The Ni-TiN nanocomposite film was successfully electrodeposited on brass copper substrates.The microstructures of the Ni-TiN nanocomposite film were investigated using scanning electron microscopy（SEM） and transmiss...The Ni-TiN nanocomposite film was successfully electrodeposited on brass copper substrates.The microstructures of the Ni-TiN nanocomposite film were investigated using scanning electron microscopy（SEM） and transmission electron microscopy（TEM）.Its average grain size was analyzed through X-ray diffraction（XRD）,and its anti-corrosion property was studied through potentiodynamic scanning curves and electrochemical impedance spectroscopy（EIS）.The results show that the morphology of Ni-TiN composite film is sensitively dependent on the electroplating current density,TiN nanoparticle concentration,solution stirring speed,bath temperature and pH value of solution.The average grain size of the optimized nanocomposite film is about 50 nm.Meanwhile,the Ni-TiN nanocomposite films are much more resistant to corrosion than pure Ni coatings.展开更多
The microstructure and corrosion behavior of as-cast and friction stir processed in-situ Al-TiB2 based composite in 3.5 wt.% sodium chloride solution were investigated. The microstructure was characterized using X-ray...The microstructure and corrosion behavior of as-cast and friction stir processed in-situ Al-TiB2 based composite in 3.5 wt.% sodium chloride solution were investigated. The microstructure was characterized using X-ray diffractometry, scanning electron microscopy and electron backscattered diffraction technique while corrosion behavior was evaluated using linear/cyclic potentiodynamic, electrochemical impedance spectroscopy and ASTM–G67 tests. The composite contains sub-micron TiB2 particles in an aluminum matrix with both blocky and fine clusters of Al3Ti agglomerated around TiB2 and displays a low uniform corrosion rate. It is also resistant to pitting as substantiated by the absence of a positive loop in cyclic potentiodynamic tests. This is due to the non-conductive nature of TiB2 particles and a controlled amount of blocky Al3Ti phase. However, both friction stir processed and as-cast composites are susceptible to inter-granular corrosion where Al3Ti and TiB2 at grain boundaries provide initiation sites for corrosion. Electrochemical impedance study attributes this to the adverse effect of Al3Ti and TiB2 on the protective oxide surface film, which increases with immersion time.展开更多
Silver and silver alloys usually tarnish,which causes some changes in their aesthetic appearance and electrical properties,due to their exposure to sulphide environments(H2S),and this is a problem in the field of corr...Silver and silver alloys usually tarnish,which causes some changes in their aesthetic appearance and electrical properties,due to their exposure to sulphide environments(H2S),and this is a problem in the field of corrosion and conservation of cultural heritage metallic artefacts.In this study,the role of copper content in the tarnishing process of 0.925,0.800 and 0.720 silver alloys in a 0.07 vol.%ammonium sulphide solution for different immersion periods was analyzed by electrochemical impedance spectroscopy(EIS)and scanning electron microscopy(SEM).The polarisation curves showed that the copper content and sulphide increased the corrosion current density and delayed the passivation of silver alloys.The impedance spectra collected at the open circuit potential(OCP)showed a single capacitive,incomplete and depressed loop,indicating that the charge transfer resistance decreased as the copper content increased in the alloys.In contrast,the double-layer capacitance increased as the copper content increased.The SEM-EDS analysis confirmed that the copper-rich phase in the silver alloys was selectively dissolved due to the preference of S to react with Cu,resulting in a localised attack,thus delaying the formation of a passive film.A marked localised attack was observed in alloys with lower copper content.The mechanism for the tarnishing of silver alloys in sulphide media was dependent on the nature of the alloy and the greater affinity of copper for sulphur.The dissolution of Ag and Cu to form corrosion products was proposed as the rate determining step.展开更多
The inter-line dynamic voltage restorer （IDVR） consists of several voltage source inverters connected to different independent distribution feeders with common dc bus. When one of the inverters compensates for volta...The inter-line dynamic voltage restorer （IDVR） consists of several voltage source inverters connected to different independent distribution feeders with common dc bus. When one of the inverters compensates for voltage sag that appears in its feeder （voltage control mode）, the other inverters pump the required power into the dc bus （power control mode）. Each inverter will have both voltage and power controllers; only one controller is in use during the abnormal conditions according to its feeder state. The voltage controller uses one of the dynamic voltage restoration techniques. In this paper, the in-phase technique is applied and two types of loads are considered （constant impedance and three phase induction motor）. Since the voltage restoration process may need real power injection into the distribution system, the power controller injects this power via voltage injection. This voltage injection is simulated by voltage drop across series virtual impedance. A new scheme is proposed to select the impedance value. The impedance value is selected such that the power consumed by this impedance represents the required power to be transferred without perturbing the load voltage. The performance of this system is also studied during voltage swell. A scheme for operation of multi-feeder IDVR system is proposed in this paper. Simulation results substantiate the proposed concept.展开更多
