Ceramic oxide coatings were prepared on AZ91D magnesium alloys in alkaline silicate solution using micro-arc oxidation（MAO） technique.The corrosion behavior of MAO coating on AZ91D magnesium alloys in NaCl solutions...Ceramic oxide coatings were prepared on AZ91D magnesium alloys in alkaline silicate solution using micro-arc oxidation（MAO） technique.The corrosion behavior of MAO coating on AZ91D magnesium alloys in NaCl solutions with different concentrations（0.1%,0.5%,1.0%,3.5% and 5.0% in mass fraction） was evaluated by electrochemical measurements and immersion tests.The results showed that the corrosion rate of the MAO coated AZ91D increased with increasing chloride ion concentration.The main form of corrosion failure was localized corrosion for the MAO coated AZ91D immersed in higher concentration NaCl solutions（1.0%,3.5% and 5.0%）,while it was general corrosion in dilute NaCl solutions（0.1% and 0.5%）.Two different stages of the failure process of the MAO coated AZ91D could be identified：1） occurrence of the metastable pits and 2） growth of the pits.Different equivalent circuits were also proposed based on the results of electrochemical impedance spectroscopy（EIS） for the MAO coated AZ91D immersed in different concentrations of NaCl solutions for 120 h.展开更多
The effect of NaNO_3 concentration on the anodic electrochemical behavior of antimony in 4 M NaOH solution was investigated using cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) analyses. The me...The effect of NaNO_3 concentration on the anodic electrochemical behavior of antimony in 4 M NaOH solution was investigated using cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) analyses. The mechanism of NO_3^-concentration effect on the anodic electrochemical behavior of antimony was proposed, and its availability was confirmed by experimental results. The effect of NaNO_3 on the anodic behavior of antimony in Na OH solution can be interpreted as a stepwise formation of different antimony compounds with different NaNO_3 concentrations. Metallic antimony is apt to be oxidized into Sb_2O_3 within the NaNO_3 concentration range of 0–0.48 M. NaSbO_3 can be found on the antimony surface when the NaNO_3 concentration increases gradually. Insoluable NaSbO_3 inhibits the anodic oxidation of antimony due to its shielding effect on the mass transport of the reactants and products. Surface morphology and composition were analyzed by X-ray photoelectron spectroscopy(XPS), scanning electronic microscopy(SEM), and electron dispersion spectroscopy(EDS) analyses. Results indicate that the anodic oxidation layer is composed of Sb_2O_3, NaSbO_3, and Sb. The atomic proportion of antimony in the form of NaSbO_3 increases with increasing NaNO_3 concentration due to the powerful oxidizing property of NaNO_3.展开更多
In high-temperature and high-pressure water, traditional anticorrosion approaches are not suitable to be used to protect structural materials from oxidation and corrosion. In this study, monolayer graphene was explore...In high-temperature and high-pressure water, traditional anticorrosion approaches are not suitable to be used to protect structural materials from oxidation and corrosion. In this study, monolayer graphene was explored as a barrier to protect the materials from degradation. The oxidation and corrosion rate of the monolayer-graphene-coated copper is much lower than that of the bare copper, suggesting that the monolayer graphene can effectively protect the copper from oxidation and corrosion in the simulated primary water of pressurized water reactors.展开更多
Biphasic layered oxide cathodes,known for their superior electrochemical performance,are prime candidates for commercializing in Na-ion batteries.Herein,we unveil a series of P3/P2 monophasic and biphasic Al-substitut...Biphasic layered oxide cathodes,known for their superior electrochemical performance,are prime candidates for commercializing in Na-ion batteries.Herein,we unveil a series of P3/P2 monophasic and biphasic Al-substituted Na_(3/4)Mn_(5-x/8)Al_(2x/8)Ni_(3-x/8)O_(2)layered oxide cathodes that lie along the‘zero Mn^(3+)line’in the Na_(3/4)(Mn-Al-Ni)O_(2)pseudo-ternary system.The structural analysis showed a larger Na^(+)conduction bottleneck area in both P3 and P2 structures with a higher Al3+content,which enhanced their rate performance.In each composition,the P3/P2 biphasic compound with nearly equal fractions of P3 and P2 phases outperformed their monophasic counterparts in almost all electrochemical performance parameters.Operando synchrotron XRD measurements obtained for the monophasic P3 and biphasic P2/P3 samples revealed the absence of the O3 phase during cycling.The high structure stability and faster Na^(+)transport kinetics in the biphasic samples underpins the enhancement of electrochemical properties in the Al-substituted P3/P2 cathodes.These results highlight fixed oxidation state lines as a novel tool to identify and design layered oxide cathodes for Na-ion batteries in pseudo-ternary diagrams involving Jahn-Teller active cations.展开更多
