铁位掺杂对LiFePO_4-C性能的影响

本文从体相铁位掺杂出发,以二氧化钛、乙酸镍、乙酸锰、氢氧化镁等为原料,合成LiFe0.9M0.1PO4-C材料,考察了不同掺杂元素对LiFePO4性能的影响。与碳包覆LiFePO4材料相比较,Ti的掺杂使Li+扩散系数提高了两个数量级,达到4.117E-09 cm2.s-1;将材料的振实密度显著提高到了1.62 g/ml;循环30次,容量保持在79.8 mAh/g,保持率达92%。即铁位掺杂Ti的复合材料在高倍率下的性能远远好于未掺杂LiFePO4材料。

The role of titanium at the interface of hematite photoanode in multisite mechanism:Reactive site or cocatalyst site?

Hematite(α-Fe_(2)O_(3))constitutes one of the most promising photoanode materials for oxygen evolution reaction(OER).Recent research on Fe_(2)O_(3) have found a fast OER rate dependence on surface hole density,suggesting a multisite reaction pathway.However,the effect of heteroatom in Fe_(2)O_(3) on the multisite mechanism is still poorly understood.Herein we synthesized Fe_(2)O_(3) on Ti substrates(Fe_(2)O_(3)/Ti)to study the oxygen intermediates of OER by light-dark electrochemical scans.We identified the Fe-OH species disappeared and Ti-OH intermediates appeared on Fe_(2)O_(3)/Ti when pH=11‒14,which significantly improved the OER performance of Fe_(2)O_(3)/Ti.Combined with the density functional theory calculations,we propose that Ti atom acts as cocatalyst site and captures proton from neighboring Fe-OH species under highly alkaline condition,thereby promoting the coupling of Fe=O and reducing the energy barrier of the non-electrochemical step.Our work provides a new insight into the role of heteroatom in OER multisite mechanism based on clarifying the reaction intermediates.

Fe extraction from high-silicon and aluminum cyanide tailings by pretreatment of water leaching before magnetic separation

Pretreatment of high content of Si- and Al-containing cyanide tailings by water leaching to remove some impurities, such as the major impurities minerals of Si and A1, as well as its effect on Fe extraction in the water leaching process was investigated. The effects of different parameters on iron recovery were studied, and the reaction parameters were proposed as follows： sodium carbonate content of 30%, water leaching at 60 ~C for 5 min, liquid/solid ratio of 15：1, and exciting current of 2 A. Under these optimal conditions, magnetic concentrate containing 59.11% total iron and a total iron recovery rate of 76.12% was obtained. In addition, the microstructure and phase transformation of the process of water leaching were studied by X-ray powder diffraction technique （XRD）, Electronic image of backscattering （BEI）, X-ray fluorescence （XRF）, and energy dispersive spectrometry （EDS）. The results indicate that the soluble compound impurities generated in the roasting process are washed out, and the dissoluble substances enter into nonmagnetic materials by water leaching, realizing the effective separation of impurities and Fe.

In-situ Raman observation on crack tips of Vickers indent in PLZT ceramics

Vickers indentation was introduced into the originally in-plane and out-of-plane poled PLZT ceramics.The Raman spectra were in-situ recorded at selected crack tips before and after the indentations,as well as after the applications of external electric field.The results show that the changes in Raman intensities of optical modes could be sensitively related to 90° domain switching around the crack tips which are strongly dependent on the directions of original polarization and geometric locations.When the direction of electric field was perpendicular to the direction of original polarization,the 90° domain switching at crack tips of the Vickers indentation on the originally in-plane poled PLZT ceramics caused most significant change in the Raman intensity,which inhibited the crack growth.However,when the direction of electric field was parallel to the direction of original polarization,the growth of crack tips became predominantly without the 90° domain switching,which led to the crack growth.

Relationship and effect of redox potential,jarosites and extracellular polymeric substances in bioleaching chalcopyrite by acidithiobacillus ferrooxidans

The changes of pH,redox potential,concentrations of soluble iron ions and Cu^2＋ with the time of bioleaching chalcopyrite concentrates by acidithiobacillus ferrooxidans were investigated under the different conditions of initial total-iron amount as well as mole ratio of Fe（III） to Fe（II） in the solutions containing synthetic extracellular polymeric substances （EPS）.When the solution potential is lower than 650 mV （vs SHE）,the inhibition of jarosites to bioleaching chalcopyrite is not vital as EPS produced by bacteria can retard the contamination through flocculating jarosites even if concentration of Fe（III） ions is up to 20 g/L but increases with increasing the concentration of Fe（III） ions;jarosites formed by bio-oxidized Fe3＋ ions are more easy to adhere to outside surface of EPS space on chalcopyrite;the EPS layer with jarosites acts as a weak diffusion barrier to further rapidly create a high redox potential of more than 650 mV by bio-oxidizing Fe^2＋ ions inside and outside EPS space into Fe^3＋ ions,resulting in a rapid deterioration of ion diffusion performance of the EPS layer to inhibit bioleaching chalcopyrite severely and irreversibly.

