Iron-rich electrolytic manganese residue(IREMR)is an industrial waste produced during the processing of electrolytic metal manganese,and it contains certain amounts of Fe and Mn resources and other heavy metals.In thi...Iron-rich electrolytic manganese residue(IREMR)is an industrial waste produced during the processing of electrolytic metal manganese,and it contains certain amounts of Fe and Mn resources and other heavy metals.In this study,the slurry electrolysis technique was used to recover high-purity Fe powder from IREMR.The effects of IREMR and H2SO4 mass ratio,current density,reaction temper-ature,and electrolytic time on the leaching and current efficiencies of Fe were studied.According to the results,high-purity Fe powder can be recovered from the cathode plate,and the slurry electrolyte can be recycled.The leaching efficiency,current efficiency,and purity of Fe reached 92.58%,80.65%,and 98.72wt%,respectively,at a 1:2.5 mass ratio of H2SO4 and IREMR,reaction temperature of 60℃,electric current density of 30 mA/cm^(2),and reaction time of 8 h.In addition,vibrating sample magnetometer(VSM)analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m,which reached the advanced magnetic grade of electrical pure-iron powder(DT4A coercivity standard).The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.展开更多
In this study, a method for preparing pure manganese sulfate from low-grade ores with a granule mean size of 0.47 mm by direct acid leaching was developed. The effects of the types of leaching agents, sulfitric acid c...In this study, a method for preparing pure manganese sulfate from low-grade ores with a granule mean size of 0.47 mm by direct acid leaching was developed. The effects of the types of leaching agents, sulfitric acid concentration, reaction temperature, and agitation rate on the leaching efficiency of manganese were investigated. We observed that sulfuric acid used as a leaching agent provides a similar leach- ing efficiency of manganese and superior selectivity against calcium compared to hydrochloric acid. The optimal leaching conditions in sul- furic acid media were determined; under the optimal conditions, the leaching efficiencies of Mn and Ca were 92.42% and 9.61%, respec- tively. Moreover, the kinetics of manganese leaching indicated that the leaching follows the diffusion-controlled model with an apparent ac- tivation energy of 12.28 kJ·mol-l. The purification conditions of the leaching solution were also discussed. The results show that manganese dioxide is a suitable oxidant of ferrous ions and sodium dimethyldithiocarbamate is an effective precipitant of heavy metals. Finally, through chemical analysis and X-ray diffraction analysis, the obtained product was determined to contain 98% of MnSOa4·H20.展开更多
A low-cost and easily prepared manganese carbonate(Mn CO_3) has been synthesized for catalytic conversion of 5-hydroxymethylfurfural(5-HMF) to 2,5-diformylfuran(DFF). The properties and morphology of the manganese car...A low-cost and easily prepared manganese carbonate(Mn CO_3) has been synthesized for catalytic conversion of 5-hydroxymethylfurfural(5-HMF) to 2,5-diformylfuran(DFF). The properties and morphology of the manganese carbonate were measured by SEM,XRD,TGA,BET and XPS. In this method,no harsh reaction conditions were required,and it was a simple and green process for the oxidation of 5-HMF into DFF. To achieve an optimum DFF yield,different reaction conditions,including reaction temperature,reaction time,catalyst amount,and solvents were investigated. Results from the experiments indicated that the highest DFF yield of 86.9% was obtained at 120 °C under atmospheric oxygen pressure after 6h. Finally,Mn CO_3 could be used at least five times with considerable stability.展开更多
Crystalline manganese carbonate was found to be a versatile green, non corrosive and environmental friendly catalyst for transesterification of vegetable oils. Its use as catalyst in the transesterification process in...Crystalline manganese carbonate was found to be a versatile green, non corrosive and environmental friendly catalyst for transesterification of vegetable oils. Its use as catalyst in the transesterification process involving methanol and vegetable oils (palm, rapeseed, groundnut, coconut and caster oils) resulted in a conversion rate of 80% - 95% in the production of biodiesel. The chemical composition of the obtained biodiesel was studied by GC-MS analysis and showed the presence of linoleic, oleic, palmitic, and stearic acids methyl esters to be the major compounds. Manganese carbonate in comparison with other solid catalysts was found to decrease the reaction time and temperature concomitant with an increase of biodiesel yield. Finally, the effect of various parameters including methanol quantity, catalyst amount, reaction time and temperatures on the production of biodiesel was investigated.展开更多
