The effects of cathode potentials and initial nitrate concentrations on nitrate reduction in bio- electrochemical systems （BESs） were reported. These factors could partition nitrate reduction between denitrification...The effects of cathode potentials and initial nitrate concentrations on nitrate reduction in bio- electrochemical systems （BESs） were reported. These factors could partition nitrate reduction between denitrification and dissimilatory nitrate reduction to ammonium （DNRA）. Pseudomonas alcaliphilastrain MBR utilized an electrode as the sole electron donor and nitrate as the sole electron acceptor. When the cathode potential was set from -0.3 to -I.1 V （vs. Ag/AgC1） at an initial nitrate concentration of 100 mg NO^-N/L, the DNRA electron recovery increased from （10.76 ± 1.6）% to （35.06 ± 0.99）%; the denitrification electron recovery decreased from （63.42 ± 1,32）% to （44.33 ± 1.92）%. When the initial nitrate concentration increased from （29.09 ± 0.24） to （490.97 ± 3.49） mg NO3-N/L at the same potential （-0.9 V）, denitrification electron recovery increased from （5.88 ± 1.08）% to （50.19 ±2.59）%; the DNRA electron recovery declined from （48.79 ±1.32）% to （16.02 ± 1.41）%. The prevalence of DNRA occurred at high ratios of electron donors to acceptors in the BESs and denitrification prevailed against DNRA under a lower ratio of electron donors to acceptors. These results had a potential application value of regulating the transformation of nitrate to N2 or ammonium in BESs for nitrate removal.展开更多
A biocathode with microbial catalyst in place of a noble metal was successfully developed for hydrogen evolution in a microbial electrolysis cell （MEC）. The strategy for fast biocathode cultivation was demonstrated....A biocathode with microbial catalyst in place of a noble metal was successfully developed for hydrogen evolution in a microbial electrolysis cell （MEC）. The strategy for fast biocathode cultivation was demonstrated. An exoelectrogenic reaction was initially extended with an H2-full atmosphere to enrich Ha-utilizing bacteria in a MEC bioanode. This bioanode was then inversely polarized with an applied voltage in a half-cell to enrich the hydrogen-evolving biocathode. The electrocatalytic hydrogen evolution reaction （HER） kinetics of the biocathode MEC could be enhanced by increasing the bicarbonate buffer concentration from 0.05 mol·L-1 to 0.5 mol· L-1 and/or by decreasing the cathode potential from -0.9 V to - 1.3 V vs. a saturated calomel electrode （SCE）. Within the tested potential region in this study, the HER rate of the biocathode MEC was primarily influenced by the microbial catalytic capability. In addition, increasing bicarbonate concentration enhances the electric migration rate of proton carriers. As a consequence, more mass H＋ can be released to accelerate the biocathode-catalyzed HER rate. A hydrogen production rate of 8.44 m3. m 3. d1 with a current density of 951.6 A. m-3 was obtained using the biocathode MEC under a cathode potential of - 1.3 V vs. SCE and 0.4 mol· L-1 bicarbonate. This study provided information on the optimization of hydrogen production in biocathode MEC and expanded the practical applications thereof.展开更多
In this work,the stress corrosion cracking(SCC)behavior of E690 steel base metal(BM)and different heat-affected zone(HAZ)microstructures,i.e.,coarse grain HAZ(CGHAZ),fine grain HAZ(FGHAZ),and intercritical HAZ(ICHAZ),...In this work,the stress corrosion cracking(SCC)behavior of E690 steel base metal(BM)and different heat-affected zone(HAZ)microstructures,i.e.,coarse grain HAZ(CGHAZ),fine grain HAZ(FGHAZ),and intercritical HAZ(ICHAZ),was investigated at different cathodic potentials in artificial seawater by slow strain rate tensile tests,scanning electron microscopy and electron back-scattered diffraction measurements.The results show that the HAZ microstructures and BM exhibit different SCC susceptibilities:FGHAZ<ICHAZ<BM<CGHAZ,which are controlled by anodic