The oxidation of oxygen ions and the generation of an anode effect at a low oxygen content of 150 mg/kg were discussed in this paper.Cyclic voltammetry and square-wave voltammetry tests were conducted to explore the a...The oxidation of oxygen ions and the generation of an anode effect at a low oxygen content of 150 mg/kg were discussed in this paper.Cyclic voltammetry and square-wave voltammetry tests were conducted to explore the anodic processes of LiF-NdF_(3)melt after a lengthy period of pre-electrolysis purification at 1000℃(during which the oxygen content reduced from 413 to 150 mg/kg).The oxidation process of oxygen ions was found to have two stages:oxidation product adsorption and CO/CO_(2)gas evolution.The adsorption stage was controlled by diffusion,whereas the gas evolution was controlled by the electrochemical reaction.In comparison with oxygen content of 413 mg/kg,the decrease in the amplitude of the current at low oxygen content of 150 mg/kg was much gentler during the forward scanning process when the anode effect occurred.Fluorine-ion oxidation peaks that occurred at about 4.2 V vs.Li/Li+could be clearly observed in the reverse scanning processes,in which fluorine ions were oxidized and perfluorocarbons were produced,which resulted in an anode effect.展开更多
The cyclic voltammetry, chronopotentiometry and chronoamperometry were used to study the behaviors of Fe 2+ on Pt, Cu, Ag and Ti electrodes in urea NaBr melt at 373 K. Electroreduction of Fe 2+ to metallic ...The cyclic voltammetry, chronopotentiometry and chronoamperometry were used to study the behaviors of Fe 2+ on Pt, Cu, Ag and Ti electrodes in urea NaBr melt at 373 K. Electroreduction of Fe 2+ to metallic Fe is irreversible in one step. The exchange current density determined on Ti electrode is 2 68×10 -5 A·cm -2 . Sm 3+ does not reduce to Sm alone, but can be inductively codeposited with Fe 2+ . Sm Fe alloy film contained over 90% Sm (mass fraction) can be obtained by potentiostatic electrolysis and galvanostatic electrolysis on Cu substrate. The Sm content in the alloy is related to the cathode potential, current density and the Sm 3+ /Fe 2+ molar ratio. The surface state of the Sm Fe deposit was studied by scanning electron microscopy.展开更多
Many studies have investigated the selective laser melting(SLM)of AlSi10Mg and AlSi7Mg alloys,but there are still lack of researches focused on Al-Si-Mg alloys specifically tailored for SLM.In this work,a novel high M...Many studies have investigated the selective laser melting(SLM)of AlSi10Mg and AlSi7Mg alloys,but there are still lack of researches focused on Al-Si-Mg alloys specifically tailored for SLM.In this work,a novel high Mg-content AlSi8Mg3 alloy was specifically designed for SLM.The results showed that this new alloy exhibited excellent SLM processability with a lowest porosity of 0.07%.Massive lattice distortion led to a high Vickers hardness in samples fabricated at a high laser power due to the precipitation of Mg_(2)Si nanoparticles from theα-Al matrix induced by high-intensity intrinsic heat treatment during SLM.The maximum microhardness and compressive yield strength of the alloy reached HV(211±4)and(526±12)MPa,respectively.After aging treatment at 150℃,the maximum microhardness and compressive yield strength of the samples were further improved to HV(221±4)and(577±5)MPa,respectively.These values are higher than those of most known aluminum alloys fabricated by SLM.This paper provides a new idea for optimizing the mechanical properties of Al-Si-Mg alloys fabricated using SLM.展开更多
TiC/Ni_3Al composites have been prepared using upward infiltration method. The densification was performed by both Ni_3Al melt filling and TiC sintering during the infiltration. The dissolution of TiC in liquid Ni_3A...TiC/Ni_3Al composites have been prepared using upward infiltration method. The densification was performed by both Ni_3Al melt filling and TiC sintering during the infiltration. The dissolution of TiC in liquid Ni_3Al has been evidenced by finding Ni_3(Al,Ti)C after fast cooling in the TiC/Ni_3Al composites. The dissolution may be responsible for the infiltration and sintering. Compared with downward infiltration, the upward infiltration brought about higher strength and fracture toughness and shorter infiltration time. TiC/20 vol. pct Ni_3Al composite processed by upward infiltration had a flexural strength of 1476 MPa with a statistic Weibull modulus of 20.2 and a fracture toughness of 20.4 MPa . Better mechanical properties may be attributed to melt unidirectional movement in upward infiltration.展开更多