Precipitation was carried out to obtain manganese carbonate by adding a precipitating agent, sodium carbonate (NaCO<sub>3</sub>). This was followed by calcination of the manganese carbonate (MnCO<sub>...Precipitation was carried out to obtain manganese carbonate by adding a precipitating agent, sodium carbonate (NaCO<sub>3</sub>). This was followed by calcination of the manganese carbonate (MnCO<sub>3</sub>) to obtain manganese dioxide (MnO<sub>2</sub>). For precipitation tests, a pH ranging from 8 to 10, a time of one to two hours, and a temperature of 25°C and 50°C are the parameters that are considered. The calcination of MnCO<sub>3</sub> is carried out under the following conditions: time (1, 2, 3, and 4 hours) and temperature (370°C, 420°C, and 470°C). It should be noted that the temperature range selected for the calcination tests is based on thermodynamic data obtained using the HSC CHEMISTRY software. The results obtained show an effective recovery of manganese at 25°C, in one hour, with a pH of 8.5 with a precipitation yield and manganese content in the precipitate around 98.43% and 24.21%, respectively. During calcination tests, results show an increase in mass loss, for a constant calcination time, as temperature increases. On the other hand, increasing the calcination time at a given temperature causes an increase in mass loss. However, a significant decrease in mass loss is noted at 3 hours of calcination. The highest mass loss is obtained at a temperature of 470°C after 4 hours of calcination.展开更多
Manganese carbonate can be converted to many kinds of manganese oxides when it is aerated in air and oxygen. Pure manganese carbonate can be changed into Mn 3O 4 and γ MnOOH, and manganese carbonate ore can be conver...Manganese carbonate can be converted to many kinds of manganese oxides when it is aerated in air and oxygen. Pure manganese carbonate can be changed into Mn 3O 4 and γ MnOOH, and manganese carbonate ore can be converted to MnO 2 under the air aerating and oxygen aerating circumstances. The oxidation process of manganese carbonate is a changing process of mineral association, and is also a converting process of valence of manganese itself. Not only equilibrium state, but also nonequilibrium state are involved in this whole process. This process is an irreversible heterogeneous complex reaction, and obeys the nonequilibrium thermodynamic model. The oxidation rate of manganese carbonate is controlled by many factors, especially nonmanganese metallic ions which play an important role in the oxidation process of manganese carbonate.展开更多
The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope (HRTEM), scanning elecetron microscopy(SEM ), energy dispersiv...The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope (HRTEM), scanning elecetron microscopy(SEM ), energy dispersive spectrometer (EDS) and X-ray diffraction(XRD) analysis. The existing forms of rare earths (RE) in clean steel were as follows: dissolved in sohd solution, forming inclusion or second phase containing RE (RE-Fe-P, La-P, Fe-La eutectic and Fe-Ce phase). The dissolved La or Ce segregated at grain boundaries. The segregation of both S and P at gram boundaries was reduced with suitable RE content. The impact toughness of the steel was improved obviously. La and Ce had effecets on purifying molten steel and modifying inclusions in clean steel, whereas with excessive La or Ce, La-Fe-P, La-P and Fe-La eutecetic phase or Ce-Fe-P and Fe-Ce intermetallic compound would form along grain boundaries, causing the impact energy to decrease significantly.展开更多
In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnOnanoparticles(α-MnO@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO@C was prepared via a g...In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnOnanoparticles(α-MnO@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO@C was prepared via a gel formation, using maleic acid(CHO) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnOnanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnOelectrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.展开更多
