Non-isothermal modelling of the all-vanadium redox flow battery

An non-isothermal model for the all-vanadium redox flow battery (RFB) is presented. The two-dimensional model is based on a comprehensive description of mass, charge, energy and momentum transport and conservation, and is combined with a global kinetic model for reactions involving vanadium species. Heat is generated as a result of activation losses, electrochemical reaction and ohmic resistance. Numerical simulations demonstrate the effects of changes in the operating temperature on performance. It is shown that variations in the electrolyte flow rate and the magnitude of the applied current substantially alter the charge/discharge characteristics, the temperature rise and the distribution of temperature. The influence of heat losses on the charge/discharge behaviour and temperature distribution is investigated. Conditions for localised heating and membrane degradation are discusse

Some issues in the 'archaeology' of software evolution

During a software project's lifetime, the software goes through many changes, as components are added, removed and modified to fix bugs and add new features. This paper is intended as a lightweight introduction to some of the issues arising from an `archaeological' investigation of software evolution. We use our own work to look at some of the challenges faced, techniques used, findings obtained, and lessons learnt when measuring and visualising the historical changes that happen during the evolution of software

Electrodeposition of copper from mixed sulphate–chloride acidic electrolytes at rotating disc electrode

The effect of chloride ion on the deposition of copper from low metal concentrations in aqueous, acid sulphate solutions was investigated. The electrolytes contained 0·05 mol dm?3 CuSO4 and 0·5 mol dm?3 Na2SO4 at pH 2 and 296 K. The chloride ion concentration was varied in a wide range from 0·03 to 2·0 mol dm?3. Linear sweep voltammetry was carried out under well defined flow conditions at a smooth platinum rotating disc electrode. The progressive transition from a single, two-electron reaction for the reduction of Cu(II)?Cu(0) to two, single-electron reactions for the reduction sequence: Cu(II)?Cu(I)?Cu(0) was clearly evident as the chloride ion concentration increased. The charge transfer and mass transport characteristics of these reactions were evaluated. The formal potential for the Cu II) reduction to Cu(I), the shift in the potential region for complete mass transport controlled reduction of Cu(I) to Cu(0) and the potential for hydrogen evolution at the deposited copper were also studied. A semi-logarithmic relationship between exchange current density and half-wave potential for Cu(II)?Cu(I) with chloride ion was achieved when the Cl?/Cu(II) ratio in the electrolytes exceeded 2, due to the presence of the Cu(I) dichlorocuprous anion, CuCl2?

TINDAKAN LEMBAGA PEMASYARAKATAN DALAM PEMBINAAN PELAKU TINDAK PIDANA BERLATAR BELAKANG ALIRAN SESAT (SUATU PENELITIAN DI RUTAN KELAS II B BANDA ACEH DAN RUTAN CABANG LHOKNGA)

Banda Ace

Oxidation of the borohydride Ion at silver nanoparticles on a glassy carbon electrode (GCE) using pulsed potential techniques

Direct oxidation borohydride fuel cells are very attractive energy conversion devices. Silver has been reported as one of the few materials which can catalyze an 8-electron oxidation. Potential step amperometric pulse techniques to synthesize nanostructured silver material on flat glassy carbon electrodes is reported and significant differences with bulk silver deposit have been observed. The oxidation of borohydride ion on the silver particles occurs at -0.025 V vs. SCE and the potential decreases towards negative values at longer cycle times. The oxidation current also decreases with the number of cycles, suggesting that the silver active sites become partially blocked by oxidation products of borohydride. The electroactive area per unit electrode area of silver was relatively low for particles deposited using potential step amperometric techniques on glassy carbon (0.002 cm2 per cm-2) compared with the area found at a polycrystalline silver electrode (0.103 cm2 per cm-2

The 3D printing of a polymeric electrochemical cell body and its characterisation

