Merrick R. Mahoney

Intense raman spectra of surface carbon and hydrocarbons on silver electrodes

Abstract Raman spectra have been recorded from silver electrodes in salt solutions at −0.2 V (SCE). Enhancement of the spectra is interpreted in terms of red-light transmittance of high surface area carbons on the electrodes. The kinetics of diffusion of the hydrocarbons away from the electrode is shown to be much slower than the rate of formation of hydrocarbons.

Chemical reactivity and surface-enhanced raman scattering

Abstract A mechanism is proposed for surface-enhanced Raman scattering for pyridine which explains the enhancement, the anodizalion “activation”, the significance of silver, the photographitization of coordinated pyridine and formate, the participation of surface roughness, and the irreversibly held yet liquid-like nature of surface pyridine.

Pilot scale simulation of cokemaking in integrated steelworks

Abstract Pilot scale coke ovens are widely used to produce coke samples for characterisation and also to assess the coking behaviour of coal blends. The Newcastle Technology Centre of BHP Billiton has built a sophisticated 400 kg oven, which can produce cokes under a range of carefully controlled bulk densities and heating rates. A freely movable heating wall allows the thrust generated at this wall at the different stages of coking oven to be determined. This paper describes comparative work carried out to determine a laboratory stabilisation technique for laboratory cokes. The strength of stabilised cokes are characterised using a number of tumble tests, and correlations between different drum sizes are also given since a major constraint in laboratory testing is the limitation in the mass of sample available. Typical oven wall pressure results, and results obtained from embedded temperature and pressure probes in the charge during coking, are also presented.

Raman spectra of carbon monoxide adsorbed on silver electrodes

Abstract Weak Raman spectra of carbon monoxide on silver electrode surfaces exhibit frequency and intensity variations with changing potential. The frequency-potential dependence is rationalized in terms of electron-transfer to the antibonding π * state of electrosorbed CO.

The evidence for a stoichiometric silver oxide-cyanide phase in cyanide SERS from silver electrodes

Abstract Nine candidates for the intensely scattering phase in silver/cyanide SERS are compared on the basis of eight experimental criteria. New criteria include complex dissociation studies, tests for radical involvement and the cathodic displacement of SERS with increasing electrolyte alkalinity. The favoured phase is a silver oxide-cyanide compound.

Chemical origins of surface-enhanced Raman scattering by cyanide on copper electrodes

A simple potential-step oxidation–reduction cycle pretreatment is reported for the surface-enhanced Raman scattering (SERS) system Cu/0.1 mol dm–3 Na2SO4, 0.01 mol dm–3 KCN. Laser-assisted corrosion and dissolution processes are suggested by a combination of uniform-laser-flux perturbations of the cyclic voltammetry and laser-interruption effects in the intensity against time decay curve for the system at –1.25 V (vs SCE). The pH dependence of v(CN) intensities for both the copper/cyanide SERS surface and for related cyanocopper(I) complexes is attributed partly to the decomposition of such complexes (pH ⩽ 4.6) and partly to the decomposition of associated copper oxides (pH > 2). The identification of cyanocopper(I) complexes stabilized by copper(I) oxide as the intensely-scattering phase compares with the oxide–cyanide phase proposed for silver/cyanide SERS. The copper/cyanide SERS system is classified as type III (inorganic microzone).

The effect of combinations of iron-bearing minerals and quartz on coke reactivity

ABSTRACT The effect of combinations of iron-bearing minerals and quartz on the reactivity of coke analogues with CO2 was examined in a TGA. Troilite–quartz, pyrite–quartz and magnetite–troilite binary combinations and the troilite–magnetite–quartz ternary combination were examined. For the troilite–quartz and pyrite–quartz binary combinations the reactivity in general decreased non linearly with increasing Si:Fe ratio. The magnetite–troilite combination had a non-linear effect on the reactivity in that mixes of these two minerals show a higher reactivity than would be expected from a simple proportional mixing approach. Some evidence of sulphur transfer from the troilite to the magnetite was observed. The reactivity of the ternary magnetite–troilite–quartz combination can largely be understood from the trends in the axes. These were largely followed across all compositions, allowing better understanding and prediction of the effect of these minerals on the reactivity of industrial cokes.

Cesium Formate as a Dense Medium Liquid for Laboratory Coal Washability Testing

ABSTRACT Laboratory washability testing on coal is used to determine the anticipated yield of coal versus density and coal quality data. The organic liquids which are commonly used are simple to use, but there are several concerns associated with their use: occupational health and safety risks, availability and cost, accuracy, and effect on coal properties. Aqueous Caesium Formate was tested as a feasible alternate dense liquid. Six coals with ranks ranging from Ro Max 0.55 to 1.63% were tested in organic liquids and caesium formate. The results from this test-work show that caesium formate is a possible alternative to organic liquids for laboratory coal washability testing.

Intensely-scattering phase in surface-enhanced Raman scattering by cyanide on gold electrodes

Surface-enhanced Raman scattering (SERS) by cyanide on gold and silver electrodes in 0.1 mol dm–3 KOH, 0.1 mol dm–3 KCN appears to arise from metal oxide–cyanide compounds and not from cyanometal complexes. The similarity of v(CN) for the two metals indicates that metal(ion)–cyanide interactions within the SERS compounds are relatively unimportant. Possible involvement of cyanogold(I) complexes {e.g.[Au(CN)2]–} is ruled out by substantial differences between the v(CN) band for the SERS phase (ca. 2110 cm–1) and for these complexes (>2164 cm–1). The existence of analogous SERS compounds for both silver and gold is indicated by similar SERS frequencies under both controlled-potential and withdrawn (dry)-electrode conditions for the two metals. The involvement of a hydrolysed component (oxide/hydroxide) in gold/cyanide SERS is suggested by previous electrochemical studies of the gold dissolution system and by the similarity of gold/cyanide SERS to SERS from the system Ag/0.1 mol dm–3 Na2SO4, 0.1 mol dm–3 KCN, which appears to arise from a hydrolysed cyanide compound. Some indications of laser damage exist in the gold/cyanide SERS system, which is classified as an SERS type III (inorganic microzone).