Metal ions like Fe（Ⅲ） were testified to be efficient co-photocatalyst in the field of environmental governance. Hence, a series of BiPO_4/Fe（Ⅲ） materials were prepared via a hydrothermal method and impregnation....Metal ions like Fe（Ⅲ） were testified to be efficient co-photocatalyst in the field of environmental governance. Hence, a series of BiPO_4/Fe（Ⅲ） materials were prepared via a hydrothermal method and impregnation. The experimental results indicated that normal organic dye was effectively removed by BiPO_4 with the presence of Fe（Ⅲ） as a co-photocatalyst. The enhanced removal mechanism was attributed to the easy transfer of photo-induced electron-hole pairs and relatively high productivity of active redical by synergism of Fe（Ⅲ）.展开更多
Fe3O4 nanoparticles were prepared by chemistry co-precipitation and the mean crystal size was 17.9 nm measured by XRD. After it had been treated by silane-coupling agents KH570, magnetic micro-spheres dispersed in org...Fe3O4 nanoparticles were prepared by chemistry co-precipitation and the mean crystal size was 17.9 nm measured by XRD. After it had been treated by silane-coupling agents KH570, magnetic micro-spheres dispersed in organic medium glycol were gained and the mean size of Fe3O4 nanopowders was 33.7 nm. So it can be concluded that magnetic micro-sphere is made of a few Fe3O4 crystals. Many factors of modification were researched, such as the time of ball milling, the content of Fe3O4 and the content of KH570. The modification of Fe3O4 is relative to the time of ball milling, but the dominant function is affected by the content of Fe3O4 and KH570. When the content of Fe3O4 is known, there is a suitable content of KH570. Different content of Fe3O4 will make the different suitable content of KH570, but the range of latter is less than former, which is relative to the distribution of KH570 on Fe3O4 surface or in the solution.展开更多
The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electro...The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electrolyte,Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3),utilizing cyclic voltammetry and square wave voltammetry techniques.The results show that Fe(Ⅲ)reduction occurs in two steps:Fe(Ⅲ)+e^(−)→Fe(Ⅱ),Fe(Ⅱ)+2e^(−)→Fe,and that the redox process of Fe(Ⅲ)/Fe(Ⅱ)at the tungsten electrode is an irreversible reaction controlled by diffusion.The diffusion coefficients of Fe(Ⅲ)in the molten Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)in the temperature range of 1248–1278 K are between 1.86×10^(−6)cm^(2)/s and 1.58×10^(−4)cm^(2)/s.The diffusion activation energy of Fe(Ⅲ)in the molten salt is 1825.41 kJ/mol.As confirmed by XRD analysis,potentiostatic electrolysis at−0.857 V(vs.O_(2)/O_(complex)^(2-))for 6 h produces metallic iron on the cathode.展开更多
The surface organic modification of Fe3O4 nanoparticles with silane coupling reagent KH570 was studied. The modified and unmodified nanoparticles were characterized by FT-IR, XPS and TEM. The spectra of FT-IR and XPS ...The surface organic modification of Fe3O4 nanoparticles with silane coupling reagent KH570 was studied. The modified and unmodified nanoparticles were characterized by FT-IR, XPS and TEM. The spectra of FT-IR and XPS revealed that KH570 was coated onto the surface of Fe3O4 nanoparticles to get Fe-O- Si bond and an organic coating layer also was formed. Fe3O4 nanoparticles were spheres partly with mean size of 18,8 nm studied by TEM, which was consistent with the result 17.9 nm calculated by Scherrer＇s equation. KH570 was adsorbed on surface and formed chemistry bond to be steric hindrance repulsion which prevented nanoparticles from reuniting. Then glycol-based Fe3O4 magnetic liquids dispersed stably was gained.展开更多
