The structures of the Mn-Zn ferrites synthesized under different sintering conditions by the sol-gel method were investigated by the X-ray diffraction (XRD) and the scanning electron microscopy (SEM) with focus on...The structures of the Mn-Zn ferrites synthesized under different sintering conditions by the sol-gel method were investigated by the X-ray diffraction (XRD) and the scanning electron microscopy (SEM) with focus on two factors: the pre-sintering treatment and the calcining time. The results show that the sintering conditions have significant effects on the structures and the particle size of the Mn-Zn ferrites. Compared with the products without pre-sintering, those pre-sintered at 500℃ have a single phase and no diffraction peaks of Fe2O3 that could be found. The effects of the pre-sintering temperature on the structures of the ferrites were also studied. As a result, 500℃ proves to be the favorite in the pre-sintering treatment. The XRD patterns of the ferrites calcined at 1 200℃ for 6 h will present diffraction peaks of pure crystallization of spinel phase while those for 2 h or 4 h will show peaks of Fe2O3. The SEM also bears witness to well-grown grains of pure Mn-Zn ferrites if calcined for 6 hours.展开更多
Aqueous zinc-ion batteries(AZIBs)are regarded as promising electrochemical energy storage devices owing to its low cost,intrinsic safety,abundant zinc reserves,and ideal specific capacity.Compared with other cathode m...Aqueous zinc-ion batteries(AZIBs)are regarded as promising electrochemical energy storage devices owing to its low cost,intrinsic safety,abundant zinc reserves,and ideal specific capacity.Compared with other cathode materials,manganese dioxide with high voltage,environmental protection,and high theoretical specific capacity receives considerable attention.However,the problems of structural instability,manganese dissolution,and poor electrical conductivity make the exploration of high-performance manganese dioxide still a great challenge and impede its practical applications.Besides,zinc storage mechanisms involved are complex and somewhat controversial.To address these issues,tremendous efforts,such as surface engineering,heteroatoms doping,defect engineering,electrolyte modification,and some advanced characterization technologies,have been devoted to improving its electrochemical performance and illustrating zinc storage mechanism.In this review,we particularly focus on the classification of manganese dioxide based on crystal structures,zinc ions storage mechanisms,the existing challenges,and corresponding optimization strategies as well as structure-performance relationship.In the final section,the application perspectives of manganese oxide cathode materials in AZIBs are prospected.展开更多
MnFe204 nanoparticles (NPs) with various sizes and tight size-distribution were synthesized by a chemical solution- phase method. The as-synthesized NPs were coated with a silica shell of 4 nm-5 nm in thickness, ena...MnFe204 nanoparticles (NPs) with various sizes and tight size-distribution were synthesized by a chemical solution- phase method. The as-synthesized NPs were coated with a silica shell of 4 nm-5 nm in thickness, enabling the water- solubility and biocompatibility of the NPs. The MnFe204 NPs with a size of less than 18 nm exhibit superparamagnetic behavior with high saturated magnetization. The capacity of the heat production was enhanced by increasing particle sizes and radio frequency (RF) field strengths. MnFe204/SiO2 NPs with 18-nm magnetic cores showed the highest heat- generation ability under an RF field. These MnFe204/SiO2 NPs have great potentiality to cancer treatments, controlled drug releases, and remote controls of single cell functions.展开更多
Monodispersed manganese ferrite (MnFe2O4) nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor,in which octade...Monodispersed manganese ferrite (MnFe2O4) nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor,in which octadecene was used as solvent,and oleic acid and oleylamine were used as capping ligands.MnFe2O4 nanocrystals were obtained with size in a tunable range of 4-15 nm and their morphologies could be tuned from spherical to triangle-shaped by varying the surfactants.The phase structure,morphology,and size of the products were characterized in detail by X-ray diffraction (XRD) and transmission electron microscopy (TEM).Magnetic properties of MnFe2O4 nanocrystals with different morphologies were measured using a superconducting quantum interference device (SQUID).Both monodisperse MnFe2O4 nanocrystals with spherical and triangle-shapes are superparamagnetic at room temperature while ferromagnetic at 2 K.The pyrolysis method may provide an effective route to synthesize other spinel ferrites or metal oxides nanocrystals.展开更多
Mn-Zn ferrite powders were produced from low-grade manganese ore(LMO) via the chemical coprecipitation method combined with the ceramic method,after the LMO was leached in sulfuric acid and the obtained solution was p...Mn-Zn ferrite powders were produced from low-grade manganese ore(LMO) via the chemical coprecipitation method combined with the ceramic method,after the LMO was leached in sulfuric acid and the obtained solution was purified.The effect of the pH on the magnetic properties of Mn-Zn ferrite was investigated by the varying pH of the co-precipitation system.The crystal structure and phases of the samples were characterized by X-ray diffraction and infrared spectrum,respectively.The magnetic measurements were carried out on a vibrating sample magnetometer.The optimal sample was obtained with a saturation magnetization of 55.02 emu/g,a coercivity of 8.20 G and a remanent magnetization of1.71 emu/g when pH is 7.5.展开更多
