Enhanced conversion mechanism of Al-goethite in gibbsitic bauxite under reductive Bayer digestion process

The conversion mechanism of Al-goethite under the action of different additives(lime or reductant for typical or reductive Bayer digestion)was investigated by thermodynamic calculation,XRD,and SEM-EDS.The results show that the formation of Fe-substituted hydrocalumite is crucial to converting Al-goethite to hematite during Bayer digestion by adding lime.However,the conversion proceeds more easily under the action of reductant due to the rapid formation of magnetite.Additionally,Bayer liquor composition significantly affects the product composition and also the conversion rate of Al-goethite.Compared to typical Bayer digestion with Al-goethite containing gibbsitic bauxite as raw material,the red mud yield of reductive Bayer digestion decreases from 39.02%to 31.19%,and the grade of TFe in red mud increases from 41.66%to 53.80%.

Electrothermal energy conversion mechanism of micro-scale semiconductor bridge

The response characteristics of resistance is observed by the analysis of experimental data of micro scale semiconductor bridge （MSCB） under different voltage inputs. Two critical voltages are found. One is called exploding voltage, above which the MSCB can be melted and vaporized without generating a plasma, and the other is called producing a plasma voltage, above which the MSCB is entirely vaporized, and then the current flows through the vapor producing the plasma. Based on the non Fourier heat conduction theory, the electrothermal energy conversion model is es tablished for the stage from heating to exploding, and then the correlation of MSCB and time is ob tained by graphic calculation. Importantly, the critical exploding voltage and exploding time are also derivate. With the comparison between the analytical result from the theoretical model and that from experimental data, it has been demonstrated that the theoretical model is reasonable and feasible for designing the exploding voltage and exploding time.

Preparation and Photoelectric Conversion Mechanism of Semiconducting ITO/Cu_2O Electrodes

Semiconducting cuprous oxide films were electrodeposited onto conducting glasses coated with Indium Tin Oxide （ITO） using potentiostatic method. The electrodes were examined by means of X-Ray Diffraction （XRD） and X-ray Photoelectron Spectrum （XPS）. The results indicate that the prepared films are cubic Cu2O crystals, and annealing enhances the size and preferred orientation of the films. The photoelectric conversion mechanism of semiconducting ITO/Cu2O electrodes in 0.1 mol/L potassium sulfate （K2SO4） solution is further discussed by using Linear Sweep Voltammetry （LSV） method. The differences of photoelectric conversion of electrodes are reasonably deduced and proved through surfactant modifying, annealing or not, respectively.

Microemulsion synthesis of ZnMn2O4/Mn3O4 sub-microrods for Li-ion batteries and their conversion reaction mechanism

The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.

Porous core–shell CoMn_2O_4 microspheres as anode of lithium ion battery with excellent performances and their conversion reaction mechanism investigated by XAFS

Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electrochemical properties. The CoMn204 anode can deliver a large capacity of 1070 mAh g-1 in thefirst discharge, a reversible capacity of 500 mAh g^-1 after 100 cycles with a coulombic efficiency of 98.5% at a charge-discharge current density of 200 mA g^-l, and a specific capacity of 385 mAh g^-1 at a muchhigher charge-discharge current density of 1600mA g^-1. Synchrotron X-ray absorption fine structure（XAFS） techniques were applied to investigate the conversion reaction mechanism of the CoMn204 anode.The X-ray absorption near edge structure （XANES） spectra revealed that, in the first discharge-charge cy-cle, Co and Mn in CoMn204 were reduced to metallic Co and Mn when the electrode was discharged to0.01 V, while they were oxidized respectively to CoO and MnO when the electrode was charged to 3.0V.Experiments of both XANE5 and extended X-ray absorption fine structure （EXAFS） revealed that neithervalence evolution nor phase transition of the porous core-shell CoMn204 microspheres could happen inthe discharge plateau from 0.8 to 0.6V, which demonstrates the formation of solid electrolyte interface（SEI） on the anode.

