Search results for "COATINGS"
showing 10 items of 2386 documents
Influence Of The Electrical Parameters On The Fabrication Of Copper Nanowires Into Anodic Alumina Templates
2009
Abstract Metallic copper nanowires have been grown into the pores of alumina membranes by electrodeposition from an aqueous solution containing CuSO 4 . and H 3 BO 3 at pH 3. In order to study the influence of the electrical parameters on growth and structure of nanowires, different deposition potentials (both in the region where hydrogen evolution reaction is allowed or not) and voltage perturbation modes (constant potential or unipolar pulsed depositions) were applied. In all cases, pure polycrystalline Cu nanowires were fabricated into template pores, having lengths increasing with the total deposition time. These nanowires were self-standing, because they retain their vertical orientati…
Phase and structural transformations in annealed copper coatings in relation to oxide whisker growth
2015
Abstract We describe structural and phase transformation in copper coatings made of microparticles during heating and annealing in air in the temperature range up to 400 °C. Such thermal treatment is accompanied by intensive CuO nanowhisker growth on the coating surface and the formation of the layered oxide phases (Cu 2 O and CuO) in the coating interior. X-ray diffraction and focused ion beam (FIB) are employed to characterize the multilayer structure of annealed copper coatings. Formation of volumetric defects such as voids and cracks in the coating is demonstrated.
Segregation of copper oxide on calcium copper titanate surface induced by Graphene Oxide for Water splitting applications
2020
Abstract Photoelectrochemical cells (PEC) are promising devices for hydrogen production via sunlight energy. One of the important challenges in this area is to design photoactive electrodes able to absorb visible light. A good photoelectrochemical behavior depends on the presence of surface active sites to photogenerate current at the lower possible potential for water splitting. Recent investigations in this field are focusing on perovskite materials such as CaCu3Ti4O12 (CCTO) as visible light active electrode due its outstanding structure in which CCTO encloses in its structure a visible light absorbance component (CuO). The presence CuO on the material surface is mainly responsible for t…
Grafting and characterization of dodecylphosphonic acid on copper: Macro-tribological behavior and surface properties
2013
International audience; Thin film of n-dodecylphosphonic acid (DDPA) was prepared on a copper oxide substrate via a molecular self-assembly process. The composition, structure, organization, surface energy, morphology, and electrochemical behavior of the DDPA filmwere characterized bymeans of X-ray photoelectron spectroscopic analysis (XPS), polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), contact angle measurement v(CAM), microscopic observations, and electrochemistry. The friction behavior of the DDPA film adsorbed on copper oxide substrate sliding against a Si3N4 ball was examined on a linear reciprocating tribological tester. Worn surfaces of the DDPA film…
Thermally Induced Structural Modification of Silica Nanoparticles Investigated by Raman and Infrared Absorption Spectroscopies
2010
We report an experimental investigation by Raman and infrared (IR) absorption spectroscopies on the structural modifications induced by isochronal thermal treatments on amorphous SiO2 nanoparticles (fumed silica). In particular, three different commercial types of this material, characterized by particle mean diameters of 7, 14, and 40 nm, were subjected to thermal treatments from 100 up to 1000 °C. We found that some properties of fumed silica, such as the SiOSi mean bond angle, ring size distribution, and surface adsorbed water content, are drastically different from those of common bulk silica materials and intimately related to the particles' dimension. The SiOSi mean bond angle, probed…
Preparation and characterization of brass-based coatings
2018
Cold Spray (CS) has been widely investigated owing to its high deposition efficiency and retention of the properties of starting materials. Thus, this process has shown obvious advantages over the fabrication of different copper-based deposits and its alloys over other techniques, such as electroplating, Laser Cladding or thermal spraying. As one of the main copper alloys, brass is implanted in the fields of architecture or industry. Nevertheless, nowadays it is clear that there is very little work on brass coatings, and they were mainly made by electroplating and any other deposition methods, which has severely limits their uses in many applications.This study was applied to develop the br…
Nuclear Spin Relaxation in Viscous Liquids: Relaxation Stretching of Single-Particle Probes
2021
Spin-lattice relaxation rates R1(ω,T), probed via high-field and field-cycling nuclear magnetic resonance (NMR), are used to test the validity of frequency-temperature superposition (FTS) for the reorientation dynamics in viscous liquids. For several liquids, FTS is found to apply so that master curves can be generated. The susceptibility spectra are highly similar to those obtained from depolarized light scattering (DLS) and reveal an excess wing. Where FTS works, two approaches are suggested to access the susceptibility: (i) a plot of deuteron R1(T) vs the spin-spin relaxation rate R2(T) and (ii) a plot of R1(T) vs an independently measured reference time τref(T). Using single-frequency s…
O Triclusters Revisited: Classical MD and Quantum Cluster Results for Glasses of Composition (Al2O3)2(SiO2)
2006
The (17)O NMR spectrum of CaAl(2)Si(2)O(8) glass shows two types of O sites that are not present in the crystalline material. One of these, with (17)O NMR parameters C(Q) = 2.3 MHz and delta = +20 ppm, has been assigned to a "tricluster" O, a local geometry in which the O is coordinated to three tetrahedrally coordinated atoms, either Al or Si. For crystalline CaAl(4)O(7), a tricluster site (with three Al linkages to O, i.e., OAl(3)) has been characterized experimentally, with a C(Q) of 2.5 MHz and a delta of about +40 ppm. Thus, a C(Q) value of 2.5 MHz or less seems to be a characteristic of such sites, although they may show a range of delta values. However, several different quantum chem…
A Microscopic Interpretation of Pump–Probe Vibrational Spectroscopy Using Ab Initio Molecular Dynamics
2018
What happens when extra vibrational energy is added to water? Using nonequilibrium molecular dynamics simulations, also including the full electronic structure, and novel descriptors, based on projected vibrational density of states, we are able to follow the flow of excess vibrational energy from the excited stretching and bending modes. We find that the energy relaxation, mostly mediated by a stretching-stretching coupling in the first solvation shell, is highly heterogeneous and strongly depends on the local environment, where a strong hydrogen bond network can transport energy with a time scale of 200 fs, whereas a weaker network can slow down the transport by a factor 2-3.
Chemical and Structural Trends in the Spin-Admixture Parameter of Organic Semiconductor Molecules
2019
Spin mixing in organic semiconductors is related to spin–orbit coupling (SOC). However, a detailed study analyzing the dependence of the spin-admixture parameter (γ) on structural and material para...