首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
As a kind of lithium-ion battery cathode material, monoclinic lithium vanadium phosphate/carbon Li3V2(PO4)3/C was synthesized by adopting phenolic resin as carbon source, both for reducing agent and coating material. The crystal structure and morphology of the samples were characterized through X-ray diffraction (XRD) and scanning electron microscope (SEM). Galvanostatic charge-discharging experiments and electrochemical impedance spectrum (EIS) were utilized to determine the electrochemical insertion properties of the samples. XRD data revealed that phenolic resin does not change the crystal structure of Li3V2(PO4)3/C. Furthermore, the morphology of grains and the electronic conductivity of Li3V2(PO4)3/C were improved. Galvanostatic charge-discharging and EIS results showed that the optimal electrochemical properties and the minimum charge-transfer resistance of Li3V2(PO4)3/C can be reached when added by 5 wt.% of redundant carbon (except the carbon needed to reduce V5+ to V3+). The initial discharge capacity is 128.4 mAh g?1 at 0.2 C rate and 101.2 mAh g?1 at 5 C in the voltage range of 3.0~4.3 V.  相似文献   

2.
Titanium butyl phosphates (TiBP) synthesized by reacting Ti(SO4)2 with a mixture of mono-(C4H9PO4H2) and dibutyl phosphates ((C4H9)2PO4H) in aqueous ethanol solution at 25 °C were characterized by various conventional techniques. XRD pattern of TiBP possessed a peak at 2θ?=?5.5° and a broad hump at 2θ?=?15–30°. This fact indicated that the material was composed of a multilayer alternating bilayer of butyl groups of the phosphates and amorphous titanium phosphate phase. The TiBP was spherical particles with a size of ca. 100 nm and the chemical formula of this material was Ti((C4H9O)2PO2)x(C4H9OPO3)y(OH)z. The TiBP possessed a UV absorption property due to charge transfer of O2? ? Ti4+. The layered structure of TiBP was exfoliated in ethanol at 25 °C up to TiBP concentration of 1.0?×?105 ppm to form nanosheet. The nanosheet dispersing solution exhibited a UV absorption property and the property depends on nanosheet concentration.  相似文献   

3.
The novel Li3V2(PO4)3 glass-ceramic nanocomposites were synthesized and investigated as electrodes for energy storage devices. They were fabricated by heat treatment (HT) of 37.5Li2O–25V2O5–37.5P2O5?mol% glass at 450 °C for different times in the air. XRD, SEM, and electrochemical methods were used to study the effect of HT time on the nanostructure and electrochemical performance for Li3V2(PO4)3 glass-ceramic nanocomposites electrodes. XRD patterns showed forming Li3V2(PO4)3 NASICON type with monoclinic structure. The crystalline sizes were found to be in the range of 32–56 nm. SEM morphologies exhibited non-uniform grains and changed with variation of HT time. The electrochemical performance of Li3V2(PO4)3 glass-ceramic nanocomposites was investigated by using galvanostatic charge/discharge methods, cyclic voltammetry, and electrochemical impedance spectroscopy in 1 M H2SO4 aqueous electrolyte. The glass-ceramic nanocomposites annealed for 4 h, which had a lower crystalline size, exhibited the best electrochemical performance with a specific capacity of 116.4 F g?1 at 0.5 A g?1. Small crystalline size supported the lithium ion mobility in the electrode by decreasing the ion diffusion pathway. Therefore, the Li3V2(PO4)3 glass-ceramic nanocomposites can be promising candidates for large-scale industrial applications in high-performance energy storage devices.  相似文献   

4.
Cathode material LiFe0.7?V0.2PO4/C is successfully synthesized by multistep sintering through carbon thermal reaction including 650 °C for 10 h and 750 °C for 6 h. The crystal structure and surface morphology of the synthesized materials are characterized by X-ray diffractometer and scanning electron microscope, respectively. Cycle voltammetry, electrochemical impedance spectroscopy, and charge–discharge test are used to investigate the electrochemical performances of these samples. The results revealed that the synthesized LiFe0.7?V0.2PO4/C material simultaneously contains olivine structure LiFePO4 and monoclinic structure Li3V2(PO4)3. It shows improved conductivity, Li-ion diffusion coefficient, excellent charge/discharge performance, and reversibility due to both the incorporation of Li3V2(PO4)3 fast ion conductor and the employed multistep sintering. The initial discharge specific capacities of LiFe0.7?V0.2PO4/C by multistep sintering are 167.8, 154.7, and 140.8 mAh g?1 at 0.5, 1, and 2 C, respectively. After a total of 230 cycles at different rates, the sample still shows good performances. After 100 cycles at 2 C, the capacity retention is 99.1 %, and the capacity is 139.6 mAh g?1. The LiFe0.7?V0.2PO4/C material synthesized by this method can be used as a cathode material for advanced lithium-ion batteries.  相似文献   