Doping effects of manganese (Mn) on catalytic performance and structure evolution of NiMgO catalysts for synthesis of multi-walled carbon nanotubes (MWCNTs) from methane were investigated for the first time. Addit...Doping effects of manganese (Mn) on catalytic performance and structure evolution of NiMgO catalysts for synthesis of multi-walled carbon nanotubes (MWCNTs) from methane were investigated for the first time. Addition of Mn in NiMgO catalyst can greatly improve the MWCNTs yield. Mno.2NiMgO catalyst among the tested ones gives the highest MWCNTs yield as 2244%, which is two times higher than that of the catalyst without Mn. The structure evolution, reduction behaviors and surface chemical properties of MnNiMgO catalysts with various Mn contents were studied in detail. It was found that the stable solid solution of NiMgO2 formed in NiMgO catalyst was disturbed by the addition of Mn. Instead, another solid solution of MnMg608 is formed. More amount of Ni can be reduced and dispersed on the catalyst surface to be acted as active sites. Importantly, the changes of Ni content on the surface are correlated with the Ni particle size and the outer diameter of MWCNTs, suggesting the controllable synthesis of MWCNTs over MnNiMgO catalysts.展开更多
Nine steels with different deoxidizing degrees and two comparative steels were selected. Their pitting initiation susceptibility was compared by means of potentiodynamic polarization tests in 3wt% NaCl solution. The p...Nine steels with different deoxidizing degrees and two comparative steels were selected. Their pitting initiation susceptibility was compared by means of potentiodynamic polarization tests in 3wt% NaCl solution. The pit propagation rate was evaluated in artificial sea water and 3wt% sea salt solution by simulating occluded corrosion cell (SOCC) test and hanging plate test, respectively. The composition of inclusions and corrosive feature were studied by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and optical microscopy (OM). The results indicate that sulfide inclusions in steel are the sites for pit nucleation. The sulphide inclusions vary in shape from short spindle-like to long strip-like with increasing deoxidizing degree. Under the same conditions, the lower the deoxidizing degree gets, the lower the pitting initiation susceptibility becomes, and the stronger the resistance to pit propagation exhibits. For steels with different deoxidizing degrees, their pitting initiation susceptibility is mainly influenced by thermodynamic stability, while the pit propagation rate is primarily subject to the characteristics of inclusions in steel.展开更多
Manuscript received 30 July 1999 Abstract The shielded metal arc welding (SMAW) of a manganese steel part as a crossing of railway track to a carbon steel part as the rails of the railroad is the welding of dissimil...Manuscript received 30 July 1999 Abstract The shielded metal arc welding (SMAW) of a manganese steel part as a crossing of railway track to a carbon steel part as the rails of the railroad is the welding of dissimilar steel. It are was known that it is not possible to the the rail of railroad directly to the cross- ing of railway track made from a steel containing about 14% of manganese (wt. ) because of so many differences between the two kinds of steels such as composition, microstructure,mechanical properties and weldability.A method was used to solve the problem by presetting an intermediate layer on each side of the joint and other special procedures were used.The result of test indicated that a good weld joint was obtained.展开更多
The online flow injection preconcentration and electrothermal atomic absorption spectrometry method were used for the determination of trace nickel in electrolytic manganese samples by sorption on a conical minicolumn...The online flow injection preconcentration and electrothermal atomic absorption spectrometry method were used for the determination of trace nickel in electrolytic manganese samples by sorption on a conical minicolumn packed with activated carbon at pH 9.0. The nickel was eluted from the minicolumn with 10%(v/v) nitric acid. An enrichment factor of 190-fold for a sample volume of 10mL was obtained. The detection limit (DL) of nickel with the use of the preconcentration method was 13ng·g -1in the original solid sample. The precision for 10 replicate determinations at 150ng·g -1 nickel concentration was 5.2% relative standard deviation (RSD). The calibration graph was linear with a correlation coefficient of r=0.9996 up to concentration of 660ng·g -1 nickel.展开更多