Rational design and low-cost fabrication of multifunctional separators enabling high sulfur utilization in long-life lithium-sulfur batteries

The lithium-sulfur(Li-S)battery with an ultrahigh theoretical energy density has emerged as a promising rechargeable battery system.However,the practical applications of Li-S batteries are severely plagued by the sluggish reaction kinetics of sulfur species and notorious shuttling of soluble lithium polysulfides(LiPSs)intermediates that result in low sulfur utilization.The introduction of functional layers on separators has been considered as an effective strategy to improve the sulfur utilization in Li-S batteries by achieving effective regulation of LiPSs.Herein,a promising self-assembly strategy is proposed to achieve the low-cost fabrication of hollow and hierarchically porous Fe_(3)O_(4)nanospheres(p-Fe_(3)O_(4)-NSs)assembled by numerous extremely-small primary nanocrystals as building blocks.The rationally-designed p-Fe_(3)O_(4)-NSs are utilized as a multifunctional layer on the separator with highly efficient trapping and conversion features toward LiPSs.Results demonstrate that the nanostructured p-Fe_(3)O_(4)-NSs provide chemical adsorption toward LiPSs and kinetically promote the mutual transformation between LiPSs and Li_(2)S_(2)/Li_(2)S during cycling,thus inhibiting the LiPSs shuttling and boosting the redox reaction kinetics via a chemisorption-catalytic conversion mechanism.The enhanced wettability of the p-Fe_(3)O_(4)-NSs-based separator with the electrolyte enables fast transportation of lithium ions.Benefitting from these alluring properties,the functionalized separator with p-Fe_(3)O_(4)-NSs endows the battery with an admirable rate performance of 877 mAh g^(−1)at 2 C,an ultra-durable cycling performance of up to 2176 cycles at 1 C,and a promising areal capacity of 4.55 mAh cm^(−2)under high-sulfur-loading and lean-electrolyte conditions(4.29 mg cm^(−2),electrolyte/ratio:8μl mg^(−1)).This study will offer fresh insights on the rational design and low-cost fabrication of multifunctional separator to strengthen electrochemical reaction kinetics by regulating LiPSs conversion for developing efficient and long-life Li-S batteries.

CFD Simulation and Experimental Study of a New Elastic Blade Wave Energy Converter

Small moving vehicles represent an important category of marine engineering tools and devices(equipment)typically used for ocean resource detection and maintenance of marine rights and interests.The lack of efficient power supply modes is one of the technical bottlenecks restricting the effective utilisation of this type of equipment.In this work,the performance characteristics of a new type of elastic-blade/wave-energy converter(EBWEC)and its core energy conversion component(named wave energy absorber)are comprehensively studied.In particular,computational fluid dynamics(CFD)simulations and experiments have been used to analyze the hydrodynamics and performance characteristics of the EBWEC.The pressure cloud diagrams relating to the surface of the elastic blade were obtained through two-way fluid-solid coupling simulations.The influence of blade thickness and relative speed on the performance characteristics of EBWEC was analyzed accordingly.A prototype of the EBWEC and its bucket test platform were also developed.The power characteristics of the EBWEC were analyzed and studied by using the blade thickness and motion cycle as control variables.The present research shows that the EBWEC can effectively overcome the performance disadvantages related to the transmission shaft torque load and power curve fluctuations of rigid blade wave energy converters(RBWEC).

Selective lithium recovery from black powder of spent lithiumion batteries via sulfation reaction:phase conversion and impurities influence

The aim of this study is to present a new understanding for the selective lithium recovery from spent lithium-ion batteries(LIBs)via sulfation roasting.The composition of roasting products and reaction behavior of impurity elements were analyzed through thermodynamic calculations.Then,the effects of sulfuric acid dosage,roasting temperature,roasting time,and impurity elements were assessed on the leaching efficiency of valuable metals.Characterization methods such as X-ray diffraction(XRD),scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS),and X-ray photoelectron spectroscopy(XPS)were employed to analyze the phase transformation mechanism during roasting process.The results indicate that after sulfation roasting(n(H_(2)SO_(4)):n(Li)=0.5,550℃,2 h),94%lithium can be selectively recovered by water leaching and more than 95%Ni,Co,and Mn can be leached through acid leaching without the addition of reduction agent.During the sulfation roasting process,the lithium in LiNi_(x)Mn_(y)Co_zO_(2)is mainly converted to Li_(2)SO_(4),while the Ni,Co and Mn are first transformed to sulfate and then converted into oxide form.In addition,impurity elements such as Al and F will combine with lithium to form LiF and LiAlO_(2),which will reduce the leaching rate of lithium.These results provide a new understanding on the mechanisms of phase conversion during sulfation roasting and reveal the influence of impurity elements for the lithium recovery from spent LIBs.