Fe(Ⅲ)has been proved to be a more eff ective oxidant than dissolved oxygen at ambient temperature,however,the role of Fe(Ⅲ)in pyrite acidic pressure oxidation was rarely discussed so far.In this paper,in-situ electr...Fe(Ⅲ)has been proved to be a more eff ective oxidant than dissolved oxygen at ambient temperature,however,the role of Fe(Ⅲ)in pyrite acidic pressure oxidation was rarely discussed so far.In this paper,in-situ electrochemical investigation was performed using a flow-through autoclave system in acidic pressure oxidation environment.The results illustrated that increasing Fe(Ⅲ)concentrations led to raising in redox potential of the solution,and decreased passivation of pyrite caused by deposition of elemental sulfur.Reduction of Fe(Ⅲ)at pyrite surface was a fast reaction with low activation energy,it was only slightly promoted by rising temperatures.While,the oxidation rate of pyrite at all investigated Fe(Ⅲ)concentrations increased obviously with rising temperatures,the anodic reaction was the rate-limiting step in the overall reaction.Activation energy of pyrite oxidation decreased from 47.74 to 28.79 kJ/mol when Fe(Ⅲ)concentration was increased from 0.05 to 0.50 g/L,showing that the reaction kinetics were limited by the rate of electrochemical reaction at low Fe(Ⅲ)concentrations,while,it gradually turned to be diffusion control with increasing Fe(Ⅲ)concentrations.展开更多
The effects of Sr,Mg,Cr,Sr/Mg and Sr/Cr combined additions on the Fe-containing intermetallic phase in a recycled Al-Si-Fe cast alloy are investigated.The experimental results show that the additions of Cr and Sr/Cr s...The effects of Sr,Mg,Cr,Sr/Mg and Sr/Cr combined additions on the Fe-containing intermetallic phase in a recycled Al-Si-Fe cast alloy are investigated.The experimental results show that the additions of Cr and Sr/Cr successfully modified the platelet and flake-likeβ-Al-5FeSi phases （β-compound） into the fibrousα-Al-8Fe-2Si （α-compound）.The additions of Sr and Sr/Mg were less effective to modify theβ-compound into theα-compound,while the eutectic Si was fully modified into the fibrous morphology.A small secondary dendrite arm spacing （DAS） was found in the Sr-added,Cr-added and Sr/Cr-added alloys,especially in a steel mold.The Sr,Sr/Cr and Sr/Mg combined additions modify the eutectic Si simultaneously.A sludge phase was found in the addition of Cr-added,Sr/Cr-added and Mg-added alloys,especially in the graphite mold casting.The volume fraction ofβ-compounds was decreased by the addition of various modifying elements. The Cr and Sr/Cr combined additions are very effective to modify theβ-compound for the recycled Al-Si-Fe based alloys.展开更多
Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe^2＋ and Fe^3＋ in an ammonia solution, and its size was about 36 nm measured by an atomic force microscope. Fe3O4 magnetic nanoparticles were modifi...Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe^2＋ and Fe^3＋ in an ammonia solution, and its size was about 36 nm measured by an atomic force microscope. Fe3O4 magnetic nanoparticles were modified by L-dopa or dopamine using sonication method. The analysis of FTIR clearly indicated the formation of Fe-O-C bond. Direct immobilization of trypsin （EC： 3.4.21.4） on Fe3O4 magnetic nanoparticles with L-dopa and dopamine spacer was investigated using glutaraldehyde as a coupling agent. No significant changes in the size and magnetic property of the three kinds of magnetic nanoparticles linked with or without trypsin were observed. The existence of the spacer molecule on magnetic nanoparticles could greatly improve the activity and the storage stability of bound trypsin through increasing the flexibility of enzyme and changing the microenvironment on nanoparticles surface compared to the naked magnetic nanoparticles.展开更多
The short-range repulsive interactions of any force field must be modified to be applicable for high energy atomic collisions because of extremely far from equilibrium state when used in molecular dynamics(MD)simulati...The short-range repulsive interactions of any force field must be modified to be applicable for high energy atomic collisions because of extremely far from equilibrium state when used in molecular dynamics(MD)simulations.In this work,the short-range repulsive interaction of a reactive force field(ReaxFF),describing Fe-Ni-Al alloy system,is well modified by adding a tabulated function form based on Ziegler-Biersack-Littmark(ZBL)potential.The modified interaction covers three ranges,including short range,smooth range,and primordial range.The short range is totally predominated by ZBL potential.The primordial range means the interactions in this range is the as-is ReaxFF with no changes.The smooth range links the short-range ZBL and primordial-range ReaxFF potentials with a taper function.Both energies and forces are guaranteed to be continuous,and qualified to the consistent requirement in LAMMPS.This modified force field is applicable for simulations of energetic particle bombardments and reproducing point defects'booming and recombination effectively.展开更多