A kind of La doped ferrite was prepared with marine manganese nodules derived from East Pacific sea-bottom as raw material, NaOH as fluxing reagent, La(NO3)3 as doping agent, by calcination at 1000 ℃ for 5 h. XRD ana...A kind of La doped ferrite was prepared with marine manganese nodules derived from East Pacific sea-bottom as raw material, NaOH as fluxing reagent, La(NO3)3 as doping agent, by calcination at 1000 ℃ for 5 h. XRD analysis showed that the ferrite products were of a spinel structure, and that its molecular formula could be expressed as MnFe2-xRxO4. SEM images proved that these ferrites showed octahedral and cubic aspects. It was found that there is some relationship between the La doping amount and the magnetic property of the ferrite. When the La doping amount was 0.03, the susceptibility of the ferrite was maximal. The as-prepared La doped ferrite is a kind of soft magnetic material that is easy to be magnetized with rather weak coercive force.展开更多
A novel method for recovering zinc from zinc ferrite by reduction roasting–ammonia leaching was studied in this paper. The reduction thermodynamic of zinc ferrite by CO was analyzed. The effects of roasting parameter...A novel method for recovering zinc from zinc ferrite by reduction roasting–ammonia leaching was studied in this paper. The reduction thermodynamic of zinc ferrite by CO was analyzed. The effects of roasting parameters on the phase transformation and conversion rate of zinc ferrite, and the leaching behavior of zinc from the reductive roasted samples by ammonia leaching, were experimentally investigated. The mineralogical phase compositions and chemical compositions of the samples were characterized by X-ray diffraction and chemical titration methods, respectively. The results showed that most of the zinc ferrite was transformed to zinc oxide and magnetite after weak reduction roasting. 86.43% of the zinc ferrite was transformed to zinc oxide under the optimum conditions: CO partial pressure of 25%, roasting temperature of 750°C, and roasting duration of 45 min. Finally, under the optimal leaching conditions, 78.12% of zinc was leached into the solution from the roasted zinc ferrite while all iron-bearing materials were kept in the leaching residue. The leaching conditions are listed as follows: leaching duration of 90 min,ammonia solution with 6 mol/L concentration, leaching temperature of 50°C, solid-to-liquid ratio of 40 g/L, and stirring speed of 200 r/min.展开更多
Advanced integrated gasification combined cycle (IGCC) power generation systems require the development of high-temperature, regenerable desulfurization sorbents, which are capable of removing hydrogen sulfide from ...Advanced integrated gasification combined cycle (IGCC) power generation systems require the development of high-temperature, regenerable desulfurization sorbents, which are capable of removing hydrogen sulfide from coal gasifier gas to very low levels. In this paper, zinc ferrites prepared by co-precipitation were identified as a novel coal gas desulfurization sorbent at high temperature. Preparation of zinc ferrite and effects of binders on pore volume, strength and desulfurization efficiency of zinc ferrite desulfurizer were studied. Moreover, the behavior of zinc ferrite sorbent during desulfurization and regeneration under the temperature range of 350-400 ℃ are investigated. Effects of binders on the pore volume, mechanical strength and desulfurization efficiency of zinc ferrite sorbents indicated that the addition of kaolinite to zinc ferrite desulfurizer seems to be superior to other binders under the experimental conditions.展开更多
Concentrations of copper (Cu), zinc (Zn) and manganese (Mn) were measured in four tissues of Tree Sparrow (Passer montanus) from three sites in Heilongjiang province, China, during four seasons. Among the four...Concentrations of copper (Cu), zinc (Zn) and manganese (Mn) were measured in four tissues of Tree Sparrow (Passer montanus) from three sites in Heilongjiang province, China, during four seasons. Among the four measured tissues (primary feathers, liver, heart, and pectoral muscle), the highest concentrations were found in feathers (Zn) or liver (Cu and Mn), and the lowest concentrations were in muscle, except Cu. For Mn, mean concentrations of the birds from the three study sites were, in decreasing order: Didao mining area (DMA) 〉 urban district of Jixi (UDJ) 〉 Phoenix Mountain national nature reserve (PMR, the reference site), but not for Zn and Cu. There were significant differences between metal concentrations at the three sites, but differences were not significant for Mn (in muscle and feathers) and Cu (in feathers). For most elements, the mean concentrations were greatest in summer.展开更多
