Papers by Keyword: Oxide

Abstract: An area of increasing interest for SiC device processing is the processing and qualification of silicon oxides. In this article a contactless corona CV (CnCV) measurement procedure is evaluated as a way to gain more knowledge about the different processes related to oxides. A 21-point measurement pattern is used to gain information about uniformity of oxide properties. Two different types of oxides have been considered, low pressure chemical vapor deposited (CVD) oxides using tetraethylorthosilicate (TEOS) and thermally grown oxides. The two different groups have received different combinations of pre- and post-processing steps prior to measurements. As expected, low pressure CVD (LPCVD) and thermally grown SiO₂ without any post oxidation annealing (POA) showed significantly different electrical characteristics compared to the wafers that did get a POA. This difference could clearly be distinguished by CnCV, meaning that individual process steps can be analyzed without the fabrication of any test structures on the wafers. As the individual process steps can be analyzed, the uniformity of the individual steps can be accessed. Using a 21-point pattern it was possible to show that there is a non-uniformity in the LPCVD process used prior to the POA. This makes the CnCV technique suitable for in-line characterization and process monitoring.

Abstract: Stainless steel is widely employed in a variety of industries, including aerospace, chemical processing, and transportation. It can be recycled indefinitely with no loss of property. The Gas Tungsten Arc Welding (GTAW) or Tungsten Inert Gas (TIG) technique is widely used for connecting thin pieces of stainless-steel. However, it is ineffective for combining heavy parts in a single pass. Activated TIG (A-TIG) dramatically enhances weld penetration up to 1.5- 4 times in a single pass. A-TIG is the centre of investigation among researchers because of its deep penetrating capacity. This article discusses the effects of particular flux powders, such as NaF and Fe₂O₃, on surface appearance and geometric shape. Weld of satisfactory appearance is produced using NaF powder as a flux in TIG welding, whereas, Fe₂O₃ powder results in a substantial increase in both the joint-penetration and weld-aspect ratio.

Abstract: The dealloying technique has been a well-known process since antiquity, but recently it has started to be used to produce nonporous metals and metal oxide semiconductors for various electrochemical applications. The dealloying process is carried out in both acidic and basic solutions, depending on the base material and the desired application. In this study, Cu-based amorphous ribbons were dealloyed in alkaline aqueous solution at room temperature, keeping the temperature constant and varying the concentration of the solution. This process has the advantage that both dealloying of the ribbons and nanostructured copper oxide synthesis on their surface is obtained in one step. For the preparation of copper-based amorphous ribbons, the melt-spinning process was used, and the composite obtained consisting of nanopores decorated with Cu₂O/CuO nanoparticles makes it an ideal candidate for electrochemical applications. For the investigation of the structural, morphological, and optical properties of the obtained materials, X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Abstract: VPC (Vapor Phase Cleaning) is studied to etch various types oxide film using a mixture of HF gas and H₂O vapor. We focused on controlling the amount of gas molecules adsorbed on the oxide surface and investigated the H₂O amount included in oxide films, which will contribute to the oxide etching reaction. We have verified that selective etching between different oxide films can be achieved by controlling the gas adhesion amount by varying process parameters and utilizing the different amounts of H₂O in the oxide films for several deposition methods.

Abstract: Dense oxide coated AZ 31 magnesium alloy surfaces were uniformly formed using a radio frequency magnetron sputtering method. The magnesium oxide thin film thickness was about 240 nm. XRD results of the film indicated that film of magnesium oxide single phase was deposited. The surface of the film was uniform and no crack was observed. The Vickers hardness measured by the nanoindenter was about Hv80 and Hv200 for the AZ31 substrate and the sample coated with the thin film, respectively. The dynamic hardness of the AZ31 substrate and the sample coated with the thin film were almost the same. In the curve at the time of pressurization, a step was observed in the sample coated with the thin film. On the other hand, many steps were observed in the data curve for the thin film deposited on the glass substrate.

