The surface of ZrO2 nanoparticles was modified by styrene coupling grafting method to improve the dispersion and interaction of the nanoparticles with the epoxy coating in which the modified ZrO2 nanoparticles were us...The surface of ZrO2 nanoparticles was modified by styrene coupling grafting method to improve the dispersion and interaction of the nanoparticles with the epoxy coating in which the modified ZrO2 nanoparticles were used as an additive. The grafting performance and microstructure of the nano- ZrO2/epoxy coating were analyzed by Fourier transformation infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The corrosion behavior of the nano-ZrO2/epoxy coating on mild steel was evaluated in neutral 3.5 wt% NaC1 solution using electrochemical impedance spectroscopy （EIS）. Both the coating capacitance and coating resistance fitted by the equivalent circuit from EIS were used to evaluate the protective performance of the coating towards the mild steel. The results show a superior stability and efficient corrosion protection by the modified ZrO2 nanoparticles. The epoxy coating containing 2 wt% modified ZrO2 nanoparticles exhibited the best corrosion performance among all the coating specimens. This research may provide an insight into the protection of mild steel using modified epoxy coatings.展开更多
Experiments were designed to simulate the corrosion of a low-carbon steel exposed to a marine splash zone. The composition and morphology of the rust were investigated using Raman spectroscopy, X-ray photoelectron spe...Experiments were designed to simulate the corrosion of a low-carbon steel exposed to a marine splash zone. The composition and morphology of the rust were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive spectrometry and scanning electron microscopy. Corrosion resistance of the rust films was demonstrated by the electrochemical impedance spectroscopy. The wettability of the steel surface was calculated from the data conceruing the wetting degree and the conductivity. The results showed that, in the initial stage, the products of the outer rust layer were mainly made up of Fe（Ⅲ） oxyhydroxide, while the main component of the inner rust layer was magnetite. With an increase in the corrosion time, the inner rust layer continuously turned into the outer rust layer. In addition, both rust layers became dense, thus playing a protective role with respect to matrix. The existence of the rust layer significantly prolonged the residence time of the seawater on the sample surface, a result that tends to improve the cathodic protection effect for steel structures exposed to marine splash zones.展开更多
The effect of the grain orientation on corrosion behavior of rolled AZ31 magnesium alloy is investigated in this study. The test samples have a similar surface roughness to the Mg alloy in practical application. The i...The effect of the grain orientation on corrosion behavior of rolled AZ31 magnesium alloy is investigated in this study. The test samples have a similar surface roughness to the Mg alloy in practical application. The immersion test and electrochemical impedance spectroscopy show that the TD-ND planes dominated by （101-0）, （1120） and （1011） oriented grains show a higher corrosion resistance compared with these of the RD-TD planes which consist mainly of （0001） oriented grains. Here, RD, ND and TD represent the rolling direction, the normal direction and the transverse direction of the alloy sheet, respectively. The surface morphologies of the alloys at various immersion stages are observed by scanning electron microscopy, and the surface topography of the alloy substitutes is also observed by laser scanning confocal microscopy. The TD-ND planes show a regular corrosion along the TD direction, but the RD-TD plane shows an irregular corrosion.展开更多
For many years, intermetallic materials promise applications in a wide variety of technology areas. NiAl intermetallic compound is material that exhibits important characteristics such as high corrosion resistance and...For many years, intermetallic materials promise applications in a wide variety of technology areas. NiAl intermetallic compound is material that exhibits important characteristics such as high corrosion resistance and low density besides its ability to retain strength and stiffness at elevated temperatures. However NiAl intermetallic is too hard, brittle and exhibits very low ductility at room temperature being the reason because this material is not yet available for structural applications. In order to increase the ductility of the NiAl intermetallic compound, the addition of a third alloying element has been proved, nevertheless it is important to determine if such additions decrease or increase the hardness and the corrosion resistance of the alloy. So, the present investigation reports the corrosion performance of the NiAl intermetallic compound modified with Cu, emphasizing the EIS analysis and the relation between physical parameters and the modelling equations used in the Equivalent Electric Circuit. It was found that the addition of Cu promotes the formation of the γ’-Ni<sub>3</sub>Al phase in Cu contents greater than 15 at. %, in addition to a decrease in micro hardness and an increment in the I<sub>corr</sub> values. In this way, the electrochemical characterization evidenced a high corrosion resistance of these intermetallic alloys.展开更多
