Li2FeSiO4 is deemed to be a potential candidate for large-scale applications because of its abundance,low cost and high safety,etc.Unfortunately,its low conductivity,resulting in poor rate performance,has become a mai...Li2FeSiO4 is deemed to be a potential candidate for large-scale applications because of its abundance,low cost and high safety,etc.Unfortunately,its low conductivity,resulting in poor rate performance,has become a main obstacle to its applications in power battery and energy storage system.In this work,C-Ag coated Li2FeSiO4 is introduced to improve the innate electronic conductivity and Li-ion diffusion ability.The results demonstrate that Li2FeSiO4/C/Ag composite exhibits better electrochemical performance.It possesses a specific discharge capacity of 152,121,108 mA.h/g at 0.2C,5C and 10C,respectively.At the same time,the Li2FeSiO4/C/Ag composite shows good cycle stability and a capacity retention ratio of 97.9%after 100 cycles at 1C.展开更多
Abstract： Maghemite-silica particulate nanocomposites were prepared by modified 2-step sol-gel process. Superparamagnetic maghemite nanoparticles were successfully produced using Massart＇s procedure. Nanocomposites ...Abstract： Maghemite-silica particulate nanocomposites were prepared by modified 2-step sol-gel process. Superparamagnetic maghemite nanoparticles were successfully produced using Massart＇s procedure. Nanocomposites consisting of synthesized maghemite nanoparticles and silica were produced by dispersing the as-synthesized maghemite nanoparticles into the silica particulate form. The system was then heated at 140 ℃for 3 d. A variety of mass ratios of Fe2O3/SiO2 was investigated. Moreover, no surfactant or other unnecessary precursor was involved. The nanocomposites were characterized using XRD, BET and AGM. The XRD diffraction patterns show the reflection corresponding to maghemite nanoparticles and a visible wide band at 20 from 20° to 35° which are the characteristics of the amorphous phase of the silica gel. The patterns also exhibit the presence of only maghemite and SiO2 amorphous phase, which indicates that there is no chemical reaction between the silica particulate gel and maghemite nanoparticles to form other compounds. The calculated crystallite size for encapsulated maghemite nanoparticles is smaller than the as-synthesized maghemite nanoparticles indicating the dissolution of the nanoparticles. Very high surface area is attained for the produced nanocomposites （360-390 m^2/g）. This enhances the sensitivity and the reactivity of the nanocomposites. The shapes of the magnetization curves for nanocomposites are very similar to the as-synthesized maghemite nanoparticles. Superparamagnetic behaviour is exhibited by all samples, indicating that the size of the maghemite nanoparticles is always within the nanometre range. The increase in iron content gives rise to a small particle growth.展开更多
[SiO2/FePt]5/Ag thin films were deposited by RF magnetron sputtering on the glass substrates and post annealing at 550 ℃ for 30 min in vacuum. Vibrating sample magnetometer and X-ray diffraction analyser were applied...[SiO2/FePt]5/Ag thin films were deposited by RF magnetron sputtering on the glass substrates and post annealing at 550 ℃ for 30 min in vacuum. Vibrating sample magnetometer and X-ray diffraction analyser were applied to study the magnetic properties and microstructures of the films. The results show that without Ag underlayer [SiO2/FePt]5 films deposited onto the glass are FCC disordered; with the addition of Ag underlayer [SiO]FePt]5/Ag films are changed into L10 and （111） mixed texture. The variation of the SiO2 nonmagnetic layer thickness in [SiO2/FePt]5/Ag films indicates that SiO2-doping plays an important role in improving the order parameter and the perpendicular magnetic anisotropy, and reducing the grain size and intergrain interactions. By controlling SiO2 thickness the highly perpendicular magnetic anisotropy can be obtained in the [SiO2 （0.6 nm）/FePt （3 nm）]5/Ag （50 nm） films and highly （001）-oriented films can be obtained in the [SiO2 （2 nm）/FePt （3 nm）]5/Ag （50 nm） films.展开更多