The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electro...The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electrolyte,Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3),utilizing cyclic voltammetry and square wave voltammetry techniques.The results show that Fe(Ⅲ)reduction occurs in two steps:Fe(Ⅲ)+e^(−)→Fe(Ⅱ),Fe(Ⅱ)+2e^(−)→Fe,and that the redox process of Fe(Ⅲ)/Fe(Ⅱ)at the tungsten electrode is an irreversible reaction controlled by diffusion.The diffusion coefficients of Fe(Ⅲ)in the molten Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)in the temperature range of 1248–1278 K are between 1.86×10^(−6)cm^(2)/s and 1.58×10^(−4)cm^(2)/s.The diffusion activation energy of Fe(Ⅲ)in the molten salt is 1825.41 kJ/mol.As confirmed by XRD analysis,potentiostatic electrolysis at−0.857 V(vs.O_(2)/O_(complex)^(2-))for 6 h produces metallic iron on the cathode.展开更多
The catalytic performance of two oxides coated anodes （OCSs） meshes and one OCA plate was investigated in a zinc electrowinning electrolyte at 38 ℃. Their electrochemical behaviors were compared with that of a conv...The catalytic performance of two oxides coated anodes （OCSs） meshes and one OCA plate was investigated in a zinc electrowinning electrolyte at 38 ℃. Their electrochemical behaviors were compared with that of a conventional Pb-0.7%Ag alloy anode. Electrochemical measurements such as cyclic voltammetric, galvanostatic, potentiodynamic, open-circuit potential （OCP） and in situ electrochemical noise measurements were considered. After 2 h of OCP test, the linear polarization shows that the corrosion current density of the Ti/（IrO2-Ta2O5） mesh electrode is the lowest （3.37μA/cm^2） among the three OCAs and shows excellent performance. Additionally, after 24 h of galvanostatic polarization at 50 mA/cm^2and 38 ℃, the Ti/MnO2mesh anode has the highest potential （1.799 V）, followed by the Ti/（IrO2-Ta2O5） plate （1.775 V） and Ti/（IrO2-Ta2O5） mesh （1.705 V） anodes. After 24 h of galvanostatic polarization followed by 16 h of decay, the linear polarization method confirms the sequence obtained after 2 h of OCP test, and the Ti/（IrO2-Ta2O5） mesh attains the lowest corrosion current density. The Ti/（IrO2-Ta2O5） mesh anode also shows better performance after 24 h of galvanostatic polarization with the overpotential lower than that of the conventional Pb-Ag anode by about 245 mV.展开更多
Zn and Co multi-doped CeO2 thin films have been prepared using an anodic electrochemical method. The structures and magnetic behaviors are characterized by several techniques, in which the oxygen states in the lattice...Zn and Co multi-doped CeO2 thin films have been prepared using an anodic electrochemical method. The structures and magnetic behaviors are characterized by several techniques, in which the oxygen states in the lattice and the absorptive oxygen bonds at the surface are carefully examined. The absorptive oxygen bond is about 50% of the total oxygen bond by using a semi-quantitative method. The value of actual stoichiometry δ′ is close to 2. The experimental results indicate that the thin films are of a cerium oxide-based solid solution with few oxygen vacancies in the lattice and many absorptive oxygen bonds at the surface. Week ferromagnetic behaviors were evidenced by observed M-H hysteresis loops at room temperature. Furthermore, an evidence of relative ferromagnetic contributions was revealed by the temperature dependence of magnetization. It is believed that the ferromagnetic contributions exhibited in the M-H loops originate from the absorptive oxygen on the surface rather than the oxygen vacancies in the lattice.展开更多
基金Project (2007CB613700) supported by the National Basic Research Program of ChinaProject supported by Research Program of Excellent Scholars Studying Abroad of Ministry of Human Resources and Social Security,China
文摘Ceramic oxide coatings were prepared on AZ91D magnesium alloys in alkaline silicate solution using micro-arc oxidation（MAO） technique.The corrosion behavior of MAO coating on AZ91D magnesium alloys in NaCl solutions with different concentrations（0.1%,0.5%,1.0%,3.5% and 5.0% in mass fraction） was evaluated by electrochemical measurements and immersion tests.The results showed that the corrosion rate of the MAO coated AZ91D increased with increasing chloride ion concentration.The main form of corrosion failure was localized corrosion for the MAO coated AZ91D immersed in higher concentration NaCl solutions（1.0%,3.5% and 5.0%）,while it was general corrosion in dilute NaCl solutions（0.1% and 0.5%）.Two different stages of the failure process of the MAO coated AZ91D could be identified：1） occurrence of the metastable pits and 2） growth of the pits.Different equivalent circuits were also proposed based on the results of electrochemical impedance spectroscopy（EIS） for the MAO coated AZ91D immersed in different concentrations of NaCl solutions for 120 h.