dissolution(AD)at the open circuit potential.With the cathodic potential equaling to-750 mV,the SCC susceptibility of the four microstructures increases because of the synergistic effect of AD and weak hydrogen embrittlement(HE).At-850 mV,AD is inhibited,and the SCC susceptibility of BM decreases,while the SCC susceptibility of the HAZ microstructures increases.At a potential below-850 mV,the SCC susceptibility of the four microstructures gradually increases because of the augment of HE,and the SCC susceptibility of the HAZ microstructures is higher than that of BM.The distinction reveals that the HAZ microstructures have the greater HE susceptibility than BM.展开更多
The environment at crack tip and its effect on the crack growth behaviour of low alloy steel-E690 steel were studied at cathodic potentials in artificial seawater.The results showed that the micro environment at crack...The environment at crack tip and its effect on the crack growth behaviour of low alloy steel-E690 steel were studied at cathodic potentials in artificial seawater.The results showed that the micro environment at crack tip and crack growth behaviour were related to the electrochemical reactions at crack tip,which were affected by the stress state and applied potentials.The crack tip environment was acidified under cyclic loading,resulting from the crack tip anodic dissolution reaction and corresponding hydrolysis reaction.Because of the hydrogen evolution and the inhibited anodic dissolution inside the crack,the crack tip p H increases as the cathodic potential decreases.The effect of cathodic potentials on the electrochemical reactions caused the variation of the hydrogen content,which influenced the crack growth rate because the crack growth behaviour was controlled by hydrogen embrittlement mechanism.This resulted in a fact that with the negative decrease of potential,the crack growth rate first decreased and then increased,with the minimum rate at-0.75 V.And the crack growth path exhibited transgranular fracture.展开更多
This study aims at providing systematically insights to clarify the impact of cathodic polarization on the stress corrosion cracking(SCC)behavior of 21 Cr2 NiMo steel.Slow-strain-rate tensile tests demonstrated that 2...This study aims at providing systematically insights to clarify the impact of cathodic polarization on the stress corrosion cracking(SCC)behavior of 21 Cr2 NiMo steel.Slow-strain-rate tensile tests demonstrated that 21 Cr2 NiMo steel is highly sensitive to hydrogen embrittlement at strong cathodic polarization.The lowest SCC susceptibility occurred at-775 mV vs.SCE,whereas the SCC susceptibility was remarkably higher at potentials below-950 mV vs.SCE.Scanning electron microscopy(SEM)and electron backscattered diffraction(EBSD)revealed that the cathodic potential decline caused a transition from transgranular to intergranular mode in the fracture path.The intergranular mode transformed from bainite boundaries separation to prior austenitic grain boundaries separation under stronger cathodic polarization.Furthermore,corrosion pits promoted the nucleation of SCC cracks.In conclusion,with the decrease in the applied potential,the SCC mechanism transformed from the combination of hydrogen embrittlement and anodic dissolution to typical hydrogen embrittlement.展开更多
Hollow cathodes serve as electron sources in Hall thrusters,ion thrusters and other electric propulsion systems.One of the vital problems in their application is the cathode erosion.However,the basic erosion mechanism...Hollow cathodes serve as electron sources in Hall thrusters,ion thrusters and other electric propulsion systems.One of the vital problems in their application is the cathode erosion.However,the basic erosion mechanism and the source of high-energy ions cause of erosion are not fully understood.In this paper,both potential measurements and simulation analyses were performed to explain the formation of high-energy ions.A high-speed camera,a