5.
In this investigation, HAp powders were synthesized using the wet chemical precipitation technique. The temperature of the heat treatment (80 °C, 120 °C, and 160 °C) and the addition of glutamic acid were the considered process parameters. After the reaction between the precursors calcium nitrate [Ca(NO3)2] and ammonium phosphate [(NH4)H2PO4], decantation of the residue, drying, and finally, heat treatment of the residue were done sequentially. X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) observations, and X-ray fluorescence (XRF) analysis were carried out to characterize the synthesized HAp powders. It was found that at a high heat treatment temperature plus the addition of glutamic acid are suitable process parameters to acquire uniform HAp powders with plate morphology and fibers with an average particle size of ~100–200 µm. The Ca/P ratio obtained was like the hydroxyapatite present in the bones in the order of 1.72. This situation can be indicated as an essential advantage in the biocompatibility of the synthesized material. The use of glutamic acid suggests crystal growth in a preferential direction as reported in our previous work. The manufacture of hydroxyapatite, especially in powder, is of great interest in developing additive manufacturing systems for the biomedical market.  相似文献   

6.
Four new network organic–inorganic hybrid supramolecular compounds [PW12O40](C2H4N3)3·6H2O (1), [PMo12O40](C2H4N3)3·6H2O (2), [H4SiW12O40]8[C6NO2H4]4[C6NO2H5]16[C5NH6]4·39H2O (3) and [H3VW12O40] (C6H6NO2)2(CHO2)2·4H2O (4) composed by keggin type heteropolyanion and O/N-containing organic groups of 1H-1,2,4-Triazole or 2,3-Pyridinedicarboxylic acid have been successfully synthesized by hydrothermally method, and characterized by infrared spectrum (IR), thermogravimetric–differentialthermal analysis (TG–DTA), cyclic voltammetry (CV) and single crystal X-ray diffraction (XRD). Compounds 1–4 exhibit three dimensional supramolecular network via hydrogen bonds and/or π–π stacking interactions. These compounds exhibit good thermal stability and catalytic ability. They are active for catalytic oxidation of methanol in a continuous-flow fixed-bed micro-reactor, when the initial concentration of methanol is 2.5 g m?3 in air and flow rate is 10 mL min?1, the corresponding elimination rates of methanol are 65% (125 °C), 85% (125 °C), 94% (150 °C), and 80% (125 °C), respectively.  相似文献   

7.
The nickel phosphate octahydrate (Ni3(PO4)2·8H2O) was synthesized by a simple procedure and characterized by FTIR, TG/DTG/DTA, AAS, and XRD techniques. The morphologies of the title compound and its decomposition product were studied by the SEM method. The dehydration process of the synthesized hydrate occurred in one step over the temperature range of 120–250 °C, and the thermal decomposition product at 800 °C was found to be Ni3(PO4)2. The kinetic parameters (E and A) of this step were calculated using the Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods. The iterative methods of both equations were carried out to determine the exact values of E, which confirm the single-step mechanism of the dehydration process. The non-isothermal kinetic method was used to determine the mechanism function of the dehydration, which indicates the contracting disk mechanism of R1 model as the most probable mechanism function and agrees well with the isothermal data. Besides, the isokinetic temperature value (T i) was calculated from the spectroscopic data. The thermodynamic functions of the activated complex (ΔS , ΔH , and ΔG ) of the dehydration process were calculated using the activated complex theory of Eyring. The kinetic parameters and thermodynamic functions of the activated complex for the dehydration process of Ni3(PO4)2·8H2O are reported for the first time.  相似文献   

8.
(NH4)2In(OH)2PO4 was synthesized by solid-state reaction at low heating temperatures using InCl3·H2O and (NH4)3PO4·3H2O as raw materials. The orthorhombic nanocrystalline InPO4 was obtained via calcining (NH4)2In(OH)2PO4 in air. The (NH4)2In(OH)2PO4 and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and ultraviolet–visible spectroscopy (UV–Vis). The result showed that orthorhombic nanocrystalline InPO4 with space group Cmcm(63) was obtained when the product was calcined above 600 °C for 3 h. The (NH4)2In(OH)2PO4 and its calcined products behaved with excellent UV–Vis ray transmission ability.  相似文献   

