In order to ameliorate the electrochemical hydrogen storage performance of La-Mg-Ni system A2B7-type electrode alloys, a small amount of Si was added. The La0.8Mg0.2Ni3.3Co0.2Six （x=0-0.2） electrode alloys were prep...In order to ameliorate the electrochemical hydrogen storage performance of La-Mg-Ni system A2B7-type electrode alloys, a small amount of Si was added. The La0.8Mg0.2Ni3.3Co0.2Six （x=0-0.2） electrode alloys were prepared by casting and annealing. The effects of adding Si on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated systematically. The results indicate that the as-cast and annealed alloys hold multiple structures, involving two major phases of （La, Mg）2Ni7 with a Ce2Ni7-type hexagonal structure and LaNi5 with a CaCu5-type hexagonal structure as well as one residual phase LaNi3. The addition of Si results in a decrease in （La, Mg）2Ni7 phase and an increase in LaNi5 phase without changing the phase structure of the alloys. What is more, it brings on an obvious effect on electrochemical hydrogen storage characteristics of the alloys. The discharge capacities of the as-cast and annealed alloys decline with the increase of Si content, but their cycle stabilities clearly grow under the same condition. Furthermore, the measurements of the high rate discharge ability, the limiting current density, hydrogen diffusion coefficient as well as electrochemical impedance spectra all indicate that the electrochemical kinetic properties of the electrode alloys first increase and then decrease with the rising of Si content.展开更多
Effects of alloy elements on the microstructure and crack resistance of Fe-C-Cr weld surfacing layer were investigated. The results show that microstructures of the layer mainly consist of carbides and austenite matri...Effects of alloy elements on the microstructure and crack resistance of Fe-C-Cr weld surfacing layer were investigated. The results show that microstructures of the layer mainly consist of carbides and austenite matrix. Increasing C and Cr contents impair the crack resistance of the layer due to increased amount of brittle carbides. The addition of Ni, Nb or Mo improves the crack resistance of Fe-C-Cr weld surfacing layer by increasing the amount of austenite and forming fine NbC or M 7C 3 carbides in the layer. But, the excessive Nb (>2.50wt%) or Mo (>1.88wt%) impairs the crack resistance of the layer, which has relation with increased carbides or carbide coarsening and austenite matrix solid solution strengthening. The proper combination of C, Cr, Ni, Nb and Mo can further improve not only the crack resistance of Fe-C-Cr weld surfacing layer but also the erosion resistance as a result of fine NbC and M 7C 3 carbides distributing uniformly in austenite matrix. The optimal layer compositions are 3.05wt%C, 20.58wt%Cr, 1.75wt%Ni, 2.00wt%Nb and 1.88wt%Mo.展开更多
Effects of alloying elements on microstructure and erosion resistance of Fe-C-Cr weld surfacing layer have been studied. The experimental results show that increasing C and Cr content favors improving the erosion resi...Effects of alloying elements on microstructure and erosion resistance of Fe-C-Cr weld surfacing layer have been studied. The experimental results show that increasing C and Cr content favors improving the erosion resistance of the layer, and the excessive C and Cr result in decreasing the erosion resistance at 90 deg. erosion. That Mo, Nb or Ti improves the erosion resistance of Fe-C-Cr weld surfacing layer is mainly attributed to increasing the amount of M7C3 and forming fine NbC or TiC in austenite matrix, but the excessive Mo, Nb or Ti is unfavorable. The addition of Mo, Nb and Ti in proper combination possesses stronger effect on improving the erosion resistance and the erosion resistance (εA) of Fe-C-Cr weld surfacing layer with fine NbC, TiC and M7C3 distributing uniformly in austenite matrix obviously increases to 2.81 at 15 deg. erosion and 2.88 at 90 deg. erosion when the layer composition is 3.05C, 20.58Cr, 1.88Mo, 2.00Nb and 1.05Ti (in wt pct).展开更多
A gradient coating of Fe-based alloy was manufactured with rare earths (RE) by plasma surfacing on Q235 steel substrate. The coatings were studied by using X-ray diffraction(XRD), scanning electron microscope(SEM), di...A gradient coating of Fe-based alloy was manufactured with rare earths (RE) by plasma surfacing on Q235 steel substrate. The coatings were studied by using X-ray diffraction(XRD), scanning electron microscope(SEM), differential thermal analyzer(DTA), and electron probe micro-analyzer (EPMA). The results show that the phases of the two kinds of coatings(with and without RE) both include α-Fe, Fe7C3, Fe3C, Cr2B, Fe2B and FeB. The microstructure of F314 coating is mainly hypereutectic, the pro-phases Cr7C3 and Cr2B are loose, crassi, spiculate and contain microcracks. The brittleness of the coating is high, and the average hardness is 787 HV. When 0.8wt% RE was added into the F314 alloy, the microstructure varied from hypoeutectic to hypereutectic continuously, The hardness appears as gradient distribution with the highest value of 773 HV, meanwhile, the brittleness decreases significantly. The formation of gradient structure depends on the fallowing factors: (i) the conversion of RE. The addition of RE lowers the elements point and Fe-C eutectic temperature, thus the base metal melting acutely. (ii) the heating of plasma arc. Graded temperature results in directional solidification, thus the gradient structure forms easily. The main reasons for the hardness decrease with RE addition in the alloy are the ratio of hard phase lowering and the hardness of the hard phase decreasing.展开更多