Advances of entropy-stabilized homologous compounds for electrochemical energy storage

Recently, high-entropy materials(HEMs) have gained increasing interest in the field of energy storage technology on account of their unique structural characteristics and possibilities for tailoring functional properties. Herein, the development of this class of materials for electrochemical energy storage have been reviewed, especially the fundamental understanding of entropy-dominated phase-stabilization effects and prospective applications are presented. Subsequently, critical comments of HEMs on the different aspects of battery and supercapacitor are summarized with the underlying principles for the observed properties. In addition, we also summarize their potential advantages and remaining challenges, which will ideally provide some general guidelines and principles for researchers to study and develop advanced HEMs. The diversity of material design contributed by the entropy-mediated concept provides the researchers numerous ideas of new candidates for practical applications and ensures further research in the emerging field of energy storage.

NUMERICAL STUDY OF LOCAL BOUNDARY LAYERRECEPTIVITY TO FREESTREAM VORTICALDISTURBANCES

Method of direct numerical simulation was used for the investigation of the local receptivity of a 2-D boundary layer of a flat plate to harmonic vortical disturbances in the freestream. Under the interaction of the vortical disturbances in the freestream and the roughness element on the wall, Tollmein-Schlichting (T-S) waves were generated and detected in the boundary layer, thus confirming that the wavelength conversion mechanism and the local receptivity exist. Numerical simulations were performed to obtain the relations between the amplitude of the generated T-S wave and the amplitude of freestream disturbance, the roughness height, and the width of rectangular roughness elements, which agree with those obtained from experiments. Then the range of validity of the linear receptivity formula, which was determined by these relations,also agrees with that determined by experimental results.

Density Functional Theory Investigations on M + CO_2 towards MO + CO(M=B, Al, Si)

The catalytic activation of carbon dioxide by metals and non-metals is one of the attractive scientific challenges in scientific community. In this work, the conversion mechanisms of CO2 to CO by B, Al and Si were elucidated extensively at the B3LYP/6-311＋＋G（d,p） basis set level. Our theoretical mode testifies that the reaction mechanisms of these three systems are significantly different from each other, and both boron and silicon have good performance in the conversion of CO2 to CO.

Synthesis and Crystal Structure of a New Quinazolinone Compound 2,3-Dihydro-2-(2-hydroxyphenyl)-3-phenyl-quinazolin-4(1H)-one

A new quinazolinone compound 2,3-dihydro-2-(2-hydroxyphenyl)-3-phenyl- quinazolin-4(1H)-one 3 ([C20H16O2N2]?C2H5OH, Mr = 362.42) and compound 2-(2-hydroxy- benzylidene-amino)-N-phenyl-benzamide 2 (C20H16O2N2, Mr = 316.34) were prepared from a precursor of 2-amino-N-phenyl-benzamide 1 (C13H12ON2, Mr = 212.25). Compound 3 was characterized by single-crystal X-ray diffraction analysis. The crystal belongs to orthorhombic, space group Pbca with a = 1.2889(11), b = 1.6170(14), c = 1.7729(15) nm, V = 3.695(6) nm3, Z = 8, F(000) = 1536, Mr = 362.42, Dc = 1.303 g/cm3, μ(MoKα) = 0.087 mm-1, R = 0.0447 and wR = 0.0879. The crystal structure analysis indicates that the title compound has a two-dimensional network structure formed by hydrogen bonds and electrostatic interactions.

Cu_(2)Se@C thin film with three-dimensional braided structure as a cathode material for enhanced Cu^(2+) storage

In the face of multiple challenges brought by the changes of global climate and environment,developing clean energy and updating green energy storage equipment are important ways to achieve carbon peak and carbon neutrality.Aqueous batteries have become a research hotspot due to their advantages of using the multivalent charge carrier,high ionic conductivity,environmental friendliness and cost effectiveness.In this work,the Cu_(2)Se@C(Cu_(2)Se coated on carbon clothes)thin film with a three-dimensional braided structure is fabricated by a simple electrochemical deposition method for Cu^(2+)storage for the first time.Compared with the commercial Cu_(2)Se powder,the well-designed Cu_(2)Se@C film shows enhanced specific capacity(640 mAh/g at 0.5 A/g)and rate performance(542 mAh/g at 5 A/g)as well as superior cycling stability(82.7%capacity retention after 1000 cycles at 1 A/g).The Cu^(2+)storage mechanism of the Cu_(2)Se@C electrode is based on a reversible phase transition process of Cu_(2)Se←→Cu_(2-x)Se←→CuSe←→CuSe_(2).In kinetic characteristic analysis,the Cu_(2)Se@C electrode demonstrates faster Cu^(2+)diffusion in discharge process than charge process resulting from the phase transition and the variation of interplanar spacing.This work highlights a facile one-piece design strategy and opens a new gateway for the exploration of advanced aqueous energy storage systems.

