406 results found
Kelsall GH, Yin Q, Vaughan DJ, et al., 1999, Electrochemical oxidation of pyrite (FeS2) in aqueous electrolytes, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, Vol: 471, Pages: 116-125, ISSN: 0022-0728
Hart N, Brandon N, Shemilt J, 1999, The environmental impact of solid oxide fuel cell manufacturing, Fuel Cells Bulletin, Vol: 2, Pages: 4-7, ISSN: 1464-2859
Solid oxide fuel cells (SOFCs) offer many advantages over conventional methods of electrical generation, including higher efficiencies and lower emissions. The environmental benefits of the use phase of SOFCs have been extensively reported, but it is important that the total environmental burden is evaluated. This article compares the environmental impact of six fabrication methods which have the potential to be used within the SOFC manufacturing process: screen printing, slurry spraying, tape casting, calendering, electrochemical vapour deposition and physical vapour deposition.
Daveau S, Brandon NP, Bonanos N, 1997, Electrical conduction phenomena in coked industrial reforming catalysts, Materials Research Bulletin, Vol: 32, Pages: 205-212, ISSN: 0025-5408
Industrial Pt/Al2O3 reforming catalysts containing up to 26 wt% of carbon have been studied by admittance spectroscopy. Spectra obtained on heating in nitrogen in the range 200-500°C displayed low frequency relaxations, which were interpreted in terms of a network of carbon islands linked by surface ionic conduction. During subsequent cooling, these features disappeared, suggesting that they were generated by dissociation of strongly bound water. Isothermal ac measurements in nitrogen showed that the conductance was determined by the carbon content. Similar measurements made in dilute oxygen showed that the conductance decreased with burn-off of carbon. Analysis of gases evolved on heating revealed aqueous and chloride species, originating from acid sites on the catalyst support. The results suggest that electrical techniques could be used to characterize coked reforming catalysts. Copyright © 1997 Elsevier Science Ltd.
Bonanos N, Brandon NP, Mahmood MN, et al., 1996, The effect of imposed electrical current on torque release at the metal-mudcake interface, Journal of Applied Electrochemistry, Vol: 26, Pages: 977-980, ISSN: 0021-891X
Differential sticking arises in drilling operations when the drillstring embeds into a layer of mud on the borehole wall. The present work is aimed at proving the concept of an unconventional method of releasing the drill string, namely, the application of an electrical current. An instrument has been designed and constructed to measure the slippage torque at the interface between a steel disc and a filtercake prepared from a model aqueous drilling mud. Experiments have demonstrated that a cathodic current of 1 mA cm-2 reduced the slippage torque by about 50% with both mild and stainless steel. The same effect was obtained galvanically, using a magnesium sacrificial anode connected to the steel, thus dispensing with the need for an external power source. It is hoped that this effect could be used to inhibit differential sticking in aqueous drilling muds, as well as offering a fast method of stuck pipe release. © 1996 Chapman & Hall.
Bonanos N, Brandon NP, Mahmood MN, et al., 1994, Effect of imposed electrical current on torque release at the metal-mudcake interface, Society of Petroleum Engineers of AIME, (Paper) SPE, Pages: 1-17
Differential sticking arises in drilling operations when the drillstring embeds into a layer of mud on the borehole wall. The present work is aimed at proving the concept of an unconventional method of releasing the drill string, namely the application of an electrical current.
BRANDON NP, PANESAR SS, BONANOS N, et al., 1993, THE EFFECT OF CATHODIC CURRENTS ON FRICTION AND STUCK PIPE RELEASE IN AQUEOUS DRILLING MUDS, JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING, Vol: 10, Pages: 75-82, ISSN: 0920-4105
Brandon NP, Wood RJK, 1993, The influence of interfacial potential on friction and wear in an aqueous drilling mud, Wear, Vol: 170, Pages: 33-38, ISSN: 0043-1648
Aqueous drilling muds, whilst recognised as environmentally benign, give higher coefficients of friction than their oil-based counterparts, leading to increased torque and drag on the drillstring. This work concerns a novel approach to improving the lubricity of aqueous drilling muds, namely by controlling the electrochemical potential at the drillstring-drilling mud interface. A Cameron-Plint high-frequency friction machine, modified to accept an electrochemical cell, has been used to measure friction and wear in aqueous drilling muds for mild steel pins rubbing on mild steel or sandstone wear plates. It was found that the coefficient of friction at metal-rock contacts decreased on application of a cathodic potential, whilst friction at metal-metal contacts decreased when an anodic potential was applied. © 1993.
Brandon NP, Bonanos N, Fogarty PO, et al., 1993, Influence of potential on the friction and wear of mild steel in a model aqueous lubricant, Journal of Applied Electrochemistry, Vol: 23, Pages: 456-462, ISSN: 0021-891X
An electrochemical cell has been designed, based on a Cameron-Plint friction machine, which enables measurement of friction and wear under conditions of controlled potential. For mild steel in a pH 9 aqueous solution of sodium octanoate, varying the potential of the steel over the range -1 to + 1 V vs SHE produced three distinct friction-wear regimes: high friction/low wear, low friction/high wear, and low friction/low wear. These regimes were ascribed to potential dependent changes in the coverage and stability of a lubricating octanoate film on the surface of the steel. Increasing the contact stress amplified the effect of potential on wear, and confirmed that the surface film retained its lubricity at contact stresses capable of causing plastic deformation of the steel. © 1993 Chapman & Hall.