Coal ash melting characteristics has a direct impact on the smooth operation of entrained gasifier.Mineral conversion of coal ash is very significant to be investigated,because the mineral can affect the melting tempe...Coal ash melting characteristics has a direct impact on the smooth operation of entrained gasifier.Mineral conversion of coal ash is very significant to be investigated,because the mineral can affect the melting temperature and viscosity under high temperature conditions.In this paper,the effects of different Al2O3/CaO on the mineral conversion,melting temperature and viscosity of Ningdong coal ash are studied by the combination of experiment and simulation.The trend of melting temperature decreases firstly and rises with increasing Al_(2)O_(3)/CaO.The ashmelting point reached to the lowestwhen the ratio is 1.23.XRD and Factsage software are used to analyze crystallization behavior of samples.The results showthat the content of anorthite,albite and corundumincreases and subsequently decreases,while the content of mullite decreases firstly and then rises with increasing Al_(2)O_(3)/CaO.High content with CaO can contribute to form albite and anorthite of low-melting.Besides,high content with Al_(2)O_(3) can tend to produce mullite of high-melting.The results of experimental and simulation are basically the same,which lays a foundation for the melting characteristics of Ningdong coal ash and can provide technical support for the smooth operation of the entrained-gasifier.展开更多
The mixed-valent Pb3Rh7O15 undergoes a Verwey-type transition at Tv≈180K, below which the development of Rh3＋3＋/Rh4＋4＋ charge order induces an abrupt conductor-to-insulator transition in resistivity. Here we inve...The mixed-valent Pb3Rh7O15 undergoes a Verwey-type transition at Tv≈180K, below which the development of Rh3＋3＋/Rh4＋4＋ charge order induces an abrupt conductor-to-insulator transition in resistivity. Here we investigate the effect of pressure on the Verwey-type transition of Pb3Rh7O15 by measuring its electrical resistivity under hydrostatic pressures up to 8GPa with a cubic anvil cell apparatus. We find that the application of high pressure can suppress the Verwey-type transition around 3GPa, above which a metallic state is realized at temperatures below ～70K, suggesting the melting of charge order by pressure. Interestingly, the low-temperature metallic region shrinks gradually upon further increasing pressure and disappears completely at P〉7GPa, which indicates that the charge carriers in Pb3Rh7O15 undergo a reentrant localization under higher pressures. We have constructed a temperature-pressure phase diagram for Pb3Rh7O15 and compared to that of Fe3O4, showing an archetype Verwey transition.展开更多
Based on Archimedes principle, the densities of Na 2WO 4 WO 3 ZnO melts at a fixed mole ratio of 3.43 of Na 2WO 4 to ZnO were measured. The results indicated that there was a linear relationship between the...Based on Archimedes principle, the densities of Na 2WO 4 WO 3 ZnO melts at a fixed mole ratio of 3.43 of Na 2WO 4 to ZnO were measured. The results indicated that there was a linear relationship between the densities and temperatures at a fixed composition. At a fixed temperature, the linear relationship between densities and compositions showed different slop within different composition regions. The reasons were explained in view of ionic composition changes.展开更多
Dissolutionof La in KCl-NaCl and LaCl_3-KCl-NaCl melts has been investigated by means of a transparent cell,cyclic voltammetry and EHMO of quantum chemistry.It is shown that the La dissolved in KCl-NaCl melt exists in...Dissolutionof La in KCl-NaCl and LaCl_3-KCl-NaCl melts has been investigated by means of a transparent cell,cyclic voltammetry and EHMO of quantum chemistry.It is shown that the La dissolved in KCl-NaCl melt exists in a metallic state,the La dissolved in LaCl_3-KCl-NaCl melt can be ionized into La^(2+) as a result of reaction with La^(3+), furthermore,the La^(2+) reacts with La^(3+) forming atom cluster La_m^(n+) which is a stable state in the melt.展开更多