The Authors of this Article have done research on the cracking resistance of cold welding surfacing electrodes for blast furnace valves by adjusting the basicity of slag component, decreasing the hydrogen content and ...The Authors of this Article have done research on the cracking resistance of cold welding surfacing electrodes for blast furnace valves by adjusting the basicity of slag component, decreasing the hydrogen content and improving microstructure. The DF 2 Cold Welding Surfacing Electrodes prove to possess the following characters: 1) Excellent cracking resistance for surfacing alloys at normal temperature. 2) Excellent cracking resistance for repair welding and rewelding. 3) Excellent machinability for surfacing alloying.展开更多
The coating of D127, a surfacing electrode, was added ceria （ CeO2 ） and yttrium （Y） for possible enhanced electrode properties. The method of orthogonal test was adopted. The coating with different amount of CeO2...The coating of D127, a surfacing electrode, was added ceria （ CeO2 ） and yttrium （Y） for possible enhanced electrode properties. The method of orthogonal test was adopted. The coating with different amount of CeO2 and Y was pressed. The hardness of surfacing layer was carried on by hardness tester, microstracture was investigated by metallograph, and the content of rare earths was analyzed by X-ray energy dispersive spectrometer. The results show that the of deposited metal can be effectively made fine,accordingly, the hardness and the wear-resistanee of deposited metal are also raised. But the addition amount of the rare-earth should be proper. The deposited metal microstructure is the finest and the most homogeneous when the addition amount of CeO2 is 2 wt.% and Y 1.2 wt.% , and the hardness of the surfacing layer is the highest.展开更多
Hydrogen diffusion coefficients in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 alloy electrode as a function of state of charge (SOC) or temperature were determined by chronoamperometry. It is found that hydrogen diffusion coeffi...Hydrogen diffusion coefficients in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 alloy electrode as a function of state of charge (SOC) or temperature were determined by chronoamperometry. It is found that hydrogen diffusion coefficient decreases with the increase of SOC or the decrease of temperature. The activation energy for hydrogen diffusion in the alloy electrode with 50%SOC is evaluated to be 19.9?kJ/mol.展开更多
The effect of the hot-charging treatment on the performance of AB(2) and AB(5) hydrogen storage alloy electrodes was investigated. The result showed that the treatment can markedly improve the voltage plateau ratio (V...The effect of the hot-charging treatment on the performance of AB(2) and AB(5) hydrogen storage alloy electrodes was investigated. The result showed that the treatment can markedly improve the voltage plateau ratio (VPR), the high rate discharge ability (HRDA), the diffusion coefficient of hydrogen DH and the discharge capacity of the AB2 hydrogen storage alloy electrode. The SEM analysis showed that the hot-charging treatment brings about a Ni-rich surface due to the dissolution of Zr oxides. It is also very helpful for the improvement of the kinetic properties of AB2 hydrogen storage alloy electrode because the microcracking of the surface results in fresh surface. This can be the basic modification treatment for NiMH battery used in electric vehicles (EVs) in the future. But for AB(5) type alloys, the treatment has the disadvantage of impairing the comprehensive electrochemical properties, because the surface of the alloy may be corroded during the treatment. The mechanism of the surface modification of the electrode is also proposed.展开更多
Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stre...Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.展开更多