The corrosion behavior of plasma sprayed 8YSZ （ZrO2 stabilized by 8 wt.% Y2O3） coating on the surface of carbon steel in seawater was investigated. The electrochemical impedance spectroscopy was used as a non-destru...The corrosion behavior of plasma sprayed 8YSZ （ZrO2 stabilized by 8 wt.% Y2O3） coating on the surface of carbon steel in seawater was investigated. The electrochemical impedance spectroscopy was used as a non-destructive evaluation technique to monitor the protection properties of the coating when it was immersed in seawater, and corrosion products were characterized by scanning electron microscopy, energy dispersive spectrometry and X-ray photoelectron spectroscopy. The results indicated that three time constants were obtained dur ing the initial immersion period, and then a new time constant appeared due to the formation of rust layer, which was corresponding to the corrosion process. Corrosion products were formed on the coating surface as well as inside the coating, and the crystalline composition of the rust layer mainly consisted of γ-FeOOH.展开更多
The properties orAl based nanocomposite metal foams and their corrosion behaviors were investigated in this study. For this, the composite metal foams with different relative densities （porosity） reinforced with alu...The properties orAl based nanocomposite metal foams and their corrosion behaviors were investigated in this study. For this, the composite metal foams with different relative densities （porosity） reinforced with alumina nanoparticles were prepared using a powder me- tallurgy-based sintering-dissolution process （SDP） and NaC1 particles were used as space holders. Then, the effect of nanoparticle rein- forcement and different amounts of NaC1 space holders （corresponding porosity） on the microstructure, morphology, density, hardness, and electrochemical specifications of the samples were investigated. It was found that as the relative density increased from 60% to 70%, the wall thickness increased from about 200 to 300 pro, which led to a decrease in pore size. Also, the addition of nanoparticle reinforcement and the increased relative density result in increasing metal foam hardness. Moreover, electrochemical test results indicated that increasing the A1203 content reduced the corrosion rate, but increasing the porosity enhanced it.展开更多
The electrochemical behaviors of n-type silicon wafers pH value and solid content of the slurry on the corrosion of silicon in silica-based slurry were investigated, and the influences of the wafers were studied by us...The electrochemical behaviors of n-type silicon wafers pH value and solid content of the slurry on the corrosion of silicon in silica-based slurry were investigated, and the influences of the wafers were studied by using electrochemical DC polarization and AC impedance techniques. The results revealed that these factors affected the corrosion behaviors of silicon wafers to different degrees and had their suitable parameters that made the maximum corrosion rate of the wafers. The corrosion potential of （100） sttrface was lower than that of（111）, whereas the current density of （100） was much higher than that of（111）.展开更多
In this paper, the adsorption process of calmodulin (CaM) on Au substrate was first investigated with electrochemical impedance spectroscopy (EIS) method. The result reveals that the adsorption of the protein-calmodu...In this paper, the adsorption process of calmodulin (CaM) on Au substrate was first investigated with electrochemical impedance spectroscopy (EIS) method. The result reveals that the adsorption of the protein-calmodulin contains two steps, i.e., one short quick step followed by a slow one. The complexation of calmodulin with Ca2+ was also first probed using EIS technique, in which the complexation of CaM with Ca2+ could be reflected by the change of apparent membrane capacitance(Capp) clearly. In all above measurements, a redox couple Fe(CN)63-/ Fe(CN)64- was used as probing-pin to reflect all the changes occurring in the above process. Our work suggests that some biological processes of CaM could be studied using EIS method conveniently.展开更多
In the present work, novel blend polymer electrolyte membranes using poly(vinyl alcohol) (PVA), doped with hypophosphorous acid (H3PO2) and reinforced with porous niobium oxide (Nb2O5) microparticles in different comp...In the present work, novel blend polymer electrolyte membranes using poly(vinyl alcohol) (PVA), doped with hypophosphorous acid (H3PO2) and reinforced with porous niobium oxide (Nb2O5) microparticles in different compositions were prepared by the solution-casting technique. Their phase behavior and ionic conductivity were studied by differential scanning calorimetric (DSC), thermogravimetric analysis (TGA) and impedance spectroscopy (IS) in the radio-frequency range. Using a constant H3PO2/PVA weigh ratio of 0.25, it was found that the water content in the blended hydrogel membranes increased with increasing the filler Nb2O5 content, thus increasing the electrical conductivity. However, the suitable weight ratio of Nb2O5:(H3PO2/PVA) for the blend performance (both mechanically and electrically) was x = 0.075, with a maximum ionic conductivity of 2.7?