Boosting the cycling stability of rechargeable magnesium batteries by regulating the compatibility between nanostructural metal sulfide cathodes and non-nucleophilic electrolytes

Rechargeable magnesium batteries are attractive candidates for energy storage due to their high theoretical specific capacities,free of dendrite formation and natural abundance of magnesium.However,the development of magnesium secondary batteries is severely limited by the lack of high-performance cathode materials and the incompatibility of electrode materials with electrolytes.Herein,we report the application of CuS nanoflower cathode material based on the conversion reaction mechanism for highly reversible magnesium batteries with boosted electrochemical performances by adjusting the compatibility between the cathode and electrolyte.By applying non-nucleophilic electrolytes based on magnesium bis(hexamethyldisilazide)and magnesium chloride dissolved in the mixed solvent of tetrahydrofuran and N-butyl-N-methyl-piperidinium bis((trifluoromethyl)sulfonyl)imide(Mg(HMDS)_(2)-MgCl_(2)/THF-PP14TFSI)or magnesium bis(trifluoromethanesulfonyl)imide,magnesium chloride and aluminium chloride dissolved in dimethoxyethane(Mg(TFSI)2-MgCl_(2)-AlCl_(3)/DME),the magnesium batteries with CuS nanoflower cathode exhibit a high discharge capacity of~207 mAh·g^(–1)at 100 mA·g^(–1)and a long life span of 1,000 cycles at 500 mA·g^(–1).This work suggests that the rational regulation of compatibility between electrode and electrolyte plays a very important role in improving the performance of multi-valent ion secondary batteries.

A review of environmental characteristics and effects of low-molecular weight organic acids in the surface ecosystem

Low molecular weight organic acids （LMWOAs） are prevalent on the earth＇s surface. They are vital intermediate products during metabolic pathways of organic matter and participate in the tricarboxylic acid cycle during life activities. Photochemical reactions are pivotal for LMWOAs＇ origination and play a large role in determining their diversity and their ultimate fate. Within the long time that organic matter is preserved in sediments, it can be decomposed and converted to release organic and inorganic pollutants as well as C, N, and P nutrients, which are of potential ecological risk in causing secondary pollution to lake water. The sediment pool is a comprehensive and complex compartment closely associated with overlying water by various biochemical processes, during which LMWOAs play critical roles to transport and transform elements. This article elucidates geochemical behaviors of LMWOAs in the surface environment in details, taking natural water, soil, and aerosol as examples, focusing on reviewing research developments on sources and characteristics, migration and mineralization of LMWOAs and relevant environmental effects. Simultaneously, this review article depicts the categories and contents of LMWOAs or their contribution to DOC in environmental media, and evaluates their importance during organic matter early diagenesis. Through concluding and discussing the conversion mechanisms and influencing factors, the next research orientations on LMWOAs in lake ecosystems are determined, mainly concerning relationships with hydrochemical parameters and microorganisms, and interactions with pollutants. This will enrich the knowledge on organic matter degradation and related environmental effects, and help reconstruct a theoretical framework for organic compound succession and influencing factors, providing basic data for lake eutrophication and ecological risk assessment, conducive to better control over water pollution and proper management of water quality.

