Enhancing the Adhesion Retention by Controlling the Structure of the Adhesion Interphase Between Rubber Compound and Metal. Part I. Effect of Cobalt Salt

The adhesion between cobalt salt-containing rubber compounds and brass-plated steel cords was studied to understand the role of cobalt salt as an adhesion promoter. An improvement in adhesion was shown with the low loading of cobalt salt in the range 0.5–1 phr, while a significant decline in adhesion was observed with high loading at 2 phr and a long aging time of 15 days under humidity aging. The adhesion interphase between the rubber compound and the brass-plated steel cord studied using Auger electron spectroscopy (AES) showed stable depth profile by cobalt salt incorporation at low loading, resulting in the enhancement of the adhesion retention. For the high loading of cobalt salt, adhesion interphase grew excessively, especially ZnO layer formed under humidity aging, which resulted in reduced adhesion.     

Heavy metals in the environment. Part I: Removal of cobalt from dilute effluent streams by fluidised bed electrolysis

The fluidised bed cell is an electrolytic reactor which is designed to provide higher ion-transfer conditions during electrolysis by breaking up the barrier layer at the cathode, thus enabling metals to be removed efficiently from dilute solutions. The effectiveness of the method as a means of removing metals from effluent to meet discharge consent levels is studied for the in-situ removal of cobalt from dilute solution. The effects of cathode density, pH, reaction time, buffer solution composition, buffer concentration and agitation on the removal of cobalt are reported and expressed in terms of the percentage removal of cobalt (α_Co), the efficiency for cobalt deposition (∞_Co), and the energy consumption (W_Co) for 1 kg of cobalt deposited. The results show that cobalt can, under optimised conditions, be removed from dilute solutions to a residual level of 0.2 ppm.     

Current efficiency and kinetics of cobalt electrodeposition in acid chloride solutions. Part II: the influence of chloride and sulphate concentrations

The influence of cobalt chloride concentration, total chloride concentration and sulphate in the electrolyte on cobalt deposition were studied. The current efficiency increased and the overpotential for electrodeposition of cobalt decreased with increasing cobalt chloride concentration. Only minor changes were observed with addition of sodium chloride to the cobalt chloride solution. Sulphate electrolyte resulted in lower current efficiency and higher overpotential for electrodeposition when compared to a similar cobalt chloride electrolyte.     

Optimization of the pretreatment procedure in the design of cobalt silica supported Fischer–Tropsch catalysts

The effect of cobalt precursor, catalyst pretreatment and promotion with ruthenium and rhenium on the formation of cobalt metal nanoparticles and catalytic performance of supported Fischer–Tropsch (FT) catalysts was studied using a combination of techniques (DSC–TGA, UV–vis spectroscopy, XPS, XRD, EXAFS–XANES, in situ magnetization measurements, propene chemisorption and catalytic measurements). The cobalt promoted and unpromoted catalysts were prepared by aqueous co-impregnation using cobalt nitrate or acetate, ruthenium nitrosyl nitrate or perrhenic acid. In both unpromoted and Ru and Re-promoted cobalt catalysts after impregnation and drying, cobalt is present mainly in octahedrally coordinated complexes. The repartition of cobalt species between Co₃O₄ and cobalt silicate depends essentially on the exothermicity of precursor decomposition. Cobalt nitrate precursor, with an endothermic decomposition, favors Co₃O₄ crystallites. Lower temperature of cobalt nitrate decomposition and catalyst calcination generally leads to higher dispersion of supported cobalt oxide. Cobalt acetate precursor, with an exothermic decomposition, favors cobalt silicate. By optimizing the conditions of cobalt acetate decomposition, the fraction of cobalt silicate can be decreased favoring a more reducible Co₃O₄ phase. For the catalysts prepared from cobalt nitrate, promotion with ruthenium increases the cobalt dispersion, while maintaining high reducibility. For the catalyst prepared via low temperature decomposition of cobalt acetate, addition of ruthenium increases the fraction of Co₃O₄ crystalline phase and decreases the concentration of barely reducible cobalt silicate. The Fischer–Tropsch reaction rates over unpromoted and promoted cobalt catalysts were found to be primarily a function of the number of cobalt metal sites, which are generated by the reduction of Co₃O₄ crystallites.     