In this experiment,the cancer tissues and cells,Which were derived from Lewis lung cancer and A549 lung Cancer cell line,were respectively divided into four groups and zinc, manganese and selenium were respectively ad...In this experiment,the cancer tissues and cells,Which were derived from Lewis lung cancer and A549 lung Cancer cell line,were respectively divided into four groups and zinc, manganese and selenium were respectively added to the medium for 24 hours. The superoxide dismutase activity in the tissues and the cells was estimated. It was found that the SOD activity was enhanced by zinc and manganese and the effect of zinc on SOD activity was superior to that of manganese. We supposed that the enhance of the SOD activity was relative to the activation of the SOD apoenzymes. This experimental result indicated that the inhibitory effect of zinc and manganese on carcinogenesis was achieved by SOD and the elements might be considered a SOD activator.展开更多
Li-Zn mixed ferrites with composition formula ZnxLi0.5-x/2Fe2.5-x/2O4 (0.2≤x≤0.8) were prepared by the usual ceramic method in 1000~1150℃. The effects of Zn substitution and sintering temperature on the formation, ...Li-Zn mixed ferrites with composition formula ZnxLi0.5-x/2Fe2.5-x/2O4 (0.2≤x≤0.8) were prepared by the usual ceramic method in 1000~1150℃. The effects of Zn substitution and sintering temperature on the formation, densification, microstructure and a.c. electrical conductivity have been studied. Under the effect of changing the firing temperature and Zn content, high sintered Li-Zn ferrite bodies are achieved. More fine structure bodies having high electrical resistance are obtained at high Zn content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
Nanostructured ZnFe2O4 was synthesized by the heat treatment of a mechanically activated mixture of ZnO/α-Fe2O3.X-ray diffraction(XRD)and differential thermal analysis(DTA)results demonstrated that,after 5 h of the m...Nanostructured ZnFe2O4 was synthesized by the heat treatment of a mechanically activated mixture of ZnO/α-Fe2O3.X-ray diffraction(XRD)and differential thermal analysis(DTA)results demonstrated that,after 5 h of the mechanical activation of the mixture,ZnFe2O4 was formed by heat treatment at 750°C for 2 h.To improve the characteristics of ZnFe2O4 for adsorption applications,the chemical activation process was performed.The 2 h chemical activation with 1 mol·L?1 HNO3 and co-precipitation of 52%?57%dissolved ZnFe2O4 led to an increase in the saturated magnetization from 2.0 to 7.5 emu·g?1 and in the specific surface area from 5 to 198 m2·g?1.In addition,the observed particle size reduction of chemically activated ZnFe2O4 in field emission scanning electron microscopy(FESEM)micrographs was in agreement with the specific surface area increase.These improvements in ZnFe2O4 characteristics considerably affected the adsorption performance of this adsorbent.Adsorption results revealed that mechano-thermally synthesized ZnFe2O4 had the maximum arsenic adsorption of 38%with the adsorption capacity of 0.995 mg·g?1 in a 130 mg·L?1 solution of As(V)after 30 min of agitation.However,chemically activated ZnFe2O4 showed the maximum arsenic adsorption of approximately 99%with the adsorption capacity of 21.460 mg·g?1 under the same conditions.These results showed that the weak adsorption performance of mechano-thermally synthesized ZnFe2O4 was improved by the chemical activation process.展开更多
Zinc manganese oxide(ZMO)system represents a notable family of mixed transition metal oxides(MTMOs)because of their superiority of the high theoretical capacity,adequacy of natural content,and low cost.However,the met...Zinc manganese oxide(ZMO)system represents a notable family of mixed transition metal oxides(MTMOs)because of their superiority of the high theoretical capacity,adequacy of natural content,and low cost.However,the methods to match both the reliable synthesis and the designable construction of large-sized two-dimensional(2D)ZMO nanosheets are still considered as grand challenges.Herein,we have successfully realized the preparation of 2D ZMO nanosheets with large lateral sizes up to~20 mm by simple pyrolysis of 2D metal–organic framework(MOF)nanosheets precursor.The growth mechanism of 2D MOF is proposed to be based on the lamellar micelles formed by polyvinyl pyrrolidone(PVP).The obtained 2D and porous ZMO nanosheets exhibit high specific capacity as well as good rate capability.More importantly,the as-prepared ZMO electrode shows a remarkable capacity increment upon cycling(from 832 mAh g^(-1) at the 2nd cycle to 1418 mAh g^(-1) at the 700th cycle,at 1 A g^(-1)).Through simple adjustment of the calcination temperature,the valence state of Mn species in the yielding ZMO samples can be fine-tuned.Through systematic investigation towards these ZMOs containing different Mn species,the extra specific capacity is revealed to be chiefly on account of the arising of the valence state of Mn upon the cycling process.Moreover,it is disclosed that the higher-valent Mn the pristine ZMO contains,the more additional capacity it gains upon cycling.We believe that this work will inspire more detailed analysis on the relationship between the valence state of Mn and extra capacity.展开更多
