The cyclic oxidation behavior of Hf/Y-doped B2 FeAl intermetallics at 1373 K was investigated.For an undoped FeAl alloy,premature spallation of the alumina film occurs due to the formation of numerous voids at the fil...The cyclic oxidation behavior of Hf/Y-doped B2 FeAl intermetallics at 1373 K was investigated.For an undoped FeAl alloy,premature spallation of the alumina film occurs due to the formation of numerous voids at the film/alloy interface and apparent shrinkage in the film.In contrast to this,doping with either Hf or Y significantly improves the interfacial adhesion between the alumina film and the alloy substrate,particularly with Hf-doping.Microstructural observation in combination with Anger electron spectroscopic analysis suggests that in addition to prohibiting interfacial void formation and alleviating film shrinkage,the addition of Hf in the FeAl alloy could consolidate the film/alloy interface by directly participating in chemical bonding across the interface as a Hf ion.This causes the spallation of alumina film from the equiaxed grains/columnar grains interface rather than the bottom of the film.展开更多
Methods of coating Al_(2)O_(3) on nickel micro-foam were compared and screened,aiming to overcome the capillary force and prepare the micro-foam monolithic catalyst coatings.The surface of micro-foam substrate was pre...Methods of coating Al_(2)O_(3) on nickel micro-foam were compared and screened,aiming to overcome the capillary force and prepare the micro-foam monolithic catalyst coatings.The surface of micro-foam substrate was pretreated by a chemical etching method to improve the adhesion of the coatings on the substrate.The results showed that the slurry circulation at 162 ml·min^(-1) was evaluated as the optimal method.The pore size on the substrate surface can be controlled by changing the pretreatment conditions.An empirical correlation was also proposed,showing an excellent practicality for predicting the pore size.The adhesion of the coatings with substrate pretreatment was significantly better than that without substrate pretreatment.The minimum value of mass loss after ultrasonic vibration was 3.9%.This mainly attributes to the squeezing of Al_(2)O_(3) particles in the pores of substrate surface.The coatings on nickel micro-foam are hopefully used in micropacked beds for catalytic reactions.展开更多
FeCrAI （Ce） stainless steel was functionalized by a conversion treatment in order to allow alumina by diffusion coatings with strong interfacial bonding. The very porous conversion coating produced in a pack alumini...FeCrAI （Ce） stainless steel was functionalized by a conversion treatment in order to allow alumina by diffusion coatings with strong interfacial bonding. The very porous conversion coating produced in a pack aluminization technique had excellent adhesion and was conductive enough to permit conditions favorable for the precipitation of alumina oxyhydroxide during aluminum diffusion coatings. In this work, the bed was prepared as a mixture of A1, NH4C1 and A1203. In the high-activity bed were heat-treated at 1,173 K in an atmosphere made up of team with subsequent air-cooling. The effect of the bed content on the coating was examined. With the high-activity, the desired Fe2Al5 was formed as the outermost coating layer. The coating presented chemical composition gradients suitable for strong adhesion. The improvement of the thermal oxidation behaviour was studied at 1,373 K. Two different aqueous environments, which are （1） NaC1 and （2） H2SO4, are employed for using the technique of potentiodynamic polarization curve. The obtained experimental electrochemical parameters （Ecorr, Jcorr etc,） were used to compare the corrosion resistance of the tested steel state complemented by MEB （electronic scanning microscopy） in combination with dispersive analysis X in energy （EDS） or X ray diffraction indicated that the elements concentration maximum was located in the vicinity of the interface especially in the FeCrAI （Ce） coated by spherical A1203 powder. These results an discussed in terms of an addition effect on the development of the microstructure of oxide films.展开更多
基金financially supported by the Basic Research Program of State Grid(No.GCB17201600179)
文摘The cyclic oxidation behavior of Hf/Y-doped B2 FeAl intermetallics at 1373 K was investigated.For an undoped FeAl alloy,premature spallation of the alumina film occurs due to the formation of numerous voids at the film/alloy interface and apparent shrinkage in the film.In contrast to this,doping with either Hf or Y significantly improves the interfacial adhesion between the alumina film and the alloy substrate,particularly with Hf-doping.Microstructural observation in combination with Anger electron spectroscopic analysis suggests that in addition to prohibiting interfacial void formation and alleviating film shrinkage,the addition of Hf in the FeAl alloy could consolidate the film/alloy interface by directly participating in chemical bonding across the interface as a Hf ion.This causes the spallation of alumina film from the equiaxed grains/columnar grains interface rather than the bottom of the film.
基金National Key Research and Development Program of China(2019YFA0905100)National Natural Science Foundation of China(21978146,21991103,22008138)on this work.
文摘Methods of coating Al_(2)O_(3) on nickel micro-foam were compared and screened,aiming to overcome the capillary force and prepare the micro-foam monolithic catalyst coatings.The surface of micro-foam substrate was pretreated by a chemical etching method to improve the adhesion of the coatings on the substrate.The results showed that the slurry circulation at 162 ml·min^(-1) was evaluated as the optimal method.The pore size on the substrate surface can be controlled by changing the pretreatment conditions.An empirical correlation was also proposed,showing an excellent practicality for predicting the pore size.The adhesion of the coatings with substrate pretreatment was significantly better than that without substrate pretreatment.The minimum value of mass loss after ultrasonic vibration was 3.9%.This mainly attributes to the squeezing of Al_(2)O_(3) particles in the pores of substrate surface.The coatings on nickel micro-foam are hopefully used in micropacked beds for catalytic reactions.
文摘FeCrAI （Ce） stainless steel was functionalized by a conversion treatment in order to allow alumina by diffusion coatings with strong interfacial bonding. The very porous conversion coating produced in a pack aluminization technique had excellent adhesion and was conductive enough to permit conditions favorable for the precipitation of alumina oxyhydroxide during aluminum diffusion coatings. In this work, the bed was prepared as a mixture of A1, NH4C1 and A1203. In the high-activity bed were heat-treated at 1,173 K in an atmosphere made up of team with subsequent air-cooling. The effect of the bed content on the coating was examined. With the high-activity, the desired Fe2Al5 was formed as the outermost coating layer. The coating presented chemical composition gradients suitable for strong adhesion. The improvement of the thermal oxidation behaviour was studied at 1,373 K. Two different aqueous environments, which are （1） NaC1 and （2） H2SO4, are employed for using the technique of potentiodynamic polarization curve. The obtained experimental electrochemical parameters （Ecorr, Jcorr etc,） were used to compare the corrosion resistance of the tested steel state complemented by MEB （electronic scanning microscopy） in combination with dispersive analysis X in energy （EDS） or X ray diffraction indicated that the elements concentration maximum was located in the vicinity of the interface especially in the FeCrAI （Ce） coated by spherical A1203 powder. These results an discussed in terms of an addition effect on the development of the microstructure of oxide films.