9.
Potassium fluorophosphate hafnates (PFPH) K3H3Hf3F3(PO4)5 and KHf2F3(PO4)2 · 2H2O were synthesized for the first time, and a KZr2F3(PO4)2 · 2H2O phase was found to exist. The compounds were studied by crystal-optical, elemental, X-ray powder diffraction, thermogravimetric, IR spectroscopic, and electron microscopic analyses. It was found that PFPH crystallize as one-dimensional nanoparticles. The IR spectra showed that PFPH K3H3M3F3(PO4)5 (M = Zr, Hf) are crystal solvate K3M3(PO4)5 · 3HF. Annealing of K3H3Hf3F3(PO4)5 and KHf2F3(PO4)2 · 2H2O at 1000°C gives rise to mixtures that mostly contain various phosphate hafnates.  相似文献   

10.
Powders of composition Ni3(XO4)2 with X = P and V were synthesized by both the ceramic conventional and the Pechini-type in situ polymerizable complex (IPC) method. The Pechini-type IPC technique produces these materials as single phases at reduced temperatures (750–810 °C) as opposed to the conventional solid-state reaction methods in which processing temperatures higher than 800 °C are usually required to obtain a single-phase of these materials. Reflections peaks of the samples obtained in both cases can be indexed well with the standard patterns for Ni3(PO4)2 and Ni3(VO4)2 compounds. The lattice parameters of these materials were calculated by the Rietveld refinement method from X-ray diffraction data (XRD). The average crystal size as well as the crystallinity and morphology of the powder samples were characterized by scanning electron microscopy (SEM). The results show a clearly minor particle size by using the Pechini-IPC method than the ceramic one. Moreover, the magnetic behaviour was studied on powered samples by using magnetic susceptibility data.  相似文献   

11.
Synthesis and Crystal Structure of K2(HSO4)(H2PO4), K4(HSO4)3(H2PO4), and Na(HSO4)(H3PO4) Mixed hydrogen sulfate phosphates K2(HSO4)(H2PO4), K4(HSO4)3(H2PO4) and Na(HSO4)(H3PO4) were synthesized and characterized by X‐ray single crystal analysis. In case of K2(HSO4)(H2PO4) neutron powder diffraction was used additionally. For this compound an unknown supercell was found. According to X‐ray crystal structure analysis, the compounds have the following crystal data: K2(HSO4)(H2PO4) (T = 298 K), monoclinic, space group P 21/c, a = 11.150(4) Å, b = 7.371(2) Å, c = 9.436(3) Å, β = 92.29(3)°, V = 774.9(4) Å3, Z = 4, R1 = 0.039; K4(HSO4)3(H2PO4) (T = 298 K), triclinic, space group P 1, a = 7.217(8) Å, b = 7.521(9) Å, c = 7.574(8) Å, α = 71.52(1)°, β = 88.28(1)°, γ = 86.20(1)°, V = 389.1(8)Å3, Z = 1, R1 = 0.031; Na(HSO4)(H3PO4) (T = 298 K), monoclinic, space group P 21, a = 5.449(1) Å, b = 6.832(1) Å, c = 8.718(2) Å, β = 95.88(3)°, V = 322.8(1) Å3, Z = 2, R1 = 0,032. The metal atoms are coordinated by 8 or 9 oxygen atoms. The structure of K2(HSO4)(H2PO4) is characterized by hydrogen bonded chains of mixed HnS/PO4 tetrahedra. In the structure of K4(HSO4)3(H2PO4), there are dimers of HnS/PO4 tetrahedra, which are further connected to chains. Additional HSO4 tetrahedra are linked to these chains. In the structure of Na(HSO4)(H3PO4) the HSO4 tetrahedra and H3PO4 molecules form layers by hydrogen bonds.  相似文献   