Floc flotation of marmatite fines in aqueous suspensions induced by butyl xanthate and ammonium dibutyl dithiophosphate

The hydrophobic flocculation of marmatite fines in aqueous suspensions induced by butyl xanthate （KBX） and ammonium dibutyl dithiophosphate （ADD） was investigated using laser particle size analysis, microscopy analysis, electrophoretic light scattering, contact angle measurement and infrared spectroscopy. The studies were performed on single minerals with size 〈20 μm by varying several parameters, including pH, collector concentration and kerosene addition. The results show that the floc fotation closely correlated with the size of flocs and the particle hydrophobicity, but was not lowered with increasing the particle surface charges due to collector adsorption. Under good operating conditions, the floc flotation of marmatite fines as a function of KBX and ADD can all reach floatability over 90%, in comparison with conventional flotation obtaining floatability of about 60%. It also has been found that a small addition of kerosene greatly improved the floc flotation because of the formation of oil films on marmatite particles. The results of FTIR spectra indicate that adsorption of the two collectors onto marmatite were chemical adsorption.

Selection of Chelated Fe(Ⅲ)/Fe(Ⅱ) Catalytic Oxidation Agents for Desulfurization Based on Iron Complexation Method

Optimization of factors influencing the experiments on reactions involving 8 different chelating agents and soluble Fe(III)/Fe(II) salts was carried out to yield chelated iron complexes. A combination of optimized influencing factors has resulted in a Fe chelating capacity of the iron-based desulfurization solution to be equal to 6.83—13.56 g/L at a redox potential of 0.185—0.3. The desulfurization performance of Fe(III)/Fe(II) chelating agents was investigated on a simulated sulfur-containing industrial gas composed of H2 S and N2 in a cross-flow rotating packed bed. Test results have revealed that the proposed iron-based desulfurization solution showed a sulfur removal efficiency of over 99% along with a Fe chelating capacity exceeding 1.35 g/L. This desulfurization technology which has practical application prospect is currently in the phase of commercial scale-up study.

Location of anemometer along Lanzhou-Xinjiang railway

Using structured mesh to discretize the calculation region, the wind velocity and pressure distribution in front of the wind barrier under different embankment heights are investigated based on the Detached Eddy Simulation(DES) with standard SpalartAllmaras(SA) model. The Reynolds number is 4.0×105 in this calculation. The region is three-dimensional. Since the wind barrier and trains are almost invariable cross-sections, only 25 m along the track is modeled. The height of embankment ranges from 1 m to 5 m and the wind barrier is 3 m high. The results show that the wind speed changes obviously before the wind barrier on the horizontal plane, which is 4.5 m high above the track. The speed of wind reduces gradually while approaching the wind barrier. It reaches the minimum value at a distance about 5 m before the wind barrier, and increases dramatically afterwards. The speed of wind at this location is linear with the speed of far field. The train aerodynamic coefficients decrease sharply with the increment of the embankment height. And they take up the monotonicity. Meanwhile, when the height increases from 3 m to 5 m, they just change slightly. It is concluded that the optimum anemometer location is nearly 5 m in front of the wind barrier.

Separation of hematite from banded hematite jasper(BHJ) by magnetic coating

The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that besides hematite and goethite,jasper, a microcrystalline form of quartzite, is the major impurity associated with this ore. Beneficiation by conventional magnetic separation technique could yield a magnetic concentrate containing 60.8% Fe with 51% Fe recovery. In order to enhance the recovery of the iron oxide minerals, fine magnetite, colloidal magnetite and oleate colloidal magnetite were used as the coating material. When subjected to magnetic separation, the coated ore produces an iron concentrate containing 60.2% Fe with an enhanced recovery of56%. The AFM studies indicate that the coagulation of hematite particles with the oleate colloidal magnetite facilitates the higher recovery of iron particles from the low grade BHJ iron ore under appropriate conditions.

Stepwise dissolution of chalcopyrite bioleaching by thermophile A.manzaensis and mesophile L. ferriphilum

Chalcopyrite dissolution was evaluated by bioleaching and electrochemical experiments with thermophile A. manzaensis（Acidianus manzaensis） and mesophile L. ferriphilum（Leptospirillum ferriphium） cultures at 65 ℃ and 40 ℃, respectively. It was investigated that the bioleaching of chalcopyrite was stepwise. It was reduced to Cu2 S at a lower redox potential locating in the whole bioleaching process by A. manzaensis at high temperature while only at initial days of bioleaching by L. ferriphilum at a relative low temperature. No reduced product was detected when the redox potential was beyond a high level（e.g., 550 m V（vs SCE）） bioleached by L. ferriphilum. Chalcopyrite bioleaching efficiency was substantially improved bioleached by A. manaensis compared to that by L. ferriphilum, which was mainly attributed to the reduction reaction occurring during bioleaching. The reductive intermediate Cu2 S was more amenable to oxidation than chalcopyrite, causing enhanced copper extraction.

