Effect of coke properties and its blending recipe on performances of carbon anode for aluminium electrolysis

The properties and blending recipe of petroleum cokes used to make high quality carbon anodes for aluminium electrolysis were studied. Three kinds of green cokes were selected for bench scale study to illustrate the effects of cokes properties and its blending recipe on anode performances. The results show that impurities derived mainly fi＇om cokes remarkably affect the CO2 reactivity and air reactivity of carbon anodes. Ca, Na and V can increase CO2 reactivity of calcined cokes but S has the contrary effect, and the cokes of high V level generally present high air reactivity. The anodes with good quality can be made by properly selecting and scientifically blending of cokes, some poor quality cokes can also be used to produce high quality anodes with a reasonable blending recipe. Na contaminated anodes have high CO2 reactivity and air reactivity, so the recycled anode butts should be well cleaned to reduce Na content before being introduced into anode production, which is especially important to the low S cokes.     

Influence of particle structure on electrochemical character of composite graphite

The natural graphite has been used as the anode material for Lithium-Ion batteries, because of its low cost, chemical stability and excellent reversibility for Li+ insertion. However, the slow diffusion rate of lithium ion and poor compatibility with electrolyte solutions make it difficult to use in some conditions. In order to solve these problems, an epoxy-coke/graphite composite has been manufactured. The particle of composite carbonaceous material coated on non-graphitizable (hard) carbon matrix. Due to the disordered structure, the diffusion rate of lithium species in the non-graphitzable carbon is remarkably fast and less anisotropic. The process for preparing a composite carbon powder provides a promising new anode material with superior electrochemical properties for Li-ion batteries. The unique structure of epoxy-coke/graphite composite electrodes results in much better kinetics, also better recharge ability and initial charge/discharge efficiency.     

Effect of metallic phase species on the corrosion resistance of 17M/（10NiO-NiFe2O4） cermet inert anode of aluminum electrolysis

1 INTRODUCTIONThere are many disadvantages in the presentaluminumelectrolysis with carbon anode ,such assevere energy consumption,carbon wasting,envi-ronmental pollution and so on.Inert electrode sys-tem can overcome these disadvantages[1 3]. Re-cently ,the researches of the inert anode materialshave mainly been concentrated on alloys[4]and cer-met materials[5 ,6]. NiFe2O4based cermets , whichpossess not only high electrical conductivity ofmetal but also good corrosion resistance of cera…     

Adsorption behavior of heavy metal ions by carbon nanotubes grown on microsized Al2O3 particles

Carbon nanotubes （CNTs） were grown on the surface of microsized Al2O3 particles in CH4 atmosphere at 700℃ under the catalysis of Fe-Ni nanoparticles. The CNTs on Al2O3 were used for adsorbing Pb^2＋, Cu^2＋, and Cd^2＋ from the solution and the results were compared with active carbon powders, commercial carbon nanotubes, and Al2O3 particles. The as-grown CNTs/Al2O3 have demonstrated extraordinary absorption capacity with further treatment or oxidation, as well as hydrophilic ability that other CNTs lacked. The adsorption capacity of CNTs on Al2O3 is superior to other adsorbents and the preference order of adsorption on composite Al2O3 is pb^2＋〉Cu^2＋〉Cd^2＋. It seemed that the adsorption of those Pb^2＋, Cu^2＋, and Cd^2＋ did not change the surface properties of composite particles. The adsorption behaviors of Pb^2＋, Cu^2＋, and Cd^2＋ by CNTs on Al2O3 match well with the Langmuir isothermal adsorption model and the second order kinetic model. The calculated saturation amount adsorbed by 1 g of CNTs on Al2O3 are 67.11, 26.59, and 8.89 mg/g for Pb^2＋, Cu^2＋, and Cd^2＋ in single adsorption test, respectively.     

Anodic behavior and microstructure of Al/Pb-Ag-Co anode during zinc electrowinning简

In order to study the anodic behavior and microstmctures of A1/Pb-Ag-Co anode during zinc electrowinning, by means of potentiodynamic investigations, scanning electron microscopy （SEM） and X-ray diffraction （XRD） analyses, the mechanism of the anodic processes playing on the surface of A1/Pb-0.8%Ag and A1/Pb-0.75%Ag-0.03%Co anodes prepared by electro-deposition from methyl sulfonic acid bath for zinc electrowinning from model sulphate electrolytes have been measured. On the basis of the cyclic voltammograms obtained, information about the corrosion rate of the composite in PbO2 region has been concluded. The microstructures were also observed by means of SEM and XRD which showed Pb-0.75%Ag-0.03%Co alloy composite coating has uniform and chaotic orientation tetragonal symmetry crystallites of PbSO4, but Pb-0.8%Ag alloy composite coating has well-organized orientation crystallites of PbSO4 concentrated in the certain zones after 24 h of anodic polarization. It is important that Al/Pb-0.75%Ag-0.03%Co anode oxide film consists of non-conductive dense MnO2 and PbSO4 and a, fl-PbO2 penetrated into which, in fact, are the active centers of the oxygen evolution after 24 h of anodic polarization.     