Effect of ion nitriding modification on surface hardness, corrosion resistance and magnetostriction of （Tb0.3Dy0.7）Fe1.95 alloy was investigated. Results demonstrated that a 100-200 nm thick nitrided layer was forme...Effect of ion nitriding modification on surface hardness, corrosion resistance and magnetostriction of （Tb0.3Dy0.7）Fe1.95 alloy was investigated. Results demonstrated that a 100-200 nm thick nitrided layer was formed on the sample surface by ion nitriding treatment, which improved obviously surface hardness, wear, and corrosion resistance properties of （Tb0.3Dy0.7）Fe1.95 alloys. The surface hardness was increased from HV587 to HV622 after ion nitriding at 650 K for 6 h. Furthermore, ion nitriding treatment had almost no influence on mag- netostrictive performance as the nitrided layer was quite thin and the treatment temperature was not too high. The results might provide us a new approach for surface modification of （Tb0.3Dy0.7）Fe1.95 alloy.展开更多
An efficient porous spherical polyethyleneimine-cellulose （PEI-cell） absorbent was synthesized and char- acterized. The main influencing factors and adsorption mechanism for two typical metal ions, Cr3＋ and Fe3＋, ...An efficient porous spherical polyethyleneimine-cellulose （PEI-cell） absorbent was synthesized and char- acterized. The main influencing factors and adsorption mechanism for two typical metal ions, Cr3＋ and Fe3＋, were investigated. The adsorption performance primarily depends on the initial concentration of metal ions, pH value and temperature, and the chelation action between N atoms of PEl-cell and metal ions plays an important role. Under dynamic adsorption conditions, the saturation adsorption of polyethyleneimine-cellulose is 83.98 mg.g-1 for Cr（Ⅲ） and 377.19 mg-g-1 for Fe（Ⅲ）, higher than report- ed data and that of unmodified cellulose. The adsorption can be well described with second-order kinetic equation and Freundlich adsorption model, and AH, AG and 5 of the adsorption are all negative. With 5% HCI as eluent, the elution ratio of Cr（Ill） and Fe（llI） achieved 99.88% and 97.74% at 313 K, respectively. After the porous PEI-cell was reused 6 times, it still presented satisfactory adsorption performance. Above results show the advantages such as easily-acquired raw material, high efficiency, stable recycling oerformance and biodegradability.展开更多
The influence of cooling rate and Fe-containing phases on Sr-modification of Si phases in hypoeutectic Al-Si alloys, a problem with great industrial importance, was investigated. The microstructures of samples were ex...The influence of cooling rate and Fe-containing phases on Sr-modification of Si phases in hypoeutectic Al-Si alloys, a problem with great industrial importance, was investigated. The microstructures of samples were examined using scanning electron microscopy(SEM) with energy-dispersive X-ray spectroscopy(EDX). A new method of electron probe microanalysis(EPMA) map scanning was used to analyze the Sr distribution, which gave quantitative results covering more Si particles. EPMA map scanning, together with SEM with EDX, was also used in analyzing the distribution of Fe phases. Results show that Fe-containing phase was related to the unmodified Si particles in samples with partial modification failure and the plate-like Si phases in samples without modification failure. Such a relationship was further confirmed by the microstructure observation.In conclusion, a partial failure of Sr-modification can be caused by both slow cooling rate and Fe-containing phases.展开更多