The influences of Ca substitution for Ml and surface treatment on electrochemical performances of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 hydrogen storage alloy electrode were investigated. Ca substitution with x <0.2 ...The influences of Ca substitution for Ml and surface treatment on electrochemical performances of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 hydrogen storage alloy electrode were investigated. Ca substitution with x <0.2 for Ml could improve its discharge capacity, but Ca substitution with x >0.2 could decrease the capacity. It was also found that Ca substitution deteriorates the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode. In order to improve these properties of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 alloy electrode, the alloy was treated in 6 mol/L KOH+0.02 mol/L KBH 4 solution. The results showed that the surface treatment improves the electrochemical performances such as the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode. :The influences of Ca substitution for Ml and surface treatment on electrochemical performances of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 hydrogen storage alloy electrode were investigated. Ca substitution with x <0.2 for Ml could improve its discharge capacity, but Ca substitution with x >0.2 could decrease the capacity. It was also found that Ca substitution deteriorates the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode. In order to improve these properties of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 alloy electrode, the alloy was treated in 6 mol/L KOH+0.02 mol/L KBH 4 solution. The results showed that the surface treatment improves the electrochemical performances such as the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode.展开更多
We report a feasible method to realize tun able surface plasm on-polarit on(SPP)res onance in orga nic light-emitt ing devices(OLEDs)by emplo ying corrugated Ag-Al alloy electrodes.The excited SPP res onance in duced ...We report a feasible method to realize tun able surface plasm on-polarit on(SPP)res onance in orga nic light-emitt ing devices(OLEDs)by emplo ying corrugated Ag-Al alloy electrodes.The excited SPP res onance in duced by the periodic corrugations can be precisely tuned based on the composition ratios of the Ag-Al alloy electrodes.With an appropriate composition ratio of the corrugated alloy electrode,the photons trapped in SPP modes are recovered and extracted effectively.The 25%in creaseme nt in luminance and 21%enhan ceme nt in curre nt efficie ncy have bee n achieved by using the corrugated Ag-Al alloy electrodes in OLEDs.展开更多
The crystallographic structure, microstructure, composition homogeneity and electrode charge-discharge cycling stability were investigated of the as-cast and annealed La-rich mischmetal (designating Ml)-based hydrogen...The crystallographic structure, microstructure, composition homogeneity and electrode charge-discharge cycling stability were investigated of the as-cast and annealed La-rich mischmetal (designating Ml)-based hydrogen storage alloy with a composition of MlNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3). X-ray diffraction analysis shows that the MlNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3) alloy is composed of the dominant phase with a CaCu_5-type hexagonal structure and small amounts of the second phase with a La_2Ni_7-type structure. The annealing heat treatment conducted at 1273 K for 10 h results in decrease of the crystal lattice strain and composition segregation, disappearance of the dendrite structure and growth of the crystal grain of the MlNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3) alloy. The annealing causes the cycle life to be increased by about 30% over the as-cast alloy electrode. The cycling stability of the alloy electrode is improved significantly upon annealing. The cause of the improvement in the cycling stability was discussed based on the alloy composition distribution and microstructure changes due to annealing.展开更多
A new pretreatment method has been developed to improve the catalytic activity of the Ni-Fe-Mo-Co alloy electrode for hydrogen evolution reaction （HER）. The procedure involves pre-electrolyzing the Ni-Fe-Mo-Co alloy...A new pretreatment method has been developed to improve the catalytic activity of the Ni-Fe-Mo-Co alloy electrode for hydrogen evolution reaction （HER）. The procedure involves pre-electrolyzing the Ni-Fe-Mo-Co alloy electrode in 30% KOH solution containing 10% potassium sodium tartrate at 70℃ for 2 h, until some of the Mo and Fe elements are leached out. The surface morphology of the Ni-Fe-Mo-Co alloy demonstrates a unique hive-like structure after the pre- treatment, which has the pore size in a nanometer range （about 50 nm）, a very large real surface area, and good stability. The results of the electrochemical studies show that compared to other similar electrode materials and the treated Ni-Fe-Mo-Co electrode by leaching method, the pre-treated Ni-Fe-Mo-Co electrode has a much lower overpotential and much higher exchange current density for HER. In addition, a long-term continuous electrolysis test with a current interruption shows that the Ni-Fe-Mo-Co alloy has excellent catalytic stability.展开更多