There is an urgent need for low-cost,high-energy-density,environmentally friendly energy storage devices to fulfill the rapidly increasing need for electrical energy storage.Multi-electron redox is considerably crucia...There is an urgent need for low-cost,high-energy-density,environmentally friendly energy storage devices to fulfill the rapidly increasing need for electrical energy storage.Multi-electron redox is considerably crucial for the development of high-energy-density cathodes.Here we present highperformance aqueous zinc-manganese batteries with reversible Mn2+/Mn4+ double redox.The active Mn4+is generated in situ from the Mn2+-containing MnOx nanoparticles and electrolyte.Benefitting from the low crystallinity of the birnessite-type MnO2 as well as the electrolyte with Mn2+additive,the MnOX cathode achieves an ultrahigh energy density with a peak of845.1 Wh kg-1 and an ultralong lifespan of 1500 cycles.The combination of electrochemical measurements and material characterization reveals the reversible Mn2+/Mn4+double redox(birnessite-type MnO2? monoclinic MnOOH and spinel ZnMn2O4 H?Mn2+ions).The reversible Mn2+/Mn4+double redox electrode reaction mechanism offers new opportunities for the design of low-cost,high-energy-density cathodes for advanced rechargeable aqueous batteries.展开更多
The magnetic particles of nickel-zinc ferrite with chemical composition Ni1-xZnxFe2O4 were synthesized successfully by citrate precursor auto-combustion method using high purity nitrates and citric acid as chelating a...The magnetic particles of nickel-zinc ferrite with chemical composition Ni1-xZnxFe2O4 were synthesized successfully by citrate precursor auto-combustion method using high purity nitrates and citric acid as chelating agent. The prepared powder of nickel-zinc ferrites was sintered at 1000℃ for 1 hr to obtain good crystalline phase and was used for further study. The X-ray diffraction technique was employed to confirm the single phase formation of nickel ferrite. The X-ray diffraction pattern shows the Bragg’s peak which belongs to cubic spinel structure. The values of lattice constant, X-ray density, bulk density, and porosity were calculated. The temperature dependence of the electrical conductivity plot shows the kink, which can be attributed to ferromagnetic-paramagnetic transition. The activation energy obtained from resistivity plots in paramagnetic region is found to be more than that in ferrimagnetic region. The conduction mechanism in nickel-zinc ferrite particles has been discussed on the basis of hopping of electrons.展开更多
Nano domain Al substituted Zinc ferrite was prepared by chemical route using Ethylene Diamine as ligand.High purity precursors nitrate salts of Zinc,Fe(3+),Al(3+)were utilized along with citric acid which acts as both...Nano domain Al substituted Zinc ferrite was prepared by chemical route using Ethylene Diamine as ligand.High purity precursors nitrate salts of Zinc,Fe(3+),Al(3+)were utilized along with citric acid which acts as both fuel and complexing agent.Two different molar ratios of Zn(2+):(Fe3+):Al(3+)is 1:1.5:0.5 and 1:1.25:0.75.After ensuring proper mix of the solution Ethylene diamine was added dropwise to form a gel like mass with proper pH control.Before annealing,thermal analysis was carried to determine the crystallization/phase transition zone.Drying was carried in several stages.Initially,gel like mass was obtained after drying at 40°C while pH was about 7.Drying of gel was carried in oil bath at about 90°C and powdered mass obtained was grinded followed by auto combustion at 150°C for 60 minutes before annealing at 150°C,350°C,650°C,950°C for 2 hours to ensure the phase formation.Crystallite size,lattice strain and lattice parameters were studied from XRD analysis.展开更多
Flexible energy-storage devices play a critical role in the development of portable, flexible and wearable electronics. In addition, biological materials including plants or plant-based materials are known for their s...Flexible energy-storage devices play a critical role in the development of portable, flexible and wearable electronics. In addition, biological materials including plants or plant-based materials are known for their safety, biodegradability, biocompatibility, environmental benignancy, and low cost. With respect to these advances, a flexible alkaline zinc-manganese dioxide (Zn-MnO2) battery is fabricated with a kelp-based electrolyte in this study. To the best of our knowledge, pure kelp is utilized as a semi-solid electrolyte for flexible Zn-MnO2 alkaline batteries for the first time, with which the as-assembled battery exhibited a specific capacity of 60 mA·h and could discharge for 120 h. Furthermore, the as-assembled Zn-MnO2 battery can be bent into a ring-shape and power a light-emitting diode screen, showing promising potential for the practical application in the future flexible, portable and biodegradable electronic devices.展开更多