The rare earth elements(REE)geochemistry and the isotope(δ^(13)C,δ^(18)O)composition of manganese ores of the Chiatura(Georgia)deposit were studied.One of the major features of all types of manganese ores is negativ...The rare earth elements(REE)geochemistry and the isotope(δ^(13)C,δ^(18)O)composition of manganese ores of the Chiatura(Georgia)deposit were studied.One of the major features of all types of manganese ores is negative cerium(Ce/Ce*_(PAAS))anomaly and the absence of europium(Eu/Eu*_(PAAS))anomaly.Oxide oolitic manganese ores were formed in oxic shallow marine environments.The content and distribution of REEs(in particular Ce and Eu)in these ores are connected mainly with ferrous oxides.The performed C-and O-isotope research in Mn-carbonates(oolitic and massive)has indicated that carbonate ores were formed by the participation of isotopic ally light CO_(2)which is a result of the oxidation of organic matter in the sediment strata by reducing environments of early diagenesis(and,partially,catagenesis)zone.Obtained negative cerium anomalies in the studied carbonate ores reflect the specific REE patterns in pore waters of sediments of earlier isdiagenesis zone of the Oligocene Chiatura's basin.The deficiency of cerium in this zone remains debatable and requires further study.Formation of manganese carbonates took place multistage by the input of incisional solutions of different chemistry into sea bottom waters and sediments.The absence of europium anomaly indicates about lack of hydrothermal solution input.展开更多
The multiwall carbon nanotube (MWCNT) bonded to 2, 9, 16, 23-tetraamino manganese phthalocyanine (TAMnPc) was obtained by covalent functionalization, and its chemical structure was characterized by TEM. The photocondu...The multiwall carbon nanotube (MWCNT) bonded to 2, 9, 16, 23-tetraamino manganese phthalocyanine (TAMnPc) was obtained by covalent functionalization, and its chemical structure was characterized by TEM. The photoconductivity of single-layered photoreceptors, where MWCNT bonded by TAMnPc (MWCNT-b-TAMnPc) served as the charge generation material (CGM), was also studied.展开更多
Using high temperature carbon tube furnace, reduction of manganese ore pellets containing carbon was investigated. The reaction was divided into two stages at five minutes after reaction, and the kinetics model of red...Using high temperature carbon tube furnace, reduction of manganese ore pellets containing carbon was investigated. The reaction was divided into two stages at five minutes after reaction, and the kinetics model of reduction process was established. The experimental results showed that, the reaction rate in the earlier stage was controlled by the chemical reactions between FeO, MnO and carbon reductant, and the activation energy was 28.85 KJ/mol. In the later stage, as the carbon reductant replaced by CO, the reaction rate was controlled by CO-diffusing in solid products, and the cor- responding activation energy was 86.56 KJ/mol. Reaction rate of the later stage was less than the earlier one.展开更多
The effect of RE-modifier on the microstructure and mechanical properties of high carbon-medium manganese steel has been investigated in present work.The results showed that the RE-modifier can refine the crystalline ...The effect of RE-modifier on the microstructure and mechanical properties of high carbon-medium manganese steel has been investigated in present work.The results showed that the RE-modifier can refine the crystalline grain of high-carbon medium-manganese steel.The shape and distribution of carbides are improved and the columnar grains and phosphide in grain boundary are eliminated.Consequently,the impact toughness of the steel is increased by more than one time,compared with no addition of RE-modifier.展开更多
Electrochemistry experiments were made on carbon-manganese clean steel with rare earths Ce and La respectively to observe corrosion parameters such as corrosion current i_(corr), and characteristic potential of pittin...Electrochemistry experiments were made on carbon-manganese clean steel with rare earths Ce and La respectively to observe corrosion parameters such as corrosion current i_(corr), and characteristic potential of pitting E_b. The results indicate that the rare earths have effect on corrosion resisting properties of carbon-manganese clean steel, and the optimum contents of La is about 0.011% (mass fraction) and Ce about 0.014% (mass fraction) respectively. The change of corrosion resistance is related to the action of rare earths on microstructure and effect on surface state of samples in the process of polarization.展开更多