A Novel Modification Approach for Natural Graphite Anode of Li-ion Batteries

To improve the rate caqability and cyclability of natural graphite anode for Li-ion batteries, a novel modifwatio, approach was developed. The modification approach included two steps:(a) high-energy ball milling in a rotary aatoelave containing alumina balls, H3PO4 and ethanol;( b ) coating with pyrolytic carbon from phenlic resin. The treated graphite sluws obrious improvement compared with the original natural graphite in electroehemical properties such as cyclahility and rate capability, especially at high current density. The primaryreasons leading to the improvement in rate capability and cyclability are that the diffusion impedance of Li^ in graphite is reduced due to the fact that P filtered into graphite layers can mildly increase interlayer distances, and the fact that the structural stability of graphite surface is enhanced since the coated pyrolytic carbon can depress the co-intercalation of solvated lithium ion.     

CFD simulation of effect of anode configuration on gas–liquid flow and alumina transport process in an aluminum reduction cell

Numerical simulations of gas–liquid two-phase flow and alumina transport process in an aluminum reduction cell were conducted to investigate the effects of anode configurations on the bath flow, gas volume fraction and alumina content distributions. An Euler–Euler two-fluid model was employed coupled with a species transport equation for alumina content. Three different anode configurations such as anode without a slot, anode with a longitudinal slot and anode with a transversal slot were studied in the simulation. The simulation results clearly show that the slots can reduce the bath velocity and promote the releasing of the anode gas, but can not contribute to the uniformity of the alumina content. Comparisons of the effects between the longitudinal and transversal slots indicate that the longitudinal slot is better in terms of gas–liquid flow but is disadvantageous for alumina mixing and transport process due to a decrease of anode gas under the anode bottom surface. It is demonstrated from the simulations that the mixing and transfer characteristics of alumina are controlled to great extent by the anode gas forces while the electromagnetic forces(EMFs) play the second role.     

Super-capacitive Properties of Thick RuO2·xH2O Electrodes:Effect of Thickness,Binder and Carbon Black Addition

Hydrous ruthenium oxide,RuO2·xH2O,was synthesized through a sol-gel reaction of ruthenium chloride aqueous solution.The annealed RuO2·xH2O powders are aggregate of very small particles in nano-size of 70-80 nm and have abundant porous structure as observed by SEM.The effect of electrode thickness,PTFE binder and carbon black addition on the super-capacitive properties of thick RuO2·nH2O electrodes was investigated.At low scan rate of 5 mV/s,the specific capacitance of RuO2·xH2O (SCR,based on the weight of RuO2·xH2O only) for pure RuO2·xH2O and RuO2·xH2O-PTFE-CB electrodes can reach 665 F/g.Increasing electrode thickness and mixing PTFE into RuO2·xH2O lead to a degradation of SCR and rate capacity.By adding carbon black into RuO2·xH2O-PTFE mixture,the rate capacity of the thick electrode (RuO2·xH2O-PTFE-CB) can be improved close to the thick pure RuO2·xH2O electrode.However,mixing with PTFE and carbon black leads to a loss of the overall mass-specific capacitance.The reason for the dependence of SCR and rate capacity on electrode thickness,binder and carbon black addition was discussed based on the relation between the resistance and utilization rate of electrodes.     

Effect of electrolysis superheat degree on anticorrosion performance of 5 Cu/（10NiO-NiFe2O4） cermet inert anode

5Cu/(10NiO-NiFe2O4) cermet inert anodes were prepared by cold-pressing and sintering process, and the effect of superheat degree of melting K3AlF6-Na3AlF6-AlF3 on their anticorrosion performance was studied under electrolysis conditions. The results show that, the fluctuation of cell becomes small with increasing of superheat degree, which is helpful to inhibit the formation of cathodic encrustation; the concentration of impurities from inert anode in bath goes up to certain degree, but it is far smaller than those in traditional high-temperature bath. Increasing the superheat degree of melting K3AlF6-Na3AlF6-AlF3 has unconspicuous effect on the contents of impurities in cathodic aluminum. The total mass fractions of Fe, Ni and Cu in aluminum are 15.38% and 15.09% respectively under superheat degree of 95 and 195 ℃. From micro-topography of anode used view, increasing the superheat degree can aggravate corrosion of metal Cu in inert anode, and has negative influence on electrical conductivity of electrode to some extent.     