To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide(rGO) via a chemical reduction process. Results indicated that rGO sh...To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide(rGO) via a chemical reduction process. Results indicated that rGO sheets uniformly coated on the alloy surface, yielding a threedimensional network layer. The coated surfaces contained numerous hydrophilic functional groups, leading to better wettability of the alloy in aqueous alkaline media. This, in turn, increased the concentration of electro-active species at the interface between the electrode and the electrolyte, improving the electrochemical kinetics and the rate discharge of the electrodes. The high rate dischargeability at 1500 mA·g^(–1) increased from 53.2% to 83.9% after modification. In addition, the modification layer remained stable and introduced a dense metal oxide layer to the alloy surface after a long cycling process. Therefore, the protective layer prevented the discharge capacity from quickly decreasing and improved cycling stability.展开更多
Sputtering method was used to prepare Ni-Mo alloy electrodes for hydrogen production in alkaline solution. The influences of the working pressure during deposition and the substrate temperature on the electrochemical ...Sputtering method was used to prepare Ni-Mo alloy electrodes for hydrogen production in alkaline solution. The influences of the working pressure during deposition and the substrate temperature on the electrochemical behavior of electrode were characterized by steady-state polarization plot and Tafel polarization curve measurements. And the physical properties of electrodes were characterized by XRD, SEM, AFM and EDS. It is found that the overpotential is significantly influenced by the working pressure which affects critically the electrode surface morphology, and two Tafel regions are observed for each sample. The overpotential value does not change very much with the substrate temperature. The XRD results indicates that the electrodes should be considered nanocrystalline. Thornton model for the microstructure of sputter-deposited electrodes is referred to explain the observed microstructure change.展开更多
Ni-Fe-Mo-Co alloy electrode was prepared in a citrate solution by electrodeposition, and then Mo and Fe were partially leached out from the electrode in 30% KOH solution. The unique surface micromorphology of a hive-l...Ni-Fe-Mo-Co alloy electrode was prepared in a citrate solution by electrodeposition, and then Mo and Fe were partially leached out from the electrode in 30% KOH solution. The unique surface micromorphology of a hive-like structure was obtained with an average pore size of about 50 nm. The electrode has a very large real surface area and a stable structure. The effects of sodium molybdate concentration on the composition, surface morphology, and structure of electrodes were analyzed by EDS, SEM and XRD. The polarization curves of the different electrodes show that the catalytic activity of electrodes is strongly correlated with the mole fraction of alloy elements (Ni, Fe, Mo, Co), and the addition of cobalt element to Ni-Fe-Mo alloy improves the catalytic activity. The Ni35.63Fe24.67Mo23.52Co16.18 electrode has the best activity for hydrogen evolution reaction(HER), with an over-potential of 66.2 mV, in 30% KOH at 80 ℃ and 200 mA/cm2. The alloy maintains its good catalytic activity for HER during continuous or intermittent electrolysis. Its electrochemical activity and catalytic stability are much higher than the other iron-group with Mo alloy electrodes.展开更多
Good castability and high strength properties of Ale Si alloys are useful in defence applications like torpedoes,manufacture of Missile bodies,and parts of automobile such as engine cylinders and pistons.Poor wear res...Good castability and high strength properties of Ale Si alloys are useful in defence applications like torpedoes,manufacture of Missile bodies,and parts of automobile such as engine cylinders and pistons.Poor wear resistance of the alloys is major limitation for their use.Friction stir processing(FSP) is a recognized surfacing technique as it overcomes the problems of fusion route surface modification methods.Keeping in view of the requirement of improving wear resistance of cast aluminiumesilicon alloy,friction stir processing was attempted for surface modification with boron carbide(B4C) and molybdenum disulfide(Mo S2) powders.Metallography,micro compositional analysis,hardness and pin-on-disc wear testing were used for characterizing the surface composite coating.Microscopic study revealed breaking of coarse silicon needles and uniformly distributed carbides in the A356 alloy matrix after FSP.Improvement and uniformity in hardness was obtained in surface composite layer.Higher wear resistance was achieved in friction stir processed coating with carbide powders.Addition of solid lubricant Mo S2 powder was found to improve wear resistance of the base metal significantly.展开更多
The electrochemical process of Ti-Ni alloy electrode was studied by using cyclic voltammetry. The hydrogen-absorbing electrode could be approximately regarded as a reversible hydrogen elecrede. The con- trolling steps...The electrochemical process of Ti-Ni alloy electrode was studied by using cyclic voltammetry. The hydrogen-absorbing electrode could be approximately regarded as a reversible hydrogen elecrede. The con- trolling steps of the discharging process varying with the anodic overpotentials were investigated and the effect ofelecrode constituent modification or Zr adulteation on the electrochemical behavior was also studied.展开更多
