铁钠复合氧化物作锂离子电池负极材料的研究

研究了一种新型的锂离子电池负极材料Ｎａ２Ｏ·１．５Ｆｅ２Ｏ３的制备、电化学性能、在不同电解液中的行为以及充放电过程中结构的稳定性等问题。研究结果表明Ｎａ２Ｏ·１．５Ｆｅ２Ｏ３在ＬｉＣｌＯ４－ＰＣ溶液中具有良好的锂嵌入－脱出可逆性和较高的比容量。以０．２５ｍＡ／ｃｍ２电流密度充放电，容量可达３６０ｍＡｈ／ｇ。Ｘ射线衍射分析证实，多次充放电后，其结构仍保持稳定，Ｎａ２Ｏ·１．５Ｆｅ２Ｏ３／ＬｉＣｌＯ４－ＰＣ／ＬｉＣｏＯ２锂离子电池试验结果表明，Ｎａ２Ｏ·１．５Ｆｅ２Ｏ３可作为锂离子电池的候选负极材料。

金属铁纳米粒子的液相制备、表面修饰及其结构表征

报道在表面活性剂存在的条件下于乙醇／水的简单液相体系中以ＡＮＨ。还原制备金属铁纳米粒子，然后再用含锌盐修饰溶液进行原位粒子的表面修饰，并通过Ｘ射线衍射（ＸＲＤ）、光电子能谱分析（ＸＰＳ）、透射电子显微分析（ＴＩＭ）、选区电子衍射（ＥＤ）表征和讨论所得产物粒子的形貌结构特征和粒子大小．结果表明，初始生成的金属铁纳米粒子与修饰溶液的电化学反应形成以金属纳米铁核为中心的具有较好稳定性的多层复合结构．

(Na[Fe(CO)_2C_5H_5]_2)n的形成和反应特性的研究

According to the reaction of [Fe (CO)2C5H5]2 with sodium amalgam (Na/Hg), the molecular structures of crystals and the IR data of L3SnFe (CO)2C5H5 (L=C6H11, C6H5),[ (C5Me5)2Ln (CO)2FeC5H5]2(Ln=Dy, Gd, Sm, Nd, Pr) complexes, the process of forma tion of (Na[Fe (CO)2C5H5]2)n, its structure changes and reaction regularities in the synthe ses of heteronuclear metal complexes were analyzed and discussed.

Removal of S^(2-) ion from sodium aluminate solutions with sodium ferrite

The synthesis of sodium ferrite and its desulfurization performance in S2 -bearing sodium aluminate solutions were investigated. The thermodynamic analysis shows that the lowest temperature is about 810 K for synthesizing sodium ferrite by roasting the mixture of ferric oxide and sodium carbonate. The results indicate that the formation process of sodium ferrite can be completed at 1173 K for 60 min, meanwhile raising temperature and reducing NazCO3 particle size are beneficial to accelerating the formation of sodium ferrite. Sodium ferrite is an efficient desulfurizer to remove the S2- in aluminate solution, and the desulfurization rate can reach approximately 70% at 373 K for 60 min with the molar ratio of iron to sulfur of 1：1-1.5：1. Furthermore, the desulfurization is achieved by NaFeS2·2H2O precipitation through the reaction of Fe（OH）4 and S^2- in aluminate solution, and the desulfurization efficiency relies on the Fe（OH）4^- generated by dissolving sodium ferrite.

Pyrite depression in marmatite flotation by sodium glycerine-xanthate

The depression of pyrite in marmatite flotation by sodium glycerine-xanthate （SGX） was investigated through microflotation, zeta potential and adsorption measurements. The flotation tests of mineral show that in the presence of SGX, marmatite can be activated by Cu^2＋ and shows good flotability, while pyrite cannot be activated and therefore shows poor flotability. At the pH value range from 4 to 11, the flotation selectivity between marmatite and pyrite is obvious when the SGX concentration is below 50 mg/L. The depression mechanism of SGX on sulfide minerals is discussed based on zeta potential and adsorption isotherm. Zeta potential measurement demonstrates that in the presence of Cu^2＋, SGX can strongly adsorb on the surface of pyrite, while it cannot adsorb on the surface of marmatite. The results of adsorption isotherms show that the adsorption density of SGX on pyrite is greater.