An undivided flow cell was designed and constructed using additive manufacturing technology and its mass transport characteristics were evaluated using the reduction of ferricyanide, hexacyanoferrate (III) ions at a nickel surface. The dimensionless mass transfer correlation Sh = aRebScdLee was obtained using the convective-diffusion limiting current observed in linear sweep voltammetry; this correlation compared closely with that reported in the literature from traditionally machined plane parallel rectangular flow channel reactors. The ability of 3D printer technology, aided by computational graphics, to rapidly and conveniently design, manufacture and re-design the geometrical characteristics of the flow cell ishighlighted

Monitoring of zincate pre-treatment of aluminium prior to electroless nickel plating

<p>Zincating is used as a pre-treatment for aluminium prior to electroless nickel deposition during preparation of magnetic computer memory discs. Four immersion zincating solutions were evaluated at 22°C using single step or double zincating followed by electroless nickel deposition from a high phosphorus hypophosphite bath at 90°C. The coating process was monitored by potential <i>vs.</i> time curves obtained under open-circuit conditions during zincating then electroless nickel plating. The surface morphology of the aluminium, at various stages, was imaged by scanning electron microscopy and atomic force microscopy. Zero resistance ammetry was used to record galvanic currents between the aluminium and an inert platinum counter electrode during zincating. This, together with potential-time measurements, provided simple and valuable methods for following the zincating process and subsequent electroless Ni plating. Double zincating enabled a shorter induction time for electroless Ni deposition and resulted in a more complete coverage of the surface by Zn.</p

A Backup Plan for Self-Protection: S-Methylation of Holomycin Biosynthetic Intermediates in Streptomyces clavuligerus

Biosynthesis of the dithiolopyrrolone antibiotic holomycin in Streptomyces clavuligerus involves the closure of a pair of enethiols to a cyclic disulfide. We have shown that the dithiol oxidase HlmI is responsible for the disulfide formation and this enzyme also plays a role in self-protection. In the present study, we examine how S. clavuligerus deals with the proposed toxic dithiol intermediates when hlmI is deleted. We used differential NMR spectroscopy and mass spectrometry to profile the metabolomes of hlmI deletion mutants along with the wild-type strain and a holomycin-overproducing strain. A number of metabolites unique to ΔhlmI strains were identified. In these metabolites the enethiols have been incapacitated by a combination of mono- and di-S-methylation. We also observed an intriguing dimeric thioether adduct in low quantities in the wild-type strain and at much higher levels in the ΔhlmI strains. The structures of these novel metabolites highlight the reactivity of the dihydrodithiolopyrrolone scaffold. Furthermore, bioassays suggest that modification of the enethiol warhead by S-alkylation provides a host strategy for detoxification, one that is shared amongst multiple species producing such bioactive disulfide natural products

Pd-Ir alloy as an anode material for borohydride oxidation

A Pd-Ir alloy (1:1) coated on microfibrous carbon (11 μm diameter) supported on a titanium plate was evaluated as an electrode for the anodic oxidation of borohydride. The hydrogen generated, due to the parallel reaction of borohydride hydrolysis, was measured during the electrolysis obtaining less than 0.1 cm 3 min -1 H 2 between -1 and 0 V vs. Hg/HgO (-0.86 and 0.14 V vs. SHE), while the current densities for the oxidation of borohydride were up to 367 mA cm -2 in 0.5 mol dm -3 NaBH 4 + 3 mol dm -3 NaOH. The low rate of hydrogen generation suggests that Pd-Ir could be a promising catalyst for borohydride oxidation. However, higher rates of hydrogen were generated at the open circuit potential, which is inconvenient in the direct borohydride fuel cell. Cyclic voltammetry allowed analysis of the oxidation peaks due to the borohydride oxidation. To obtain a further understanding of the borohydride oxidation mechanism at Pd-Ir electrodes, density functional theory (DFT) was used to examine the reaction mechanism at Pd 2 -Ir 1 (111) and Pd 2 -Ir 2 (111) surfaces. The competition between borohydride oxidation and hydrogen evolution on the Pd-Ir alloys is compared with that on pure Pd(111), suggesting that the presence of Ir favors borohydride oxidation rather than hydrogen evolution. © 2014 Elsevier B.V. All rights reserved