The influence of the addition of Cu(OH)2 to 6 mol/L KOH alkaline electrolyte on the electrochemical properties of La2Mg0.9Al0.1Ni7.5Co1.5 hydrogen storage alloy electrode was investigated by electron probe X-ray micro...The influence of the addition of Cu(OH)2 to 6 mol/L KOH alkaline electrolyte on the electrochemical properties of La2Mg0.9Al0.1Ni7.5Co1.5 hydrogen storage alloy electrode was investigated by electron probe X-ray microanalysis(EPMA),X-ray diffraction(XRD) and electrochemical measurements. EPMA micrographs and XRD patterns show that the surface of the hydride electrode is plated by metal copper film. The thickness and compactness of Cu film increase with the increment of charge-discharge cycle number. The copper film of the hydride electrode surface can keep the hydrogen storage alloy particle in the electrode interior from oxidizing availably. The addition of Cu(OH)2 to alkaline electrolyte lowers the activation property and the high rate dischargeability of the La2Mg0.9Al0.1Ni7.5Co1.5 hydride electrode,but has no negative effect on the maximum discharge capacity of the hydride electrode. Moreover,it is effective to improve the cyclic stability of the hydride electrode utilizing electrodeposit Cu film on the La2Mg0.9Al0.1Ni7.5Co1.5 hydride electrodes surface.展开更多
基金Projects(50961009,51161015)supported by the National Natural Science Foundation of ChinaProject(2011AA03A408)supported by the High-tech Research and Development Program of ChinaProjects(2011ZD10,2010ZD05)supported by the Natural Science Foundation of Inner Mongolia,China
文摘In order to ameliorate the electrochemical hydrogen storage performance of La-Mg-Ni system A2B7-type electrode alloys, a small amount of Si was added. The La0.8Mg0.2Ni3.3Co0.2Six （x=0-0.2） electrode alloys were prepared by casting and annealing. The effects of adding Si on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated systematically. The results indicate that the as-cast and annealed alloys hold multiple structures, involving two major phases of （La, Mg）2Ni7 with a Ce2Ni7-type hexagonal structure and LaNi5 with a CaCu5-type hexagonal structure as well as one residual phase LaNi3. The addition of Si results in a decrease in （La, Mg）2Ni7 phase and an increase in LaNi5 phase without changing the phase structure of the alloys. What is more, it brings on an obvious effect on electrochemical hydrogen storage characteristics of the alloys. The discharge capacities of the as-cast and annealed alloys decline with the increase of Si content, but their cycle stabilities clearly grow under the same condition. Furthermore, the measurements of the high rate discharge ability, the limiting current density, hydrogen diffusion coefficient as well as electrochemical impedance spectra all indicate that the electrochemical kinetic properties of the electrode alloys first increase and then decrease with the rising of Si content.
文摘Effects of alloy elements on the microstructure and crack resistance of Fe-C-Cr weld surfacing layer were investigated. The results show that microstructures of the layer mainly consist of carbides and austenite matrix. Increasing C and Cr contents impair the crack resistance of the layer due to increased amount of brittle carbides. The addition of Ni, Nb or Mo improves the crack resistance of Fe-C-Cr weld surfacing layer by increasing the amount of austenite and forming fine NbC or M 7C 3 carbides in the layer. But, the excessive Nb (>2.50wt%) or Mo (>1.88wt%) impairs the crack resistance of the layer, which has relation with increased carbides or carbide coarsening and austenite matrix solid solution strengthening. The proper combination of C, Cr, Ni, Nb and Mo can further improve not only the crack resistance of Fe-C-Cr weld surfacing layer but also the erosion resistance as a result of fine NbC and M 7C 3 carbides distributing uniformly in austenite matrix. The optimal layer compositions are 3.05wt%C, 20.58wt%Cr, 1.75wt%Ni, 2.00wt%Nb and 1.88wt%Mo.
文摘Effects of alloying elements on microstructure and erosion resistance of Fe-C-Cr weld surfacing layer have been studied. The experimental results show that increasing C and Cr content favors improving the erosion resistance of the layer, and the excessive C and Cr result in decreasing the erosion resistance at 90 deg. erosion. That Mo, Nb or Ti improves the erosion resistance of Fe-C-Cr weld surfacing layer is mainly attributed to increasing the amount of M7C3 and forming fine NbC or TiC in austenite matrix, but the excessive Mo, Nb or Ti is unfavorable. The addition of Mo, Nb and Ti in proper combination possesses stronger effect on improving the erosion resistance and the erosion resistance (εA) of Fe-C-Cr weld surfacing layer with fine NbC, TiC and M7C3 distributing uniformly in austenite matrix obviously increases to 2.81 at 15 deg. erosion and 2.88 at 90 deg. erosion when the layer composition is 3.05C, 20.58Cr, 1.88Mo, 2.00Nb and 1.05Ti (in wt pct).