Spinel zinc ferrites ZnFe2O4, prepared by co-precipitation method using the zinc nitrate Zn(NO3)2·6H2O and ferric nitrate Fe(NO3)3·2H2O as the raw materials, were characterized by the thermo gravimetric ...Spinel zinc ferrites ZnFe2O4, prepared by co-precipitation method using the zinc nitrate Zn(NO3)2·6H2O and ferric nitrate Fe(NO3)3·2H2O as the raw materials, were characterized by the thermo gravimetric analysis (TG) and differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscope (SEM). The influence of synthesis conditions, such as Zn/Fe molar ratio, pH value, the sintering temperature and time, on the microstructures was detailedly investigated. The relationships between the microstructures and the synthesis conditions were discussed. The results show that the pure spinel zinc ferrites ZnFe2O4 are formed when the Zn/Fe molar ratio is 1.05∶2 at pH=8.5 or Zn/Fe molar ratio is 1∶2 at Ph=9-10, and the precursors are sintered at 1100 ℃ for 4 h. Especially no other phases are observed when the Zn/Fe molar ratio is 1∶2 at pH=10 and the precursor is sintered above 700 ℃ for 4 h. The higher sintering temperature and longer sintering time contribute to grain growth.展开更多
文摘The structures of the Mn-Zn ferrites synthesized under different sintering conditions by the sol-gel method were investigated by the X-ray diffraction (XRD) and the scanning electron microscopy (SEM) with focus on two factors: the pre-sintering treatment and the calcining time. The results show that the sintering conditions have significant effects on the structures and the particle size of the Mn-Zn ferrites. Compared with the products without pre-sintering, those pre-sintered at 500℃ have a single phase and no diffraction peaks of Fe2O3 that could be found. The effects of the pre-sintering temperature on the structures of the ferrites were also studied. As a result, 500℃ proves to be the favorite in the pre-sintering treatment. The XRD patterns of the ferrites calcined at 1 200℃ for 6 h will present diffraction peaks of pure crystallization of spinel phase while those for 2 h or 4 h will show peaks of Fe2O3. The SEM also bears witness to well-grown grains of pure Mn-Zn ferrites if calcined for 6 hours.
基金supported by the National Natural Science Foundation of China(22279101,5210130199)the Natural Science Basic Research Plan in Shaanxi Province of China(2022JM-090)+2 种基金China Postdoctoral Science Foundation(2021 M693885)Science and Technology Planning Project of Beilin District(GX2111)and Young Talents Supporting Project of Xi'an Science Association(095920221359).
文摘Aqueous zinc-ion batteries(AZIBs)are regarded as promising electrochemical energy storage devices owing to its low cost,intrinsic safety,abundant zinc reserves,and ideal specific capacity.Compared with other cathode materials,manganese dioxide with high voltage,environmental protection,and high theoretical specific capacity receives considerable attention.However,the problems of structural instability,manganese dissolution,and poor electrical conductivity make the exploration of high-performance manganese dioxide still a great challenge and impede its practical applications.Besides,zinc storage mechanisms involved are complex and somewhat controversial.To address these issues,tremendous efforts,such as surface engineering,heteroatoms doping,defect engineering,electrolyte modification,and some advanced characterization technologies,have been devoted to improving its electrochemical performance and illustrating zinc storage mechanism.In this review,we particularly focus on the classification of manganese dioxide based on crystal structures,zinc ions storage mechanisms,the existing challenges,and corresponding optimization strategies as well as structure-performance relationship.In the final section,the application perspectives of manganese oxide cathode materials in AZIBs are prospected.
文摘MnFe204 nanoparticles (NPs) with various sizes and tight size-distribution were synthesized by a chemical solution- phase method. The as-synthesized NPs were coated with a silica shell of 4 nm-5 nm in thickness, enabling the water- solubility and biocompatibility of the NPs. The MnFe204 NPs with a size of less than 18 nm exhibit superparamagnetic behavior with high saturated magnetization. The capacity of the heat production was enhanced by increasing particle sizes and radio frequency (RF) field strengths. MnFe204/SiO2 NPs with 18-nm magnetic cores showed the highest heat- generation ability under an RF field. These MnFe204/SiO2 NPs have great potentiality to cancer treatments, controlled drug releases, and remote controls of single cell functions.
基金Project(2010QZZD008) supported by the Prospect Key Projects of Fundamental Research Funds for the Central UniversitiesProject(2007FJ3008) supported by the Hunan Provincial Key Science and Technology Program of China
文摘Monodispersed manganese ferrite (MnFe2O4) nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor,in which octadecene was used as solvent,and oleic acid and oleylamine were used as capping ligands.MnFe2O4 nanocrystals were obtained with size in a tunable range of 4-15 nm and their morphologies could be tuned from spherical to triangle-shaped by varying the surfactants.The phase structure,morphology,and size of the products were characterized in detail by X-ray diffraction (XRD) and transmission electron microscopy (TEM).Magnetic properties of MnFe2O4 nanocrystals with different morphologies were measured using a superconducting quantum interference device (SQUID).Both monodisperse MnFe2O4 nanocrystals with spherical and triangle-shapes are superparamagnetic at room temperature while ferromagnetic at 2 K.The pyrolysis method may provide an effective route to synthesize other spinel ferrites or metal oxides nanocrystals.