In situ synergistic strategy of sacrificial intermedium for scalablemanufactured and controllable layered double hydroxide film

Layered double hydroxides(LDHs),a class of two-dimensional(2D)brucite-like layers,have been effectively applied in diverse fields.However,the current synthesis methods restrict the in situ scaling-up and tunable production of LDH-based materials.Inspired by the growing characteristic of“Bryophyllum pinnatum”,a sacrificial co-sputtered Zn-Al transition layer was introduced for the first time to in situ grow a scalable-manufactured and thickness-controllable LDH film on arbitrary substrate materials with flexible shapes through“partial dissolution”and“solution infiltration”processes.Diverse LDH films could be tailored by the creative regulation of the component,structure and surface state of the transition layer.Results showed that the as-prepared LDH film had strong mechanical robustness under harsh abrasion conditions due to its large thickness and multi-level microstructure.Moreover,a series of galvanic couple model experiments based on Zn/Al single-metal transition layers were designed to solve the real-time monitoring issue in the complex hydrothermal solution.This work not only develops a new strategy to design and grow in situ LDH films with multifaceted features,but also reveals sophisticated LDH formation mechanisms.Hence,the findings of this study may broaden the practical application of LDH-based materials toward advanced and smart devices.

Perovskite fluoride NaNiF_(3) with hollow micron sphere structure as anode for Li-ion hybrid capacitors

Lithium-ion hybrid capacitors(LIHCs) are gaining more attention and applications because they break the performance limitations of supercapacitors(SCs) and lithium-ion batteries(LIBs).However,the difference of energy storage mechanism between anode and cathode is a problem that must be faced by Li-ion hybrid capacitors.The selection of suitable anode and cathode materials is one of the effective ways to solve this problem.Here,we synthesized hollow spherical perovskite fluoride NaNiF3 by a simple and safe method.The specific capacity of NaNiF3 is 142 mAh·g^(-1) at 0.1 A·g^(-1) for 1000 cycles.The mechanism in the cycling of NaNiF3 electrodes was investigated using ex situ X-ray photoelectron spectroscopy(XPS),which is typical of the conversion reaction.Meanwhile,the NaNiF_(3)//activated carbon(AC) Li-ion hybrid capacitor assembled and showed better energy density(69 Wh·kg^(-1)) and power density(5699 W·kg^(-1)).Its capacity retention after long cycling was 79%.The use of NaNiF3 expands the choice of electrode materials for LIHCs and extends their practical applications.

BAROTROPIC AND BAROCLINIC ENSTROPHY EQUATIONS WITH THEIR APPLICATIONS TO A BLOCKING CIRCULATION

After the manner for studying atmospheric kinetic energy,concepts of atmospheric enstrophy (ζ~2/2)_m and barotropic and baroclinic enstrophy (ζ_m^2/2,ζ_s^2/2) are developed with their relations investigated,whereupon are established,separately,equations for the 1000- 100 hPa extent- averaged ζ_m^2/2 and ζ_s^2/2 over a limited area and on a local basis.Study shows that controlling their changes are the following factors:the terms of their fluxes (viz.,divergences).β effect,their mutual conversions,production and dissipation.Analysis is undertaken of these terms-dependent physical mechanisms for the variations in barotropic and baroclinic enstrophy and by means of the equations,calculation is conducted of the terms during the development of an Okhotsk blocking circulation,indicating that the total,harotropic and haroclinic enstrophies experience noticeable variations,from which we see that the latter two factors can really characterize the development as a whole,thus revealing the mechanisms at different stages of the circulation history.

BAROTROPIC AND BAROCLINIC DIVERGENCE QUASI ENERGY EQUATIONS AND THEIR APPLICATION TO A BLOCKING EVENT

As in the case of the expression for enstrophy (1/2ζ~2) and equations for barotropic and baroclinic enstrophy,this paper presents an expression of divergence assumed to have its quasi energy because of flows (DQE,or 1/2 D^2) with which to establish the equations of barotropie and baroclinic DQE,each consisting of five factors responsible for changes in these equations:the terms of energy flux,production,conversion,geostrophic effect and dissipation,and also a case study of a blocking event over the Sea of Okhotsk whose development is characterized largely by changes in barotropic and baroclinic DQE's on the strength of upper-level strong divergence and low-level vigorous convergence.During the event's strengthening,the baroclinic net production (inclusive of geostrophie effect) mechanism acts as the dominant factor for the enhancement of the baroclinic DQE,with its net transport outward offsetting part of its growth but the conversion mechanism augmenting its growth,and during the weakening the outward net transport of baroclinic DQE is the predominant factor of its enfeebling,baroclinic net DQE production (inclusive of geostrophic effect) and the conversion mechanisms make the baroclinic DQE increased,thereby alleviating the weakening in intensity.