Interaction of sulfur with iron compounds in sodium aluminate solutions

Reaction behaviors of sulfur and iron compounds in sodium aluminate solutions were investigated. The results show that iron compounds can remarkably remove the S2 but cannot get rid of S2Oc2-, SO^2- and SO4^-2 in sodium aluminate solutions. The removal efficiency of S^2- using ferrous compound and ferric compound can reach 86.10% and 92.70% respectively when the iron compounds were added with a molar ratio of 2：1 compared with the sulfur in liquors at 100℃. Moreover, several same compounds are formed in those two desulfurization processes with ferrous or ferric compounds, including erdite, hematite, amorphous ferrous sulfide, polymerized sulfur-iron compounds and ferric sulfate. The major difference between these two processes is that the erdite generated from ferrous compounds at the initial reaction stage will convert to a sodium-free product FeS2 at the subsequent stage.

Effect of sodium hexametaphosphate on separation of serpentine from pyrite

The effect of sodium hexametaphosphate（SHMP） on the separation of serpentine from pyrite and its mechanism were studied systematically through flotation tests,sedimentation tests,surface dissolution,ζ potential tests,adsorption measurements,and infrared spectroscopic analyses.The results show that the SHMP could significantly reduce the adverse effect of serpentine on the flotation of pyrite and make the mixed sample of pyrite and serpentine more disperse in the alkaline condition,thus improve the adsorption of xanthate on pyrite.The action mechanism of the SHMP is that it lowers the pH value at the isoelectric point of serpentine and enhances the negative charge through the dissolution of magnesium from the surface of serpentine and adsorbing on the surface of serpentine.It changes the total interaction energy between serpentine and pyrite from gravitational potential energy to repulse potential energy,according to the calculation of the EDLVO theory.

Shear hydrophobic flocculation and flotation of ultrafine Anshan hematite using sodium oleate

Effects of stirring speed and time, pH and sodium oleate concentration on the shear hydrophobic flocculation of ultrafine Anshan hematite with sodium oleate as the surfactant were discussed. The results show that these parameters significantly affect the shear hydrophobic flocculation of ultrafine hematite. The optimum conditions for the flocculation are： stirring speed 1 400 r/min, flocculation time 20 min, pH 9 and sodium oleate concentration 3.94×10-4 mol/L; the flotation recovery of hematite flocs is remarkably high compared with non flocculated ultrafine hematite. According to the extended DLVO theory, the total interaction potential of Anshan ultrafine hematite was determined. The calculation results indicate that the hydrophobic flocculation state of the ultrafine hematite-sodium oleate system is mainly dominated by electric double layer repulsive interaction potential and hydrophobic interaction potential. A mechanical agitation is required to impart particles a kinetic energy to overcome potential barrier between them due to the existence of electric double layer repulsive interaction potential. Those particles further approach to form flocs due to the significant increase of the hydrophobic interaction potential.

Effects of dwell time during sintering on electrical properties of 0.98(K_(0.5)Na_(0.5))NbO_3-0.02LaFeO_3 ceramics

The effects of dwell time on the phase structure, microstructure, and electrical properties were investigated for the 0.98（K0.sNa0.5）NbO3-0.02LaFeO3 ceramics （abbreviated as 0.98KNN-0.02LF）. All the ceramics sintered for different dwell time are of pure phase and the peak intensity of the 0.98KNN-0.02LF ceramics becomes stronger with a longer dwell time. Denser microstructures with larger grain size are developed for the sample with a longer dwell time. The maximum dielectric permittivity decreases with increasing the dwell time, and the deteriorative dielectric properties are due to the increasing grain size and the domain wall motion. Ferroelectric properties results indicate that 2Pr value slightly decreases with increasing the dwell time, while the 2Ec value increases. Consequently, the 0.98KNN-0.02LF ceramic sintered at 1150 ℃ for 2 h shows optimum dielectric properties （er=2253 and tan fi〈5%） and ferroelectric properties （2Pr=34.51 gC/cm2 and 2Ec=5.07 kV/mm）.

Novel method to prepare sodium chromate from carbon ferrochrome

An oxidizing roasting process of carbon ferrochrome to prepare sodium chromate in the presence of sodium carbonate and air was investigated. The effects of reaction temperature, reaction time, mole ratio of sodium carbonate to carbon ferrochrome were studied, and thermodynamics and kinetics of the reaction were also discussed. It was observed that there was a sudden increase in reaction rate when the temperature rose to a certain value, and the sample with a smaller grain size could start the sudden increase at a lower temperature. The chromium recovery rate increased with the increase of mole ratio of sodium carbonate to carbon ferrochrome, and it reached up to 99.34% when mole ratio of sodium carbonate to carbon ferrochrome increased to 1.2:1. The chromium residue yielded from this method was only about 1/3 of the product. Moreover, the content of Fe in the residue was as high as 60.41%. Therefore, it can be easily recovered to produce sponge iron, realizing complete detoxication and zero-emission of chromium residue.