× 10﹣3 S·cm﹣1 at 120°C. For all blends prepared, the lost tangent plots show asymmetrical peaks, as a consequence of correlations in the mobile ion diffusion as a function of frequency. Although this “universal dynamic response” was observed at all temperatures, variations in the tan(δ) relaxation peaks indicate a decrease of ionic correlation when the temperature is increased. Both the dc conductivity and tan(δ) peaks frequency dependency are thermally activated, following an Arrhenius-type behavior with activation energy of the same order, indicating that the corresponding ionic processes have the same origin, i.e., proton jump among available sites in the polymer matrix. The additions of oxide particles to the membranes improve their thermal and electrical properties, attributed to an approximation effect.展开更多
New steels with different carbon contents were self-developed by thermo-mechanical controlled processing. The effects of the carbon content and the microstructure on the corrosion properties of new steels were investi...New steels with different carbon contents were self-developed by thermo-mechanical controlled processing. The effects of the carbon content and the microstructure on the corrosion properties of new steels were investigated by immersion test and SEM. The results indicated that the ferrite phase （both the proeutectoid and eutectoid ferrite） dissolved preferentially. Cementite reserved and accumulated on the surface. As carbon content increased, the content of ferrite decreased and cathode/anode area ratio increased. Therefore, the corrosion rate of new steels increased from 0.30 to 0.90 mm/years when the carbon content rose from 0.05 to 0.13 wt%. The corrosion process of new steels was studied using electrochemical impedance spectroscopy experiments during 72 h. It indicated that the impedance modulus IZlo.ol nz of the new steels reduces with the increase of the immersion time. While the corrosion process of the new steel with 0.11 wt% C developed faster than that with 0.07 wt% C, although their IZlo.ol nz was similar at the initial stage.展开更多
The semiconductive characteristics of clectron-transfrring proteins in living cells E coli was investigated by electrochemsical impedance spectroscopy(EIS). We found that the electrochemical impedance of living cells ...The semiconductive characteristics of clectron-transfrring proteins in living cells E coli was investigated by electrochemsical impedance spectroscopy(EIS). We found that the electrochemical impedance of living cells as a function of temprature followed the Arrhenius equation for semiconductors. This result shows a strong evidence to prove the semiconductive behavior of proteins展开更多
基金Supported by the National Department Public Benefit Research Foundation(No.201005028)the National Key Technology Research and Development Program during the Twelfth Five-Year Plan Period of China(No.2012BAB15B01)
文摘The surface of ZrO2 nanoparticles was modified by styrene coupling grafting method to improve the dispersion and interaction of the nanoparticles with the epoxy coating in which the modified ZrO2 nanoparticles were used as an additive. The grafting performance and microstructure of the nano- ZrO2/epoxy coating were analyzed by Fourier transformation infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The corrosion behavior of the nano-ZrO2/epoxy coating on mild steel was evaluated in neutral 3.5 wt% NaC1 solution using electrochemical impedance spectroscopy （EIS）. Both the coating capacitance and coating resistance fitted by the equivalent circuit from EIS were used to evaluate the protective performance of the coating towards the mild steel. The results show a superior stability and efficient corrosion protection by the modified ZrO2 nanoparticles. The epoxy coating containing 2 wt% modified ZrO2 nanoparticles exhibited the best corrosion performance among all the coating specimens. This research may provide an insight into the protection of mild steel using modified epoxy coatings.
基金supported by the National Science Foundation of China(No.41576076)the National Environmental Corrosion Platform(NECP)the National Key Basic Research Program(‘‘973 Program,’’No.2014CB643300)
文摘Experiments were designed to simulate the corrosion of a low-carbon steel exposed to a marine splash zone. The composition and morphology of the rust were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive spectrometry and scanning electron microscopy. Corrosion resistance of the rust films was demonstrated by the electrochemical impedance spectroscopy. The wettability of the steel surface was calculated from the data conceruing the wetting degree and the conductivity. The results showed that, in the initial stage, the products of the outer rust layer were mainly made up of Fe（Ⅲ） oxyhydroxide, while the main component of the inner rust layer was magnetite. With an increase in the corrosion time, the inner rust layer continuously turned into the outer rust layer. In addition, both rust layers became dense, thus playing a protective role with respect to matrix. The existence of the rust layer significantly prolonged the residence time of the seawater on the sample surface, a result that tends to improve the cathodic protection effect for steel structures exposed to marine splash zones.
