Papers by Keyword: Water Vapor

Abstract: Nickel based alloys are well considered materials for uses in high temperature applications. Inconel 690 is the one of outstanding candidate with the superior properties. The aim of this report is to present the influence of water vapor on thermal oxide film. Inconel 690 was oxidized under dry and wet atmosphere at 900°C for 30 hours. The oxidized samples were characterized by SEM/EDS, Raman spectroscopy, and photoelectrochemical technique. The results illustrated that typical thermal oxides grown on alloy composed of Cr, Fe, Ni, in forms of Cr₂O₃, NiFe₂O₄, NiCr₂O₄, Fe₂O₃, Fe_2–xCr_xO₃ and/or solid solution of NiFe₂O₄−NiCr₂O₄. The presence of water vapor affected on oxide morphology, its stoichiometry, and also semiconducting behavior. Oxide film grown under water vapor atmosphere show the homogeneity. Water vapor promoted the predominated oxide of Cr₂O₃ with n−type semiconducting. Moreover the characterization revealed the effect of surface orientation on oxidation mechanism in case of sample which oxidized in oxygen atmosphere.

Abstract: The various chemical compositions of stainless steels can result in complication of the formation of oxide scales in hot rolling process. The time for formation of tertiary oxide scale during finishing rolling is short. In the present study, the oxidation tests with short time period were carried out on eight stainless steel grades by Gleeble 3500 thermal mechanical simulator in a simulated water mist environment. Multi-layers of oxide scale have been developed on all the steel grades during short time oxidation. Internal and intergranular oxides were formed in the steel matrix underneath the inner spinel oxide layer. The cross section of the oxide scales were examined and measured by SEM to understand the oxide scale cross section morphology and thickness.

Abstract: The precious demand not in the push away and broad off from receive forward developed technology approaches place the hand almost several lacks of warns and in-needed developed technique and techniques for greater than before contract and analysis for several issues, no complimentary and talk to studies within the literature describe the system comes in multi component and dual phase particularly for those that ought to be investigated at offshore conditions, the novel technique and setup has been created for such scope, the recently developed set up has the flexibility to analyses the sorption isotherms and kinetic for multi component and dual phase mixtures (gas and vapor) at offshore conditions in term of temperature up to 150 ^oC and pressure up to 150 bar. Additionally to the pretreatment that would be finished to the sorbents used at temperatures up to 400 ^oC and vacuumed pressure. The primer experiments are done using 13 X zeolites for the sorption of pure CO₂ and binary mixtures (CO₂ and CH₄) at elevated conditions.

Abstract: The precious demand not in the push away and broad off from receive forward developed technology approaches place the hand almost several lacks of warns and in-needed developed technique and techniques for greater than before contract and analysis for several issues, no complimentary and talk to studies within the literature describe the system comes in multi component and dual phase particularly for those that ought to be investigated at offshore conditions, the novel technique and setup has been created for such scope, the recently developed discovered has the flexibility to analyses the sorption isotherms and kinetic for multi component and dual phase mixtures (gas and vapor) at offshore conditions in term of temperature up to 150 ^oC and pressure up to 150 bar. Additionally to the pretreatment that would be finished to the sorbents used at temperatures up to 400 ^oC and vacuumed pressure. The primer experiments are done using 13 X zeolites for the sorption of pure CO₂ at numerous conditions and binary mixtures (CO₂ and CH₄) with the existence of water vapor.

Abstract: The effect of water vapor on NO reduction by iron was experimentally investigated at 300-1100 °C in an electrically heated ceramic tubular flow reactor in N₂ atmosphere. The component changes of iron samples after reaction were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results showed that water vapor reacted as oxidizer and the metallic iron was oxidized by both NO and water vapor. Compared to the result without water, NO reduction efficiency decreased when water vapor was added. NO reduction efficiency reached 88.1%, 91.6%, 94.8% above 900 °C in the presence of 2.5%, 5%, 7% water vapor. NO reduction efficiency decreased as the water vapor increased at lower temperature, e.g., 700°C, while decreased slightly first then increased again at higher temperature, e.g., above 800°C. As water vapor increased, the iron was oxidized to Fe₃O₄/Fe₂O₃ and the surface of iron became more porous, which benefited the diffusion of NO and/or vapor into the inner of the iron to continue the reaction and resulted in the increased NO reduction. The mechanism was preliminarily analyzed.

