The porous spherical LiFePO4/C powders were prepared by spray drying and carbothermal method （SDCTM）. Cheaper trivalent iron ion was used as the precursor. The pure olivine phase can be prepared with the spray dryin...The porous spherical LiFePO4/C powders were prepared by spray drying and carbothermal method （SDCTM）. Cheaper trivalent iron ion was used as the precursor. The pure olivine phase can be prepared with the spray drying and subsequent heat-treatment. The average particle size is around 10μm, and the value of porosity is 63.04%. The results indicate that the initial discharge capacity decreases with increasing charge/ discharge rate and reduces from 138.8 mAh · g^-1 at C/20 rate to 98.3 mAh ·g^-1 at 2C rate, while the polarization between the charge and discharge plateaux is enlarged from 53 mv to 347 mv. However, the average discharge efficiency is up to 99.5% at 2C rate compared to 80.6% at C/20 rate from the second cycle.展开更多
The preparation of fine TiC powders by carbothermal reduction of TiO2 in vacuum was investigated by XRD,SEM,XRF and laser particle sizer.Thermodynamic analysis indicates that it is easy to prepare TiC in vacuum and th...The preparation of fine TiC powders by carbothermal reduction of TiO2 in vacuum was investigated by XRD,SEM,XRF and laser particle sizer.Thermodynamic analysis indicates that it is easy to prepare TiC in vacuum and the formation sequence of products are Ti4O7（Magneli phase）,Ti3O5,Ti2O3,TiCxO1-x and TiC with the increase of reaction temperature.Experimental results demonstrate that TiC powders with single phase are obtained with molar ratio of TiO2 to C ranging from 1：3.2 to 1：6 at 1 550 ℃ for 4 h when the system pressure is 50 Pa,and TiC1.0 is gained when the molar ratio of TiO2 to C is 1：4 and 1：5.In addition,fine TiC1.0 powders（D50 equals 3.04 μm） with single phase and low impurities are obtained when the molar ratio of TiO2 to C is 1：4.SEM observation shows that uniform shape,low agglomeration,and loose structure are observed on the surface of block product.展开更多
We investigated the influence of the growth temperature, O_(2) flow, molar ratio between Ga_(2)O_(3) powder and graphite powder on the structure and morphology of the films grown on the c-plane sapphire(0001) substrat...We investigated the influence of the growth temperature, O_(2) flow, molar ratio between Ga_(2)O_(3) powder and graphite powder on the structure and morphology of the films grown on the c-plane sapphire(0001) substrates by a carbothermal reduction method. Experimental results for the heteroepitaxial growth of β-Ga_(2)O_(3) illustrate that β-Ga_(2)O_(3) growth by the carbothermal reduction method can be controlled. The optimal result was obtained at a growth temperature of 1050 °C. The fastest growth rate of β-Ga_(2)O_(3) films was produced when the O_(2) flow was 20 sccm. To guarantee that β-Ga_(2)O_(3) films with both high-quality crystal and morphology properties, the ideal molar ratio between graphite powder and Ga_(2)O_(3) powder should be set at 10 : 1.展开更多
Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction （CTR） process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction （...Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction （CTR） process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electrochemical measurements. XRD studies show that the Al-doped LiVPO4F has the same triclinic structure （space group p-↑1 ） as the undoped LiVPO4F. The SEM images exhibit that the particle size of Al-doped LiVPO4F is smaller than that of the undoped LiVPO4F and that the smallest particle size is only about 1 μm. The Al-doped LiVPO4F was evaluated as a cathode material for secondary lithium batteries,and exhibited an improved reversibility and cycleability,which may be attributed to the addition of Al^3＋ ion by stabilizing the triclinic structure.展开更多