The structure of the La-LaCl_3-KCl molten system at 1223K has been investigated by computer simulation using Monte Carlo method.The partial radial distribution functions of some ion pair as well as the potential and i...The structure of the La-LaCl_3-KCl molten system at 1223K has been investigated by computer simulation using Monte Carlo method.The partial radial distribution functions of some ion pair as well as the potential and internal energy of the system at 1223K have been calculated.The results implies that about 50% of La(Ⅲ)is six coordinated and LaCl_4^(2-) tetrahedron is the predominant configuration for La(Ⅱ). It is also concluded that the distribution of free space in the molten system is not uniform.There exist many fissures and empty holes in the molten salt.展开更多
The molecular dynamics method has been used to study the YCl3 molten salt. The results of the molecular dynamics simulation agree with those of the neutron diffraction experiment. It is found that there are like-octah...The molecular dynamics method has been used to study the YCl3 molten salt. The results of the molecular dynamics simulation agree with those of the neutron diffraction experiment. It is found that there are like-octahedral structure of YCl or its fragment. The diffusion coefficients of Y3+ and Cl- in the YCl3 melt are also calculated.展开更多
With the Voter-Chen version of embedded-atom model （EAM） potential and molecular dynamics, the melting of Ni3Al alloy was simulated by one-phase （conventional） and two-phase approaches. It is shown that the simula...With the Voter-Chen version of embedded-atom model （EAM） potential and molecular dynamics, the melting of Ni3Al alloy was simulated by one-phase （conventional） and two-phase approaches. It is shown that the simulated melting point is dependent on the potential and the simulation method. The structures of the melts obtained by different simulation methods were analyzed by the pair correlation function, the coordination number, and the distribution of atom pair type （indexed by the Honeycutt-Andersen pair analysis technique）. The results show that the structures are very similar.展开更多
The morphology and the formation of Y2BaCuO5 phase in powder melting processed YBa2Cu3O7-x superconductors were investigated. The experimental results show the heat treatment can not change the shape of Y2BaCuO5 parti...The morphology and the formation of Y2BaCuO5 phase in powder melting processed YBa2Cu3O7-x superconductors were investigated. The experimental results show the heat treatment can not change the shape of Y2BaCuO5 particles in powder melting processed samples. The formation of round Y2BaCuO5 phase is due to relative content of each constitution of precursor powders in powder melting process. For powder melting process, the excessive liquid phase is eliminated, which restrains the preferred growth of Y2BaCuO5 particles.展开更多
基金the National Natural Science Foundation of China(No.51774145).The“Minjiang Scholar”Program of Department of Education,Fujian Province,China was also acknowledged.
文摘The oxidation of oxygen ions and the generation of an anode effect at a low oxygen content of 150 mg/kg were discussed in this paper.Cyclic voltammetry and square-wave voltammetry tests were conducted to explore the anodic processes of LiF-NdF_(3)melt after a lengthy period of pre-electrolysis purification at 1000℃(during which the oxygen content reduced from 413 to 150 mg/kg).The oxidation process of oxygen ions was found to have two stages:oxidation product adsorption and CO/CO_(2)gas evolution.The adsorption stage was controlled by diffusion,whereas the gas evolution was controlled by the electrochemical reaction.In comparison with oxygen content of 413 mg/kg,the decrease in the amplitude of the current at low oxygen content of 150 mg/kg was much gentler during the forward scanning process when the anode effect occurred.Fluorine-ion oxidation peaks that occurred at about 4.2 V vs.Li/Li+could be clearly observed in the reverse scanning processes,in which fluorine ions were oxidized and perfluorocarbons were produced,which resulted in an anode effect.