基金financed by the Bureau of Land Resources and Housing Management of Chongqing(Scientific & Technologic Program in 2011)the Science and Technology Bureau of Hengyang(Scientific & Technologic Program in 2013)the State Administration of Work Safety(Scientific & Technologic Program in 2013)
文摘Mn-Zn ferrite powders were produced from low-grade manganese ore(LMO) via the chemical coprecipitation method combined with the ceramic method,after the LMO was leached in sulfuric acid and the obtained solution was purified.The effect of the pH on the magnetic properties of Mn-Zn ferrite was investigated by the varying pH of the co-precipitation system.The crystal structure and phases of the samples were characterized by X-ray diffraction and infrared spectrum,respectively.The magnetic measurements were carried out on a vibrating sample magnetometer.The optimal sample was obtained with a saturation magnetization of 55.02 emu/g,a coercivity of 8.20 G and a remanent magnetization of1.71 emu/g when pH is 7.5.
基金the National Natural Science Foundation of China (NSFC 40637037)
文摘A kind of La doped ferrite was prepared with marine manganese nodules derived from East Pacific sea-bottom as raw material, NaOH as fluxing reagent, La(NO3)3 as doping agent, by calcination at 1000 ℃ for 5 h. XRD analysis showed that the ferrite products were of a spinel structure, and that its molecular formula could be expressed as MnFe2-xRxO4. SEM images proved that these ferrites showed octahedral and cubic aspects. It was found that there is some relationship between the La doping amount and the magnetic property of the ferrite. When the La doping amount was 0.03, the susceptibility of the ferrite was maximal. The as-prepared La doped ferrite is a kind of soft magnetic material that is easy to be magnetized with rather weak coercive force.
基金financially supported by the National Key Basic Research and Development Program of China (No.2014CB643403)
文摘A novel method for recovering zinc from zinc ferrite by reduction roasting–ammonia leaching was studied in this paper. The reduction thermodynamic of zinc ferrite by CO was analyzed. The effects of roasting parameters on the phase transformation and conversion rate of zinc ferrite, and the leaching behavior of zinc from the reductive roasted samples by ammonia leaching, were experimentally investigated. The mineralogical phase compositions and chemical compositions of the samples were characterized by X-ray diffraction and chemical titration methods, respectively. The results showed that most of the zinc ferrite was transformed to zinc oxide and magnetite after weak reduction roasting. 86.43% of the zinc ferrite was transformed to zinc oxide under the optimum conditions: CO partial pressure of 25%, roasting temperature of 750°C, and roasting duration of 45 min. Finally, under the optimal leaching conditions, 78.12% of zinc was leached into the solution from the roasted zinc ferrite while all iron-bearing materials were kept in the leaching residue. The leaching conditions are listed as follows: leaching duration of 90 min,ammonia solution with 6 mol/L concentration, leaching temperature of 50°C, solid-to-liquid ratio of 40 g/L, and stirring speed of 200 r/min.
基金the Ministry of Science and Technology of China under the Grant No. G2005CB221203the Natural Science Foundation of China under Contract No. 20576087.
文摘Advanced integrated gasification combined cycle (IGCC) power generation systems require the development of high-temperature, regenerable desulfurization sorbents, which are capable of removing hydrogen sulfide from coal gasifier gas to very low levels. In this paper, zinc ferrites prepared by co-precipitation were identified as a novel coal gas desulfurization sorbent at high temperature. Preparation of zinc ferrite and effects of binders on pore volume, strength and desulfurization efficiency of zinc ferrite desulfurizer were studied. Moreover, the behavior of zinc ferrite sorbent during desulfurization and regeneration under the temperature range of 350-400 ℃ are investigated. Effects of binders on the pore volume, mechanical strength and desulfurization efficiency of zinc ferrite sorbents indicated that the addition of kaolinite to zinc ferrite desulfurizer seems to be superior to other binders under the experimental conditions.
基金financially supported by Outstanding Youth Science Foundation of Heilongjiang Province (JC200709)
文摘Concentrations of copper (Cu), zinc (Zn) and manganese (Mn) were measured in four tissues of Tree Sparrow (Passer montanus) from three sites in Heilongjiang province, China, during four seasons. Among the four measured tissues (primary feathers, liver, heart, and pectoral muscle), the highest concentrations were found in feathers (Zn) or liver (Cu and Mn), and the lowest concentrations were in muscle, except Cu. For Mn, mean concentrations of the birds from the three study sites were, in decreasing order: Didao mining area (DMA) 〉 urban district of Jixi (UDJ) 〉 Phoenix Mountain national nature reserve (PMR, the reference site), but not for Zn and Cu. There were significant differences between metal concentrations at the three sites, but differences were not significant for Mn (in muscle and feathers) and Cu (in feathers). For most elements, the mean concentrations were greatest in summer.