基金financially supported by Fundamental Research Funds for the Central Universities(No. CDJZR14130009)Scientific and Technological Project of Chongqing Science and Technology Commission(No.CSTC2012GGB50003)Demonstrative Project of Chongqing Science and Technology Commission(No.CSCT2014FAZKTJCSF50004)
文摘The effect of the grain orientation on corrosion behavior of rolled AZ31 magnesium alloy is investigated in this study. The test samples have a similar surface roughness to the Mg alloy in practical application. The immersion test and electrochemical impedance spectroscopy show that the TD-ND planes dominated by （101-0）, （1120） and （1011） oriented grains show a higher corrosion resistance compared with these of the RD-TD planes which consist mainly of （0001） oriented grains. Here, RD, ND and TD represent the rolling direction, the normal direction and the transverse direction of the alloy sheet, respectively. The surface morphologies of the alloys at various immersion stages are observed by scanning electron microscopy, and the surface topography of the alloy substitutes is also observed by laser scanning confocal microscopy. The TD-ND planes show a regular corrosion along the TD direction, but the RD-TD plane shows an irregular corrosion.
文摘For many years, intermetallic materials promise applications in a wide variety of technology areas. NiAl intermetallic compound is material that exhibits important characteristics such as high corrosion resistance and low density besides its ability to retain strength and stiffness at elevated temperatures. However NiAl intermetallic is too hard, brittle and exhibits very low ductility at room temperature being the reason because this material is not yet available for structural applications. In order to increase the ductility of the NiAl intermetallic compound, the addition of a third alloying element has been proved, nevertheless it is important to determine if such additions decrease or increase the hardness and the corrosion resistance of the alloy. So, the present investigation reports the corrosion performance of the NiAl intermetallic compound modified with Cu, emphasizing the EIS analysis and the relation between physical parameters and the modelling equations used in the Equivalent Electric Circuit. It was found that the addition of Cu promotes the formation of the γ’-Ni<sub>3</sub>Al phase in Cu contents greater than 15 at. %, in addition to a decrease in micro hardness and an increment in the I<sub>corr</sub> values. In this way, the electrochemical characterization evidenced a high corrosion resistance of these intermetallic alloys.
基金Project supported by Lotus Scholars Program of Hunan (50825204) National Natural Science Foundation of China (21001017)
文摘The corrosion behavior of plasma sprayed 8YSZ （ZrO2 stabilized by 8 wt.% Y2O3） coating on the surface of carbon steel in seawater was investigated. The electrochemical impedance spectroscopy was used as a non-destructive evaluation technique to monitor the protection properties of the coating when it was immersed in seawater, and corrosion products were characterized by scanning electron microscopy, energy dispersive spectrometry and X-ray photoelectron spectroscopy. The results indicated that three time constants were obtained dur ing the initial immersion period, and then a new time constant appeared due to the formation of rust layer, which was corresponding to the corrosion process. Corrosion products were formed on the coating surface as well as inside the coating, and the crystalline composition of the rust layer mainly consisted of γ-FeOOH.
文摘The properties orAl based nanocomposite metal foams and their corrosion behaviors were investigated in this study. For this, the composite metal foams with different relative densities （porosity） reinforced with alumina nanoparticles were prepared using a powder me- tallurgy-based sintering-dissolution process （SDP） and NaC1 particles were used as space holders. Then, the effect of nanoparticle rein- forcement and different amounts of NaC1 space holders （corresponding porosity） on the microstructure, morphology, density, hardness, and electrochemical specifications of the samples were investigated. It was found that as the relative density increased from 60% to 70%, the wall thickness increased from about 200 to 300 pro, which led to a decrease in pore size. Also, the addition of nanoparticle reinforcement and the increased relative density result in increasing metal foam hardness. Moreover, electrochemical test results indicated that increasing the A1203 content reduced the corrosion rate, but increasing the porosity enhanced it.
基金This study was financially supported by the National Natural Science Foundation of China (No.59925412)the Natural Science Foundation of Hunan Province of China (No.03JJY3015).