Ten studied steels including different carbon content, silicon content, and manganese content were deformed in compression over a temperature range of 600 ?C to 1 000 ?C at the strain rate of 1 s-1. The curves of the ...Ten studied steels including different carbon content, silicon content, and manganese content were deformed in compression over a temperature range of 600 ?C to 1 000 ?C at the strain rate of 1 s-1. The curves of the mean flow stressdeformation temperature were drawn up. The mean flow stresses of higher carbon content steels decreased continuously as the applied deformation temperature increased in the whole temperature range, while the mean flow stress of lowest carbon steel displayed an abrupt drop near the two phases region. The reason for the abrupt drop phenomena was explained as the result of phase transformation. The mean flow stresses of steels with high silicon content and low manganese content also have this phenomena.展开更多
基金supported by the Key Research and Development Program of Guangxi Province,China (No.AB23075174)the National Natural Science Foundation of China (No.52174386)the Science and Technology Plan Project of Sichuan Province,China (No.2022YFS0459).
文摘Iron-rich electrolytic manganese residue(IREMR)is an industrial waste produced during the processing of electrolytic metal manganese,and it contains certain amounts of Fe and Mn resources and other heavy metals.In this study,the slurry electrolysis technique was used to recover high-purity Fe powder from IREMR.The effects of IREMR and H2SO4 mass ratio,current density,reaction temper-ature,and electrolytic time on the leaching and current efficiencies of Fe were studied.According to the results,high-purity Fe powder can be recovered from the cathode plate,and the slurry electrolyte can be recycled.The leaching efficiency,current efficiency,and purity of Fe reached 92.58%,80.65%,and 98.72wt%,respectively,at a 1:2.5 mass ratio of H2SO4 and IREMR,reaction temperature of 60℃,electric current density of 30 mA/cm^(2),and reaction time of 8 h.In addition,vibrating sample magnetometer(VSM)analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m,which reached the advanced magnetic grade of electrical pure-iron powder(DT4A coercivity standard).The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.
基金supported by the National Natural Science Foundation of China (51374249)
文摘In this study, a method for preparing pure manganese sulfate from low-grade ores with a granule mean size of 0.47 mm by direct acid leaching was developed. The effects of the types of leaching agents, sulfitric acid concentration, reaction temperature, and agitation rate on the leaching efficiency of manganese were investigated. We observed that sulfuric acid used as a leaching agent provides a similar leach- ing efficiency of manganese and superior selectivity against calcium compared to hydrochloric acid. The optimal leaching conditions in sul- furic acid media were determined; under the optimal conditions, the leaching efficiencies of Mn and Ca were 92.42% and 9.61%, respec- tively. Moreover, the kinetics of manganese leaching indicated that the leaching follows the diffusion-controlled model with an apparent ac- tivation energy of 12.28 kJ·mol-l. The purification conditions of the leaching solution were also discussed. The results show that manganese dioxide is a suitable oxidant of ferrous ions and sodium dimethyldithiocarbamate is an effective precipitant of heavy metals. Finally, through chemical analysis and X-ray diffraction analysis, the obtained product was determined to contain 98% of MnSOa4·H20.
基金supported by the Natural Science Foundation of Tianjin (No. 16JCYBJC19600)the National Natural Science Foundation of China (No. 21621004)the Beiyang Young Scholar of Tianjin University (2012)
文摘A low-cost and easily prepared manganese carbonate(Mn CO_3) has been synthesized for catalytic conversion of 5-hydroxymethylfurfural(5-HMF) to 2,5-diformylfuran(DFF). The properties and morphology of the manganese carbonate were measured by SEM,XRD,TGA,BET and XPS. In this method,no harsh reaction conditions were required,and it was a simple and green process for the oxidation of 5-HMF into DFF. To achieve an optimum DFF yield,different reaction conditions,including reaction temperature,reaction time,catalyst amount,and solvents were investigated. Results from the experiments indicated that the highest DFF yield of 86.9% was obtained at 120 °C under atmospheric oxygen pressure after 6h. Finally,Mn CO_3 could be used at least five times with considerable stability.