The Catalysis of NAD^＋ on Methanol Anode Oxidation Electrode for Direct Methanol Fuel Cell

A tentative idea of developing a liquid-catalytic system on methanol anode oxidation was proposed by analyzing the characteristics of methanol anode oxidation in direct methanol fuel cell. The kinetics of methanol oxidation at a glassy carbon electrode in the presence of nicotinamide adenine dinucleotide ( NAD^ ) was investigated. It is found that the current density of methanol oxidation increases greatly and the electrochemical reaction impedance reduces obviously in the presence of NAD^ compared with those in the adsenee of NAD^ . The catalytic activity of NAD^ is sensitive to temperature. When the temperature preponderates over 45℃, NAD^ is out of fuuction of catalysis for methanol oxidation, which is probably due to the denaturation of NAD^ at a relatively high temperature.     

Preparation and properties of 4.25Cu-0.75Ni／NiFe2O4 cermet

4.25Cu-0.75Ni/NiFe₂O₄ cermets were prepared by doping NiFe₂O₄ ceramic matrix with the mixed powders of Cu and Ni or Cu-Ni alloy powder as the electrical conducting metallic elements. The effects of technological parameters, such as the adding modes of metallic elements, the ball milling time, the sintering time and the sintering temperature, on the relative density and resistivity of the cermets were studied. The results show that the resistivity of 4.25Cu-0.75Ni/NiFe₂O₄ cermets decreases with increasing temperature, and has a turning point at 590 °C, which is similar to that of NiFe₂O₄ ceramic. The sintering temperature and adding modes of metallic elements have a great influence on the properties of 4.25Cu-0.75Ni/NiFe₂O₄ cermets. When the sintering temperature increases from 1200 °C to 1300 °C, the relative density increases from 89.86% to 95.33%, and the resistivity at 960 °C decreases from 0.11 Ω · cm to 0.03 Ω · cm, respectively. When the metallic elements are added with the mixed powders of Cu and Ni, the cermets of finely and uniformly dispersed metallic phase, high density and electric conductivity are obtained. The relative density and resistivity at 960 °C are 90.23% and 0.04 Ω · cm respectively for the cermet samples sintered at 1200 °C for 2 h, which are both better than those of the cermets prepared under the same technique conditions but with the metallic elements added as 85Cu-15Ni alloy powders. Foundation item: Project (G1999064903) supported by the National Key Fundamental Research and Development Program of China; project(2001AA335013) supported by the National High Technology Research and Development Program of China; project (50204014) supported by the National Natural Science Foundation of China     

Effect of Nb on the mechanical properties of Ti/Al2O3 composite

Ti/Al₂O₃ composite with improved mechanical properties was synthesized by the spark plasma sintering. The effect of Nb on the microstructure of the composite was analyzed by TEM, SEM and so on. The experimental results indicate that the bending strength, fracture toughness, micro-hardness and relative density of the composite are 897.29MPa, 17.38MPa·m^1/2, 17.13GPa and 99.24% respectively when adding 1.5vol Nb. The bending strength is improved by reason of forming dislocation ring and transfering fracture mode from integranular to mixture fracture of intergranular and transgranular. The crack propagating is mainly the deflection bridging. It indicates a reduction of crack driving force and an increase in crack growth resistance, which results in toughness enhanced. Funded by the National Natural Science Foundation of China (No. 50232020) and the Natural Science Foundation of Shandong Province (No. 2002F21)     

Morphology and tribological properties of Ni/n-SiO2 composite coatings by pulse-reverse current brush-plating

Ni/n-SiO₂ composite coating was electrodeposited by brush-plating with pulse-reverse current(RC). The morphology, hardness, and tribological properties of the coating were investigated and compared with those of Ni and composite coatings electrodeposited with direct current (DC). The results indicate that Ni/n-SiO₂ composite coating electrodeposited by RC, because of RC and the nano powders, has denser coating, finer crystal grains, higher hardness (HV650.0, nearly 1.5 times higher than that of Ni coating electrodeposited by DC) and lower friction coefficient (nearly 0.62), as a result, in the wearing experiment, the Ni/n-SiO₂ composite coating electrodeposited by RC has the least worn loss. So this kind of coating has better wear resistance. And RC electro brush-plating can be used as a new technology of brush-plating in the area of wear resistance. Foundation item: Project (50235030) supported by the National Natural Science Foundation of China; Project (51489020104JS9102) supported by the National Key Laboratory for Remanufacturing     

Fabrication, property characterization and toughening mechanism of HA-ZrO2(CaO)/316L fibre composite biomaterials

