The ferrites of Cuo-ZnO-Fe2o3 solid solution series near the molar ratio of ZnxCu1-x were prepared by direct heating of their coprecipitated hydroxides using NH4OH as precipitating agent where x=0.0, 0.2, 0.5, 0.8 and...The ferrites of Cuo-ZnO-Fe2o3 solid solution series near the molar ratio of ZnxCu1-x were prepared by direct heating of their coprecipitated hydroxides using NH4OH as precipitating agent where x=0.0, 0.2, 0.5, 0.8 and 1.0. Additional amounts of Cu and Zn sulphates were added to compensate the loss during the coprecipitation of the hydroxides. The ferritized samples were characterized by chemical analysis, XRD. DTA, TGA and SEM. XRD of both Zn0.2Cu0.8Fe2O4 and Zn0.5Cu0.5 Fe2O4 that indicates the formation of a heterogeneous ferrite material of ZnFe2O4 and CuFe2O4 mixed with variable amounts of α-Fe2O3. Zn and Cu ferrites were observed only in Zn0.8Cu0.2Fe2O4.From TGA-time relation, the activation energy of the different transformation phases were calculated. It is found that, the activation energy of ZnFe2O4 is slightly equal to 3/2 of that for CuFe2O4. Dielectric measurements show that the electrical behaviour depends on the ordering and disordering of the phases.展开更多
In order to obtain a new precursor for LiFePO4, Fe2P2O7 with high purity was prepared through solid phase reaction at 650 ℃ using starting materials of FeC2O4 and NH4H2PO4 in an argon atmosphere. Using the as-prepare...In order to obtain a new precursor for LiFePO4, Fe2P2O7 with high purity was prepared through solid phase reaction at 650 ℃ using starting materials of FeC2O4 and NH4H2PO4 in an argon atmosphere. Using the as-prepared Fe2P2O7, Li2CO3 and glucose as raw materials, pure LiFePO4 and LiFePO4/C composite materials were respectively synthesized by solid state reaction at 700 ℃ in an argon atmosphere. X-ray diffractometry and scanning electron microscopy（SEM） were employed to characterize the as-prepared Fe2P2O7, LiFePO4 and LiFePO4/C. The as-prepared Fe2P2O7 crystallizes in the Cl space group and belongs to β-Fe2P2O7 for crystal phase. The particle size distribution of Fe2P2O7 observed by SEM is 0.4-3.0 μm. During the Li^＋ ion chemical intercalation, radical P2O7^4- is disrupted into two PO4^3- ions in the presence of O^2-, thus providing a feasible technique to dispose this poor dissolvable pyrophosphate. LiFePO4/C composite exhibits initial charge and discharge capacities of 154 and 132 mA·h/g, respectively.展开更多
(Fe7Co3)0.15(SiO2)0.85 granular alloy solid was prepared successfully using sol-gel method. The samples with different reducing temperatures were investigated by X-ray diffractometer(XRD),transmission electron microgr...(Fe7Co3)0.15(SiO2)0.85 granular alloy solid was prepared successfully using sol-gel method. The samples with different reducing temperatures were investigated by X-ray diffractometer(XRD),transmission electron micrography(TEM) and vibrating sample magnetometer(VSM). The av-erage particIe sizes of the samples were also calculated from Scherrer formula. The magnetic properties of (Fe7Co3 )o. 15 (SiO2)0.85 were studied in detail.展开更多
The influence of transformation pH value on the performance of nano-scale Ni(OH)2 was analyzed. The measurement results of XRD and TEM indicate that the samples are composed of β-Ni(OH)2 with crystal size of 20-50 nm...The influence of transformation pH value on the performance of nano-scale Ni(OH)2 was analyzed. The measurement results of XRD and TEM indicate that the samples are composed of β-Ni(OH)2 with crystal size of 20-50 nm, and the crystal lattice parameters of nano-scale Ni(OH)2 prepared at different transformation pH values are different. With the increase of transformation pH value, the agglomeration of nano-scale Ni(OH)2 becomes obvious. Cyclic voltammograms(CV) and electrochemical impedance spectroscopy(EIS) measurement results show that transformation pH value affects the proton diffusion coefficient(D) and charge-transfer resistance(Rct) of the material. The specific capacity is up to 327.8 mA·h/g, and the discharge performance of electrodes depends on both D and Rct, so the kinetic characteristics that electrodes reaction is controlled by both mass-transfer step and charge-transfer step was put forward.展开更多
β-Fe2O3·H2O is prepared by reacting FeCl3, K2CO3, an oxidizing agent HIO4 and a metal chelating agent K3PO4 at 65~ 70℃. The prepared β-Fe2O3' H2O is introduced into the mixture of KOH, KOCl and a ferrate s...β-Fe2O3·H2O is prepared by reacting FeCl3, K2CO3, an oxidizing agent HIO4 and a metal chelating agent K3PO4 at 65~ 70℃. The prepared β-Fe2O3' H2O is introduced into the mixture of KOH, KOCl and a ferrate stabilizer KI, and reacted at room temperature for 5 h to produce a ferrate-containing cake. The cake is dried to give a water-free dried potassium ferrate (VI).展开更多