Modification conditions determine the surface topography and the active material phase composition of a catalyst.To study the influence of modification on a carbon-based sorbent,coconut husk activated carbon(AC)which ...Modification conditions determine the surface topography and the active material phase composition of a catalyst.To study the influence of modification on a carbon-based sorbent,coconut husk activated carbon(AC)which was activated using HNO3 and modified by FeSO4 and Fe(NO3)3 was examined.The pore textures and surface chemical characteristics of the carbon materials were examined by scanning electron microscopy(SEM),Brunner-Emmet-Teller(BET),X-ray diffraction(XRD)and Fourier transform infrared(FTIR)spectroscopy.The surface topography,the pore structure,active materials,and functional groups of AC,AC modificated by HNO3(HNO3/AC for short),and AC modificated by FeSO4 and Fe(NO3)3(Fe/AC for short)were systematically studied.Subsequently,the mechanism of modifying the conditions for the carbon materials was determined.Results showed that the surface micro topography of HNO3/AC became unsystematic and disordered.After modification with FeSO4,the ferriferous oxide was mainly present as a near-spherical crystal.Ferriferous oxides from Fe(NO3)3 modification mainly exhibited a plate shape.HNO3 modification could enlarge the pores but decrease the specific surface area of AC.FeSO4 modification resulted in a new net post structure in the pore canal of AC.Fe(NO3)3 modification caused the pore space structure to develop in the interior,and a higher calcination temperature was useful for ablation.The ash content of the AC was substantially reduced upon HNO3 modification.Upon FeSO4 modification,α-FeOOH,α-Fe2O3 andγ-Fe2O3 coexisted under the condition of a lower concentration of FeSO4 and a lower calcination temperature,and a higher FeSO4 concentration and calcination temperature generated moreα-Fe2O3.The same Fe(NO3)3 modification and a higher calcination temperature were beneficial to the minor chipping formation ofγ-Fe2O3.A higher Fe(NO3)3 loading produced a lower graphitization degree.HNO3 modification formed various new oxygen-containing functional groups and few nitrogen-containing groups.Based on the cover,FeSO4 and Fe(NO3)3 modification could decrease the oxygen-containing and nitrogen-containing functional groups.These results could optimize the modification condition and improve physical and chemical properties of carbon-based sorbents.展开更多
基金the National Natural Science Foundation of China(21507155 and 41201255)the Natural Science Foundation of Hubei Province of China(No.2014CFB807)
文摘Metal ions like Fe（Ⅲ） were testified to be efficient co-photocatalyst in the field of environmental governance. Hence, a series of BiPO_4/Fe（Ⅲ） materials were prepared via a hydrothermal method and impregnation. The experimental results indicated that normal organic dye was effectively removed by BiPO_4 with the presence of Fe（Ⅲ） as a co-photocatalyst. The enhanced removal mechanism was attributed to the easy transfer of photo-induced electron-hole pairs and relatively high productivity of active redical by synergism of Fe（Ⅲ）.
基金This work was financially supported by the Graduate Innovation Plan Projects of Jiangsu Province in 2005.
文摘Fe3O4 nanoparticles were prepared by chemistry co-precipitation and the mean crystal size was 17.9 nm measured by XRD. After it had been treated by silane-coupling agents KH570, magnetic micro-spheres dispersed in organic medium glycol were gained and the mean size of Fe3O4 nanopowders was 33.7 nm. So it can be concluded that magnetic micro-sphere is made of a few Fe3O4 crystals. Many factors of modification were researched, such as the time of ball milling, the content of Fe3O4 and the content of KH570. The modification of Fe3O4 is relative to the time of ball milling, but the dominant function is affected by the content of Fe3O4 and KH570. When the content of Fe3O4 is known, there is a suitable content of KH570. Different content of Fe3O4 will make the different suitable content of KH570, but the range of latter is less than former, which is relative to the distribution of KH570 on Fe3O4 surface or in the solution.