文摘Crystalline manganese carbonate was found to be a versatile green, non corrosive and environmental friendly catalyst for transesterification of vegetable oils. Its use as catalyst in the transesterification process involving methanol and vegetable oils (palm, rapeseed, groundnut, coconut and caster oils) resulted in a conversion rate of 80% - 95% in the production of biodiesel. The chemical composition of the obtained biodiesel was studied by GC-MS analysis and showed the presence of linoleic, oleic, palmitic, and stearic acids methyl esters to be the major compounds. Manganese carbonate in comparison with other solid catalysts was found to decrease the reaction time and temperature concomitant with an increase of biodiesel yield. Finally, the effect of various parameters including methanol quantity, catalyst amount, reaction time and temperatures on the production of biodiesel was investigated.
文摘Precipitation was carried out to obtain manganese carbonate by adding a precipitating agent, sodium carbonate (NaCO<sub>3</sub>). This was followed by calcination of the manganese carbonate (MnCO<sub>3</sub>) to obtain manganese dioxide (MnO<sub>2</sub>). For precipitation tests, a pH ranging from 8 to 10, a time of one to two hours, and a temperature of 25°C and 50°C are the parameters that are considered. The calcination of MnCO<sub>3</sub> is carried out under the following conditions: time (1, 2, 3, and 4 hours) and temperature (370°C, 420°C, and 470°C). It should be noted that the temperature range selected for the calcination tests is based on thermodynamic data obtained using the HSC CHEMISTRY software. The results obtained show an effective recovery of manganese at 25°C, in one hour, with a pH of 8.5 with a precipitation yield and manganese content in the precipitate around 98.43% and 24.21%, respectively. During calcination tests, results show an increase in mass loss, for a constant calcination time, as temperature increases. On the other hand, increasing the calcination time at a given temperature causes an increase in mass loss. However, a significant decrease in mass loss is noted at 3 hours of calcination. The highest mass loss is obtained at a temperature of 470°C after 4 hours of calcination.
文摘Manganese carbonate can be converted to many kinds of manganese oxides when it is aerated in air and oxygen. Pure manganese carbonate can be changed into Mn 3O 4 and γ MnOOH, and manganese carbonate ore can be converted to MnO 2 under the air aerating and oxygen aerating circumstances. The oxidation process of manganese carbonate is a changing process of mineral association, and is also a converting process of valence of manganese itself. Not only equilibrium state, but also nonequilibrium state are involved in this whole process. This process is an irreversible heterogeneous complex reaction, and obeys the nonequilibrium thermodynamic model. The oxidation rate of manganese carbonate is controlled by many factors, especially nonmanganese metallic ions which play an important role in the oxidation process of manganese carbonate.
基金Project supported by the Ministry of Science and Technology of China (2002BA315A-5)
文摘The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope (HRTEM), scanning elecetron microscopy(SEM ), energy dispersive spectrometer (EDS) and X-ray diffraction(XRD) analysis. The existing forms of rare earths (RE) in clean steel were as follows: dissolved in sohd solution, forming inclusion or second phase containing RE (RE-Fe-P, La-P, Fe-La eutectic and Fe-Ce phase). The dissolved La or Ce segregated at grain boundaries. The segregation of both S and P at gram boundaries was reduced with suitable RE content. The impact toughness of the steel was improved obviously. La and Ce had effecets on purifying molten steel and modifying inclusions in clean steel, whereas with excessive La or Ce, La-Fe-P, La-P and Fe-La eutecetic phase or Ce-Fe-P and Fe-Ce intermetallic compound would form along grain boundaries, causing the impact energy to decrease significantly.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(2014R1A2A1A10050821)
文摘In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnOnanoparticles(α-MnO@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO@C was prepared via a gel formation, using maleic acid(CHO) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnOnanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnOelectrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.