HA-ZrO₂(CaO)/316L fibre composites were successfully fabricated with vacuum sintering method and their properties and toughening mechanism were studied. The results showed that HA-ZrO₂(CaO)/316L fibre biocomposite having 20 vol% fibres had optimal comprehensive properties with bending strength, Young’s modulus, fracture toughness and relative density equal to 140.1 MPa, 117.8 GPa, 5.81 MPa·m^1/2 and 87.1%, respectively. The research also addressed that different volume ratios of the composites led to different metallographic microstructures, and that metallographic morphologies change regularly with volume ratios of the composites. 316L fibres were distributed randomly and evenly in the composites and the integration circumstance of the two phases was very well since there were no obvious flaws or pores in the composites. Two toughening mechanisms including ZrO₂ phase transformation toughening mechanism and fibre pulling-out toughening mechanism existed in the compsites with the latter being the main toughening mechanism. Supported by the National Natural Science Foundation of China (Grant No. 50604017) and the Postdoctoral Science Foundation of Central South University     

The influence of mo additive on the microstructure and property of Ti/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite

The influence of Mo on the microstructure, bending strength and HV of Ti/Al₂O₃ composite was studied, and the influence mechanism was analyzed. The results indicate that after the addition of Mo, the composite organization is finer and phases distribution is better-proportioned which make the microstructure denser, the bending strength and HV of composite are also increased to a degree. But the bending strength increases first then decreases with the increasing of Mo content, so the appropriate Mo content for the Ti/Al₂O₃ composite is to be further confirmed. WANG Zhi: Born in 1962 Funded by Natural Science Foundation of China (No. 50232020) and Natural Science Foundation of Shandong Province (No. 2002F21)     

Design and micro mechanical properties of nano-SiO2 strengthened composite coatings towards remanufacturing

Nano-SiO₂ particles strengthened Ni-based composite coating was designed and prepared on steel substrate. The structures and nanoparticle content of the nano-SiO₂/Ni composite coating were determined by SEM, EDS and TEM; and the micro mechanical properties were tested by nano-indentation technique. The results show that 56% of particles in the solution are dispersed in size of less than 100 nm, the content of nanoparticles co-deposited in the coating doubles and structure of the coating is more compact and uniform than that of Ni coating. Nano-SiO₂/Ni coating exhibits excellent micro mechanical properties, and the nanohardness and elastic modulus are 7.81 GPa and 198 GPa, respectively, which are attributed to finer crystal strengthening, dispersion strengthening and high-density dislocation strengthening of nano-SiO₂ particles to the composite coatings. Foundation item: Project (50235030) supported by the National Natural Science Foundation of China; Project (G1999065009) supported by the National Basic Research Program of China     

Characterization of functionally graded ZrO2 thermal barrier coatings sprayed by supersonic plasma spray with dual powder feed ports

The functionally graded thermal barrier coatings (FG-TBCs) with 80% ZrO₂-13%CeO₂-7%Y₂O₃ (CYSZ)/NiCoCrAlY were prepared using a recently developed supersonic plasma spraying (S-PS) with dual powder feed ports system. The thermal shock experiment of FG-TBCs specimens was carried out by means of the automatic thermal cycle device, in which the samples were heated to 1 200 °C by oxygen-acetylene flame jet then water-quenched to ambient temperature. The temperature—time curves of specimens and photographs can be watched online and recorded by a computer during the test. The results show that the totally 1 mm-thick FG-TBCs have excellent thermal shock resistance due to the fact that the coatings have no any peeling-off after 200 thermal cycles. The microstructures and morphologies of FG-TBCs were characterized and analyzed by SEM. Foundation item: Projects(50235030; 90305023) supported by the National Natural Science Foundation of China     

Densification and sintering dynamics of 10NiO-NiFe2O4 composites doped with CaO

The effects of CaO content in the range from 0 to 4.0%, and sintering temperature on the phase composition, relative density and electrical conductivity of 10NiO-NiFe2O4 composites doped with CaO were studied. The results show that there is no change of structure for NiO or NiFe2O4; there is apparent oxygen absorbing and releasing behavior during the heating process in air for 10NiO-NiFe2O4 composites. Introduction of CaO can accelerate the densification of 10NiO-NiFe2O4 composites. The maximum value of relative density is 98.75% for composite doped with 2.0% CaO and sintered at 1 200 ℃, which is beyond about 20% for the undoped composites. The sintering activated energy of sample containing 2% CaO decreases by 15.87 kJ/mol, compared with that of the undoped sample.     

Coating of Fe, Ni on α-alumina microspheres by heterogeneous precipitation

1INTRODUCTION Themagneticmetal coatedceramicoxides,core shellstructuralcompositematerials,inwhichthinmetallicfilmsarecoatedonaceramicoxide matrixwithmicrometerparticlesizes,areattrac tiveduetothecombinationofthefunctionalchar acteristicsofmetalsandmechanicalpropertiesoftheceramicmatrix.Theceramic basedtransition metal coated,core shellcompositessuchasNi coatedAl2O3[1],Fe coatedAl2O3[2],FeNi coated Al2O3[3]orCoFe coatedSiO2[4],havebeenfoundtoexhibitinterestingfunctionalperformancesdue…