single Langmuir probe and a floating emissive probe were used to determine the steady and oscillatory plasma properties in the near-field plume of a hollow cathode.The temporal structure,electron temperature,electron density,and both static and oscillation of plasma potentials of the plume have been obtained by the diagnostics mentioned above.The experimental results show that there exists a potential hill（about 30 V） and also severe potential oscillations in the near-plume region.Moreover,a simple 2 D particle-in-cell model was used to analyze the energy transition between the potential hill and/or its oscillations and the ions.The simulation results show that the energy of ions gained from the static potential background is about 20 e V,but it could reach to 60 e V when the plasma oscillates.展开更多
The gallium electrodeposition from alkaline solution has a very low current efficiency, the reason for which is still not quite understood. The effects of electrode materials used for gallium electrodeposition, as wel...The gallium electrodeposition from alkaline solution has a very low current efficiency, the reason for which is still not quite understood. The effects of electrode materials used for gallium electrodeposition, as well as the effects of NaOH concentration and the anions concentrations in the solution, including 5042-, SiO32-, CO32-, AlO2-, F-, and CI-, on the deposition were analyzed in this study. The suitable materials of SUS316-SUS316 were suggested for the gallium electrodeposition. Based on the electrode couples, the NaOH concentration of 4 mol.L-1 for gallium electrodeposition exhibits the greatest current efficiency. Moreover, the current efficiency would decrease in the electrolyte along with the increasing concentration of the anions, except that, 0.2 mol-L-1 C1- in the solution slightly improves the current efficiency of gallium elec- trodeposition. Moreover, the gallium deposited on the cathode from the solution with 0.6 mol.L-1 SiO32- appears tiny black in color and coarse. Meanwhile, SUS304 is shown to be not suitable to be used as cathode for the gallium electrodeposition from the alkaline solution.展开更多
Anomalous-energy runaway electrons(RAEs),whose energy exceeds the maximum potential difference across the discharge gap,are widely observed in various plasma phenomena.This study investigates the origination of anomal...Anomalous-energy runaway electrons(RAEs),whose energy exceeds the maximum potential difference across the discharge gap,are widely observed in various plasma phenomena.This study investigates the origination of anomalous-energy RAEs in fast ionisation waves(FIWs)formed during pulsed gas breakdown.Synchronised observation of RAEs and their induced bremsstrahlung X-ray at different locations of the FIW is performed,which is combined with measurement of spatial-temporal evolution of FIW potential.It is revealed that anomalous-energy RAEs,preceding regular RAEs,have an ultrashort beam with a picosecond pulse width,and RAEs tend to maintain their energy during FIW propagation before being deposited into the anode.Particle-in-cell Monte Carlo collision(PIC-MCC)simulation illustrates that the‘pace-matching’between initial electron acceleration through cathode potential drop and potential lift-up during FIW inception opens a narrow window for forming anomalous-energy RAEs.展开更多
The thin films of Cu2O are deposited by electrodeposition technique onto indium tin oxide（ITO）-coated glass substrate at different potentials. The precursor is an aqueous solution which contains respectively 0.05 M ...The thin films of Cu2O are deposited by electrodeposition technique onto indium tin oxide（ITO）-coated glass substrate at different potentials. The precursor is an aqueous solution which contains respectively 0.05 M of CuSO4 and citric acid at kept temperature of 60℃ and the applied potential varies within the {-0：4 V,-0：7 V}SCE range. Based on the chronocoulometry（CC） process, the electrochemical, structural and optical parameters are determined. We measured the current as function of potential within the {-0：4 V,-0：7 V} range and the higher current is found to be within the {-0：7 V,-0：3 V} band. The grain sizes are of 12.12 nm and 35.47 nm according to（110） and（221） orientations respectively. The high textural coefficient of 0.943 is recorded for the potential -0：7 V.The transmittance of 72.25 %, within the visible band, is obtained for the as-grown layer at -0：4 V and the band gap is found to be 2.2 e V for the electrodeposition potential of -0：7 V.展开更多