基金supported by the National Natural Science Foundation of China(20776089)the Fundamental Research Funds for the Central Universities(2014NZYQN20)
文摘Doping effects of manganese (Mn) on catalytic performance and structure evolution of NiMgO catalysts for synthesis of multi-walled carbon nanotubes (MWCNTs) from methane were investigated for the first time. Addition of Mn in NiMgO catalyst can greatly improve the MWCNTs yield. Mno.2NiMgO catalyst among the tested ones gives the highest MWCNTs yield as 2244%, which is two times higher than that of the catalyst without Mn. The structure evolution, reduction behaviors and surface chemical properties of MnNiMgO catalysts with various Mn contents were studied in detail. It was found that the stable solid solution of NiMgO2 formed in NiMgO catalyst was disturbed by the addition of Mn. Instead, another solid solution of MnMg608 is formed. More amount of Ni can be reduced and dispersed on the catalyst surface to be acted as active sites. Importantly, the changes of Ni content on the surface are correlated with the Ni particle size and the outer diameter of MWCNTs, suggesting the controllable synthesis of MWCNTs over MnNiMgO catalysts.
文摘Nine steels with different deoxidizing degrees and two comparative steels were selected. Their pitting initiation susceptibility was compared by means of potentiodynamic polarization tests in 3wt% NaCl solution. The pit propagation rate was evaluated in artificial sea water and 3wt% sea salt solution by simulating occluded corrosion cell (SOCC) test and hanging plate test, respectively. The composition of inclusions and corrosive feature were studied by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and optical microscopy (OM). The results indicate that sulfide inclusions in steel are the sites for pit nucleation. The sulphide inclusions vary in shape from short spindle-like to long strip-like with increasing deoxidizing degree. Under the same conditions, the lower the deoxidizing degree gets, the lower the pitting initiation susceptibility becomes, and the stronger the resistance to pit propagation exhibits. For steels with different deoxidizing degrees, their pitting initiation susceptibility is mainly influenced by thermodynamic stability, while the pit propagation rate is primarily subject to the characteristics of inclusions in steel.
文摘Manuscript received 30 July 1999 Abstract The shielded metal arc welding (SMAW) of a manganese steel part as a crossing of railway track to a carbon steel part as the rails of the railroad is the welding of dissimilar steel. It are was known that it is not possible to the the rail of railroad directly to the cross- ing of railway track made from a steel containing about 14% of manganese (wt. ) because of so many differences between the two kinds of steels such as composition, microstructure,mechanical properties and weldability.A method was used to solve the problem by presetting an intermediate layer on each side of the joint and other special procedures were used.The result of test indicated that a good weld joint was obtained.
文摘The online flow injection preconcentration and electrothermal atomic absorption spectrometry method were used for the determination of trace nickel in electrolytic manganese samples by sorption on a conical minicolumn packed with activated carbon at pH 9.0. The nickel was eluted from the minicolumn with 10%(v/v) nitric acid. An enrichment factor of 190-fold for a sample volume of 10mL was obtained. The detection limit (DL) of nickel with the use of the preconcentration method was 13ng·g -1in the original solid sample. The precision for 10 replicate determinations at 150ng·g -1 nickel concentration was 5.2% relative standard deviation (RSD). The calibration graph was linear with a correlation coefficient of r=0.9996 up to concentration of 660ng·g -1 nickel.