To explicate the thermodynamics of the chromite ore lime-free roasting process, the thermodynamics of reactions involved in this process was calculated and the phrases of sinter with different roasting times were stud...To explicate the thermodynamics of the chromite ore lime-free roasting process, the thermodynamics of reactions involved in this process was calculated and the phrases of sinter with different roasting times were studied. The thermodynamics calculation shows that all the standard Gibbs free energy changes of the reactions to form Na2CrO4, Na2O-Fe2O3, Na2O·Al2O3 and Na2O3 SiO2 via chromite ore and Na2CO3 are negative, and the standard Gibbs free energy changes of the reactions between MgO, Fe2O3 and SiO2 released from chromite spinel to form MgO-Fe2O3 and MgO·SiO2 are also negative at the oxidative roasting temperatures （1 173 1 473 K）. The phrase analysis of the sinter in lime-free roasting process shows that Na2O·Fe2O3, Na2O·Al2O3 and Na2O·SiO2 can be formed in the first 20 min, but they decrease in contents and finally disappear with the increase of roasting time. The final phase compositions of the sinter are Na2CrO4, MgO·Fe2O3, MgO·SiO2 and MgO. The results indicate that Na2CrO4 can be formed easily via the reaction ofNa2CO3 with chromite ore. Na2O·Fe2O3, Na2O-Al2O3 and Na2O·SiO2 can be formed as intermediate compounds in the roasting process and they can further react with chromite ore to form Na2CrO4. MgO released from chromite ore may react with iron oxides and silicon oxide to form stable compounds of MgO·Fe2O3 and MgO·SiO2, respectively.展开更多
Fe/Si3N4 composite powder was synthesized by the heterogeneous precipitation-thermal reduction process,and then pressed into flakes under a pressure of 10 MPa.Flakes were sintered by pressureless and hot-pressing at 1...Fe/Si3N4 composite powder was synthesized by the heterogeneous precipitation-thermal reduction process,and then pressed into flakes under a pressure of 10 MPa.Flakes were sintered by pressureless and hot-pressing at 1 600℃under 0.1 MPa N2. The chemical composition,phases and microstructure of composite powder and sintered flakes were investigated by energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy (TEM).The results show that the structure of composite powders is Si3N4 coated by nano Fe.The crystal phases of sintered flakes by pressureless are Fe(Si)compound,SiC and Si3N4.The crystal phases of the sintered samples by hot-pressing are Fe,Fe(Si) compound and Si3N4.It is found that crystal phases flakes obtained by pressureless and hot-pressing are very different.展开更多
基金Project(21771062)supported by the National Natural Science Foundation of ChinaProject(2016JJ2092)supported by the Hunan Provincial Natural Science Foundation,ChinaProject(2019013)supported by the Open Project Program of Key Laboratory of Preparation and Application of Environmental Friendly Materials,Ministry of Education,Jilin Normal University,China
文摘Li2FeSiO4 is deemed to be a potential candidate for large-scale applications because of its abundance,low cost and high safety,etc.Unfortunately,its low conductivity,resulting in poor rate performance,has become a main obstacle to its applications in power battery and energy storage system.In this work,C-Ag coated Li2FeSiO4 is introduced to improve the innate electronic conductivity and Li-ion diffusion ability.The results demonstrate that Li2FeSiO4/C/Ag composite exhibits better electrochemical performance.It possesses a specific discharge capacity of 152,121,108 mA.h/g at 0.2C,5C and 10C,respectively.At the same time,the Li2FeSiO4/C/Ag composite shows good cycle stability and a capacity retention ratio of 97.9%after 100 cycles at 1C.
基金Project(RP021-2012C)supported by University of Malaya under the UMRG Fund,Malaysia
文摘Abstract： Maghemite-silica particulate nanocomposites were prepared by modified 2-step sol-gel process. Superparamagnetic maghemite nanoparticles were successfully produced using Massart＇s procedure. Nanocomposites consisting of synthesized maghemite nanoparticles and silica were produced by dispersing the as-synthesized maghemite nanoparticles into the silica particulate form. The system was then heated at 140 ℃for 3 d. A variety of mass ratios of Fe2O3/SiO2 was investigated. Moreover, no surfactant or other unnecessary precursor was involved. The nanocomposites were characterized using XRD, BET and AGM. The XRD diffraction patterns show the reflection corresponding to maghemite nanoparticles and a visible wide band at 20 from 20° to 35° which are the characteristics of the amorphous phase of the silica gel. The patterns also exhibit the presence of only maghemite and SiO2 amorphous phase, which indicates that there is no chemical reaction between the silica particulate gel and maghemite nanoparticles to form other compounds. The calculated crystallite size for encapsulated maghemite nanoparticles is smaller than the as-synthesized maghemite nanoparticles indicating the dissolution of the nanoparticles. Very high surface area is attained for the produced nanocomposites （360-390 m^2/g）. This enhances the sensitivity and the reactivity of the nanocomposites. The shapes of the magnetization curves for nanocomposites are very similar to the as-synthesized maghemite nanoparticles. Superparamagnetic behaviour is exhibited by all samples, indicating that the size of the maghemite nanoparticles is always within the nanometre range. The increase in iron content gives rise to a small particle growth.