Ball milling and annealing graphite in the presence of cobalt

When graphite is ball milled, Raman spectra and X-ray diffractograms of the products show increasing graphitic structural disorder with 1% and 10% cobalt addition. However, if sufficient cobalt (10% weight for weight) is added, this process is reduced in rate. This process is attributed to the cobalt stabilizing the graphitic structure during ball milling, thus reducing the degree of lattice-disorder.When the mixture is annealed, well-ordered carbon strips encapsulating cobalt nanoparticles are observed in the presence of cobalt.Annealing reorganizes the disordered structures and 10% cobalt loading is more effective than a 1% loading in this process. Transmission electron microscopic (TEM) analysis showed the formation and high abundance of well-ordered carbon strips encapsulating cobalt nanoparticles in samples that have been annealed with additional cobalt loading.     

Sorption of caesium by complex hexacyanoferrates. v. a comparison of some cyanoferrates

The properties of copper cyanoferrates and potassium cobalt ferrocyanide prepared at Imperial College and similar commercial products for caesium sorption have been investigated. Copper and cobalt based cyanoferrates have different chemical compositions and appear to be good adsorbers for the removal of caesium in aqueous solutions. Different caesium sorption mechanisms were observed for these cyanoferrates. A conventional ion exchange reaction, physical adsorption and a combination of the two processes were observed. The difference in caesium sorption mechanism also reflects the kinetics of the sorption process. Potassium copper ferrocyanide has the highest effective capacity but the caesium sorption rate is the slowest, whilst potassium cobalt ferrocyanide possesses faster kinetics but considerably lower effective capacity. Copper ferrocyanide tends to have better mechanical stability and moderate sorption kinetics and caesium uptake.     

Use of gas-diffusion electrodes for high-rate electrochemical reduction of carbon dioxide. II. Reduction at metal phthalocyanine-impregnated electrodes

The use of polytetrafluoroethylene-bonded, carbon gas-diffusion electrodes, prepared with carbon impregnated with metal phthalocyanines, for the electrochemical reduction of carbon dioxide in aqueous, acidic solution has been investigated. High rates of reduction of carbon dioxide to carbon monoxide were demonstrated at electrodes impregnated with cobalt (II) phthalocyanine. In contrast, formic acid, and not carbon monoxide, was produced at low rates at electrodes impregnated with either manganese, copper or zinc phthalocyanine. This marked variation in reaction product on changing the central metal ion of the organometallic complex is rationalized in terms of a reaction mechanism involving, as the first step, the electrochemical reduction of cobalt (II) to cobalt (I).     

Reaktive polymere. V. Metallkomplexe polymergebundener schiffscher basen

The complexes of bivalent copper and cobalt with salicylidene ethylene diamine ligands bounded to macroporous glycidyl methacrylate-ethylene dimethacrylate copolymers have been studied, and characterised by I.R. spectra. The transfer of oxygen by cobalt complex has been followed.     

Investigation of cobalt deposition using the electrochemical quartz crystal microbalance

Electrodeposition of cobalt from sulfate solutions at different pH values was investigated using the EQCM technique coupled with cyclic voltammetry. The results show that cobalt hydroxide is formed simultaneously with cobalt deposition during the early stages of reduction due to the pH variation near the electrode surface caused by the parallel hydrogen evolution reaction (HER). This result was confirmed using M/z values calculated using the Sauerbrey equation and Faraday's law, which showed the presence of cobalt hydroxide in the electrodeposits. A flux model was developed and it assumes a direct reduction of cobalt, simultaneous HER and the formation of cobalt hydroxide during the early stages of deposition at pH 4.10. When the solution pH is decreased to 3.33 only the direct cobalt reduction is observed without any hydroxylated species formation.     

V. A Study of Enamel-Metal Contact Zones by Chemical Methods

Analyses were made of the material from the steel-enamel contact zones of a series of enamels containing varying amounts of cobalt oxide. The impact resistance of these enamels was determined and a method for determining cobalt in enamels was developed.     