基金Project(52074084)supported by the National Natural Science Foundation of China。
文摘The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electrolyte,Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3),utilizing cyclic voltammetry and square wave voltammetry techniques.The results show that Fe(Ⅲ)reduction occurs in two steps:Fe(Ⅲ)+e^(−)→Fe(Ⅱ),Fe(Ⅱ)+2e^(−)→Fe,and that the redox process of Fe(Ⅲ)/Fe(Ⅱ)at the tungsten electrode is an irreversible reaction controlled by diffusion.The diffusion coefficients of Fe(Ⅲ)in the molten Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)in the temperature range of 1248–1278 K are between 1.86×10^(−6)cm^(2)/s and 1.58×10^(−4)cm^(2)/s.The diffusion activation energy of Fe(Ⅲ)in the molten salt is 1825.41 kJ/mol.As confirmed by XRD analysis,potentiostatic electrolysis at−0.857 V(vs.O_(2)/O_(complex)^(2-))for 6 h produces metallic iron on the cathode.
基金the Natural Science Fund of Jiangsu province (No.BK2007586)Jiangsu Planned Projects(No.0701012B)for Postdoctoral Research Funds
文摘The surface organic modification of Fe3O4 nanoparticles with silane coupling reagent KH570 was studied. The modified and unmodified nanoparticles were characterized by FT-IR, XPS and TEM. The spectra of FT-IR and XPS revealed that KH570 was coated onto the surface of Fe3O4 nanoparticles to get Fe-O- Si bond and an organic coating layer also was formed. Fe3O4 nanoparticles were spheres partly with mean size of 18,8 nm studied by TEM, which was consistent with the result 17.9 nm calculated by Scherrer＇s equation. KH570 was adsorbed on surface and formed chemistry bond to be steric hindrance repulsion which prevented nanoparticles from reuniting. Then glycol-based Fe3O4 magnetic liquids dispersed stably was gained.
基金supported by the Science and Technology Foundation of Guizhou Province,China(No.[2020]1Y163)the National Natural Science Foundation of China(No.41827802).
文摘Fe(Ⅲ)has been proved to be a more eff ective oxidant than dissolved oxygen at ambient temperature,however,the role of Fe(Ⅲ)in pyrite acidic pressure oxidation was rarely discussed so far.In this paper,in-situ electrochemical investigation was performed using a flow-through autoclave system in acidic pressure oxidation environment.The results illustrated that increasing Fe(Ⅲ)concentrations led to raising in redox potential of the solution,and decreased passivation of pyrite caused by deposition of elemental sulfur.Reduction of Fe(Ⅲ)at pyrite surface was a fast reaction with low activation energy,it was only slightly promoted by rising temperatures.While,the oxidation rate of pyrite at all investigated Fe(Ⅲ)concentrations increased obviously with rising temperatures,the anodic reaction was the rate-limiting step in the overall reaction.Activation energy of pyrite oxidation decreased from 47.74 to 28.79 kJ/mol when Fe(Ⅲ)concentration was increased from 0.05 to 0.50 g/L,showing that the reaction kinetics were limited by the rate of electrochemical reaction at low Fe(Ⅲ)concentrations,while,it gradually turned to be diffusion control with increasing Fe(Ⅲ)concentrations.
文摘The effects of Sr,Mg,Cr,Sr/Mg and Sr/Cr combined additions on the Fe-containing intermetallic phase in a recycled Al-Si-Fe cast alloy are investigated.The experimental results show that the additions of Cr and Sr/Cr successfully modified the platelet and flake-likeβ-Al-5FeSi phases （β-compound） into the fibrousα-Al-8Fe-2Si （α-compound）.The additions of Sr and Sr/Mg were less effective to modify theβ-compound into theα-compound,while the eutectic Si was fully modified into the fibrous morphology.A small secondary dendrite arm spacing （DAS） was found in the Sr-added,Cr-added and Sr/Cr-added alloys,especially in a steel mold.The Sr,Sr/Cr and Sr/Mg combined additions modify the eutectic Si simultaneously.A sludge phase was found in the addition of Cr-added,Sr/Cr-added and Mg-added alloys,especially in the graphite mold casting.The volume fraction ofβ-compounds was decreased by the addition of various modifying elements. The Cr and Sr/Cr combined additions are very effective to modify theβ-compound for the recycled Al-Si-Fe based alloys.
