Μm Thick Oxide Film Research Articles

A Novel 1000 MPa Grade Ultrafine-Grained Dual-Phase Press Hardening Steel with Superior Oxidation Resistance and High Ductility.

1000 MPa grade low-carbon martensite press hardening steels (PHS) are widely used in energy-absorbing domains of automotive parts, such as the bottom of a B-pillar. To prevent oxide scale formation during hot forming, this PHS is often required to be protected by an additional Al-Si coating. In addition, although the low carbon martensitic microstructure grants it excellent bending toughness, the ductility tends to be limited. In this study, a novel 1000 MPa grade ultrafine-grained (UFG) martensite-ferrite (F-M) dual-phase (DP) PHS with superior oxidation resistance was designed using tailored additions of Cr, Mn, and Si, and refining the initial microstructure. Only 0.55 ± 0.18 μm thick oxide film is formed in the designed steel during austenitizing heating and stamping, which is significantly lower than the 24.6 ± 3.1 μm thick oxide film formed in conventional 1000 MPa grade low-carbon martensite PHS under the identical condition. The superior oxidation resistance of designed steel can be attributed to the rapid formation of the protective Si-rich, Cr-rich, and Mn-rich oxide layers during annealing. Moreover, due to the presence of ferrite and ultrafine microstructure, the designed steel also shows a significant improvement in ductility from 8.5% to 16.8% without sacrificing strength and bending toughness compared with conventional 1000 MPa grade low-carbon martensite PHS.

Temperature Dependency of Friction of Titanium Alloy by Forward Rod-Backward can Combined Extrusion Test

Forward rod-backward can combined extrusion test was used to investigate the tribological properties of Ti-6Al-4V titanium alloy with oxide film at cold and warm forging conditions. 0.08 and 0.10 µm-thick oxide films were formed on the test piece by atmospheric oxidation treatment. A friction test was performed without using lubricants. As a result, the oxide film was effective to prevent seizure at cold forging condition, where the friction coefficient was estimated as about 0.15. However, at warm forging condition, a decohesion of the oxide film and seizure occurred, where the estimated friction coefficient was larger than that at cold forging condition. Furthermore, thickening the oxide film was effective against the decohesion and to reduce the friction coefficient.

High-temperature phase composition, crystal stabilisation, and interfacial diffusion of (NbC-ZrC)/SiC double-layer coated C/C composites enduring the oxyacetylene flame

Among NbC-ZrC coatings, an NbC coating modified with 30 mol.% ZrC achieves the best ablation-resistant property. It generates a liquid 10 μm-thick oxide film mainly composed of NbO and highly thermal-stable NbxZr1-xO2 phases. Furthermore, Nb4+ with a smaller ionic radius replaces Zr4+ and the transformation of NbO into Nb2O5 in air produces compressive stress stabilize the t-ZrO2 crystals. Significantly, a 1−2 μm-thick Nb-rich layer formed by reaction-diffusion between SiC and niobium suboxide (NbO2 and NbO) acts as a barrier to infiltrating oxygen, which provides interfacial anti-oxidation protection for the SiC transition layer during the oxyacetylene test.

Efficient Micro-Arc Oxidation Technology for As-Cast AZ80 Magnesium Alloy

A new efficient micro-arc oxidation technology was developed for AZ80 magnesium alloy, the treating time was shorten to 3 min compared to the conventional micro-arc oxidation process. The surface morphologies and cross section morphology of the coatings were analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). The corrosion behavior and process of the coatings were investigated with potentiodynamic polarization tests and salt spry tests. The research results show that a 4 μm thick oxide film grew rapidly on the surface of AZ80 magnesium alloy under the special prepared electrolyte and high density current. The corrosion resistance of ceramic coating prepared by the new technology was greatly improved for four order of magnitude and it was mainly consisted of dense layer, the coated samples exhibit excellent corrosion resistance not only in the potentiodynamic polarization tests but also in the long term corrosion tests.

Development of a method for studying and study of the structural-phase state of E-635 alloy oxide fuel in the pre-critical stage of oxidation

The microstructure and phase composition of a 1 µm thick oxide film formed in autoclave tests on a guide channel made from the E-635 alloy are investigated. The tests are done by the method of transmission electron microscopy using x-ray spectral energy-dispersive micro-analysis. A method is developed to prepare thin foils from the oxide films. Electron-microscopic studies are performed in three different sections of an oxide film over its thickness: near the metal‐oxide interface and in the central and outer parts of the oxide film. The structural-phase composition of the oxide film and a transformation of the Laves phase over the thickness of the film are determined.

Design of a thermoelectric layer for a micro power generator

In this article, an n-type polycrystalline silicon (poly-Si) layer for a micro thermoelectric generator (TEG) was designed using Taguchi methods. Design parameters for this experiment were thicknesses of oxide and poly-Si films, and fabrication conditions in the boron ion-implantation process. Based on an L9 (34) orthogonal array, nine different poly-Si testpieces were fabricated on 525 μm-thick Si substrates. Oxide and poly-Si films were deposited using the low pressure chemical vapor deposition (LPCVD) method on cleaned wafers. Subsequently, phosphorous ions were implanted in the poly-Si layers with different process conditions. The crystalline structures of the fabricated specimens were observed using X-ray diffraction (XRD). The XRD analysis results demonstrated that each specimen was well crystallized with (2 2 0) orientation. The Seebeck coefficient and electrical conductivity including the Hall coefficient, Hall mobility, and carrier concentration were measured. The power factor of each testpiece was calculated. Through analysis, the power factor of an optimized poly-Si layer was predicted to be 798 μWm−1K−2. The optimized design parameters were 0.2 μm-thick oxide films, 1.5 μm-thick poly-Si films, 130 keV energy of the ion implantation process, and 1015 cm-2 dopant dose of the phosphorous ions.

Simple electrochemical method for the preparation of a highly oriented and highly photoactive α-PbO film

Highly oriented (110 plane parallel to the substrate) and highly photoactive α-PbO films are prepared by electrochemical anodic oxidation of Pb electrode in alkaline solution at 80 °C by polarizing at +0.3 V versus saturated calomel electrode. Within an hour of anodization, nearly 10–12 μm thick oxide film is produced which is found to be exclusively α-PbO with a preferred orientation along the 110 plane. The films show about 80% quantum efficiency and 1.55% solar to electrical energy conversion efficiency for white-light irradiation in a liquid junction solar cell containing 0.1 M Fe(CN)3−/4−6 redox solution. These values are the highest reported so far for lead oxide thin-film based solar cells.

Thickness-Dependent Frequency Shift in Infrared Spectral Absorbance of Silicon Oxide Film on Silicon

The spectral dependence of the refractive index n and extinction coefficient k of chemical-vapor-deposited (CVD) silicon oxide film on silicon wafer has been determined. The results are used to calculate spectral absorbances for 0.1–2 μm thick oxide films with unchanged structure. The dependence on thickness of the position of Si-O stretching ( vM) has been investigated. The main factor influencing the frequency is the transmission factor at the air/film and film/substrate boundaries. In the limit of d → 0, vM corresponds to the maximum of the Im (ε) function.