基金supported by the National Natural Science Foundation of China(No.51074149,31270166,31270531 and 31000070)the West Light Foundation of the Chinese Academy of Sciences
文摘The effects of cathode potentials and initial nitrate concentrations on nitrate reduction in bio- electrochemical systems （BESs） were reported. These factors could partition nitrate reduction between denitrification and dissimilatory nitrate reduction to ammonium （DNRA）. Pseudomonas alcaliphilastrain MBR utilized an electrode as the sole electron donor and nitrate as the sole electron acceptor. When the cathode potential was set from -0.3 to -I.1 V （vs. Ag/AgC1） at an initial nitrate concentration of 100 mg NO^-N/L, the DNRA electron recovery increased from （10.76 ± 1.6）% to （35.06 ± 0.99）%; the denitrification electron recovery decreased from （63.42 ± 1,32）% to （44.33 ± 1.92）%. When the initial nitrate concentration increased from （29.09 ± 0.24） to （490.97 ± 3.49） mg NO3-N/L at the same potential （-0.9 V）, denitrification electron recovery increased from （5.88 ± 1.08）% to （50.19 ±2.59）%; the DNRA electron recovery declined from （48.79 ±1.32）% to （16.02 ± 1.41）%. The prevalence of DNRA occurred at high ratios of electron donors to acceptors in the BESs and denitrification prevailed against DNRA under a lower ratio of electron donors to acceptors. These results had a potential application value of regulating the transformation of nitrate to N2 or ammonium in BESs for nitrate removal.
基金This work was financial supported by grants from the National Natural Science Foundation of China （Grant Nos. 51108014, 21373022, 21073010, 21003007 and Ul137602）, National Major Research Program （No. 2011CB935700）, Beijing Nova Program （Z1311090004 13008）, Fundamental Research Funds for the Central Universities （YWF- 10-03-021）, Research Fund for the Doctoral Program of Higher Education of China （20111102120045） and Program for New Century Excellent Talents in University.
文摘A biocathode with microbial catalyst in place of a noble metal was successfully developed for hydrogen evolution in a microbial electrolysis cell （MEC）. The strategy for fast biocathode cultivation was demonstrated. An exoelectrogenic reaction was initially extended with an H2-full atmosphere to enrich Ha-utilizing bacteria in a MEC bioanode. This bioanode was then inversely polarized with an applied voltage in a half-cell to enrich the hydrogen-evolving biocathode. The electrocatalytic hydrogen evolution reaction （HER） kinetics of the biocathode MEC could be enhanced by increasing the bicarbonate buffer concentration from 0.05 mol·L-1 to 0.5 mol· L-1 and/or by decreasing the cathode potential from -0.9 V to - 1.3 V vs. a saturated calomel electrode （SCE）. Within the tested potential region in this study, the HER rate of the biocathode MEC was primarily influenced by the microbial catalytic capability. In addition, increasing bicarbonate concentration enhances the electric migration rate of proton carriers. As a consequence, more mass H＋ can be released to accelerate the biocathode-catalyzed HER rate. A hydrogen production rate of 8.44 m3. m 3. d1 with a current density of 951.6 A. m-3 was obtained using the biocathode MEC under a cathode potential of - 1.3 V vs. SCE and 0.4 mol· L-1 bicarbonate. This study provided information on the optimization of hydrogen production in biocathode MEC and expanded the practical applications thereof.