The composites of poly[Ni（salen）] and multi-walled carbon nanotube （MWCNT） were synthesized by pulse potentiostatic method. The composites were characterized by field emission scanning electron microscopy, Fourier...The composites of poly[Ni（salen）] and multi-walled carbon nanotube （MWCNT） were synthesized by pulse potentiostatic method. The composites were characterized by field emission scanning electron microscopy, Fourier transform infrared spectra, and electrochemical impedance spectroscopy. The wrapping of carbon nanotubes with poly[Ni（salen）] varied significantly with anodic pulse duration. Variance of structure of poly[Ni（salen）] caused by anodic pulse duration affected the ability of absorption to solvent molecules or solvated ions, which was indicated by v （C≡N） intensity. The ability to store/release charge of poly[Ni（salen）] caused by redox switching was evaluated in the form of low-frequency capacitance. Correlations of chargetransfer resistance/ionic diffusion resistance with potential and anodic pulse duration were investigated.展开更多
The Co-S/x wt.% AB5 （x=0, 10, 20, 30） composite materials were prepared by simply mixing Co-S material fabricated by hy- drothermal method and AB5 alloy. The structure and morphology of the composite materials were ...The Co-S/x wt.% AB5 （x=0, 10, 20, 30） composite materials were prepared by simply mixing Co-S material fabricated by hy- drothermal method and AB5 alloy. The structure and morphology of the composite materials were characterized by XRD and SEM, respectively. The electrochemical properties of the composite electrodes were studied by the galvanostatic charge, dis- charge test and electrochemical impedance spectroscopy. The results showed that the Co-S/20 wt.% AB5 composite electrode showed the highest discharge capacity and the best cycling stability. The existence of the AB5 alloy improved the electro- chemical activity of composite electrodes, reduced the electrochemical polarization resistances and promoted the electrochem- ical conversion reaction between Co and Co（OH）2. In order to improve the utilization rate of active materials, 0.0! mol/L Na2S203 was added into the electrolyte. The electrochemical properties of the composite electrode were significantly enhanced. After fifty cycles, the discharge capacity of the composite electrode increased from 407 to 481.7 mAh/g and the capacity reten- tion increased from 79.7% to 91.2%.展开更多
基金Projects(50771092,21073162) supported by the National Natural Science Foundation of ChinaProject(2005DKA10400-Z15) supported by the Ministry of Science and Technology of China
文摘The Ni-TiN nanocomposite film was successfully electrodeposited on brass copper substrates.The microstructures of the Ni-TiN nanocomposite film were investigated using scanning electron microscopy（SEM） and transmission electron microscopy（TEM）.Its average grain size was analyzed through X-ray diffraction（XRD）,and its anti-corrosion property was studied through potentiodynamic scanning curves and electrochemical impedance spectroscopy（EIS）.The results show that the morphology of Ni-TiN composite film is sensitively dependent on the electroplating current density,TiN nanoparticle concentration,solution stirring speed,bath temperature and pH value of solution.The average grain size of the optimized nanocomposite film is about 50 nm.Meanwhile,the Ni-TiN nanocomposite films are much more resistant to corrosion than pure Ni coatings.
基金financial support from the Board for Research in Nuclear Sciences (BRNS) (Project number 36(2)/20/02/2014-BRNS/)
文摘The microstructure and corrosion behavior of as-cast and friction stir processed in-situ Al-TiB2 based composite in 3.5 wt.% sodium chloride solution were investigated. The microstructure was characterized using X-ray diffractometry, scanning electron microscopy and electron backscattered diffraction technique while corrosion behavior was evaluated using linear/cyclic potentiodynamic, electrochemical impedance spectroscopy and ASTM–G67 tests. The composite contains sub-micron TiB2 particles in an aluminum matrix with both blocky and fine clusters of Al3Ti agglomerated around TiB2 and displays a low uniform corrosion rate. It is also resistant to pitting as substantiated by the absence of a positive loop in cyclic potentiodynamic tests. This is due to the non-conductive nature of TiB2 particles and a controlled amount of blocky Al3Ti phase. However, both friction stir processed and as-cast composites are susceptible to inter-granular corrosion where Al3Ti and TiB2 at grain boundaries provide initiation sites for corrosion. Electrochemical impedance study attributes this to the adverse effect of Al3Ti and TiB2 on the protective oxide surface film, which increases with immersion time.