文摘In this experiment,the cancer tissues and cells,Which were derived from Lewis lung cancer and A549 lung Cancer cell line,were respectively divided into four groups and zinc, manganese and selenium were respectively added to the medium for 24 hours. The superoxide dismutase activity in the tissues and the cells was estimated. It was found that the SOD activity was enhanced by zinc and manganese and the effect of zinc on SOD activity was superior to that of manganese. We supposed that the enhance of the SOD activity was relative to the activation of the SOD apoenzymes. This experimental result indicated that the inhibitory effect of zinc and manganese on carcinogenesis was achieved by SOD and the elements might be considered a SOD activator.
文摘Li-Zn mixed ferrites with composition formula ZnxLi0.5-x/2Fe2.5-x/2O4 (0.2≤x≤0.8) were prepared by the usual ceramic method in 1000~1150℃. The effects of Zn substitution and sintering temperature on the formation, densification, microstructure and a.c. electrical conductivity have been studied. Under the effect of changing the firing temperature and Zn content, high sintered Li-Zn ferrite bodies are achieved. More fine structure bodies having high electrical resistance are obtained at high Zn content
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.
文摘Nanostructured ZnFe2O4 was synthesized by the heat treatment of a mechanically activated mixture of ZnO/α-Fe2O3.X-ray diffraction(XRD)and differential thermal analysis(DTA)results demonstrated that,after 5 h of the mechanical activation of the mixture,ZnFe2O4 was formed by heat treatment at 750°C for 2 h.To improve the characteristics of ZnFe2O4 for adsorption applications,the chemical activation process was performed.The 2 h chemical activation with 1 mol·L?1 HNO3 and co-precipitation of 52%?57%dissolved ZnFe2O4 led to an increase in the saturated magnetization from 2.0 to 7.5 emu·g?1 and in the specific surface area from 5 to 198 m2·g?1.In addition,the observed particle size reduction of chemically activated ZnFe2O4 in field emission scanning electron microscopy(FESEM)micrographs was in agreement with the specific surface area increase.These improvements in ZnFe2O4 characteristics considerably affected the adsorption performance of this adsorbent.Adsorption results revealed that mechano-thermally synthesized ZnFe2O4 had the maximum arsenic adsorption of 38%with the adsorption capacity of 0.995 mg·g?1 in a 130 mg·L?1 solution of As(V)after 30 min of agitation.However,chemically activated ZnFe2O4 showed the maximum arsenic adsorption of approximately 99%with the adsorption capacity of 21.460 mg·g?1 under the same conditions.These results showed that the weak adsorption performance of mechano-thermally synthesized ZnFe2O4 was improved by the chemical activation process.
基金This project is financially supported by National Natural Science Foundation of China(Grant No.51502060)Natural Science Foundation of Shandong Province,China(Grant No.ZR2015EQ010 and No.ZR2019MB027)the Fundamental Research Funds for the Central Universities(Grant No.2015DXGJMS004).
文摘Zinc manganese oxide(ZMO)system represents a notable family of mixed transition metal oxides(MTMOs)because of their superiority of the high theoretical capacity,adequacy of natural content,and low cost.However,the methods to match both the reliable synthesis and the designable construction of large-sized two-dimensional(2D)ZMO nanosheets are still considered as grand challenges.Herein,we have successfully realized the preparation of 2D ZMO nanosheets with large lateral sizes up to~20 mm by simple pyrolysis of 2D metal–organic framework(MOF)nanosheets precursor.The growth mechanism of 2D MOF is proposed to be based on the lamellar micelles formed by polyvinyl pyrrolidone(PVP).The obtained 2D and porous ZMO nanosheets exhibit high specific capacity as well as good rate capability.More importantly,the as-prepared ZMO electrode shows a remarkable capacity increment upon cycling(from 832 mAh g^(-1) at the 2nd cycle to 1418 mAh g^(-1) at the 700th cycle,at 1 A g^(-1)).Through simple adjustment of the calcination temperature,the valence state of Mn species in the yielding ZMO samples can be fine-tuned.Through systematic investigation towards these ZMOs containing different Mn species,the extra specific capacity is revealed to be chiefly on account of the arising of the valence state of Mn upon the cycling process.Moreover,it is disclosed that the higher-valent Mn the pristine ZMO contains,the more additional capacity it gains upon cycling.We believe that this work will inspire more detailed analysis on the relationship between the valence state of Mn and extra capacity.
基金Supported by the National Natural Science Foundation of China(30270924) Natural Science Foundation of Anhui Province (070411004) +1 种基金 the National Science Foundation of Education Department of Anhui Province(2006KJ184B) the Foundation of Provincial Key Lab of Biotic Environment and Ecological Safety in Anhui Province
基金supported by the National Natural Science Foundation of China(Grant No.51772331)the National Key Technologies R&D Program(Grant No.2018YFB1106000).
