Advanced Materials Research Vol. 629

Abstract: The RE–Mg–Ni-based A₂B₇-type La_0.75−xPr_xMg_0.25Ni_3.2Co_0.2Al_0.1 (x = 0, 0.1, 0.2, 0.3, 0.4) electrode alloys fabricated by melt spinning technology. The impacts of the melt spinning and the replacement of La by Pr on the microstructures and electrochemical performances of the alloys were systematically investigated. The results indicate that the as-cast and spun alloys hold a compound phase structure, containing (La, Mg)₂Ni₇ and LaNi₅ phases as well as a residual phase LaNi₂. A notable grain refinement of the alloys without altering the phase structures of the alloys obtained by melt spinning. The discharge capacity of the alloy (x = 0.2) tend to first augments and then falls with the growing spinning rate. And the as-spun (10 m/s) alloy gains the maximum discharge capacity as Pr content augmenting in the alloys. Furthermore, the measurements of the electrochemical hydrogen storage kinetics reveal that the high rate discharge ability (HRD), the hydrogen diffusion coefficient (D) and the limiting current density (IL_{Subscript text}) of the alloys first increase then decrease with the rising of the spinning rate and the amount of Pr substitution.

Abstract: GaN thin films have been deposited on Si (111) substrates by pulsed laser deposition (PLD) of a GaN target in nitrogen atmosphere. An Nd: YAG pulsed laser with a wavelength of 1064 nm was used as a laser source. The results indicate that the GaN thin films deposited only by PLD are amorphous. By annealing in an NH3 atmosphere, the quality of the GaN thin films is improved, and the crystallzinity GaN thin films were obtained. The influence of annealing temperature on the crystallinity, structure, surface morphology and optical properties of GaN films have been examined by X-ray diffraction (XRD), atomic force microscopy (AFM) and infrared spectrum. In our experimental conditions, the GaN thin films deposited by PLD with a laser energy of 250 mJ, growth temperature of 800 °C and annealed at 1000 °C have the best surface morphology and crystalline quality.

Abstract: WC-10Co-4Cr cermet coatings were deposited on low carbon steel using the HVOF technique, then heat treated by different process (300 °C × 3 hours, 400 °C × 3 hours, and 500 °C × 3 hours). The influences of heat treatment on microhardness, elasticity modulus of coatings were studied by nanoindentation method in this paper. The results show that the microhardness increased with the heat-treated temperature increasing, but the tendency of elasticity modulus was opposite. In the case of 500 °C × 3 hours heat-treated coating, the microhardness increased by approximately 30% and elasticity modulus decreased by approximately 15% in comparison with that of as-sprayed coating.

Abstract: Coatings such as Cr, Ni, Ti, and SiO₂/SnO₂ on solar-control and low-emissivity (low-E) glasses are commonly used in the energy efficient glass windows. However, coloring in the re-manufactured glass panels using recycled window glasses resulting from the coatings reduces the glass transparency significantly. Traditional ways to remove coatings by manual wheels and pneumatic removal machines are labor intense and slow processes. In this study a new way to remove the coatings on recycled coated glasses was investigated. The Ultra Violet/Visible/Infrared (UV/VIS/IR) spectra and Secondary Electron Microscope (SEM) pictures were taken before and after 30s. atmospheric pressure oxygen plasma treatments. It was confirmed that the atmospheric oxygen plasma treatment is a fast, efficient, and low pollution way to remove the coatings before the remanufacture of recycled glasses. Other than the physical sputtering off the coatings from the plasma, there are many excited oxygen species in the plasma which effectively react to the coating and the products are then removed.

Abstract: Diamond-like carbon (DLC) bilayer films with Cu interlayer were prepared on silicon substrate by direct-current and pulsed cathode arc plasma technique, and annealed at various temperatures in vacuum. Structure, morphology and mechanical properties of the bilayer films were investigated by Raman spectroscopy, Auger electron spectroscopy, scanning electron microscopy and atomic force microscopy, surface profilometer and Vickers sclerometer. The results show that Cu interlayer changes the bilayer microstructure, including the thickness and element distribution of diffusion layer, the relative fraction of sp³/sp² bonding and growth model of bilayer. A simple three-layer model was used to describe the interdiffusion between Cu and C layer. Cu interlayer could be more effective against graphitization upon annealing. Morphological characteristics of the films were studied by analyzing the surface features of substrate. Cu/DLC bilayer exhibits highly dispersed nano-agglomerates with smaller size on the surface due to low surface energy of Cu interlayer. The stress and hardness of the films were affected accordingly. Cu/DLC bilayer shows a relatively high hardness at low annealing temperature but the stress almost no change. By changing Cu interlayer and annealing temperature, excellent DLC films could be designed for the protective, hard, lubricating and wear resistant coatings on mechanical, electronic and optical applications.

Abstract: TRIP-assisted steels are ideal for lightweight automotive applications due to not only its high strength and ductility but also the fatigue resistance, which result from the special strengthening mechanism of phase transformation in deformation processes. In this paper, a kinematic transformation model is developed, based on shear-band intersections, to reasonably evaluate the transformation from austenite into martensite with cyclic loading. The transformation process is controlled by parameters, such as, increase temperature, transformation driving force, shear-band formation rate and shear-band intersection volume fraction, by which the influences of cyclic loading variables (such as, number of cycles, strain amplitude and frequency) on transformation from austenite into martensite are predicted. The microstructure volume fraction is tested by X-Ray to verify the model.

Abstract: A very simple synthesis method of AlN-SiC solid solution powder, i.e. self-combustion of Al, Si₃N₄ and C mixture in the air only with assistance of high-energy mechanical milling, was proposed in the present work. The effect of compositions on the combustion behavior and the product was studied and the results showed that the amount of Al in the starting powder was the key factor affecting the combustion behavior, the phase assemblages and the morphology of products.

Abstract: In this paper, we report our numerical study on the electrical-optical properties of the organic light emitting diodes (OLEDs) devices with n-doped layer, which is inserted in an effort to reduce the interface barrier between the cathode and the ETL(electron transport layer). In order to anlayze the electrical and optical characteristics such as the transport behavior of carriers, recombination kinetics, and emission property, we undertake the finite element method (FEM) in OLEDs. Our model includes Poisson’s equation, continuity equation to account for behavior of electrons and holes and the exciton continuity/transfer equation to account for recombination of carriers. We employ the multilayer structure that consists of indium tin oxide (ITO); 2, 2’, 7, 7’ –tetrakis (N, N-diphenylamine) - 9, 9’- spirobi-fluorene (S-TAD); 4, 4’- bis (2,2’- diphenylvinyl) - 1,1’- spirobiphenyl (S-DPVBi); tris (8-quinolinolato) aluminium (Alq3); calsium(Ca).

Abstract: The Mn-doped GaN (GaMnN) films on c-plane sapphire substrates were prepared by using Laser Molecular Beam Epitaxy (LMBE) at different base nitrogen pressure, followed by annealing in the ammonia atmosphere at 950 °C for 30 min, to study the original reason of the room-temperature ferromagnetism of GaMnN films. We found the crystalline quality was sensitive to the base nitrogen pressure during growth. X-ray photoelectron spectra (XPS) analysis confirmed that the Mn³⁺ and Mn²⁺ coexist in our samples. The room-temperature ferromagnetic behavior can be explained by double exchange. The ferromagnetism would be weakened by the nitrogen vacancies, which plays a role of donor.