文摘The electrochemical behaviors of n-type silicon wafers pH value and solid content of the slurry on the corrosion of silicon in silica-based slurry were investigated, and the influences of the wafers were studied by using electrochemical DC polarization and AC impedance techniques. The results revealed that these factors affected the corrosion behaviors of silicon wafers to different degrees and had their suitable parameters that made the maximum corrosion rate of the wafers. The corrosion potential of （100） sttrface was lower than that of（111）, whereas the current density of （100） was much higher than that of（111）.
文摘In this paper, the adsorption process of calmodulin (CaM) on Au substrate was first investigated with electrochemical impedance spectroscopy (EIS) method. The result reveals that the adsorption of the protein-calmodulin contains two steps, i.e., one short quick step followed by a slow one. The complexation of calmodulin with Ca2+ was also first probed using EIS technique, in which the complexation of CaM with Ca2+ could be reflected by the change of apparent membrane capacitance(Capp) clearly. In all above measurements, a redox couple Fe(CN)63-/ Fe(CN)64- was used as probing-pin to reflect all the changes occurring in the above process. Our work suggests that some biological processes of CaM could be studied using EIS method conveniently.
文摘In the present work, novel blend polymer electrolyte membranes using poly(vinyl alcohol) (PVA), doped with hypophosphorous acid (H3PO2) and reinforced with porous niobium oxide (Nb2O5) microparticles in different compositions were prepared by the solution-casting technique. Their phase behavior and ionic conductivity were studied by differential scanning calorimetric (DSC), thermogravimetric analysis (TGA) and impedance spectroscopy (IS) in the radio-frequency range. Using a constant H3PO2/PVA weigh ratio of 0.25, it was found that the water content in the blended hydrogel membranes increased with increasing the filler Nb2O5 content, thus increasing the electrical conductivity. However, the suitable weight ratio of Nb2O5:(H3PO2/PVA) for the blend performance (both mechanically and electrically) was x = 0.075, with a maximum ionic conductivity of 2.7?× 10﹣3 S·cm﹣1 at 120°C. For all blends prepared, the lost tangent plots show asymmetrical peaks, as a consequence of correlations in the mobile ion diffusion as a function of frequency. Although this “universal dynamic response” was observed at all temperatures, variations in the tan(δ) relaxation peaks indicate a decrease of ionic correlation when the temperature is increased. Both the dc conductivity and tan(δ) peaks frequency dependency are thermally activated, following an Arrhenius-type behavior with activation energy of the same order, indicating that the corresponding ionic processes have the same origin, i.e., proton jump among available sites in the polymer matrix. The additions of oxide particles to the membranes improve their thermal and electrical properties, attributed to an approximation effect.
基金the financial support from the National Natural Science Foundation of China(Nos. 51171025 and 51271023)Fundamental Research Funds for the Central Universities(No.FRF-TP-12-144A)the National Network of Field Observation & Scientific Research on Material Environmental Corrosion
文摘New steels with different carbon contents were self-developed by thermo-mechanical controlled processing. The effects of the carbon content and the microstructure on the corrosion properties of new steels were investigated by immersion test and SEM. The results indicated that the ferrite phase （both the proeutectoid and eutectoid ferrite） dissolved preferentially. Cementite reserved and accumulated on the surface. As carbon content increased, the content of ferrite decreased and cathode/anode area ratio increased. Therefore, the corrosion rate of new steels increased from 0.30 to 0.90 mm/years when the carbon content rose from 0.05 to 0.13 wt%. The corrosion process of new steels was studied using electrochemical impedance spectroscopy experiments during 72 h. It indicated that the impedance modulus IZlo.ol nz of the new steels reduces with the increase of the immersion time. While the corrosion process of the new steel with 0.11 wt% C developed faster than that with 0.07 wt% C, although their IZlo.ol nz was similar at the initial stage.
基金Shaanxi Provincial Science and Technology Plan Project(2010K10-08)the Scientific Research Project of Education Department of Shaanxi Province(2013JK0906)+1 种基金the Fund of Beijing Area Key Laboratory of Opto-Mechatronic Equipment Technology(KF2013-01)the Fund of Shaanxi Key Laboratory of Optoelectronic Functional Materials and Devices(ZSKJ201302)
文摘The semiconductive characteristics of clectron-transfrring proteins in living cells E coli was investigated by electrochemsical impedance spectroscopy(EIS). We found that the electrochemical impedance of living cells as a function of temprature followed the Arrhenius equation for semiconductors. This result shows a strong evidence to prove the semiconductive behavior of proteins