Influence of cobalt ions on the anodic oxidation of a lead alloy under conditions typical of copper electrowinning

The influence of cobalt ions in the solution on the anodic oxidation of a commercial Pb–Ca–Sn alloy under conditions typical of copper electrowinning was studied using cyclic voltammograms and potential decay transients. The cobalt ions changed the structure, morphology and chemical composition of the surface film from a loose porous film to a thin dense film. This change of surface film is the cause for the decreased rate of oxidation for the lead anode in the presence of cobalt ions. The steady state potential of the alloy during anodic oxidation decreased with (i) increasing cobalt ion concentration, (ii) increasing rotation speed, (iii) increasing temperature, (iv) decreasing acid concentration and (v) decreasing current density. The steady state potentials were lower in the presence of cobalt ions. This decrease in the steady state potential may indicate that oxygen evolution is more rapid on the more compact film formed in the presence of cobalt ions. Alternatively, an additional pathway of oxidation may be provided by the cobalt ions.     

Adhesion between rubber compounds and ternary-alloy-coated steel cords. Part II: Effects of sulfur and cobalt salt in rubber compounds

The adhesion properties between rubber compounds with different amounts of cobalt salt and sulfur and ternary-alloy-coated steel cord with 2 wt% cobalt plating amount were investigated to understand the effects of cobalt salt and sulfur in rubber compounds on their adhesion characteristics to the ternary-alloy-coated steel cord. The adhesion properties of the rubber compounds to ternary-alloy-coated steel cord were largely dependent on the amounts of both cobalt salt and sulfur in the rubber compounds. The pull-out force of adhesion sample increased significantly with increasing concentration of cobalt salt in the rubber compound with constant sulfur loading, while it decreased slightly with increasing sulfur into the rubber compound with constant cobalt salt loading. Adhesion retention after various hostile aging treatments improved in the rubber compounds incorporating both cobalt salt and high loading of sulfur. The interphases between the rubber compounds and the ternary-alloy-coated steel cord studied using AES showed stable adhesion patterns by incorporating cobalt salt, resulting in enhancement of the adhesion retention.     

Studies of glycolysis of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. I. Influences of glycolysis conditions

The glycolysis of recycled poly(ethylene terephthalate) flakes by ethylene glycol (EG) is investigated. Bis‐2‐hydroxyethyl terephthalate (BHET) and oligomers are predominately glycolysis products. The influences of glycolysis temperature, glycolysis time, and the amount of catalyst (cobalt acetate) are illustrated. The BHET, dimer, and oligomers are predominately glycolysis products. The optimum glycolysis temperature is found to be 190°C. If a 190°C glycolysis temperature, 1.5‐h glycolysis time, and 0.002 mol glycolysis catalyst (cobalt acetate) are used, the glycolysis conversion is almost 100%. The glycolysis conversion rate increases significantly with the glycolysis temperature, glycolysis time, and the amount of cobalt acetate. Thermal analyses of glycolysis products are examined by differential scanning calorimetry. In addition, the chemical structures of glycolysis products are also determined by a Fourier transform IR spectrophotometer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 943–948, 2001     

Study of Some Phenomena Associated with the Adherence of Sheet Iron Ground Coats

Cobalt and nickel are deposited on the surface of the base metal during the firing of sheet iron ground coats. These deposits, which are metallic in nature, at least at higher firing temperatures, increase with increasing firing temperature. They also increase with the amount of cobalt and nickel present in any one frit and with the fluidity of the enamel. One reason why cobalt is generally considered a better adherence agent than nickel is that cobalt has a greater tendency to deposit during firing. Ground-coat adherence is generally associated with a certain amount of deposition of cobalt and nickel on the metal surface. This deposition in turn is associated with a roughening of the metal surface which is believed to be a large contributory factor in enamel adherence.     

Coal liquefaction by the hydrogen produced from methanol: 2. Model compound studies

Coal can be converted into a material soluble in solvents using methanol as an in-situ hydrogen source and also as an alkylating agent. This paper presents the results of the reaction of selected model compounds with methanol using two different hydrogenation catalysts: stabilized nickel at 365 °C, and stabilized cobalt at 405 °C and 445 °C. Stabilized nickel is a much better hydrogenation catalyst than stabilized cobalt. The alkylation reaction is strongly dependent on the presence of specific functional groups (-OH, -NH, etc). Also, the alkylation reaction appears to be independent of the hydrogenation catalyst used and it seems to depend more on the temperature. The alkylated products from the reactions at 405 °C showed an order as follows: carbazole phenol ? phenanthrene dibenzofuran diphenylether dibenzothiophene diphenylmethane. A free radical mechanism is proposed for the alkylation reaction.     