基金the Key Technologies R&D Program of Hubei Province(No.2005AA301B14)
文摘Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe^2＋ and Fe^3＋ in an ammonia solution, and its size was about 36 nm measured by an atomic force microscope. Fe3O4 magnetic nanoparticles were modified by L-dopa or dopamine using sonication method. The analysis of FTIR clearly indicated the formation of Fe-O-C bond. Direct immobilization of trypsin （EC： 3.4.21.4） on Fe3O4 magnetic nanoparticles with L-dopa and dopamine spacer was investigated using glutaraldehyde as a coupling agent. No significant changes in the size and magnetic property of the three kinds of magnetic nanoparticles linked with or without trypsin were observed. The existence of the spacer molecule on magnetic nanoparticles could greatly improve the activity and the storage stability of bound trypsin through increasing the flexibility of enzyme and changing the microenvironment on nanoparticles surface compared to the naked magnetic nanoparticles.
基金Project supported by the National Magnetic Confinement Fusion Energy Research Project(Grant Nos.2019YFE03120003,2018YFE0307100,and 2017YFE0302500)the National Natural Science Foundation of China(Grant Nos.11975034,11921006,12004010,and U20B2025).
文摘The short-range repulsive interactions of any force field must be modified to be applicable for high energy atomic collisions because of extremely far from equilibrium state when used in molecular dynamics(MD)simulations.In this work,the short-range repulsive interaction of a reactive force field(ReaxFF),describing Fe-Ni-Al alloy system,is well modified by adding a tabulated function form based on Ziegler-Biersack-Littmark(ZBL)potential.The modified interaction covers three ranges,including short range,smooth range,and primordial range.The short range is totally predominated by ZBL potential.The primordial range means the interactions in this range is the as-is ReaxFF with no changes.The smooth range links the short-range ZBL and primordial-range ReaxFF potentials with a taper function.Both energies and forces are guaranteed to be continuous,and qualified to the consistent requirement in LAMMPS.This modified force field is applicable for simulations of energetic particle bombardments and reproducing point defects'booming and recombination effectively.
基金supported by National High-Tech R&D Program (2006AA03Z106)Beijing Natural Science Foundation (2062012)National Natural Science Foundation (50801006)
文摘Effect of ion nitriding modification on surface hardness, corrosion resistance and magnetostriction of （Tb0.3Dy0.7）Fe1.95 alloy was investigated. Results demonstrated that a 100-200 nm thick nitrided layer was formed on the sample surface by ion nitriding treatment, which improved obviously surface hardness, wear, and corrosion resistance properties of （Tb0.3Dy0.7）Fe1.95 alloys. The surface hardness was increased from HV587 to HV622 after ion nitriding at 650 K for 6 h. Furthermore, ion nitriding treatment had almost no influence on mag- netostrictive performance as the nitrided layer was quite thin and the treatment temperature was not too high. The results might provide us a new approach for surface modification of （Tb0.3Dy0.7）Fe1.95 alloy.