文摘The cyclic voltammetry, chronopotentiometry and chronoamperometry were used to study the behaviors of Fe 2+ on Pt, Cu, Ag and Ti electrodes in urea NaBr melt at 373 K. Electroreduction of Fe 2+ to metallic Fe is irreversible in one step. The exchange current density determined on Ti electrode is 2 68×10 -5 A·cm -2 . Sm 3+ does not reduce to Sm alone, but can be inductively codeposited with Fe 2+ . Sm Fe alloy film contained over 90% Sm (mass fraction) can be obtained by potentiostatic electrolysis and galvanostatic electrolysis on Cu substrate. The Sm content in the alloy is related to the cathode potential, current density and the Sm 3+ /Fe 2+ molar ratio. The surface state of the Sm Fe deposit was studied by scanning electron microscopy.
基金financially supported by the the National Natural Science Foundation of China(Nos.51801079 and 52001140)the Natural Science Foundation for Young Scientists of Jiangsu,China(Nos.BK20180985 and BK20180987)the Open Foundation of Zhenjiang Key Laboratory for High Technology Research on Marine Functional Films(No.ZHZ2019001)。
文摘Many studies have investigated the selective laser melting(SLM)of AlSi10Mg and AlSi7Mg alloys,but there are still lack of researches focused on Al-Si-Mg alloys specifically tailored for SLM.In this work,a novel high Mg-content AlSi8Mg3 alloy was specifically designed for SLM.The results showed that this new alloy exhibited excellent SLM processability with a lowest porosity of 0.07%.Massive lattice distortion led to a high Vickers hardness in samples fabricated at a high laser power due to the precipitation of Mg_(2)Si nanoparticles from theα-Al matrix induced by high-intensity intrinsic heat treatment during SLM.The maximum microhardness and compressive yield strength of the alloy reached HV(211±4)and(526±12)MPa,respectively.After aging treatment at 150℃,the maximum microhardness and compressive yield strength of the samples were further improved to HV(221±4)and(577±5)MPa,respectively.These values are higher than those of most known aluminum alloys fabricated by SLM.This paper provides a new idea for optimizing the mechanical properties of Al-Si-Mg alloys fabricated using SLM.
文摘TiC/Ni_3Al composites have been prepared using upward infiltration method. The densification was performed by both Ni_3Al melt filling and TiC sintering during the infiltration. The dissolution of TiC in liquid Ni_3Al has been evidenced by finding Ni_3(Al,Ti)C after fast cooling in the TiC/Ni_3Al composites. The dissolution may be responsible for the infiltration and sintering. Compared with downward infiltration, the upward infiltration brought about higher strength and fracture toughness and shorter infiltration time. TiC/20 vol. pct Ni_3Al composite processed by upward infiltration had a flexural strength of 1476 MPa with a statistic Weibull modulus of 20.2 and a fracture toughness of 20.4 MPa . Better mechanical properties may be attributed to melt unidirectional movement in upward infiltration.
基金supported by the Key Research and Development Program of Ningxia(2018BCE01004)Natural Science Foundation of Ningxia(2018AAC03013)Discipline Project of Ningxia(NXYLXK2017A04).
文摘Coal ash melting characteristics has a direct impact on the smooth operation of entrained gasifier.Mineral conversion of coal ash is very significant to be investigated,because the mineral can affect the melting temperature and viscosity under high temperature conditions.In this paper,the effects of different Al2O3/CaO on the mineral conversion,melting temperature and viscosity of Ningdong coal ash are studied by the combination of experiment and simulation.The trend of melting temperature decreases firstly and rises with increasing Al_(2)O_(3)/CaO.The ashmelting point reached to the lowestwhen the ratio is 1.23.XRD and Factsage software are used to analyze crystallization behavior of samples.The results showthat the content of anorthite,albite and corundumincreases and subsequently decreases,while the content of mullite decreases firstly and then rises with increasing Al_(2)O_(3)/CaO.High content with CaO can contribute to form albite and anorthite of low-melting.Besides,high content with Al_(2)O_(3) can tend to produce mullite of high-melting.The results of experimental and simulation are basically the same,which lays a foundation for the melting characteristics of Ningdong coal ash and can provide technical support for the smooth operation of the entrained-gasifier.