基金Project(10574085) supported by the National Natural Science Foundation of ChinaProject(207020) supported by the Science Technology Key Project of the Ministry of Education, China
文摘[SiO2/FePt]5/Ag thin films were deposited by RF magnetron sputtering on the glass substrates and post annealing at 550 ℃ for 30 min in vacuum. Vibrating sample magnetometer and X-ray diffraction analyser were applied to study the magnetic properties and microstructures of the films. The results show that without Ag underlayer [SiO2/FePt]5 films deposited onto the glass are FCC disordered; with the addition of Ag underlayer [SiO]FePt]5/Ag films are changed into L10 and （111） mixed texture. The variation of the SiO2 nonmagnetic layer thickness in [SiO2/FePt]5/Ag films indicates that SiO2-doping plays an important role in improving the order parameter and the perpendicular magnetic anisotropy, and reducing the grain size and intergrain interactions. By controlling SiO2 thickness the highly perpendicular magnetic anisotropy can be obtained in the [SiO2 （0.6 nm）/FePt （3 nm）]5/Ag （50 nm） films and highly （001）-oriented films can be obtained in the [SiO2 （2 nm）/FePt （3 nm）]5/Ag （50 nm） films.
基金Project(2009FJ1009) supported by the Major Science and Technology Program of Hunan Province,China
文摘To explicate the thermodynamics of the chromite ore lime-free roasting process, the thermodynamics of reactions involved in this process was calculated and the phrases of sinter with different roasting times were studied. The thermodynamics calculation shows that all the standard Gibbs free energy changes of the reactions to form Na2CrO4, Na2O-Fe2O3, Na2O·Al2O3 and Na2O3 SiO2 via chromite ore and Na2CO3 are negative, and the standard Gibbs free energy changes of the reactions between MgO, Fe2O3 and SiO2 released from chromite spinel to form MgO-Fe2O3 and MgO·SiO2 are also negative at the oxidative roasting temperatures （1 173 1 473 K）. The phrase analysis of the sinter in lime-free roasting process shows that Na2O·Fe2O3, Na2O·Al2O3 and Na2O·SiO2 can be formed in the first 20 min, but they decrease in contents and finally disappear with the increase of roasting time. The final phase compositions of the sinter are Na2CrO4, MgO·Fe2O3, MgO·SiO2 and MgO. The results indicate that Na2CrO4 can be formed easily via the reaction ofNa2CO3 with chromite ore. Na2O·Fe2O3, Na2O-Al2O3 and Na2O·SiO2 can be formed as intermediate compounds in the roasting process and they can further react with chromite ore to form Na2CrO4. MgO released from chromite ore may react with iron oxides and silicon oxide to form stable compounds of MgO·Fe2O3 and MgO·SiO2, respectively.
基金Project(50804016)supported by the National Natural Science Foundation of China
文摘Fe/Si3N4 composite powder was synthesized by the heterogeneous precipitation-thermal reduction process,and then pressed into flakes under a pressure of 10 MPa.Flakes were sintered by pressureless and hot-pressing at 1 600℃under 0.1 MPa N2. The chemical composition,phases and microstructure of composite powder and sintered flakes were investigated by energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy (TEM).The results show that the structure of composite powders is Si3N4 coated by nano Fe.The crystal phases of sintered flakes by pressureless are Fe(Si)compound,SiC and Si3N4.The crystal phases of the sintered samples by hot-pressing are Fe,Fe(Si) compound and Si3N4.It is found that crystal phases flakes obtained by pressureless and hot-pressing are very different.