12.
CuFe2(C2O4)3·4.5H2O was synthesized by solid-state reaction at low heat using CuSO4·5H2O, FeSO4·7H2O, and Na2C2O4 as raw materials. The spinel CuFe2O4 was obtained via calcining CuFe2(C2O4)3·4.5H2O above 400 °C in air. The CuFe2(C2O4)3·4.5H2O and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform FT-IR, X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectrometer, and vibrating sample magnetometer. The result showed that CuFe2O4 obtained at 400 °C had a saturation magnetization of 33.5 emu g?1. The thermal process of CuFe2(C2O4)3·4.5H2O experienced three steps, which involved the dehydration of four and a half crystal water molecules at first, then decomposition of CuFe2(C2O4)3 into CuFe2O4 in air, and at last crystallization of CuFe2O4. Based on KAS equation, OFW equation, and their iterative equations, the values of the activation energy for the thermal process of CuFe2(C2O4)3·4.5H2O were determined to be 85 ± 23 and 107 ± 7 kJ mol?1 for the first and second thermal process steps, respectively. Dehydration of CuFe2(C2O4)3·4.5H2O is multistep reaction mechanisms. Decomposition of CuFe2(C2O4)3 into CuFe2O4 could be simple reaction mechanism, probable mechanism function integral form of thermal decomposition of CuFe2(C2O4)3 is determined to be 1 ? (1 ? α)1/4.  相似文献   

13.
Using tri-ethyl phosphate as a phosphate source, the hydrothermal reaction of cobalt(II) oxalate di-hydrate, zinc oxide and 1,8 di-amino octane at 200°C gave purple crystals of Co6(PO4)4?·?7H2O (1), along with a mixture of open-framework zinc–cobalt phosphates Co–Zn–HPO4, and Co3(HPO4)2(2OH). Compound 1, has been characterized by thermal analysis, FTIR and single crystal X-ray diffraction. The single crystal structure of Co6(PO4)4?·?7H2O reveals cobalt in four, five and six-fold coordination with linkages through the bridging water molecules and the oxygen atoms of the phosphate in the subunits. Four subunits are connected together through the oxygen atoms (PO4), to form the three dimensional open framework structure, with a 20-member ring channel that hosts two uncoordinated water molecules. Thermal removal of the water molecules occurs between 400–600°C, with the collapse of the structure above 600°C.  相似文献   

14.
Co3xNi3−3x(PO4)2·8H2O (x = 1, 0.8, 0.6, 0.4, 0.2, and 0) were synthesized via simple wet chemical reaction and energy saving route method. The final decomposition products of hydrates are corresponding anhydrous tri(cobalt nickel) diphosphates. The metal and water contents of the synthesized hydrates were confirmed by AAS and TG/DTG/DTA techniques, respectively. The observed metal and water contents agree well with the formula of the title compounds. The crystal structures and lattice parameters as well as crystallite sizes of the studied compounds were determined using XRD data. The results from XRD and TG/DTG/DTA techniques confirmed that Co3xNi3−3x(PO4)2·8H2O at all ratios were the single phase. The FTIR spectra of studied compounds were recorded and assigned. The thermal behaviours of single and binary tri(cobalt nickel) diphosphate octahydrates were studied for the first time. The morphologies of the studied compounds were investigated by using the SEM technique. The micrographs of all studied compounds exhibited the thin plated morphology. The surface area and the pore size data of anhydrous forms were measured by N2 adsorption at −190 °C according to the BET method. The anhydrous forms of binary metal phosphate at x = 0.8, Co2.4Ni0.6(PO4)2, exhibits the highest surface area and expects to improve the catalytic activity.  相似文献   

15.
The layered nanocrystalline sodium manganese phosphate was synthesized by low‐heating solid state reaction using MnSO4·H2O and Na3PO4·12H2O as raw materials. The resulting sodium manganese phosphate and its calcined products were characterized using element analysis, thermogravimetry and differential thermal analyses (TG/DTA), Fourier transform IR (FT‐IR), X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), ultraviolet‐visible (UV‐Vis) absorption spectroscopy, and magnetic susceptibility. The results showed that the product obtained at 70°C for 3 h, NaMnPO4·3H2O, was a layered compound, and its crystallite size and interlayer distance were 27 nm and 1.124 nm, respectively. The thermal process of NaMnPO4·3H2O between room temperature and 700°C experienced three steps, the dehydration of the one adsorption water at first, and then dehydration of the two crystal waters, at last crystallization of NaMnPO4. Magnetic susceptibility measurements of NaMnPO4· 3H2O from room temperature to 2.5 K point to ferrimagnetic ordering at TN‐35 K.  相似文献   

