Papers by Keyword: Oxidation

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Authors: Lei Yang, Hua Li, He Zhou Liu, Yang Yang Zhang
Abstract: Mixture powders with different ratio of Ag/γ-TiAl were deposited on titanium alloy by low presure plasma spray and thermal treatment was applied to convert the mixture coatings into Ti-Al-Ag ternary ones. The experimental results indicated that the oxidation resistance of ternary coatings was better than sheer γ-TiAl coating and increased with increasing Ag from 2at.% to 4at.% at 700 and 800°C. The outside oxide scale consisted of alumina and a small amount of rutile due to the insufficient diffusion of Ag in γ-TiAl.
Authors: Matthieu Florentin, Mihaela Alexandru, Aurore Constant, Bernd Schmidt, Philippe Godignon
Abstract: This work presents the 10 MeV protons irradiation effects on 4H-SiC MOSFETs at different fluences. MOSFETs main electrical parameters, such as the channel mobility (µEFF), threshold voltage (VTH), transconductance (gm) and subthreshold current, were analyzed using the time bias stress instability (BSI) technique. Applying this method allowed us to study the effect of carriers interaction with generated interface traps, whether in the bulk or at the interface. Improvements, such as VTH stabilization in time and a significant increase of the µEFF at high fluencies, have been noticed. We assume that this behavior is connected with the atomic diffusion from the SiO2/SiC interface, towards the epilayer during proton irradiation. These atoms, in majority Nitrogen, may create other bonds by occupying various vacancies coming from Silicon and Carbon’s dangling bond. Therefore, by enhancing the passivated Carbon atoms number, we show that high irradiation proton could be a way to improve the SiO2/SiC interface quality.
Authors: H. Maupas, Jean-Louis Chermant
Authors: Robert S. Okojie, Ming Xhang, P. Pirouz, Sergey P. Tumakha, Gregg Jessen, Leonard J. Brillson
Authors: Jody Fronheiser, Kevin Matocha, Vinayak Tilak, Leonard C. Feldman
Abstract: The SiO2/SiC interface is characterized for carbon accumulation using the carbon isotope 13C as a marker layer combined with secondary ion mass spectroscopy (SIMS). SiC was epitaxially grown using an isotopically enriched propane source and subsequently oxidized to a thickness required to consume the entire 13C layer. Mass specific depth profiles through the oxide film yield residual carbon concentrations at or below 3x1011 cm-2. The depth resolution of SIMS and natural abundance of 13C in the bulk SiC film limit sensitivity but allow us to set a limit of 2.5x1014 cm-2 carbon build up at or near the interface.
Authors: Takahiro Yamasaki, Nobuo Tajima, Tomoaki Kaneko, Nobutaka Nishikawa, Jun Nara, Tatsuo Schimizu, Koichi Kato, Takahisa Ohno
Abstract: The 4H-SiC(000-1)C and (0001)Si surface reconstructed structures and the oxidation processes of these surfaces are investigated using a first-principles calculation method. The most stable reconstructed 4H-SiC(000-1)C and (0001)Si surfaces have p-bonded chains. In the topmost SiC bilayer, half of Si and C atoms exchange their positions and C-C or Si-Si bonds formed densely below the surfaces. When we place a SiO2 layer on the p-bonded chain (000-1)C surface, C-C bonds are formed more densely below the interface. We simulate a sequence of O2 molecules arrivals at an interface of tridymite-phase-SiO2 and 4H-SiC(000-1)C. Dissociated O atoms at the interface tended to make bonds with Si atoms. The C-C bonds in the SiC substrate break easily and a local C surface occasionally appears. We have examined how the surface structure changes through an O2 molecule exposure by using a classical molecular dynamics simulation program and confirmed the formation of C-C bonds below the surface and the interface.
Authors: Jadesada Rujisomnapa, Surasak Surinphong, Pornwasa Wongpanya
Abstract: The objective of this research is to study wear behaviors of TiN, nanolaminated AlCrN and nanocomposite TiAlSiN coated on cemented carbide end mill deposited by cathodic arc physical vapor deposition methods in comparison with uncoated end mill. Wear behaviors were investigated by nanoindentation hardness test, scratch test and cutting test. Oxidation test was also done in air at temperatures of 700°- 900°C in order to evaluate resistance of oxidation. In the nanoindentation hardness and scratch tests, nanocomposite TiAlSiN coating exhibited higher hardness than TiN and nanolaminated AlCrN coatings. The nanolaminated AlCrN coating represented the highest adhesion ability in terms of critical load and the lowest coefficient of friction in comparison with the TiAlSiN and TiN coatings, respectively. The cutting performance, represented in terms of maximum flank wear as a function of cutting length, was found to be highest in the AlCrN coating. Oxides of these coatings, i.e., TiO2 for TiN, TiO2 for TiAlSiN and Cr2O3 for AlCrN, generated at different temperatures of 700°, 800° and 900°C, respectively. From all of results, it is obvious that the AlCrN coating exhibited more excellent wear resistance and oxidation resistance than the uncoated end mill, TiN coating and TiAlSiN coating.
Authors: Shun Myung Shin, Jei Pil Wang
Abstract: Stainless steel materials (FeCr and FeCrNi-based alloys) are employed in a wide range of modern applications due to their ability to withstand corrosive environments while maintaining good mechanical properties. Their corrosion resistance originates from Cr-rich oxide layer which serves as a barrier against ion diffusion between the alloy and the ambient phase. Custom steel grades can be designed for specific applications by optimizing their properties throughout alloy composition [1].
Authors: R.M. Persoons, P. Diels, M. Mertens
Authors: Hai Chen, Tao Yang, Guo Chao Li, Ke Cheng Hu
Abstract: In order to improve the steady permeate fluxes during the emulsified oil wastewater treatment using precoated dynamic membrane, a coupling process of precoating dynamic membrane with ultraviolet photocatalysis was studied. Impacts of the ultraviolet light power, pH values and the oil concentrations on improvement of the steady permeate fluxes were investigated. The results showed that the ultraviolet photocatalysis effectively improved the steady permeate fluxes and reduced the membrane fouling resistances during the emulsified oil wastewater treatment. The dynamic membrane steady membrane fluxes increased with the rise of ultraviolet light power and decrease in liquid pH values and oil concentrations. Impact of the ultraviolet photocatalysis on the oil retention ratio of precoating dynamic membrane was not obvious.
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