基金financially supported by the National Natural Science Foundation of China (No. 51564031)the Independent Research Project of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilizationthe Cooperation between School and Enterprise of China (No. 0201352042)
文摘The effect of NaNO_3 concentration on the anodic electrochemical behavior of antimony in 4 M NaOH solution was investigated using cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) analyses. The mechanism of NO_3^-concentration effect on the anodic electrochemical behavior of antimony was proposed, and its availability was confirmed by experimental results. The effect of NaNO_3 on the anodic behavior of antimony in Na OH solution can be interpreted as a stepwise formation of different antimony compounds with different NaNO_3 concentrations. Metallic antimony is apt to be oxidized into Sb_2O_3 within the NaNO_3 concentration range of 0–0.48 M. NaSbO_3 can be found on the antimony surface when the NaNO_3 concentration increases gradually. Insoluable NaSbO_3 inhibits the anodic oxidation of antimony due to its shielding effect on the mass transport of the reactants and products. Surface morphology and composition were analyzed by X-ray photoelectron spectroscopy(XPS), scanning electronic microscopy(SEM), and electron dispersion spectroscopy(EDS) analyses. Results indicate that the anodic oxidation layer is composed of Sb_2O_3, NaSbO_3, and Sb. The atomic proportion of antimony in the form of NaSbO_3 increases with increasing NaNO_3 concentration due to the powerful oxidizing property of NaNO_3.
基金financially supported by the National Basic Research Program of China(No.2011CB610502)the National Natural Science Fund for Distinguished Young Scholars (No.51025104)
文摘In high-temperature and high-pressure water, traditional anticorrosion approaches are not suitable to be used to protect structural materials from oxidation and corrosion. In this study, monolayer graphene was explored as a barrier to protect the materials from degradation. The oxidation and corrosion rate of the monolayer-graphene-coated copper is much lower than that of the bare copper, suggesting that the monolayer graphene can effectively protect the copper from oxidation and corrosion in the simulated primary water of pressurized water reactors.
基金the Science and Engineering Research Board(SERB),Govt.of India,for the financial support(grant number:CRG/2021/005548).
文摘Biphasic layered oxide cathodes,known for their superior electrochemical performance,are prime candidates for commercializing in Na-ion batteries.Herein,we unveil a series of P3/P2 monophasic and biphasic Al-substituted Na_(3/4)Mn_(5-x/8)Al_(2x/8)Ni_(3-x/8)O_(2)layered oxide cathodes that lie along the‘zero Mn^(3+)line’in the Na_(3/4)(Mn-Al-Ni)O_(2)pseudo-ternary system.The structural analysis showed a larger Na^(+)conduction bottleneck area in both P3 and P2 structures with a higher Al3+content,which enhanced their rate performance.In each composition,the P3/P2 biphasic compound with nearly equal fractions of P3 and P2 phases outperformed their monophasic counterparts in almost all electrochemical performance parameters.Operando synchrotron XRD measurements obtained for the monophasic P3 and biphasic P2/P3 samples revealed the absence of the O3 phase during cycling.The high structure stability and faster Na^(+)transport kinetics in the biphasic samples underpins the enhancement of electrochemical properties in the Al-substituted P3/P2 cathodes.These results highlight fixed oxidation state lines as a novel tool to identify and design layered oxide cathodes for Na-ion batteries in pseudo-ternary diagrams involving Jahn-Teller active cations.