Abstract: Grain refinement tendency of pure Fe and Fe-X (X=5~10at%Al, 2~10at%Ti) alloys produced by laser powder bed fusion (LPBF) process was investigated. Pure Fe, Al, and Ti powders were dry mixed and cubic samples were built from the mixtures. The microstructure analysis revealed that (1) the microstructure of pure Fe consisted of equiaxed grains having an average diameter of 1.7 μm with fine iron oxide particles. (2) Fe-5 and 10at%Al alloys showed coarse columnar grains. (3) Fe-2at%Ti shows a mixture of fine equiaxed and columnar shape grains. (4) the microstructures of Fe-5at%Ti and 10at%Ti alloys are fully equiaxed, and grain refinement tendency was confirmed with increasing Ti content. Ti(N,O) oxi-nitrides are efficient in reducing the grain size because of the low lattice misfit with the ferrite matrix. Additionally, the effectiveness of Ti(N,O) particles as grain refiners was confirmed by building samples using TiN powder mixed with Fe-10at%Al and Fe-2at%Ti. While these alloys alone are coarse grained, a dispersion of Ti(N,O) particles achieved a fine-grained microstructure.

Abstract: In this study, Zinc oxide (ZnO) undoped and Lanthanum doped (ZnO: La) thin films were deposited on 400°C heated glass using spray pyrolysis technique with moving nozzle. The components (Zn (CH₃COO)2, 2H₂O) and (LaCl₃, 7H₂O) were used as sources to produce ZnO thin film and doped Lanthanum, respectively. Effects of dopant on the optical and structural properties of undoped and 0, 2 and 4 wt. % Lanthanum doped ZnO thin films were studied. Optical transmittance spectra of the films showed high transparency of about 98% in visible region. The optical gap for ZnO and 0, 2 and 4 wt. % La doped ZnO thin films were found to be in 3.25-3.28 [eV] range. The X-ray diffraction showed that the thin films have hexagonal wurtzite structure with a strong (002) as preferred orientation, whereas the crystalline size was ranged in 15.89-33.45 nm. The ZnO thin films are promising to be used a light emitting diodes, gas sensor and UV detectors applications.

Abstract: The aim of this work is to study the difference between the crystalline phases of used fluxes and obtained slags after Shielded Metal Arc Welding (SMAW). It is well known that The weld pool solidifies into the weld metal while the lighter molten flux floats on the top surface and solidifies as a slag layer that can be easily removed .The effects of individual flux ingredients as well as their interaction effects on weld metal composition have been investigated in this paper. The mass concentrations between fluxes (FA, FB and FC) and slags (SA, SB and SC) summarize the physico-chemical behavior of elements transfer between base metal, filler metal, flux and slag forming during welding of pipelines by SMAW process. The analysis of different fluxes phases and slags by X-ray diffraction allowed to detect the presence of different crystalline phases, which were formed at low temperature (T <1000°C) heat treatments, and during fluxes confection. As for the slags, the presence of new crystalline phases which have been formed at high temperatures.

Abstract: We successfully synthesized Li_1+x-yM_1-x-3yTi_x+4yO₃ solid solutions (M = Nb or Ta, LMT, 0.07 ≤ x ≤ 0.33, 0 ≤ y ≤ 0.175) that have a superstructure. The materials formed a superstructure known as the M-phase, which is formed by the periodical insertion of an intergrowth layer in a matrix having a trigonal structure. The homogeneous and periodical structure of M-phase in LNT needed to sinter at 1393 K for 40 h-200 h using a conventional electric furnace. In order to form the homogeneous intergrowth layers rapidly, millimeter-wave or air-pressure control atmos furnaces were also used as smart processing techniques. We concluded that atomic diffusion was promoted in the useful reaction-fields: millimeter-wave radiation or high oxygen pressure.

Abstract: The present study is focused on analysing the change of colours of anodized titanium and effects of applied electrolytic voltages on chromatics. The titanium specimens were anodized in 20 g/L citric acid and 20 g/L baking soda electrolyte by use of different voltages. The colours of anodized titanium were measured with a spectrophotometer and then evaluated in the CIELAB colour space. It is found that different volt produces different colours. Anodizing in the range of 15 V to 150 V produces respectively a wide spectrum of colour ranging from brown to fuchsia. It can be concluded that the colours of the anodized titanium are dependent upon the applied voltages.