Search results for "Surfaces"
showing 10 items of 2837 documents
Development of microwave gas sensors
2011
Abstract This work presents a novel approach in gas detection by an original method of microwave transduction. The design of the sensor includes a coplanar grounded wave guide with a gas sensing material to study its sensitivity to ammonia in argon flux. The sensing material can play the role of the substrate or can be deposited as a thin layer on a microstrip structure used in electronics. Submitted to an electromagnetic excitation in microwave energies, the sensor response in the presence of a gas results in a specific modification of the reflected wave (real and imaginary parts). The goals of this study include an examination of the form of the sensitive material and its influence on the…
Prediction and analysis of high velocity oxy fuel (HVOF) sprayed coating using artificial neural network
2019
Abstract Thermal spray comprises a group of coating processes for coating manufacturing in which metallic or nonmetallic materials are deposited in a molten or semi-molten condition. Most often, the coating properties are significantly influenced by the operating parameters. However, obtaining a comprehensive modeling or analytical analysis of the thermal spray process is too difficult to be practical due to the complex chemical and thermodynamic reactions. Accordingly, the present study aims at applying an artificial neural network (ANN) model to predict the HVOF sprayed Cr3C2−25NiCr coatings and analyze the influence of operating parameters regardless of the intermediate process. The proce…
Silica-based powders and monoliths with bimodal pore systemsElectronic supplementary information (ESI) available: UV–Vis spectrum of sample 3. See ht…
2002
Porous pure and doped silicas with pore sizes at two length scales (meso/macroporous) have been prepared and shaped both as powders and monoliths through a one-pot surfactant assisted procedure by using a simple template agent and starting from atrane complexes as inorganic precursors.
Quantification of Plasma Sprayed Coating Adhesion Using Pulsed Laser Induced Decohesion Technique
2001
Abstract The aim of the present study is to compare a laser ultrasonic technique with a conventional indentation test for the determination of intrinsic properties and the adhesion of alumina coatings, of different thicknesses (30–350 µm), deposited on stainless steel substrates by atmospheric plasma spraying (APS). For this purpose, a pulsed Nd:YAG laser is used to irradiate the coated specimens, and the ultrasonic waves generated by the laser are recorded at the epicenter using a laser interferometer. In the thermoelastic regime, the good agreement between the experiment and computation allows determination of the longitudinal wave velocity as well as the Young's modulus of the oxide coat…
Assisted-assembly of coordination materials into advanced nanoarchitectures by Dip Pen nanolithography
2011
3 páginas, 4 figuras.
Preparation and properties of radio-frequency-sputtered half-Heusler films for use in solar cells
2011
Abstract The class of half-Heusler compounds opens possibilities to find alternatives for II–VI or III–V compound semiconductors. We aim to find suitable substitutes for the cadmium sulphide buffer layer in chalcopyrite-based thin film solar cells, where the buffer layer is located between the p-type chalcopyrite absorber and an n-type transparent window layer. We report here the preparation of radio-frequency-sputtered lithium copper sulphide “LiCuS” and lithium zinc phosphide “LiZnP” films. The optical analysis of these films revealed band gaps between 1.8 and 2.5 eV, respectively. Chemical properties of the film surface and both interfaces between the film and a Cu ( In , Ga ) Se 2 layer…
Tuning the Direct and Indirect Excitonic Transitions of h-BN by Hydrostatic Pressure
2021
The pressure dependence of the direct and indirect bandgap transitions of hexagonal boron nitride is investigated using optical reflectance under hydrostatic pressure in an anvil cell with sapphire windows up to 2.5 GPa. Features in the reflectance spectra associated with the absorption at the direct and indirect bandgap transitions are found to downshift with increasing pressure, with pressure coefficients of −26 ± 2 and −36 ± 2 meV GPa–1, respectively. The GW calculations yield a faster decrease of the direct bandgap with pressure compared to the indirect bandgap. Including the strong excitonic effects through the Bethe–Salpeter equation, the direct excitonic transition is found to have a…
Geometry, electronic structure, morphology, and photoluminescence emissions of BaW1-xMoxO4 (x = 0, 0.25, 0.50, 0.75, and 1) solid solutions: Theory a…
2019
Abstract The design of a solid solution with tunable electro-optical properties and multifunctionality is a promising strategy for developing novel materials. In this work, BaW1-xMoxO4 (x = 0, 0.25, 0.5, 0.75, and 1) solid solutions have been successfully prepared for the first time by a co-precipitation method. Their crystal structure and phase composition were determined by X-ray diffraction and Rietveld refinements. Fourier transform infrared and micro Raman spectroscopy in combination with field-emission scanning electron microscopy (FE-SEM) were used to describe the microstructures and chemical compositions of the synthesized materials. The influence of chemical composition on morpholo…
Structural and Optical Study of Ga3+ Substitution in CuInS2 Nanoparticles Synthesized by a One-Pot Facile Method
2014
A one-pot method was used to synthesize CuInxGa1–xS2 nanoparticles by substituting In3+ with Ga3+. The samples with composition of gallium ranging from 0% to 100% were synthesized by solving copper chloride, indium trichloride, gallium acetylacetonate, and thiourea as precursors in 1-octadecene, oleylamine, and oleic acid as noncoordinating, coordinating, and capping agent solvents, respectively. Depending on the chemical composition and synthesis conditions, the morphology of the as-synthesized nanoparticles obtained was trigonal, semitrigonal, hexagonal, and quasi-spherical. X-ray photoelectron spectroscopy and X-ray diffraction confirmed that Ga3+ substituted In3+ without any segregation…
Properties of Ni–Zn ferrite thin films deposited using spray pyrolysis
2012
Abstract Nanocrystalline, homogeneous spinel Ni 1 − x Zn x Fe 2 O 4 thin films were deposited on glass substrates by using spray pyrolysis of metal nitrate aqueous solutions. The thickness of deposited films was below 500 nm, but crystallite size was under 30 nm. It has been shown that the DC resistivity, dielectric loss and optical band gap of deposited films are influenced by the zinc content. High DC resistivity and low dielectric losses of thin Ni 1 − x Zn x Fe 2 O 4 films are explained by mixed n-p conductivity and nanograin structure of spray pyrolysis deposited coatings which are changing with the ratio of Ni/Zn.