Y-doped LiVPO4F cathode materials were prepared by a carbothermal reduction（CTR） process. The properties of the Y-doped LiVPOaF samples were investigated by X-ray diffraction （XRD） and electrochemical measurements...Y-doped LiVPO4F cathode materials were prepared by a carbothermal reduction（CTR） process. The properties of the Y-doped LiVPOaF samples were investigated by X-ray diffraction （XRD） and electrochemical measurements. XRD studies show that the Y-doped LiVPOaF samples have the same triclinic structure as the undoped LiVPO4F. The Li extraction/insertion performances of Y-doped LiVPO4F samples were investigated through charge/discharge, cyclic voltammogram （CV） , and electrochemical impedance spectra（EIS）. The optimal doping content of Y is x=0.04 in LiYxV1-xPO4F system. The Y-doped LiVPO4F samples show a better cyclic ability. The electrode reaction reversibility is enhanced, and the charge transfer resistance is decreased through the Y-doping. The improved electrochemical performances of the Y-doped LiVF＇OaF cathode materials are atlributed to the addidon of Y^3＋ ion by stabilizing the Iriclinic structure.展开更多
Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scannin...Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scanning electron microscopic （SEM）, and electrochemical measurements Results show that the Cr-doped Li3V2（PO4）3 has the same monoclinic structure as the undoped Li3V2（PO4）3, and the particle size of Cr-doped Li3V2（PO4）3 is smaller than that of the undoped Li3V2（PO4）3 and the smallest particle size is only about 1 1μm. The Cr-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram （CV）, and electrochemical impedance spectra（EIS）. The optimal doping content of Cr was that x=0.04 in the Li3V2-xCrx（PO4）3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2（PO4）3 cathode materials are attributed to the addition of Cr^3＋ ion by stabilizing the monoclinic structure.展开更多
The nanowire and whisker heterostructures of tin dioxide were fabricated by the chemical vapor deposition technique.It was demonstrated that various structures of tin oxide can be obtained by controlling the thickness...The nanowire and whisker heterostructures of tin dioxide were fabricated by the chemical vapor deposition technique.It was demonstrated that various structures of tin oxide can be obtained by controlling the thickness of gold layer and the partial pressure of source vapor at growing sites.12.5 and 25 nm thicknesses are preferable for the epitaxial growth of nanowires and heterostructure through vapor–liquid–solid mechanism,respectively.The tin dioxide whiskers with core-shell structure were fabricated by vapor–solid mechanism.Meanwhile,the influences of various factors on the tin dioxide growth are also discussed.展开更多
文摘The porous spherical LiFePO4/C powders were prepared by spray drying and carbothermal method （SDCTM）. Cheaper trivalent iron ion was used as the precursor. The pure olivine phase can be prepared with the spray drying and subsequent heat-treatment. The average particle size is around 10μm, and the value of porosity is 63.04%. The results indicate that the initial discharge capacity decreases with increasing charge/ discharge rate and reduces from 138.8 mAh · g^-1 at C/20 rate to 98.3 mAh ·g^-1 at 2C rate, while the polarization between the charge and discharge plateaux is enlarged from 53 mv to 347 mv. However, the average discharge efficiency is up to 99.5% at 2C rate compared to 80.6% at C/20 rate from the second cycle.
基金Project(u0837604)supported by the Natural Science Foundation of Yunnan Province,ChinaProject(51004058)supported by the National Natural Science Foundation of ChinaProject(20095314110003)supported by Specialized Research Fund for the Doctoral Program of Higher Education
文摘The preparation of fine TiC powders by carbothermal reduction of TiO2 in vacuum was investigated by XRD,SEM,XRF and laser particle sizer.Thermodynamic analysis indicates that it is easy to prepare TiC in vacuum and the formation sequence of products are Ti4O7（Magneli phase）,Ti3O5,Ti2O3,TiCxO1-x and TiC with the increase of reaction temperature.Experimental results demonstrate that TiC powders with single phase are obtained with molar ratio of TiO2 to C ranging from 1：3.2 to 1：6 at 1 550 ℃ for 4 h when the system pressure is 50 Pa,and TiC1.0 is gained when the molar ratio of TiO2 to C is 1：4 and 1：5.In addition,fine TiC1.0 powders（D50 equals 3.04 μm） with single phase and low impurities are obtained when the molar ratio of TiO2 to C is 1：4.SEM observation shows that uniform shape,low agglomeration,and loose structure are observed on the surface of block product.