文摘There is an urgent need for low-cost,high-energy-density,environmentally friendly energy storage devices to fulfill the rapidly increasing need for electrical energy storage.Multi-electron redox is considerably crucial for the development of high-energy-density cathodes.Here we present highperformance aqueous zinc-manganese batteries with reversible Mn2+/Mn4+ double redox.The active Mn4+is generated in situ from the Mn2+-containing MnOx nanoparticles and electrolyte.Benefitting from the low crystallinity of the birnessite-type MnO2 as well as the electrolyte with Mn2+additive,the MnOX cathode achieves an ultrahigh energy density with a peak of845.1 Wh kg-1 and an ultralong lifespan of 1500 cycles.The combination of electrochemical measurements and material characterization reveals the reversible Mn2+/Mn4+double redox(birnessite-type MnO2? monoclinic MnOOH and spinel ZnMn2O4 H?Mn2+ions).The reversible Mn2+/Mn4+double redox electrode reaction mechanism offers new opportunities for the design of low-cost,high-energy-density cathodes for advanced rechargeable aqueous batteries.
文摘The magnetic particles of nickel-zinc ferrite with chemical composition Ni1-xZnxFe2O4 were synthesized successfully by citrate precursor auto-combustion method using high purity nitrates and citric acid as chelating agent. The prepared powder of nickel-zinc ferrites was sintered at 1000℃ for 1 hr to obtain good crystalline phase and was used for further study. The X-ray diffraction technique was employed to confirm the single phase formation of nickel ferrite. The X-ray diffraction pattern shows the Bragg’s peak which belongs to cubic spinel structure. The values of lattice constant, X-ray density, bulk density, and porosity were calculated. The temperature dependence of the electrical conductivity plot shows the kink, which can be attributed to ferromagnetic-paramagnetic transition. The activation energy obtained from resistivity plots in paramagnetic region is found to be more than that in ferrimagnetic region. The conduction mechanism in nickel-zinc ferrite particles has been discussed on the basis of hopping of electrons.
文摘Nano domain Al substituted Zinc ferrite was prepared by chemical route using Ethylene Diamine as ligand.High purity precursors nitrate salts of Zinc,Fe(3+),Al(3+)were utilized along with citric acid which acts as both fuel and complexing agent.Two different molar ratios of Zn(2+):(Fe3+):Al(3+)is 1:1.5:0.5 and 1:1.25:0.75.After ensuring proper mix of the solution Ethylene diamine was added dropwise to form a gel like mass with proper pH control.Before annealing,thermal analysis was carried to determine the crystallization/phase transition zone.Drying was carried in several stages.Initially,gel like mass was obtained after drying at 40°C while pH was about 7.Drying of gel was carried in oil bath at about 90°C and powdered mass obtained was grinded followed by auto combustion at 150°C for 60 minutes before annealing at 150°C,350°C,650°C,950°C for 2 hours to ensure the phase formation.Crystallite size,lattice strain and lattice parameters were studied from XRD analysis.
文摘Flexible energy-storage devices play a critical role in the development of portable, flexible and wearable electronics. In addition, biological materials including plants or plant-based materials are known for their safety, biodegradability, biocompatibility, environmental benignancy, and low cost. With respect to these advances, a flexible alkaline zinc-manganese dioxide (Zn-MnO2) battery is fabricated with a kelp-based electrolyte in this study. To the best of our knowledge, pure kelp is utilized as a semi-solid electrolyte for flexible Zn-MnO2 alkaline batteries for the first time, with which the as-assembled battery exhibited a specific capacity of 60 mA·h and could discharge for 120 h. Furthermore, the as-assembled Zn-MnO2 battery can be bent into a ring-shape and power a light-emitting diode screen, showing promising potential for the practical application in the future flexible, portable and biodegradable electronic devices.
基金Funded by the National Science Foundation in China (No. 10804117)Natural Science Foundation of Shanghai (No. 08ZR1421900)the Major Program for the Fundamental Research of Shanghai (No. 06JC14033)
文摘Spinel zinc ferrites ZnFe2O4, prepared by co-precipitation method using the zinc nitrate Zn(NO3)2·6H2O and ferric nitrate Fe(NO3)3·2H2O as the raw materials, were characterized by the thermo gravimetric analysis (TG) and differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscope (SEM). The influence of synthesis conditions, such as Zn/Fe molar ratio, pH value, the sintering temperature and time, on the microstructures was detailedly investigated. The relationships between the microstructures and the synthesis conditions were discussed. The results show that the pure spinel zinc ferrites ZnFe2O4 are formed when the Zn/Fe molar ratio is 1.05∶2 at pH=8.5 or Zn/Fe molar ratio is 1∶2 at Ph=9-10, and the precursors are sintered at 1100 ℃ for 4 h. Especially no other phases are observed when the Zn/Fe molar ratio is 1∶2 at pH=10 and the precursor is sintered above 700 ℃ for 4 h. The higher sintering temperature and longer sintering time contribute to grain growth.