基金financially supported by the National Environmental Corrosion Platform of China(NECP)the National Key Research and Development Program of China(Nos.2016YFB0300604 and 2017YFB0304701)the National Natural Science Foundation of China(Nos.51771028 and 51871024)。
文摘In this work,the stress corrosion cracking(SCC)behavior of E690 steel base metal(BM)and different heat-affected zone(HAZ)microstructures,i.e.,coarse grain HAZ(CGHAZ),fine grain HAZ(FGHAZ),and intercritical HAZ(ICHAZ),was investigated at different cathodic potentials in artificial seawater by slow strain rate tensile tests,scanning electron microscopy and electron back-scattered diffraction measurements.The results show that the HAZ microstructures and BM exhibit different SCC susceptibilities:FGHAZ<ICHAZ<BM<CGHAZ,which are controlled by anodic dissolution(AD)at the open circuit potential.With the cathodic potential equaling to-750 mV,the SCC susceptibility of the four microstructures increases because of the synergistic effect of AD and weak hydrogen embrittlement(HE).At-850 mV,AD is inhibited,and the SCC susceptibility of BM decreases,while the SCC susceptibility of the HAZ microstructures increases.At a potential below-850 mV,the SCC susceptibility of the four microstructures gradually increases because of the augment of HE,and the SCC susceptibility of the HAZ microstructures is higher than that of BM.The distinction reveals that the HAZ microstructures have the greater HE susceptibility than BM.
基金the Open Fund of Shandong Key Laboratory of Corrosion Science(No.KLCS201909)the National Natural Science Foundation of China(Nos.51771028,51871024 and 51601182)。
文摘The environment at crack tip and its effect on the crack growth behaviour of low alloy steel-E690 steel were studied at cathodic potentials in artificial seawater.The results showed that the micro environment at crack tip and crack growth behaviour were related to the electrochemical reactions at crack tip,which were affected by the stress state and applied potentials.The crack tip environment was acidified under cyclic loading,resulting from the crack tip anodic dissolution reaction and corresponding hydrolysis reaction.Because of the hydrogen evolution and the inhibited anodic dissolution inside the crack,the crack tip p H increases as the cathodic potential decreases.The effect of cathodic potentials on the electrochemical reactions caused the variation of the hydrogen content,which influenced the crack growth rate because the crack growth behaviour was controlled by hydrogen embrittlement mechanism.This resulted in a fact that with the negative decrease of potential,the crack growth rate first decreased and then increased,with the minimum rate at-0.75 V.And the crack growth path exhibited transgranular fracture.
基金financially supported by the National Science and Technology Major Project,China(No.2017-Ⅶ0012-0109)。
文摘This study aims at providing systematically insights to clarify the impact of cathodic polarization on the stress corrosion cracking(SCC)behavior of 21 Cr2 NiMo steel.Slow-strain-rate tensile tests demonstrated that 21 Cr2 NiMo steel is highly sensitive to hydrogen embrittlement at strong cathodic polarization.The lowest SCC susceptibility occurred at-775 mV vs.SCE,whereas the SCC susceptibility was remarkably higher at potentials below-950 mV vs.SCE.Scanning electron microscopy(SEM)and electron backscattered diffraction(EBSD)revealed that the cathodic potential decline caused a transition from transgranular to intergranular mode in the fracture path.The intergranular mode transformed from bainite boundaries separation to prior austenitic grain boundaries separation under stronger cathodic polarization.Furthermore,corrosion pits promoted the nucleation of SCC cracks.In conclusion,with the decrease in the applied potential,the SCC mechanism transformed from the combination of hydrogen embrittlement and anodic dissolution to typical hydrogen embrittlement.
基金financial support from National Natural Science Foundation of China under Grant Nos.11402025 and 11475019China Academy of Space Technology under Grant Nos.YJJ0701 and ZWK1608
文摘Hollow cathodes serve as electron sources in Hall thrusters,ion thrusters and other electric propulsion systems.One of the vital problems in their application is the cathode erosion.However,the basic erosion mechanism and the source of high-energy ions cause of erosion are not fully understood.In this paper,both potential measurements and simulation analyses were performed to explain the formation of high-energy ions.A high-speed camera,a single Langmuir probe and a floating emissive probe were used to determine the steady and oscillatory plasma properties in the near-field plume of a hollow cathode.The temporal structure,electron temperature,electron density,and both static and oscillation of plasma potentials of the plume have been obtained by the diagnostics mentioned above.The experimental results show that there exists a potential hill（about 30 V） and also severe potential oscillations in the near-plume region.Moreover,a simple 2 D particle-in-cell model was used to analyze the energy transition between the potential hill and/or its oscillations and the ions.The simulation results show that the energy of ions gained from the static potential background is about 20 e V,but it could reach to 60 e V when the plasma oscillates.