文摘A gradient coating of Fe-based alloy was manufactured with rare earths (RE) by plasma surfacing on Q235 steel substrate. The coatings were studied by using X-ray diffraction(XRD), scanning electron microscope(SEM), differential thermal analyzer(DTA), and electron probe micro-analyzer (EPMA). The results show that the phases of the two kinds of coatings(with and without RE) both include α-Fe, Fe7C3, Fe3C, Cr2B, Fe2B and FeB. The microstructure of F314 coating is mainly hypereutectic, the pro-phases Cr7C3 and Cr2B are loose, crassi, spiculate and contain microcracks. The brittleness of the coating is high, and the average hardness is 787 HV. When 0.8wt% RE was added into the F314 alloy, the microstructure varied from hypoeutectic to hypereutectic continuously, The hardness appears as gradient distribution with the highest value of 773 HV, meanwhile, the brittleness decreases significantly. The formation of gradient structure depends on the fallowing factors: (i) the conversion of RE. The addition of RE lowers the elements point and Fe-C eutectic temperature, thus the base metal melting acutely. (ii) the heating of plasma arc. Graded temperature results in directional solidification, thus the gradient structure forms easily. The main reasons for the hardness decrease with RE addition in the alloy are the ratio of hard phase lowering and the hardness of the hard phase decreasing.
文摘The Authors of this Article have done research on the cracking resistance of cold welding surfacing electrodes for blast furnace valves by adjusting the basicity of slag component, decreasing the hydrogen content and improving microstructure. The DF 2 Cold Welding Surfacing Electrodes prove to possess the following characters: 1) Excellent cracking resistance for surfacing alloys at normal temperature. 2) Excellent cracking resistance for repair welding and rewelding. 3) Excellent machinability for surfacing alloying.
文摘The coating of D127, a surfacing electrode, was added ceria （ CeO2 ） and yttrium （Y） for possible enhanced electrode properties. The method of orthogonal test was adopted. The coating with different amount of CeO2 and Y was pressed. The hardness of surfacing layer was carried on by hardness tester, microstracture was investigated by metallograph, and the content of rare earths was analyzed by X-ray energy dispersive spectrometer. The results show that the of deposited metal can be effectively made fine,accordingly, the hardness and the wear-resistanee of deposited metal are also raised. But the addition amount of the rare-earth should be proper. The deposited metal microstructure is the finest and the most homogeneous when the addition amount of CeO2 is 2 wt.% and Y 1.2 wt.% , and the hardness of the surfacing layer is the highest.
文摘Hydrogen diffusion coefficients in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 alloy electrode as a function of state of charge (SOC) or temperature were determined by chronoamperometry. It is found that hydrogen diffusion coefficient decreases with the increase of SOC or the decrease of temperature. The activation energy for hydrogen diffusion in the alloy electrode with 50%SOC is evaluated to be 19.9?kJ/mol.
文摘The effect of the hot-charging treatment on the performance of AB(2) and AB(5) hydrogen storage alloy electrodes was investigated. The result showed that the treatment can markedly improve the voltage plateau ratio (VPR), the high rate discharge ability (HRDA), the diffusion coefficient of hydrogen DH and the discharge capacity of the AB2 hydrogen storage alloy electrode. The SEM analysis showed that the hot-charging treatment brings about a Ni-rich surface due to the dissolution of Zr oxides. It is also very helpful for the improvement of the kinetic properties of AB2 hydrogen storage alloy electrode because the microcracking of the surface results in fresh surface. This can be the basic modification treatment for NiMH battery used in electric vehicles (EVs) in the future. But for AB(5) type alloys, the treatment has the disadvantage of impairing the comprehensive electrochemical properties, because the surface of the alloy may be corroded during the treatment. The mechanism of the surface modification of the electrode is also proposed.
文摘Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.