At room temperature and in the presence of trace EDTA, the formation of δ-FeOOH was studied by the rapid oxidation of Fe（OH）2 suspension with O2. The structural and morphological changes were characterized by vario...At room temperature and in the presence of trace EDTA, the formation of δ-FeOOH was studied by the rapid oxidation of Fe（OH）2 suspension with O2. The structural and morphological changes were characterized by various techniques such as XRD, FTIR and TEM. γ-FeOOH and （δ-FeOOH） formed simutaneously in the early period of oxidation. But as the rate of mass transfer was in equilibrium, trace （γ-FeOOH） vanished gradually. Accordingly, pure phase δ-FeOOH was obtained. At the same time, critical amount ratio K of EDTA to Fe2+ was verified. The experiments show that the reactivity, rate of the oxidizing agent and pH of the initial medium were important factors for the formation of pure phase （δ-FeOOH）. Under the auxiliary effect of EDTA, the reactivity of O2 was nearly improved to that of H2O2. And the process of the oxidation that Fe（OH）2 suspension was oxidized by O2 under that condition was discussed.展开更多
文摘The ferrites of Cuo-ZnO-Fe2o3 solid solution series near the molar ratio of ZnxCu1-x were prepared by direct heating of their coprecipitated hydroxides using NH4OH as precipitating agent where x=0.0, 0.2, 0.5, 0.8 and 1.0. Additional amounts of Cu and Zn sulphates were added to compensate the loss during the coprecipitation of the hydroxides. The ferritized samples were characterized by chemical analysis, XRD. DTA, TGA and SEM. XRD of both Zn0.2Cu0.8Fe2O4 and Zn0.5Cu0.5 Fe2O4 that indicates the formation of a heterogeneous ferrite material of ZnFe2O4 and CuFe2O4 mixed with variable amounts of α-Fe2O3. Zn and Cu ferrites were observed only in Zn0.8Cu0.2Fe2O4.From TGA-time relation, the activation energy of the different transformation phases were calculated. It is found that, the activation energy of ZnFe2O4 is slightly equal to 3/2 of that for CuFe2O4. Dielectric measurements show that the electrical behaviour depends on the ordering and disordering of the phases.
基金Project(50604018)supported by the National Natural Science Foundation of China
文摘In order to obtain a new precursor for LiFePO4, Fe2P2O7 with high purity was prepared through solid phase reaction at 650 ℃ using starting materials of FeC2O4 and NH4H2PO4 in an argon atmosphere. Using the as-prepared Fe2P2O7, Li2CO3 and glucose as raw materials, pure LiFePO4 and LiFePO4/C composite materials were respectively synthesized by solid state reaction at 700 ℃ in an argon atmosphere. X-ray diffractometry and scanning electron microscopy（SEM） were employed to characterize the as-prepared Fe2P2O7, LiFePO4 and LiFePO4/C. The as-prepared Fe2P2O7 crystallizes in the Cl space group and belongs to β-Fe2P2O7 for crystal phase. The particle size distribution of Fe2P2O7 observed by SEM is 0.4-3.0 μm. During the Li^＋ ion chemical intercalation, radical P2O7^4- is disrupted into two PO4^3- ions in the presence of O^2-, thus providing a feasible technique to dispose this poor dissolvable pyrophosphate. LiFePO4/C composite exhibits initial charge and discharge capacities of 154 and 132 mA·h/g, respectively.
文摘(Fe7Co3)0.15(SiO2)0.85 granular alloy solid was prepared successfully using sol-gel method. The samples with different reducing temperatures were investigated by X-ray diffractometer(XRD),transmission electron micrography(TEM) and vibrating sample magnetometer(VSM). The av-erage particIe sizes of the samples were also calculated from Scherrer formula. The magnetic properties of (Fe7Co3 )o. 15 (SiO2)0.85 were studied in detail.
基金Project(20271015) supported by the National Natural Science Foundation of China
文摘The influence of transformation pH value on the performance of nano-scale Ni(OH)2 was analyzed. The measurement results of XRD and TEM indicate that the samples are composed of β-Ni(OH)2 with crystal size of 20-50 nm, and the crystal lattice parameters of nano-scale Ni(OH)2 prepared at different transformation pH values are different. With the increase of transformation pH value, the agglomeration of nano-scale Ni(OH)2 becomes obvious. Cyclic voltammograms(CV) and electrochemical impedance spectroscopy(EIS) measurement results show that transformation pH value affects the proton diffusion coefficient(D) and charge-transfer resistance(Rct) of the material. The specific capacity is up to 327.8 mA·h/g, and the discharge performance of electrodes depends on both D and Rct, so the kinetic characteristics that electrodes reaction is controlled by both mass-transfer step and charge-transfer step was put forward.
文摘β-Fe2O3·H2O is prepared by reacting FeCl3, K2CO3, an oxidizing agent HIO4 and a metal chelating agent K3PO4 at 65~ 70℃. The prepared β-Fe2O3' H2O is introduced into the mixture of KOH, KOCl and a ferrate stabilizer KI, and reacted at room temperature for 5 h to produce a ferrate-containing cake. The cake is dried to give a water-free dried potassium ferrate (VI).
文摘At room temperature and in the presence of trace EDTA, the formation of δ-FeOOH was studied by the rapid oxidation of Fe（OH）2 suspension with O2. The structural and morphological changes were characterized by various techniques such as XRD, FTIR and TEM. γ-FeOOH and （δ-FeOOH） formed simutaneously in the early period of oxidation. But as the rate of mass transfer was in equilibrium, trace （γ-FeOOH） vanished gradually. Accordingly, pure phase δ-FeOOH was obtained. At the same time, critical amount ratio K of EDTA to Fe2+ was verified. The experiments show that the reactivity, rate of the oxidizing agent and pH of the initial medium were important factors for the formation of pure phase （δ-FeOOH）. Under the auxiliary effect of EDTA, the reactivity of O2 was nearly improved to that of H2O2. And the process of the oxidation that Fe（OH）2 suspension was oxidized by O2 under that condition was discussed.