基金financially supported by the National High Technology Research and Development Program of China(No.2011AA060701)the National Natural Science Foundation of China(No.21276258)
文摘The gallium electrodeposition from alkaline solution has a very low current efficiency, the reason for which is still not quite understood. The effects of electrode materials used for gallium electrodeposition, as well as the effects of NaOH concentration and the anions concentrations in the solution, including 5042-, SiO32-, CO32-, AlO2-, F-, and CI-, on the deposition were analyzed in this study. The suitable materials of SUS316-SUS316 were suggested for the gallium electrodeposition. Based on the electrode couples, the NaOH concentration of 4 mol.L-1 for gallium electrodeposition exhibits the greatest current efficiency. Moreover, the current efficiency would decrease in the electrolyte along with the increasing concentration of the anions, except that, 0.2 mol-L-1 C1- in the solution slightly improves the current efficiency of gallium elec- trodeposition. Moreover, the gallium deposited on the cathode from the solution with 0.6 mol.L-1 SiO32- appears tiny black in color and coarse. Meanwhile, SUS304 is shown to be not suitable to be used as cathode for the gallium electrodeposition from the alkaline solution.
基金supported by the National Natural Science Foundation of China(Grants 52350072,52437007,52277167)the Beijing Nova Program(Grant 20240484512)the Beijing Natural Science Foundation(Grant 1242030).
文摘Anomalous-energy runaway electrons(RAEs),whose energy exceeds the maximum potential difference across the discharge gap,are widely observed in various plasma phenomena.This study investigates the origination of anomalous-energy RAEs in fast ionisation waves(FIWs)formed during pulsed gas breakdown.Synchronised observation of RAEs and their induced bremsstrahlung X-ray at different locations of the FIW is performed,which is combined with measurement of spatial-temporal evolution of FIW potential.It is revealed that anomalous-energy RAEs,preceding regular RAEs,have an ultrashort beam with a picosecond pulse width,and RAEs tend to maintain their energy during FIW propagation before being deposited into the anode.Particle-in-cell Monte Carlo collision(PIC-MCC)simulation illustrates that the‘pace-matching’between initial electron acceleration through cathode potential drop and potential lift-up during FIW inception opens a narrow window for forming anomalous-energy RAEs.
基金Project supported the PNR (Nos. 8/U311/R77, U311/R81)the "Agencethematique de rechercheen science ettechnologie" (ATRST)+2 种基金the National Administration of Scientific Researchthe CNEPRU of Oran University of Sciences and Technology (No. B00L02UN310220130011)the Scientific Research Projects Coordination (Nos. 2012-01-01-KAP05, 2012-01-01-KAP06) Yildiz Technical University
文摘The thin films of Cu2O are deposited by electrodeposition technique onto indium tin oxide（ITO）-coated glass substrate at different potentials. The precursor is an aqueous solution which contains respectively 0.05 M of CuSO4 and citric acid at kept temperature of 60℃ and the applied potential varies within the {-0：4 V,-0：7 V}SCE range. Based on the chronocoulometry（CC） process, the electrochemical, structural and optical parameters are determined. We measured the current as function of potential within the {-0：4 V,-0：7 V} range and the higher current is found to be within the {-0：7 V,-0：3 V} band. The grain sizes are of 12.12 nm and 35.47 nm according to（110） and（221） orientations respectively. The high textural coefficient of 0.943 is recorded for the potential -0：7 V.The transmittance of 72.25 %, within the visible band, is obtained for the as-grown layer at -0：4 V and the band gap is found to be 2.2 e V for the electrodeposition potential of -0：7 V.