Page PW, Brandon NP, Mahmood MN, et al., 1992, One-step recovery of nickel by an electrohydrometallurgical process, Journal of Applied Electrochemistry, Vol: 22, Pages: 779-786, ISSN: 0021-891X
The one-step electroleaching-electrowinning of nickel from violarite and pentlandite iron-nickel sulphide concentrates has been demonstrated using an electrochemical cell fitted with a cation exchange membrane. Oxidants were electrogenerated in the anode compartment, which contained a slurry of the concentrate, and dissolved nickel electrowon in the cathode compartment. Nickel powder of greater than 99% purity with an iron content of 0.2% was obtained. © 1992 Chapman & Hall.
Brandon NP, Bonanos N, Fogarty PO, et al., 1992, The Effect of Interfacial Potential on Friction in a Model Aqueous Lubricant, Journal of the Electrochemical Society, Vol: 139, Pages: 3489-3492, ISSN: 0013-4651
A tilting electrochemical cell was used to study the effect of potential on the static coefficient of friction of iron on mild steel in a model aqueous lubricant consisting of octanoic acid neutralized to pH 9.2 with sodium hydroxide. A sharp fall in friction was observed at potentials positive of -400 mV vs. standard hydrogen electrode. Both impedance and radiotracer measurements indicated that the decrease in friction coincided with an increase in the thickness of a lubricating surface film. This potential dependent behavior is interpreted in terms of electrostatic interactions between the iron and the negatively charged octanoate species. © 1991, The Electrochemical Society, Inc. All rights reserved.
Brandon NP, Mahmood MN, Page PW, et al., 1987, The direct electrowinning of gold from dilute cyanide leach liquors, Hydrometallurgy, Vol: 18, Pages: 305-319, ISSN: 0304-386X
A cylindrical electrowinning cell employing a three-dimensional steel wool cathode has been used to investigate the effect of free cyanide concentration, pH, solution conductivity and base metal impurities on the electrowinning of gold from alkaline cyanide leach liquors containing up to 5 mg/l gold. The recovery of gold in a given time decreased: (a) as the pH decreased below 13, (b) if more than 10 mg/l of Fe, Cu, Zn or Hg were present in solution, (c) as the free NaCN concentration was increased, (d) with decreasing conductivity of the solution. High gold recoveries can be obtained with relatively low electrical energy consumption; greater than 96% recovery in one hour from 5 mg/l gold solutions with an electrical energy consumption of 112 kWh/kg at a current efficiency of 0.33% is possible. Experimentally derived graphs of solution concentration versus time of electrolysis were analysed by means of a simple reactor model and approximate mass transfer coefficients were calculated. These were compared with coefficients calculated from data on the performance of Mintek cells in South African gold recovery operations. The application of these data to the prediction of required electrode area and hence cost for a commercial dilute electrowinning installation is discussed. © 1987.
BRANDON NP, KELSALL GH, 1985, GROWTH-KINETICS OF BUBBLES ELECTROGENERATED AT MICROELECTRODES, JOURNAL OF APPLIED ELECTROCHEMISTRY, Vol: 15, Pages: 475-484, ISSN: 0021-891X
BRANDON NP, KELSALL GH, LEVINE S, et al., 1985, INTERFACIAL ELECTRICAL-PROPERTIES OF ELECTROGENERATED BUBBLES, JOURNAL OF APPLIED ELECTROCHEMISTRY, Vol: 15, Pages: 485-493, ISSN: 0021-891X
Brandon N, Fleischmann M, Kelsall G, et al., 1984, ANALYSIS OF 'NOISE' IN ELECTROCHEMICAL REACTORS., Pages: 398-399, ISSN: 0160-4619
Fluctuations in current or potential are generated in electrochemical cells either on a macroscopic or a microscopic scale by a wide variety of processes. For the special case of metal winning, refining or plating these are listed. The listing includes an indication of the observed (or in some cases the expected) time scales of the phenomena. It can be seen that the time scales of many of the phenomena (or the related frequency domains) overlap so that clear cut distinctions are not necessarily possible: at this stage it is usually necessary to identify phenomena with experiments on simple model systems. The application of noise measurements is illustrated using particle/particle collisions in fluidised beds and bubble induced mixing as the main examples. It is shown that the influence of stochastic processes is frequently large so that these effects must be included in the modelling of electrochemical reactors e. g. fluidised beds. In other cases several phenomena contribute to the generation of fluctuations e. g. localised perturbation of boundary layers by bubble growth and detachment accompanied by vortex shedding on bubbles acting as turbulence promoters. The interaction of noise sources is also discussed.
Brandon N, Fleischmann M, Kelsall G, et al., 1984, ANALYSIS OF 'NOISE' IN ELECTROCHEMICAL REACTORS., Pages: 562-571, ISSN: 0161-6374
Current (or potential) fluctuations in electrochemical cells are classified according to the nature of the processes. It is shown that detailed information about the noise sources can be derived from analyses of the fluctuations. Measurement techniques range from the determination of amplitude probability densities to power spectral density functions. Bubble-induced mixing and the modelling of fluidised bed electrodes are used as illustrations.
BRANDON N, FLEISCHMANN M, KELSALL G, et al., 1984, ANALYSIS OF NOISE IN ELECTROCHEMICAL REACTORS, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 131, Pages: C101-C101, ISSN: 0013-4651
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