基金Supported by the"Shi-Pei Ji Hua",the National Science Foundation of China under Grant Nos 51402019 and 11574377the Beijing Natural Science Foundation under Grant No 2152011+5 种基金the National Basic Research Program of China under Grants No2014CB921500the Strategic Priority Research ProgramKey Research Program of Frontier Sciences of the Chinese Academy of Sciences under Grant Nos XDB07020100 and QYZDB-SSW-SLH013the U.S.Department of Energy,Office of Science,Basic Energy Sciences,Materials Sciences and Engineering Divisionthe CEMNSF MRSEC under Grant No DMR-1420451
文摘The mixed-valent Pb3Rh7O15 undergoes a Verwey-type transition at Tv≈180K, below which the development of Rh3＋3＋/Rh4＋4＋ charge order induces an abrupt conductor-to-insulator transition in resistivity. Here we investigate the effect of pressure on the Verwey-type transition of Pb3Rh7O15 by measuring its electrical resistivity under hydrostatic pressures up to 8GPa with a cubic anvil cell apparatus. We find that the application of high pressure can suppress the Verwey-type transition around 3GPa, above which a metallic state is realized at temperatures below ～70K, suggesting the melting of charge order by pressure. Interestingly, the low-temperature metallic region shrinks gradually upon further increasing pressure and disappears completely at P〉7GPa, which indicates that the charge carriers in Pb3Rh7O15 undergo a reentrant localization under higher pressures. We have constructed a temperature-pressure phase diagram for Pb3Rh7O15 and compared to that of Fe3O4, showing an archetype Verwey transition.
文摘Based on Archimedes principle, the densities of Na 2WO 4 WO 3 ZnO melts at a fixed mole ratio of 3.43 of Na 2WO 4 to ZnO were measured. The results indicated that there was a linear relationship between the densities and temperatures at a fixed composition. At a fixed temperature, the linear relationship between densities and compositions showed different slop within different composition regions. The reasons were explained in view of ionic composition changes.
文摘Dissolutionof La in KCl-NaCl and LaCl_3-KCl-NaCl melts has been investigated by means of a transparent cell,cyclic voltammetry and EHMO of quantum chemistry.It is shown that the La dissolved in KCl-NaCl melt exists in a metallic state,the La dissolved in LaCl_3-KCl-NaCl melt can be ionized into La^(2+) as a result of reaction with La^(3+), furthermore,the La^(2+) reacts with La^(3+) forming atom cluster La_m^(n+) which is a stable state in the melt.
文摘The structure of the La-LaCl_3-KCl molten system at 1223K has been investigated by computer simulation using Monte Carlo method.The partial radial distribution functions of some ion pair as well as the potential and internal energy of the system at 1223K have been calculated.The results implies that about 50% of La(Ⅲ)is six coordinated and LaCl_4^(2-) tetrahedron is the predominant configuration for La(Ⅱ). It is also concluded that the distribution of free space in the molten system is not uniform.There exist many fissures and empty holes in the molten salt.
文摘The molecular dynamics method has been used to study the YCl3 molten salt. The results of the molecular dynamics simulation agree with those of the neutron diffraction experiment. It is found that there are like-octahedral structure of YCl or its fragment. The diffusion coefficients of Y3+ and Cl- in the YCl3 melt are also calculated.
基金This study was financially supported by the National Natural Science Foundation of China (No.50431030).
文摘With the Voter-Chen version of embedded-atom model （EAM） potential and molecular dynamics, the melting of Ni3Al alloy was simulated by one-phase （conventional） and two-phase approaches. It is shown that the simulated melting point is dependent on the potential and the simulation method. The structures of the melts obtained by different simulation methods were analyzed by the pair correlation function, the coordination number, and the distribution of atom pair type （indexed by the Honeycutt-Andersen pair analysis technique）. The results show that the structures are very similar.
基金Funded by the National Natural Science Foundation of China (50432050)the National High Technology Research and Development Program of China(2007AA03Z241)
文摘The morphology and the formation of Y2BaCuO5 phase in powder melting processed YBa2Cu3O7-x superconductors were investigated. The experimental results show the heat treatment can not change the shape of Y2BaCuO5 particles in powder melting processed samples. The formation of round Y2BaCuO5 phase is due to relative content of each constitution of precursor powders in powder melting process. For powder melting process, the excessive liquid phase is eliminated, which restrains the preferred growth of Y2BaCuO5 particles.