Redox behavior and chemical species of arsenic in acidic aqueous system

Arsenic(As)removal from smelting acidic wastewater is an urgent task.The most common method is oxidation of trivalent As(III)to pentavalent As(V)subsequently precipitated by ferric(Fe(III))salts.Foundations of redox behavior and chemical species are of great importance for understanding As removal.In this work,cyclic voltammetry(CV)and UV?Vis spectroscopy were used for laboratory observation;meanwhile HSC and MINTEQ software were employed for theoretical analyses.It is found that As(III)oxidation,a multiple electron transfer reaction,is diffusion-controlled.The oxidation over-potential is very high(about0.9V)in sulfuric acid solutions(pH1.0).In addition,Fe(III)?As(V)complexes are evidenced by UV?Vis spectra and chemical species analyses in series of Fe(III)?As(V)?H2SO4?H2O solutions.Therefore,the Fe(III)and As(V)species distribution against pH values are determined and a newφ?pH diagram with inclusion of Fe?As complexes is consequently compiled based on thermodynamic data predicted by other researchers.

Mineral processing plant location using the analytic hierarchy process——a case study:the Sangan iron ore mine(phase 1)

Locating the mineral processing plant near a mine is the most important parameter that affects the whole process.Many factors,and their preferences,should be considered in this stage.The factors include economical,geological,technical,environmental and tectonic parameters.A multi-criteria decision making method is necessary to rank the alternatives.In this paper we describe how plant location is selected by using the Analytic Hierarchy Process(AHP).This method,with eight criteria,was used to select a location for the mineral processing plant at the Sangan iron ore mine(phase 1).Three alternatives for the processing plant were evaluated.The main criteria were distance from the mine,access to heavy machinery transport,the amount of excavation required for grading,bed mixture capacity,belt conveyor length,distance from the tailing dam,distance from the waste dumps and surface water diversion requirements.Finally,the alternatives were ranked and the best location was proposed.

Indications of c-axis Charge Transport in Hole Doped Triangular Antiferromagnets

The c-axis charge transport of the hole doped triangular antiferromagnet is investigated within the t-J model by considering the incoherent interlayer hopping. It is shown that the c-axis charge transport of the hole doped triangular antiferromagnet is essentially determined by the scattering from the in-plane fluctuation. The c-axis conductivity spectrum shows a low-energy peak and the unusual high-energy broad band, while the c-axis resistivity is characterized by a crossover from the high temperature metallic-like behavior to the low temperature insulating-like behavior, which is qualitatively consistent with those of the hole doped square lattice antiferromagnet.

A novel iron-chelating polyimide network as a visible-light-driven catalyst for photoinduced radical polymerization

With the aim of developing a low-cost and efficient visible-light-driven photocatalyst for radical polymerization,iron-chelating polyimide networks(Fe@MPI)was fabricated by firstly synthesizing photoactive melamine-containing polyimide(MPI)networks and then incorporating Fe(III)cations into the polymer networks.Fe@MPI exhibits a wide absorption spectrum ranging from 220 to 1250 nm and 3.5 times higher photocurrent intensity as compared with the pristine MPI.Based on its excellent photo-electric properties,Fe@MPI was employed as a recyclable heterogeneous catalyst,providing sufficient activity for the visible-light driven radical polymerization to synthesize poly(methyl methacrylate)with molecular weight up to 31.×10^4 g mol.Taking advantage of the heterogeneous nature of the catalyst,Fe@MPI could be facilely regenerated from the polymerization solution by filtration without an obvious loss of its activity.This research provides a novel recyclable catalyst for visible-light driven radical polymerization.