文摘The influences of Ca substitution for Ml and surface treatment on electrochemical performances of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 hydrogen storage alloy electrode were investigated. Ca substitution with x <0.2 for Ml could improve its discharge capacity, but Ca substitution with x >0.2 could decrease the capacity. It was also found that Ca substitution deteriorates the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode. In order to improve these properties of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 alloy electrode, the alloy was treated in 6 mol/L KOH+0.02 mol/L KBH 4 solution. The results showed that the surface treatment improves the electrochemical performances such as the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode. :The influences of Ca substitution for Ml and surface treatment on electrochemical performances of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 hydrogen storage alloy electrode were investigated. Ca substitution with x <0.2 for Ml could improve its discharge capacity, but Ca substitution with x >0.2 could decrease the capacity. It was also found that Ca substitution deteriorates the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode. In order to improve these properties of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 alloy electrode, the alloy was treated in 6 mol/L KOH+0.02 mol/L KBH 4 solution. The results showed that the surface treatment improves the electrochemical performances such as the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode.
基金This work was supported by the National Key Research and Development Program of China and the National Natural Science Foundation of China(NSFC)under Grants No.2020YFA0715000 and No.61825402.
文摘We report a feasible method to realize tun able surface plasm on-polarit on(SPP)res onance in orga nic light-emitt ing devices(OLEDs)by emplo ying corrugated Ag-Al alloy electrodes.The excited SPP res onance in duced by the periodic corrugations can be precisely tuned based on the composition ratios of the Ag-Al alloy electrodes.With an appropriate composition ratio of the corrugated alloy electrode,the photons trapped in SPP modes are recovered and extracted effectively.The 25%in creaseme nt in luminance and 21%enhan ceme nt in curre nt efficie ncy have bee n achieved by using the corrugated Ag-Al alloy electrodes in OLEDs.
文摘The crystallographic structure, microstructure, composition homogeneity and electrode charge-discharge cycling stability were investigated of the as-cast and annealed La-rich mischmetal (designating Ml)-based hydrogen storage alloy with a composition of MlNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3). X-ray diffraction analysis shows that the MlNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3) alloy is composed of the dominant phase with a CaCu_5-type hexagonal structure and small amounts of the second phase with a La_2Ni_7-type structure. The annealing heat treatment conducted at 1273 K for 10 h results in decrease of the crystal lattice strain and composition segregation, disappearance of the dendrite structure and growth of the crystal grain of the MlNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3) alloy. The annealing causes the cycle life to be increased by about 30% over the as-cast alloy electrode. The cycling stability of the alloy electrode is improved significantly upon annealing. The cause of the improvement in the cycling stability was discussed based on the alloy composition distribution and microstructure changes due to annealing.
文摘A new pretreatment method has been developed to improve the catalytic activity of the Ni-Fe-Mo-Co alloy electrode for hydrogen evolution reaction （HER）. The procedure involves pre-electrolyzing the Ni-Fe-Mo-Co alloy electrode in 30% KOH solution containing 10% potassium sodium tartrate at 70℃ for 2 h, until some of the Mo and Fe elements are leached out. The surface morphology of the Ni-Fe-Mo-Co alloy demonstrates a unique hive-like structure after the pre- treatment, which has the pore size in a nanometer range （about 50 nm）, a very large real surface area, and good stability. The results of the electrochemical studies show that compared to other similar electrode materials and the treated Ni-Fe-Mo-Co electrode by leaching method, the pre-treated Ni-Fe-Mo-Co electrode has a much lower overpotential and much higher exchange current density for HER. In addition, a long-term continuous electrolysis test with a current interruption shows that the Ni-Fe-Mo-Co alloy has excellent catalytic stability.
基金financially supported by the National Natural Science Foundation of China(NOs.21303157 and51771164)the Natural Science Foundation of Hebei Province(No.E2019203161)Scientific Research Projects in Colleges and Universities in Hebei Province(No.QN2016002)
文摘To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide(rGO) via a chemical reduction process. Results indicated that rGO sheets uniformly coated on the alloy surface, yielding a threedimensional network layer. The coated surfaces contained numerous hydrophilic functional groups, leading to better wettability of the alloy in aqueous alkaline media. This, in turn, increased the concentration of electro-active species at the interface between the electrode and the electrolyte, improving the electrochemical kinetics and the rate discharge of the electrodes. The high rate dischargeability at 1500 mA·g^(–1) increased from 53.2% to 83.9% after modification. In addition, the modification layer remained stable and introduced a dense metal oxide layer to the alloy surface after a long cycling process. Therefore, the protective layer prevented the discharge capacity from quickly decreasing and improved cycling stability.