基金Supported by the National Natural Science Foundation of China(81373284,81102344)the Project of Education Department in Sichuan(14ZB0267)the Bureau of Science and Technology of Mianyang City of China(10Y003-8)
文摘An efficient porous spherical polyethyleneimine-cellulose （PEI-cell） absorbent was synthesized and char- acterized. The main influencing factors and adsorption mechanism for two typical metal ions, Cr3＋ and Fe3＋, were investigated. The adsorption performance primarily depends on the initial concentration of metal ions, pH value and temperature, and the chelation action between N atoms of PEl-cell and metal ions plays an important role. Under dynamic adsorption conditions, the saturation adsorption of polyethyleneimine-cellulose is 83.98 mg.g-1 for Cr（Ⅲ） and 377.19 mg-g-1 for Fe（Ⅲ）, higher than report- ed data and that of unmodified cellulose. The adsorption can be well described with second-order kinetic equation and Freundlich adsorption model, and AH, AG and 5 of the adsorption are all negative. With 5% HCI as eluent, the elution ratio of Cr（Ill） and Fe（llI） achieved 99.88% and 97.74% at 313 K, respectively. After the porous PEI-cell was reused 6 times, it still presented satisfactory adsorption performance. Above results show the advantages such as easily-acquired raw material, high efficiency, stable recycling oerformance and biodegradability.
基金supported by the International Science & Technology Cooperation Program of China(No.2015DFR50470)
文摘The influence of cooling rate and Fe-containing phases on Sr-modification of Si phases in hypoeutectic Al-Si alloys, a problem with great industrial importance, was investigated. The microstructures of samples were examined using scanning electron microscopy(SEM) with energy-dispersive X-ray spectroscopy(EDX). A new method of electron probe microanalysis(EPMA) map scanning was used to analyze the Sr distribution, which gave quantitative results covering more Si particles. EPMA map scanning, together with SEM with EDX, was also used in analyzing the distribution of Fe phases. Results show that Fe-containing phase was related to the unmodified Si particles in samples with partial modification failure and the plate-like Si phases in samples without modification failure. Such a relationship was further confirmed by the microstructure observation.In conclusion, a partial failure of Sr-modification can be caused by both slow cooling rate and Fe-containing phases.
基金General Project of Science and Technology Plan of Yunnan Science and Technology Department,China(No.2019FB077)Open Fund of Key Laboratory of Ministry of Education for Metallurgical Emission Reduction and Comprehensive Utilization of Resources,China(No.JKF19-08)。
文摘Modification conditions determine the surface topography and the active material phase composition of a catalyst.To study the influence of modification on a carbon-based sorbent,coconut husk activated carbon(AC)which was activated using HNO3 and modified by FeSO4 and Fe(NO3)3 was examined.The pore textures and surface chemical characteristics of the carbon materials were examined by scanning electron microscopy(SEM),Brunner-Emmet-Teller(BET),X-ray diffraction(XRD)and Fourier transform infrared(FTIR)spectroscopy.The surface topography,the pore structure,active materials,and functional groups of AC,AC modificated by HNO3(HNO3/AC for short),and AC modificated by FeSO4 and Fe(NO3)3(Fe/AC for short)were systematically studied.Subsequently,the mechanism of modifying the conditions for the carbon materials was determined.Results showed that the surface micro topography of HNO3/AC became unsystematic and disordered.After modification with FeSO4,the ferriferous oxide was mainly present as a near-spherical crystal.Ferriferous oxides from Fe(NO3)3 modification mainly exhibited a plate shape.HNO3 modification could enlarge the pores but decrease the specific surface area of AC.FeSO4 modification resulted in a new net post structure in the pore canal of AC.Fe(NO3)3 modification caused the pore space structure to develop in the interior,and a higher calcination temperature was useful for ablation.The ash content of the AC was substantially reduced upon HNO3 modification.Upon FeSO4 modification,α-FeOOH,α-Fe2O3 andγ-Fe2O3 coexisted under the condition of a lower concentration of FeSO4 and a lower calcination temperature,and a higher FeSO4 concentration and calcination temperature generated moreα-Fe2O3.The same Fe(NO3)3 modification and a higher calcination temperature were beneficial to the minor chipping formation ofγ-Fe2O3.A higher Fe(NO3)3 loading produced a lower graphitization degree.HNO3 modification formed various new oxygen-containing functional groups and few nitrogen-containing groups.Based on the cover,FeSO4 and Fe(NO3)3 modification could decrease the oxygen-containing and nitrogen-containing functional groups.These results could optimize the modification condition and improve physical and chemical properties of carbon-based sorbents.