基金Project(52074084)supported by the National Natural Science Foundation of China。
文摘The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electrolyte,Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3),utilizing cyclic voltammetry and square wave voltammetry techniques.The results show that Fe(Ⅲ)reduction occurs in two steps:Fe(Ⅲ)+e^(−)→Fe(Ⅱ),Fe(Ⅱ)+2e^(−)→Fe,and that the redox process of Fe(Ⅲ)/Fe(Ⅱ)at the tungsten electrode is an irreversible reaction controlled by diffusion.The diffusion coefficients of Fe(Ⅲ)in the molten Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)in the temperature range of 1248–1278 K are between 1.86×10^(−6)cm^(2)/s and 1.58×10^(−4)cm^(2)/s.The diffusion activation energy of Fe(Ⅲ)in the molten salt is 1825.41 kJ/mol.As confirmed by XRD analysis,potentiostatic electrolysis at−0.857 V(vs.O_(2)/O_(complex)^(2-))for 6 h produces metallic iron on the cathode.
基金Project(RDCPJ 428402)supported by the Natural Sciences and Engineering Research Council of Canada
文摘The catalytic performance of two oxides coated anodes （OCSs） meshes and one OCA plate was investigated in a zinc electrowinning electrolyte at 38 ℃. Their electrochemical behaviors were compared with that of a conventional Pb-0.7%Ag alloy anode. Electrochemical measurements such as cyclic voltammetric, galvanostatic, potentiodynamic, open-circuit potential （OCP） and in situ electrochemical noise measurements were considered. After 2 h of OCP test, the linear polarization shows that the corrosion current density of the Ti/（IrO2-Ta2O5） mesh electrode is the lowest （3.37μA/cm^2） among the three OCAs and shows excellent performance. Additionally, after 24 h of galvanostatic polarization at 50 mA/cm^2and 38 ℃, the Ti/MnO2mesh anode has the highest potential （1.799 V）, followed by the Ti/（IrO2-Ta2O5） plate （1.775 V） and Ti/（IrO2-Ta2O5） mesh （1.705 V） anodes. After 24 h of galvanostatic polarization followed by 16 h of decay, the linear polarization method confirms the sequence obtained after 2 h of OCP test, and the Ti/（IrO2-Ta2O5） mesh attains the lowest corrosion current density. The Ti/（IrO2-Ta2O5） mesh anode also shows better performance after 24 h of galvanostatic polarization with the overpotential lower than that of the conventional Pb-Ag anode by about 245 mV.
基金supported by the Natural Science Foundation of Zhejiang Province,China(Grant No.LY12A01002)the National Natural Science Foundation of China(Grant Nos.11204058 and 21073162)the Hangzhou Dianzi University,China(Grant No.KYF09150603)
文摘Zn and Co multi-doped CeO2 thin films have been prepared using an anodic electrochemical method. The structures and magnetic behaviors are characterized by several techniques, in which the oxygen states in the lattice and the absorptive oxygen bonds at the surface are carefully examined. The absorptive oxygen bond is about 50% of the total oxygen bond by using a semi-quantitative method. The value of actual stoichiometry δ′ is close to 2. The experimental results indicate that the thin films are of a cerium oxide-based solid solution with few oxygen vacancies in the lattice and many absorptive oxygen bonds at the surface. Week ferromagnetic behaviors were evidenced by observed M-H hysteresis loops at room temperature. Furthermore, an evidence of relative ferromagnetic contributions was revealed by the temperature dependence of magnetization. It is believed that the ferromagnetic contributions exhibited in the M-H loops originate from the absorptive oxygen on the surface rather than the oxygen vacancies in the lattice.
基金supported by the National Natural Science Foundation of China (No.51901018)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology (Nos.YESS,2019QNRC001)+2 种基金the Fundamental Research Funds for the Central Universities,China (Nos.FRF-AT-20-07,06500119)the Natural Science Foundation of Beijing Municipality,China (No.2212037)the National Science and Technology Resources Investigation Program of China (No.2019FY101400).