基金Project(2003CB214501) supported by the National Basic Research Program of China Project(48010) supported by the Excellent Doctor’s Science and Technology Innovation Foundation of Beijing Jiaotong University, China
文摘Sputtering method was used to prepare Ni-Mo alloy electrodes for hydrogen production in alkaline solution. The influences of the working pressure during deposition and the substrate temperature on the electrochemical behavior of electrode were characterized by steady-state polarization plot and Tafel polarization curve measurements. And the physical properties of electrodes were characterized by XRD, SEM, AFM and EDS. It is found that the overpotential is significantly influenced by the working pressure which affects critically the electrode surface morphology, and two Tafel regions are observed for each sample. The overpotential value does not change very much with the substrate temperature. The XRD results indicates that the electrodes should be considered nanocrystalline. Thornton model for the microstructure of sputter-deposited electrodes is referred to explain the observed microstructure change.
基金Project(20374021) supported by the National Natural Science Foundation of China
文摘Ni-Fe-Mo-Co alloy electrode was prepared in a citrate solution by electrodeposition, and then Mo and Fe were partially leached out from the electrode in 30% KOH solution. The unique surface micromorphology of a hive-like structure was obtained with an average pore size of about 50 nm. The electrode has a very large real surface area and a stable structure. The effects of sodium molybdate concentration on the composition, surface morphology, and structure of electrodes were analyzed by EDS, SEM and XRD. The polarization curves of the different electrodes show that the catalytic activity of electrodes is strongly correlated with the mole fraction of alloy elements (Ni, Fe, Mo, Co), and the addition of cobalt element to Ni-Fe-Mo alloy improves the catalytic activity. The Ni35.63Fe24.67Mo23.52Co16.18 electrode has the best activity for hydrogen evolution reaction(HER), with an over-potential of 66.2 mV, in 30% KOH at 80 ℃ and 200 mA/cm2. The alloy maintains its good catalytic activity for HER during continuous or intermittent electrolysis. Its electrochemical activity and catalytic stability are much higher than the other iron-group with Mo alloy electrodes.
基金DRDO-ER&IPR (No:1104584\M\1387), New Delhi, India for the sponsoring the research project
文摘Good castability and high strength properties of Ale Si alloys are useful in defence applications like torpedoes,manufacture of Missile bodies,and parts of automobile such as engine cylinders and pistons.Poor wear resistance of the alloys is major limitation for their use.Friction stir processing(FSP) is a recognized surfacing technique as it overcomes the problems of fusion route surface modification methods.Keeping in view of the requirement of improving wear resistance of cast aluminiumesilicon alloy,friction stir processing was attempted for surface modification with boron carbide(B4C) and molybdenum disulfide(Mo S2) powders.Metallography,micro compositional analysis,hardness and pin-on-disc wear testing were used for characterizing the surface composite coating.Microscopic study revealed breaking of coarse silicon needles and uniformly distributed carbides in the A356 alloy matrix after FSP.Improvement and uniformity in hardness was obtained in surface composite layer.Higher wear resistance was achieved in friction stir processed coating with carbide powders.Addition of solid lubricant Mo S2 powder was found to improve wear resistance of the base metal significantly.
文摘The electrochemical process of Ti-Ni alloy electrode was studied by using cyclic voltammetry. The hydrogen-absorbing electrode could be approximately regarded as a reversible hydrogen elecrede. The con- trolling steps of the discharging process varying with the anodic overpotentials were investigated and the effect ofelecrode constituent modification or Zr adulteation on the electrochemical behavior was also studied.
基金Project(50171021) supported by the National Natural Science Foundation of China
文摘The influence of the addition of Cu(OH)2 to 6 mol/L KOH alkaline electrolyte on the electrochemical properties of La2Mg0.9Al0.1Ni7.5Co1.5 hydrogen storage alloy electrode was investigated by electron probe X-ray microanalysis(EPMA),X-ray diffraction(XRD) and electrochemical measurements. EPMA micrographs and XRD patterns show that the surface of the hydride electrode is plated by metal copper film. The thickness and compactness of Cu film increase with the increment of charge-discharge cycle number. The copper film of the hydride electrode surface can keep the hydrogen storage alloy particle in the electrode interior from oxidizing availably. The addition of Cu(OH)2 to alkaline electrolyte lowers the activation property and the high rate dischargeability of the La2Mg0.9Al0.1Ni7.5Co1.5 hydride electrode,but has no negative effect on the maximum discharge capacity of the hydride electrode. Moreover,it is effective to improve the cyclic stability of the hydride electrode utilizing electrodeposit Cu film on the La2Mg0.9Al0.1Ni7.5Co1.5 hydride electrodes surface.