Preparation and Investigation on Lattice Distortion and Electrochemical Performances of Li0.95Na0.05FePO4/C

Na^＋ doped sample Li0.95Na0.05FePO4 was prepared through solid state method. Structure characterization shows Na^＋ is successfully introduced into the LiFePO4 matrix. Scanning electron microscopy shows the particle size mainly ranges in 1-3 μm. X-ray diffraction Rietveld refinement demonstrates lattice distortion with an increased cell volume. As one cathode material, it has a discharge capacity of 150 mAh/g at 0.1 C rate. The material exhibits a capacity of 109 and 107 mAh/g at 5 and 7.5 C respectively. When cycled at 1 and 5 C, the material retains 84% （after 1000 cycles） and 86% （after 350 cycles） of the initial discharge capacity respectively indicating excellent structure stability and cycling performance. Na^＋ doping enhances the electrochemical activity especially the cycle performance effectively.

Na2FePO4F/C composite synthesized via a simple solid state route for lithium-ion batteries

Using low-cost FePO4·2H2O as iron source,Na2FePO4F/C composite is prepared by alcohol-assisted ball milling and solid-state reaction method.The XRD pattern of Na2FePO4F/C composite demonstrates sharp peaks,indicating high crystalline and phase purity.The SEM and TEM images reveal that diameter of the spherical-like Na2FePO4F/C particles ranges from 50 to 300 nm,and HRTEM image shows that the surface of Na2FePO4F/C composite is uniformly coated by carbon layer with a average thickness of about 3.6 nm.The carbon coating constrains the growth of the particles and effectively reduces the agglomeration of nanoparticles.Using lithium metal as anode,the composite delivers a discharge capacities of 102.8,96.4 and 90.3 mA·h/g at rates of 0.5C,1C and 2C,respectively.After 100 cycles at 0.5C,a discharge capacity of 98.9 mA·h/g is maintained with capacity retention of 96.2%.The Li+diffusion coefficient(D)of Na2FePO4F/C composite is calculated as 1.71×10^–9 cm^2/s.This study reveals that the simple solid state reaction could be a practical and effective synthetic route for the industrial production of Na2FePO4F/C material.

Thermodynamics of chromite ore oxidative roasting process

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.

Separation of aluminosilicates and diaspore from diasporic-bauxite by selective flocculation

The flocculation tests of four pure minerals(diaspore,kaolinite,illite,pyrophyllite)and bauxite ore were investigated by the sedimentation.The dispersion behavior of the four pure minerals shows a very good consistency with the variation of zeta potential.The concentrate with the mass ratio of Al2O3 to SiO2(m(Al2O3)/m(SiO2))8.90 and the recovery of Al2O3 86.98%is obtained from bauxite ore(m(Al2O3)/m(SiO2)=5.68)in pH range of 9.5-10.0 by using sodium carbonate(5 kg/t)and sodium polyacrylate(7 g/t)as dispersant and flocculant respectively.Sodium carbonate acts as both pH modifier and favorable dispersant for aluminosilicates.The high performance of sodium polyacrylate on flocculation for diaspore is contributed to the carboxyl of sodium polyacrylate that interacts with active Al sites on diaspore by chemical absorption,and the hydrogen bond effects between hydroxyl group of macromolecule and surface Al—OH on diaspore to accelerate the sedimentation of diaspore.

Interaction mechanism between arsenate and fayalite-type copper slag at high temperatures

The interaction mechanism between sodium arsenate and fayalite-type copper slag at 1200℃was investigated through XRD,XPS,HRTEM,TCLP and other technical means and methods.The results indicated that the proportions of sodium arsenate in the slag and flue gas phases were approximately 30%and 70%,respectively.The addition of sodium arsenate depolymerized the fayalite structure and changed it from a crystalline state to an amorphous state.The fayalite structural changes indicated that the[AsO_(4)]tetrahedron in sodium arsenate combined with the[SiO_(4)]tetrahedron and[FeO_(4)]tetrahedron through bridging oxygen to form a silicate glass structure.The TCLP test results of the samples before and after the high temperature reaction of fayalite and sodium arsenate showed that after high temperature reaction,fayalite could effectively reduce the leaching toxicity of sodium arsenate,reducing the leaching concentration of arsenic from 3025.52 to 12.8 mg/L before and after reaction,respectively.