基金CONACyT for their support:scholarship to JOC 45653 and the Basic Science Projects 239938LANCIC CONACyT LN 232619,260779 and 271614the Chemistry School at UNAM for the financial support given for this work through the Program for Research and Graduate Studies Sponsorship(PAIP)
文摘Silver and silver alloys usually tarnish,which causes some changes in their aesthetic appearance and electrical properties,due to their exposure to sulphide environments(H2S),and this is a problem in the field of corrosion and conservation of cultural heritage metallic artefacts.In this study,the role of copper content in the tarnishing process of 0.925,0.800 and 0.720 silver alloys in a 0.07 vol.%ammonium sulphide solution for different immersion periods was analyzed by electrochemical impedance spectroscopy(EIS)and scanning electron microscopy(SEM).The polarisation curves showed that the copper content and sulphide increased the corrosion current density and delayed the passivation of silver alloys.The impedance spectra collected at the open circuit potential(OCP)showed a single capacitive,incomplete and depressed loop,indicating that the charge transfer resistance decreased as the copper content increased in the alloys.In contrast,the double-layer capacitance increased as the copper content increased.The SEM-EDS analysis confirmed that the copper-rich phase in the silver alloys was selectively dissolved due to the preference of S to react with Cu,resulting in a localised attack,thus delaying the formation of a passive film.A marked localised attack was observed in alloys with lower copper content.The mechanism for the tarnishing of silver alloys in sulphide media was dependent on the nature of the alloy and the greater affinity of copper for sulphur.The dissolution of Ag and Cu to form corrosion products was proposed as the rate determining step.
文摘The inter-line dynamic voltage restorer （IDVR） consists of several voltage source inverters connected to different independent distribution feeders with common dc bus. When one of the inverters compensates for voltage sag that appears in its feeder （voltage control mode）, the other inverters pump the required power into the dc bus （power control mode）. Each inverter will have both voltage and power controllers; only one controller is in use during the abnormal conditions according to its feeder state. The voltage controller uses one of the dynamic voltage restoration techniques. In this paper, the in-phase technique is applied and two types of loads are considered （constant impedance and three phase induction motor）. Since the voltage restoration process may need real power injection into the distribution system, the power controller injects this power via voltage injection. This voltage injection is simulated by voltage drop across series virtual impedance. A new scheme is proposed to select the impedance value. The impedance value is selected such that the power consumed by this impedance represents the required power to be transferred without perturbing the load voltage. The performance of this system is also studied during voltage swell. A scheme for operation of multi-feeder IDVR system is proposed in this paper. Simulation results substantiate the proposed concept.
基金supports of this work by Beijing Natural Science Foundation(2093039)Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-09-0215)State Key Laboratory of Multiphase Complex Systems (MPCS-2011-D-08)
文摘The composites of poly[Ni（salen）] and multi-walled carbon nanotube （MWCNT） were synthesized by pulse potentiostatic method. The composites were characterized by field emission scanning electron microscopy, Fourier transform infrared spectra, and electrochemical impedance spectroscopy. The wrapping of carbon nanotubes with poly[Ni（salen）] varied significantly with anodic pulse duration. Variance of structure of poly[Ni（salen）] caused by anodic pulse duration affected the ability of absorption to solvent molecules or solvated ions, which was indicated by v （C≡N） intensity. The ability to store/release charge of poly[Ni（salen）] caused by redox switching was evaluated in the form of low-frequency capacitance. Correlations of chargetransfer resistance/ionic diffusion resistance with potential and anodic pulse duration were investigated.
基金supported by the National Natural Science Foundation of China(Grant No.51201089)the Priority Academic Program Development of Jiangsu Higher Education Institutions of China(PAPD)Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20133221110009)
文摘The Co-S/x wt.% AB5 （x=0, 10, 20, 30） composite materials were prepared by simply mixing Co-S material fabricated by hy- drothermal method and AB5 alloy. The structure and morphology of the composite materials were characterized by XRD and SEM, respectively. The electrochemical properties of the composite electrodes were studied by the galvanostatic charge, dis- charge test and electrochemical impedance spectroscopy. The results showed that the Co-S/20 wt.% AB5 composite electrode showed the highest discharge capacity and the best cycling stability. The existence of the AB5 alloy improved the electro- chemical activity of composite electrodes, reduced the electrochemical polarization resistances and promoted the electrochem- ical conversion reaction between Co and Co（OH）2. In order to improve the utilization rate of active materials, 0.0! mol/L Na2S203 was added into the electrolyte. The electrochemical properties of the composite electrode were significantly enhanced. After fifty cycles, the discharge capacity of the composite electrode increased from 407 to 481.7 mAh/g and the capacity reten- tion increased from 79.7% to 91.2%.