Abstract: The oxidation behavior of T91 steel in Ar-10%H₂O atmosphere at 750°C was investigated. The morphology, microstructures and composition of oxide scales were examined by SEM/EDS and XRD. The results showed that the oxidation kinetics followed logarithmic law in the initial stage and parabolic law in the latter stage. At the early stage Cr-rich oxide film formed on the sample surface, which led to slow mass gain stage. In the latter oxidation stage, Fe ions diffused outward, resulting in fast oxidation stage. The oxidation scales consisted of two layers, an porous Fe₂O₃ outer layer and an denser Cr-rich inner layer. Some cracks were formed between the inner and outer layers. The oxidation mechanism of T91 in water-vapor atmosphere at high temperature was discussed in brief.

Abstract: High quality cuprous oxide thin films with large grain size were grown by thermal oxidation of copper foil in water vapor with N₂ gas. It was found that in water vapor (111) oriented Cu₂O is preferentially formed, whereas mixtures of random oriented CuO and Cu₂O are formed when oxidized in air. The effects of the film oxidation method and heating temperature are investigated. In addition, the optical band gaps of cuprous oxide thin films have been determined by measuring the transmittance and reflectance spectra.

Abstract: To explore the influence of the water vapor cooling conditions on grinding temperature field of titanium alloy TC4 material, ANSYS simulation and test methods are adopted in this paper. Simulation and experimental studies show that: water vapor as coolant can reduce the surface temperature of the workpiece quickly by changing the wheel speed, workpiece speed and cutting depth; Water vapor cooling can control the grinding zone temperature below 400 °C on certain conditions, and compared with dry grinding it can reduce more than 50%; The grinding zone temperature can significantly be reduced by optimizing the grinding process parameters and improving the quality of the machined surface.

Abstract: High temperature oxidation of ferritic stainless steel 21Cr-0.6Mo-Nb-Ti was carried out isothermally at 1100 oC under different water vapour content conditions in an electrical furnace. Water vapour does accelerate the formation of oxide scale of stainless steel 21Cr-0.6Mo-Nb-Ti, however, it is not significant. Some oxide grains consist of spinel crystal structure, which should be spinel Manganese Chromite. In dry air atmosphere, the grain of the spinel is more and bigger than that in wet air. No breakaway oxidation occurs in the experiment indicating that 21Cr-0.6Mo-Nb-Ti has very high oxidation resistance, which might be contributed by the formation of MnCr₂O₄ and compact protective chromia. In addition, continuous silica formed along and accumulated at the oxide metal interface performs like a diffusion barrier.

Abstract: NiPtAl coatings are widely used as bondcoats for thermal barrier coating (TBC) systems during high temperature exposure. Pt modified aluminide coatings on the CMSX-4 Ni-base alloy were oxidized at 1150°C in different atmospheres. Cross-section oxide layer morphologies on the NiPtAl coatings after TBC failure were similar in air with that in air+15%H₂O. The surface morphologies of as-received low and high-Pt bondcoats showed great effect on the oxide layer growth and morphologies due to the different compositions within the two bondcoats. The irregular alumina surface on the low-Pt bondcoat was showed due to the slipping of the NiPtAl grains. Raman spectroscopy illustrated that the alumina mainly consisted θ and α-Al₂O₃ during the Ar+20%O₂ exposure, however, only α-Al₂O₃ could be found in Ar+4%H₂+2%H₂O during short time exposure. Low oxygen partial pressure of Ar+4%H₂+2%H₂O perhaps is the reason that spinel and θ-Al₂O₃ can not formed, and directly promotes the α-Al₂O₃ formation.