Current efficiency and kinetics of cobalt electrodeposition in acid chloride solutions. Part I: The influence of current density,pH and temperature

In the electrodeposition of cobalt in chloride electrolytes the evolution of hydrogen is a parasitic reaction. On a rotating platinum disc electrode the current efficiency was calculated as the charge used for anodic dissolution of cobalt at a potential where no other reactions were taking place, divided by the total cathodic charge used for cobalt deposition. The results show that the current efficiency could be measured accurately in this way. In part I the current efficiency and deposition potential are studied as a function of current density and pH. The results show an increase in current efficiency with increasing current density, pH and temperature. The results also indicate a change in the reaction mechanism for electrodeposition when the pH is changed.     

硫酸化焙烧从锰矿中回收钴—─I.硫酸化焙烧工艺

采用两段硫酸化焙烧工艺对从废弃菱锰矿中回收钴进行了实验研究．详细考查了酸比、焙烧温度、焙烧时间的影响以及硫酸钠在焙烧中的催化作用．实验结果表明，在适宜的工艺条件下，钴的提取率可达９５％，锰的提取率达１００％，而铁的溶出率则低于８％，取得了令人满意的结果．     

Co(OH)_2的电化学性能研究

合成了结晶程度较高的Co(OH)2,并对其电化学性能进行了研究。充放电实验表明:Co(OH)2具有一定的放电比容量:98.4mAh/g,多次充放电实验表明它的容量较为稳定。循环伏安实验表明:氢氧化钴电极具有一定的可逆性。X射线衍射实验结果说明:电极反应是在CoOOH和Co(OH)2之间进行的。通过对氢氧化钴的电化学性能研究,能进一步了解Co(OH)2作为添加剂的作用机理。     

Studies on the interaction between ruthenium and cobalt in supported catalysts in favor of hydroformylation

The interaction between ruthenium and cobalt atoms in SiO₂‐supported catalysts prepared from various precursors by H₂ treatment at 350 °C has been studied by ethylene hydroformylation, temperature‐programmed reduction (TPR) technique and IR spectroscopy. Incorporation of cobalt with ruthenium gives a catalyst with remarkably enhanced hydroformylation activity with respect to those of monometallic catalysts, irrespective of the ruthenium and cobalt precursors used. The synergistic effect of ruthenium and cobalt on the catalysis is consistent with TPR and IR results. TPR analysis shows regularly a promoted reduction of cobalt due to the “hydrogen spillover” effect, which indicates that ruthenium and cobalt atoms are in intimate contact in the catalysts. CO adsorption IR study demonstrates a strong decrease of CO chemisorption on Ru in the presence of cobalt, proposing that ruthenium and cobalt atoms interact on the SiO₂ surface to form Ru–Co bimetallic particles. The results suggest that the catalysts thus obtained contain Ru–Co bimetallic particles, at least atoms of the two metals in intimate contact. However, in situ surface IR spectra of ethylene hydroformylation exhibit little modification by the presence of cobalt on Ru/SiO₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Study of the deactivation mechanism of Al2O3-supported cobalt Fischer-Tropsch catalysts

The influence of water on alumina-supported cobalt catalysts has been studied. The deactivation of supported Co catalysts was studied in a fixed-bed reactor using synthesis gas feeds containing different concentrations of water vapour. Supporting model studies were carried out using H₂O/H₂ feeds in conjunction with XPS and gravimetry. Rapid deactivation occurs on Re-promoted CO/Al₂O₃ catalysts when H₂/CO/H₂O feeds are used, whereas unpromoted CO/Al₂O₃ shows more stable activity. The results from the gravimetric studies suggest that only a small fraction of the bulk cobalt metal initially present reoxidizes to cobalt oxide during reaction. However, the XPS results indicate significant reoxidation of surface cobalt atoms or highly dispersed cobalt phases, which is likely to be the cause of the observed deactivation. Rhenium is shown to have a marked effect on the extent of reoxidation of alumina-supported cobalt catalysts.