Materials Science Forum Vols. 561-565

Abstract: The Cold spray or cold gas dynamic spraying is the new progressive step in the direction of development of high kinetic energy coating processes. The cold spray is a method for coating substrates under atmospheric conditions. In this process micron sized solid particles are accelerated and transported to substrates by means of supersonic free jets. Upon impacting the substrates, particles stick to the surface and form coatings which possess very low porosity. The paper outlines the principles involved in cold spray method and the equipment used for the technique. The cold spray method is related to classical thermal spray methods but it has some interesting additional features, which has been discussed in the paper. A fundamental feature of cold spray method i.e. concept of critical velocity along with the plausible mechanism theory responsible for the deposition of coating has been discussed briefly. Successful applications of cold spray process and its environment friendly aspect has been elaborated. It is reported that well founded cold spray technology will be able to compete for a good market share of VPS/PVD coatings in various fields like power, electronic/electrical, biotechnology, turbines and other industries. The cold spray process is still primarily in the research and development stage and only now becoming commercially available, and has been accepted as a new and novel thermal spray technique mainly in developed countries. The technology has great potential for future research especially with reference to its application to real industrial solution.

Abstract: In this paper, ZnO films are deposited on Freestanding Thick Diamond (FTDF) by plasma-assisted Metal Organic Chemical Vapour Deposition (MOCVD). Diethyl zinc, O2, and N2O are applied as precursors and different substrate temperatures are used to achieve high quality ZnO films. The influence of substrate temperature on the properties of ZnO films is systematically investigated by X-ray diffraction, Hall measurements, and electron probe microanalysis. Experimental results demonstrate that ZnO films deposited at 600°C and 73Pa displays fine electrical quality and Zn/O atomic ratio plays an important role in the electrical property of ZnO films.

Abstract: Dislocation structure of {1120}/<1100> 2º tilt grain boundary in alumina was observed by transmission electron microscopy (TEM). The grain boundary consisted of periodical array of basal dislocations, which were dissociated into pairs of 1/3<1010> and 1/3<0110> partials with {1120} stacking-fault in between. The relationship between the separation distance of partials and the stacking-fault was modeled by considering the force balances of periodical dislocations. The estimated stacking-fault energy for 2o tilt grain boundary was consistent with the previous reports.

Abstract: It is shown using aluminum single crystals with kink bands like a plate through the depth that the nucleation and growth of recrystallized grains (RGs) on/in the surface precede those in the interior.

Abstract: The atomic sulfur adsorption on the metastable, unreconstructed Ir(100) surface is studied from density functional theory calculations with two exchange correlation functionals. The fourfold hollow site is energetically preferred for both the p(2×2) and c(2×2) structures. Based on the most favored adsorption georemetries, vibrational frequency and work function are also calculated. Moreover, a detailed comparison is presented between two functional performances.

Abstract: Due to the special heating mode of High Current Pulsed Electron Beam (HCPEB) irradiation, intense stresses such as thermoelastic stress, quasi-static stress, and shock wave stress can be generated by a dynamic thermal field. A dynamic thermo-stress is the origins of these stresses. The simulations for non-melting and melting modes are respectively compared with related phenomena such as bending, surface plastic deformation, and residual stress (non-melting mode, quasi-static stress-related), crater formation, depth distribution of microhardness, fragmentation of pearlites (melting mode, shock-stress wave-related).

Abstract: A Ti-Al-V alloy was implanted with Al and Nb to flounces ranging from 1 × 1017 to 1 × 1018 ions cm-2. Glancing Angle XRD measurement revealed α-Ti on Al-implanted samples and (α+β)-Ti on Nb-implanted samples. The (α+β)-phase samples exhibit better corrosion resistance. In the aerated solution with pH = 10, all the implanted surfaces are passive. Enhanced reoxidation was confirmed on implanted surfaces by Auger electron spectroscopy and X-ray photoelectron spectroscopy analysis. The corrosion in the solution with pH = 10 was governed predominantly by a TiO2 surface film.

Abstract: Lead-containing glasses coated with lead metal have been used for decoration in Thailand for a long time, were a high refractive index glass. Due to harmful effects of lead, time degradation of glass and because of many kinds of local raw materials for glass production especially sand, colorless lead-free high refractive index glasses were prepared by using local raw materials. In this work, the various kinds of metals; silver and aluminum, were coated on the surface of the prepared glasses using both chemical and physical methods. The joining interfacial layer between the glass body and the coated layer was studied using a scanning electron microscope and the hardness of the coated glasses was measured by a microhardness tester to compare with those of lead coating. It was found that the structures between the joining interfacial layers were similar. The values of the Knoop hardness were approximately 520±20 kg/mm2. This glass can be used to replace the lead glass for restoration glass or decoration onto the surface of the new wood or the metal carving products.

Abstract: Sliding wear and hardness tests in Ni/Cu multilayers electrodeposited on polycrystalline copper substrate were carried out. The multilayers had a total thickness of 5 μm and an individual layer thickness from 5 to 100 nm. Hardness of the multilayers measured with a nanoindentation tester was found to be dependent on layer thickness. The multilayer with the layer thickness of 20 nm showed the highest value among them. It was found that the wear resistances of all the multilayers tested were higher than that of an electrodeposited nickel coating. It was also revealed that the specific wear rate of multilayers decreased with decreasing the layer thickness although the highest hardness was attained at the 20 nm layer thickness. Scanning ion microscope observation showed that the subsurface area kept the layered structure of nickel and copper even after sliding wear. The multilayer had plasticity sufficient to accommodate deformation coming from the sliding wear, because fine grains peculiar to severe plastic deformation process were formed near the worm surface.

Abstract: Specific studies were carried out on the characteristic component from interior surfaces (IS) of cavities in metallic fire debris by Auger electron spectroscopy (AES), especially in order to distinguishing the primary and secondary electrical short circuit (ESC) arc beads. From the results of AES, we can see that the components from interior surfaces of cavities in the primary and secondary ESC are different, which help in probing the cause of the fire.