aging processes of petroleum asphalt cements by solid state electrochemical monitoring
2018
Abstract The changes in the chemistry of organosulfur compounds from asphalt cements during aging are studied using solid state voltammetry of immobilized microparticles. Five Brazilian asphalt cements were evaluated after three forced aging processes: Rolling Thin Film Oven Test (RTFOT), Pressure Aging Vessel (PAV) and SUNTEST. It was possible to identify the presence of thiophenes, sulfides and sulfoxides in the different samples and the reactional changes during the aging processes were proposed. Voltammetric data, supported by ATR-FTIR spectroscopy, indicate that aging asphalts involve the increase of the proportion of sulfoxide and thiophene components and that polythiophene compounds …
Polystyrene as Graphene Film and 3D Graphene Sponge Precursor
2019
[EN] Polystyrene as a thin film on arbitrary substrates or pellets form defective graphene/graphitic films or powders that can be dispersed in water and organic solvents. The materials were characterized by visible absorption, Raman and X-ray photoelectron spectroscopy, electron and atomic force microscopy, and electrochemistry. Raman spectra of these materials showed the presence of the expected 2D, G, and D peaks at 2750, 1590, and 1350 cm(-1), respectively. The relative intensity of the G versus the D peak was taken as a quantitative indicator of the density of defects in the G layer.
Curvature radius measurement by optical profiler and determination of the residual stress in thin films
2019
Abstract The Stoney formula, based on the measurement of the substrate curvature, is often used for the determination of the thin films' residual stress. In this study, titanium nitride coatings were deposited by DC reactive magnetron sputtering on silicon substrates. An optical profiler was used to determine the curvature of the surface before and after coating. Two radii were then obtained, along the principal perpendicular directions of the surface curvature. A simple and efficient method to determine the experimental error on the stress calculation was developed taking into account the film thickness dispersion and the radii dispersion. Using constant deposition parameters, some samples…
X-ray multiple diffraction in the characterization of TiNO and TiO2 thin films grown on Si(001)
2006
Abstract TiO 2 and TiN x O y thin films grown by low pressure metal-organic chemical vapor deposition (LP-MOCVD) on top of Si(0 0 1) substrate were characterized by X-ray multiple diffraction. X-ray reflectivity analysis of TiO 2 [1 1 0] and TiNO[1 0 0] polycrystalline layers allowed to determine the growth rate (−80 A/min) of TiO 2 and (−40 A/min) of TiNO films. X-ray multiple diffraction through the Renninger scans, i.e., ϕ -scans for (0 0 2)Si substrate primary reflection is used as a non-conventional method to obtain the substrate lattice parameter distortion due to the thin film conventional deposition, from where the information on film strain type is obtained.
Electrophoretically deposited α-Fe2O3 and TiO2 composite anchored on rGO with excellent cycle performance as anode for lithium ion batteries
2018
Abstract Two nanostructured oxides, α-Fe2O3 and TiO2 with a particle diameters 50 nm and 21 nm, were mixed with graphene oxide (GO). Composite thin films on a stainless steel substrate were obtained by electrophoretic deposition (EPD) procedure from water suspensions: α-Fe2O3/GO, TiO2/GO and α-Fe2O3/TiO2/GO. Subsequently reduction of as-prepared thin films was performed. Thicknesses of acquired films were evaluated in the range of 2–6 μm. Structure and morphology were investigated as well as electrochemical properties of all samples were studied. The results revealed that α-Fe2O3/TiO2/rGO (in this article denoted as FTGO) exhibited the specific discharge capacity of 790 mAh·g−1 after 150 cy…
Metal thin-film temperature sensor embedded in heat-sink for CPV cells characterization
2014
The efficiency of a photovoltaic cell is dependent on its temperature, for this reason an accurate measurement of this parameter is important to fully characterize the device and to optimize its performance. For CPV applications a significant heat flux is needed to remove excess heat from the cell towards a heat sink, making it difficult to derive the cell temperature. In fact, measurements performed directly between the cell and the heat-sink, by use of commercial bulk sensors, would produce a significant disturbance in the heat flow; on the other hand, a measurement performed out of the cell / heat sink axis would be subject to large uncertainties, due to the high radial temperature gradi…
Aqueous synthesis of Z-scheme photocatalyst powders and thin-film photoanodes from earth abundant elements
2018
Riga Technical University supported the preparation of this manuscript from the Scientific Research Project Competition for Young Researchers No. ZP 2017/8
Temperature Effects on the Phonon Spectrum in YBa2Cu3O7 Single Crystals and Thin Films
1989
We have performed a detailed investigation of the temperature dependence of the 385cm-1 phonon in single crystals and thin films of the YBa2Cu3O7 superconductor by means of Raman spectroscopy. In the single crystal the frequency of this phonon shows a downshift of about 5 cm-1 on passing the superconducting transition from above, which is referred to a strong electron-phonon interaction in the superconductor. The shift of the phonon in thin epitaxial films on MgO or SrTiO3 substrates is only about 2.5 cm-1. This difference may be a result of a structural transition in the single crystal which is possibly suppressed in the films because of the epitaxy. The electron-phonon interaction is also…
Influence of the age of amorphous nonannealed As2S3 thin films on holographic properties
1998
The dependences of the maximal first order diffraction efficiency and the corresponding specific recording energy on the holographic grating period were studied. Grating period was varied from 0.40 to 70.0 μm. Both fresh and aged films were used. A large holographic recording efficiency decrease in the course of aging is found to take place. These changes are due to the effective film grain size increase caused by the relaxational structural changes and atmospheric oxygen exposure. Results are explained with the aid of stress fields induced by the evaporation and holographic recording. The obtained results can be used to optimize the hologram recording in amorphous chalcogenide films.
Metal-organic chemical vapor deposition of Cr2O3 and Nd2O3 coatings. Oxide growth kinetics and characterization
2000
Thin oxide films of Cr2O3 and Nd2O3 were prepared, using Metal-Organic Chemical Vapor Deposition (MOCVD) technique, to protect stainless steels against corrosion at high temperature. The conditions of precursor volatilization were studied by thermogravimetry. Deposited film growth kinetics depended on the deposition parameters, particularly substrate temperature, gas flow rate and location of substrate in the coating reactor. The influence of the deposition parameters on the deposition rate and the uniformity of the films is discussed. The oxide films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force mi…