Efficient destruction of sodium cyanide by thermal decomposition with addition of ferric oxide

Efficient destruction of cyanide by thermal decomposition with ferric oxide addition was proposed. The mechanism of destruction of sodium cyanide with or without ferric oxide addition under various conditions was examined by XRD, DSC-TG, and chemical analysis technologies. In the absence of ferric oxide, sodium cyanide decomposes at 587.4 ℃ in air and 879.2 ℃ in argon atmosphere. In the presence of ferric oxide, about 60% of sodium cyanide decomposes at 350 ℃ for 30 min in argon, while almost all sodium cyanide decomposes within 30 min in air or O2 with mass ratio of ferric oxide to sodium cyanide of 1:1. The increase of ferric oxide addition, temperature, and heating time facilitates the destruction of sodium cyanide. It is believed that with ferric oxide addition, NaCN reacts with Fe2O3 to form Na4Fe(CN)6, Na2CO3, NaNO2 and Fe3O4 in argon. NaCN decomposes into NaCNO, Na4Fe(CN)6, minor NaNO2, and the formed NaCNO and Na4Fe(CN)6 further decompose into Na2CO3, CO2, N2, FeOx, and minor NOx in air or O2.

Effect and mechanism of dolomite with different size fractions on hematite flotation using sodium oleate as collector

The effect of dolomite with different particle size fractions on hematite flotation was studied using sodium oleate as collector at p H of about 9. The effect mechanism of dolomite on hematite flotation was investigated by means of solution chemistry, ultraviolet spectrophotometry(UV), inductively coupled plasma atomic emission spectrometry(ICP-AES) and X-ray photoelectron spectroscopy(XPS). It is observed that dolomite with different size fractions has depressing effect on hematite flotation using sodium oleate as collector, and dolomite could be the "mineral depressant" of hematite using sodium oleate as collector. The reasons for that are concerned with sodium oleate consumption and the adsorption onto hematite of dissolved species of dolomite.

Epitaxial α″-Fe_(16)N_2 Films Grown on NaCl (001) by Facing Target Sputtering

There is a gr eat interest in obtaining epitaxial α″ nitride phase of iron because of their special ferromagnetic properties. α″ Fe 16 N 2 thin films have been prep ared by facing target sputtering (FTS) onto NaCl (001) substrates in a mixture of argon(Ar) and N 2 gases. The base pressure was 6×10 -5 Pa. During sput tering, the partial pressures of Ar and N 2 gases were kept constant at 0.3 Pa and 0.05 Pa respectively. The deposition rate was about 0.2 nm/s. The substrate temperature was held at about 100 ℃. Annealing of the films was sequentially ca rried out at 150 ℃ for 1 h in vacuum ( at least 10 -4 Pa ) to obtain α″ phase. Transmission electron microscope (TEM) observations and X ray diffract ion (XRD) patterns showed that the α″ Fe 16 N 2 epitaxially grew on the NaCl substrates. It was found that the arrangement of the SAD patterns exhibits perfect symmetries.By using super lattice reflections, the lattice constants a=b=(5.71±0.02)×10 -1 nm and c=(6.30±0.04) ×10 -1 nm of the α″ phase with a body centered tetragonal (BCT) structu re were determined, which was very close to the results obtained by Jack (a=b= 5.72×10 -1 nm, c= 6.29×10 -1 nm). The X ray diffraction patterns and the selected area diffraction patterns showed t hat α″ Fe 16 N 2 epitaxially grew on the NaCl (001) substrate with orien tation relationships α″ Fe 16 N 2 (001) ‖NaCl (001),α″ Fe 16 N 2 ‖NaCl .

Enhancing storage performance of P2-type Na_(2/3)Fe_(1/2)Mn_(1/2)O_(2)cathode materials by Al_(2)O_(3)coating

The P2-type Na_(2/3)Fe_(1/2)Mn_(1/2)O_(2)materials were synthesized by an ultrasonic spray pyrolysis followed by solid-state sintering method.The structures,morphologies and electrochemical performances of Na_(2/3)Fe_(1/2)Mn_(1/2)O_(2)materials were characterized thoroughly by means of X-ray diffractometer,scanning electron microscope and electrochemical charge/discharge instruments.Moreover,a thin layer of Al_(2)O_(3),which was formed on the surface of Na_(2/3)Fe_(1/2)Mn_(1/2)O_(2),can enhance the storage performance by preventing the formation of Na_(2)CO_(3)·H_(2)O,which is believed to enhance the electrochemical performances of Na_(2/3)Fe_(1/2)Mn_(1/2)O_(2)materials.This facile surface modification method may pave a way to synthesize advanced cathode materials for sodium-ion batteries.