Fate of Urea Applied to Peanut (Arachis hypogaea L.) on a Sloping Udic Ferrosol in Subtropical China

A field experiment was conducted to study the outcome of N using isotope-labeled urea with a peanut cropping system in a Udic Ferrosol on a 7% slope at the Ecological Experimental Station of Red Soil, Chinese Academy of Sciences. The micro-plots were designed in two sets with three replicates and four N treatments. An iron frame with its edge 10 cm above the ground was used to control soil erosion and runoff in set A, but in set B the upper edge of the frame was level with the ground. Randomly positioned 15…

Effect of Lattice Distortion on Charge Order in Manganites at Doping x=0.5

In the present paper, we continue our investigation on the antiferromagneticorigin of the charge order observed in the halt-doped manganese. By introducing aSu-Schrieffer-Heeger (SSH) type of perturbation interaction to the double-exchange Hamiltonian, wecalculate again its ground-state phase diagram at Glling x = 0.5 by the unrestricted real-spaceHartree-Fock approximation method. We find that, as the SSH electron-phonon interaction increases,the charge order parameter decreases to zero rapidly but the CE-type antiferromagnetic order becomesmore stable. In other words, the charge order is much more fragile than the CE-type or theNeel-type antiferromagnetic orders under the electron-phonon perturbation. These results support theproposed theory in the recent publications that the charge order in these systems is induced by theantiferromagnetic correlations.

Magnetizing roast and magnetic separation of iron in rare-earth tailings

Magnetic separation of iron in rare-earth tailings was achieved by magnetizing roast process with coal as reductant. Effects of the temperature, carbon to oxygen ratio, and cooling type on magnetic susceptibility and composition of rare-earth tailings were investigated. The results show that roast conditions with the temperature of 650℃, carbon to oxygen ratio of 3.85, and holding time of 2.5 h are in favor of reduction of Fe_2O_3 to Fe_3O_4 when the roasted rare-earth tailings is cooled along with furnace. Under these roast conditions, magnetic susceptibility of rare-earth tailings is 2.36 that is very close to theoretical value（2.33）. However, magnetic separation results of iron in rare-earth tailings cooled along with furnace are not satisfactory. Through comparing magnetic separation results of iron in rare-earth tailings cooled by different ways, it is found that water cooling is more favored of magnetic separation of iron in the roasted rare-earth tailings than furnace cooling and air cooling. Grade and recovery of iron in concentrate from rare-earth tailings cooled by water are 45.00%-49.00% and 65.00%-77.50%, respectively.

Metro passenger flow control with station-to-station cooperation based on stop-skipping and boarding limiting

Metro passenger flow control problem is studied under given total inbound demand in this work,which considers passenger demand control and train capacity supply.Relevant connotations are analyzed and a mathematical model is developed.The decision variables are boarding limiting and stop-skipping strategies and the objective is the maximal passenger profit.And a passenger original station choice model based on utility theory is built to modify the inbound passenger distribution among stations.Algorithm of metro passenger flow control scheme is designed,where two key technologies of stopping-station choice and headway adjustment are given and boarding limiting and train stopping-station scheme are optimized.Finally,a real case of Beijing metro is taken for example to verify validity.The results show that in the three scenarios with different ratios of normal trains to stop-skipping trains,the total limited passenger volume is the smallest and the systematic profit is the largest in scenario 3.

Subway location method based on SINS/DR integrated navigation and map-matching technology

With the development of rail transit,subway is playing an increasingly important role in peoples daily life.The positioning technology of subway is the key of communication based on train control system(CBTC).Considering that the global positioning system(GPS)cant be utilized in the subway and the ground equipment is complex and expensive,a self-positioning method based on inertial measurement unit(IMU)and speed sensor is put forward,and the track electronic map is used to reduce the error.This method can suppress the error divergence of Strapdown inertial navigation system(SINS)and reduce the cumulative error of dead reckoning(DR)due to attitude error.In accordance with the particularity of railway lines,using the least squares method to match the line and revise the error caused by the navigation,can greatly improve the positioning accuracy and reduce the dependency on the ground equipment,and the costs of construction and maintenance can be lowered.

Combination Effect of Cation Vacancies and O2 Adsorption on Ferromagnetism of Na0.5Bi0.5TiO3（100） Surface:ab initio Study

The combination effect of cation vacancies and O2 adsorption on ferromagnetism of Na0.5Bi0.5TiO3（100） surface is studied by using density functional theory. An ideal Na0.5Bi0.5TiO3（100） surface is non-magnetic and the cation vacancy could induce the magnetism. By comparing the formation energies for Na, Bi and Ti vacancy, the Na vacancy is more stable than the others. Therefore, we focus on the configuration and electric structure for the system of O2 molecule adsorption on the Na0.5Bi0.5TiO3（100） surface with a Na vacancy. Among the five physisorption configurations we considered, the most likely adsorption position is Na vacancy. The O2 adsorption enhances the magnetism of the system. The contribution of spin polarization is mainly from the O 2p orbitals. The characteristics of exchange coupling are also calculated, which show that the ferromagnetic coupling is favorable. Compared with the previous calculation results, our calculations could explain the room-temperature ferromagnetism of Na0.5Bi0.5TiO3 nanocrytalline powders more reasonably, because of taking into account adsorbed oxygen and cation vacancies. Moreover, our results also show that adsorption of O2 molecule as well as introduction of cation vacancies may be a promising approach to improve multiferroic materials.