16.
Natural graphite treated by mechanical activation can be directly applied to the preparation of Li3V2(PO4)3. The carbon-coated Li3V2(PO4)3 with monoclinic structure was successfully synthesized by using natural graphite as carbon source and reducing agent. The amount of activated graphite is optimized by X-ray diffraction, scanning electron microscope, transmission electron microscope, Raman spectrum, galvanostatic charge/discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy tests. Our results show that Li3V2(PO4)3 (LVP)-10G exhibits the highest initial discharge capacity of 189 mAh g?1 at 0.1 C and 162.9 mAh g?1 at 1 C in the voltage range of 3.0–4.8 V. Therefore, natural graphite is a promising carbon source for LVP cathode material in lithium ion batteries.  相似文献   

17.
A revised version of the Ca3(PO4)2–YPO4 phase diagram has been proposed on the basis of results obtained by thermal analysis (DTA/DSC/TG) and X-ray diffraction methods. A limited solid solution with the structure of β-Ca3(PO4)2 exists in the system. At 1,100 °C the maximal concentration of YPO4 in the solid solution is ~15 mass%. The solid-solution phase field exists in the temperature range upto ~1,380 °C. Two high-temperature solid solutions with the structure of α′ and α-Ca3(PO4)2 form in system as well, however only the α phase can be obtained by quenching from high temperatures. The Ca3Y(PO4)3 compound with the structure of eulytite forms in the Ca3(PO4)2–YPO4 system at temperatures exceeding 1,255 °C and does not show any polymorphic transition.  相似文献   

18.
Hybrid materials xLiFePO4·(1 − x)Li3V2(PO4)3 were synthesized by sol–gel method, with phenolic resin as carbon source and chelating agent, methylglycol as surfactant. The crystal structure, morphology and electrochemical performance of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge–discharge test and particle size analysis. The results show that LiFePO4 and Li3V2(PO4)3 co-exist in hybrid materials, but react in single phase. Compared with individual LiFePO4 and Li3V2(PO4)3 samples, hybrid materials have smaller particle size and more uniform grain distribution. This structure can facilitate Li ions extraction and insertion, which greatly improves the electrochemical properties. The sample 0.7LiFePO4·0.3Li3V2(PO4)3 retains the advantages of LiFePO4 and Li3V2(PO4)3, obtaining an initial discharge capacity of 166 mA h/g at 0.1 C rate and 109 mA h/g at 20 C rate, with a capacity retention rate of 73.3% and an excellent cycle stability.  相似文献   

19.
ZrWMoO8 powders with different morphologies were obtained using ammonium tungstate, molybdate tungstate and zirconium tungstate as the starting materials by dehydrating the precursor ZrWMoO7(OH)2(H2O)2. The precursor was studied by thermo-gravimetric and differential scanning calorimetry (TG-DSC). The influence of the gelling agents (HCl, HClO4, HNO3, H2SO4 and H3PO4) on the crystallization process and crystal morphology of the products prepared was investigated by X-ray powder diffraction (XRD), scanning electron micrograph (SEM) and X-ray fluorescence spectrometer (XRF). Results showed that the morphology of the ZrWMoO8 particles can be simply adjusted by changing the gelling agents, and the thermal expansion coefficients of cubic ZrWMoO8 prepared in HCl solution are −3.84 × 10−6 K−1 from 100°C to 700°C. __________ Translated from Chemical Journal of Chinese University, 2007, 28(3): 397–401 [译自: 高等学校化学学报]  相似文献   

20.
Phase formation in the ZrO(NO3)2-NaF(HF)-H3PO4-H2O system was studied at 20°C and 2.0–14.5 wt % ZrO2 in the initial solution along sections with molar ratios PO 4 3? /Zr = 0.5 and 1.5 and also in the presence of hydrogen fluoride at Na/Zr = 1 and PO 4 3? /Zr = 0.5, 1.0, and 1.5. Crystalline zirconium hydrophosphate Zr(HPO4)2 · H2O, fluorozirconates Na5Zr2F13 and Na7Zr6F31 · 12H2O, fluorophosphatozirconates NaH2Zr3F3(PO4)4 · 3H2O and NaZr2F6(PO4) · 4H2O, and amorphous NaZrO0.5F(PO4) · 4H2O (provisional composition) were separated at room temperature. NaH2Zr3F3(PO4)4 · 3H2O and NaZr2F6(PO4) · 4H2O were prepared for the first time and were studied by crystal-optical, elemental, and thermal analyses, X-ray powder diffraction, IR spectroscopy, scanning electron microscopy (SEM), and X-ray microanalysis. Na7Hf6F31 · 12H2O was found to exist in a mixture with the hydrophosphate.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号