基金supported by the National Natural Science Foundation of China under Grant 62104024, Grant 11875097, Grant 12075045, Grant 11975257, Grant 11961141014, and Grant 62074146the Fundamental Research Funds for the Central Universities under Grant DUT19RC (3)074the Natural Science Foundation of Liaoning Province under Grant 2021MS124, Grant 2022020474JH2/1013。
文摘We investigated the influence of the growth temperature, O_(2) flow, molar ratio between Ga_(2)O_(3) powder and graphite powder on the structure and morphology of the films grown on the c-plane sapphire(0001) substrates by a carbothermal reduction method. Experimental results for the heteroepitaxial growth of β-Ga_(2)O_(3) illustrate that β-Ga_(2)O_(3) growth by the carbothermal reduction method can be controlled. The optimal result was obtained at a growth temperature of 1050 °C. The fastest growth rate of β-Ga_(2)O_(3) films was produced when the O_(2) flow was 20 sccm. To guarantee that β-Ga_(2)O_(3) films with both high-quality crystal and morphology properties, the ideal molar ratio between graphite powder and Ga_(2)O_(3) powder should be set at 10 : 1.
文摘Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction （CTR） process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electrochemical measurements. XRD studies show that the Al-doped LiVPO4F has the same triclinic structure （space group p-↑1 ） as the undoped LiVPO4F. The SEM images exhibit that the particle size of Al-doped LiVPO4F is smaller than that of the undoped LiVPO4F and that the smallest particle size is only about 1 μm. The Al-doped LiVPO4F was evaluated as a cathode material for secondary lithium batteries,and exhibited an improved reversibility and cycleability,which may be attributed to the addition of Al^3＋ ion by stabilizing the triclinic structure.
基金Funded by the Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning(GuiJiaoRen [2007]71)Guangxi Natural Science Foundation(No.0832259)the Research Funds of the Guangxi Key Laboratory of Environmental Engineering, Protection and Assessment Program to Sponsor Teams for Innovation in the Construction of Talent High-lands in Guangxi Institutions of Higher Learning(GuiJiaoRen [2007]71)
文摘Y-doped LiVPO4F cathode materials were prepared by a carbothermal reduction（CTR） process. The properties of the Y-doped LiVPOaF samples were investigated by X-ray diffraction （XRD） and electrochemical measurements. XRD studies show that the Y-doped LiVPOaF samples have the same triclinic structure as the undoped LiVPO4F. The Li extraction/insertion performances of Y-doped LiVPO4F samples were investigated through charge/discharge, cyclic voltammogram （CV） , and electrochemical impedance spectra（EIS）. The optimal doping content of Y is x=0.04 in LiYxV1-xPO4F system. The Y-doped LiVPO4F samples show a better cyclic ability. The electrode reaction reversibility is enhanced, and the charge transfer resistance is decreased through the Y-doping. The improved electrochemical performances of the Y-doped LiVF＇OaF cathode materials are atlributed to the addidon of Y^3＋ ion by stabilizing the Iriclinic structure.
基金Funded by the Guangxi Natural Science Foundation(No. 0832259)the National Basic Research Program of China (No. 2007CB613607)
文摘Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scanning electron microscopic （SEM）, and electrochemical measurements Results show that the Cr-doped Li3V2（PO4）3 has the same monoclinic structure as the undoped Li3V2（PO4）3, and the particle size of Cr-doped Li3V2（PO4）3 is smaller than that of the undoped Li3V2（PO4）3 and the smallest particle size is only about 1 1μm. The Cr-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram （CV）, and electrochemical impedance spectra（EIS）. The optimal doping content of Cr was that x=0.04 in the Li3V2-xCrx（PO4）3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2（PO4）3 cathode materials are attributed to the addition of Cr^3＋ ion by stabilizing the monoclinic structure.
基金supported by Deakin University under a postgraduate research scholarship,the Fundamental Scientific Research Funds for Chinese Academy of Tropical Agricultural Sciences (Nos.1630022011033 and 1630062013011)the Natural Science Foundation of Hainan Province,China (No.20155197)
文摘The nanowire and whisker heterostructures of tin dioxide were fabricated by the chemical vapor deposition technique.It was demonstrated that various structures of tin oxide can be obtained by controlling the thickness of gold layer and the partial pressure of source vapor at growing sites.12.5 and 25 nm thicknesses are preferable for the epitaxial growth of nanowires and heterostructure through vapor–liquid–solid mechanism,respectively.The tin dioxide whiskers with core-shell structure were fabricated by vapor–solid mechanism.Meanwhile,the influences of various factors on the tin dioxide growth are also discussed.