基金accomplished in accordance with the Research Program of the Geological Institute of the Russian Academy of Sciences。
文摘The rare earth elements(REE)geochemistry and the isotope(δ^(13)C,δ^(18)O)composition of manganese ores of the Chiatura(Georgia)deposit were studied.One of the major features of all types of manganese ores is negative cerium(Ce/Ce*_(PAAS))anomaly and the absence of europium(Eu/Eu*_(PAAS))anomaly.Oxide oolitic manganese ores were formed in oxic shallow marine environments.The content and distribution of REEs(in particular Ce and Eu)in these ores are connected mainly with ferrous oxides.The performed C-and O-isotope research in Mn-carbonates(oolitic and massive)has indicated that carbonate ores were formed by the participation of isotopic ally light CO_(2)which is a result of the oxidation of organic matter in the sediment strata by reducing environments of early diagenesis(and,partially,catagenesis)zone.Obtained negative cerium anomalies in the studied carbonate ores reflect the specific REE patterns in pore waters of sediments of earlier isdiagenesis zone of the Oligocene Chiatura's basin.The deficiency of cerium in this zone remains debatable and requires further study.Formation of manganese carbonates took place multistage by the input of incisional solutions of different chemistry into sea bottom waters and sediments.The absence of europium anomaly indicates about lack of hydrothermal solution input.
文摘The multiwall carbon nanotube (MWCNT) bonded to 2, 9, 16, 23-tetraamino manganese phthalocyanine (TAMnPc) was obtained by covalent functionalization, and its chemical structure was characterized by TEM. The photoconductivity of single-layered photoreceptors, where MWCNT bonded by TAMnPc (MWCNT-b-TAMnPc) served as the charge generation material (CGM), was also studied.
文摘Using high temperature carbon tube furnace, reduction of manganese ore pellets containing carbon was investigated. The reaction was divided into two stages at five minutes after reaction, and the kinetics model of reduction process was established. The experimental results showed that, the reaction rate in the earlier stage was controlled by the chemical reactions between FeO, MnO and carbon reductant, and the activation energy was 28.85 KJ/mol. In the later stage, as the carbon reductant replaced by CO, the reaction rate was controlled by CO-diffusing in solid products, and the cor- responding activation energy was 86.56 KJ/mol. Reaction rate of the later stage was less than the earlier one.
基金supported by the Synchrotron Light Research Institute(Public Organization)Thailand(GS-54-D01)+7 种基金the Commission on Higher EducationMinistry of EducationThailandperformed under the project"Sustainable Chemical Synthesis(Sus Chem Sys)"which is co-financed by the European Regional Development Fund(ERDF)the state of North Rhine-WestphaliaGermanyunder the Operational Programme"Regional Competitiveness and Employment"2007–2013
文摘The effect of RE-modifier on the microstructure and mechanical properties of high carbon-medium manganese steel has been investigated in present work.The results showed that the RE-modifier can refine the crystalline grain of high-carbon medium-manganese steel.The shape and distribution of carbides are improved and the columnar grains and phosphide in grain boundary are eliminated.Consequently,the impact toughness of the steel is increased by more than one time,compared with no addition of RE-modifier.
文摘Electrochemistry experiments were made on carbon-manganese clean steel with rare earths Ce and La respectively to observe corrosion parameters such as corrosion current i_(corr), and characteristic potential of pitting E_b. The results indicate that the rare earths have effect on corrosion resisting properties of carbon-manganese clean steel, and the optimum contents of La is about 0.011% (mass fraction) and Ce about 0.014% (mass fraction) respectively. The change of corrosion resistance is related to the action of rare earths on microstructure and effect on surface state of samples in the process of polarization.
基金Funded by Shanghai Pujiang Program(No.16PJ1430200)
文摘Ten studied steels including different carbon content, silicon content, and manganese content were deformed in compression over a temperature range of 600 ?C to 1 000 ?C at the strain rate of 1 s-1. The curves of the mean flow stressdeformation temperature were drawn up. The mean flow stresses of higher carbon content steels decreased continuously as the applied deformation temperature increased in the whole temperature range, while the mean flow stress of lowest carbon steel displayed an abrupt drop near the two phases region. The reason for the abrupt drop phenomena was explained as the result of phase transformation. The mean flow stresses of steels with high silicon content and low manganese content also have this phenomena.