Synthetic pentlandite surfaces were subjected to oxidation by a range of inorganic oxidants, and the resultant alteration of the surface studied by a range of surface-sensitive spectroscopic techniques. The oxidants used were air during heating to relatively low temperatures (150°C), steam, ammonium hydroxide, hydrogen peroxide, and sulphuric acid. Electrochemical oxidation was also undertaken. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), conversion electron Mössbauer spectroscopy (CEMS), and spectral reflectance measurements were used to characterize the surface compositions. New data for the binding energies of core electrons in pentlandite and violarite, based on the fitted XPS spectra, are proposed. For pentlandite and violarite respectively, values of 707.3 eV and 708.4 eV for the Fe 2p3/2, 853.0 eV and 853.2 eV for the Ni 2p3/2, and 161.2 eV for the S 2p in both sulphides, were obtained. After oxidation the pentlandite surfaces indicated nickel enrichment in the subsurface, with the formation of violarite. The immediate oxidized surface, of approximately 10Å thickness, indicated a range of iron oxides and hydroxides (Fe3O4, Fe2O3 and FeOOH, with possible Fe1−xO and Fe(OH)3), nickel oxide (NiO), and iron sulphates (FeSO4, Fe2(SO4)3). The proportions of the phases present in the surface layer are inferred to be a consequence of both the strength of the oxidant employed, and the thermodynamic stability of the phases, as can be illustrated using partial pressure and Eh/pH diagrams. A sequence of oxidation is proposed, accounting for the sub-surface enrichment in violarite, and the development of the oxidized surface, which is inferred to have a major affect on the rates of oxidation.

Surfaces of a natural sample of arsenopyrite (FeAsS) were oxidized by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The oxidants used were air during heating to relatively low temperatures (150°C), steam, ammonium hydroxide, hydrogen peroxide, and sulphuric acid. Electrochemical oxidation in water was also undertaken. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and spectral reflectance measurements, were used to characterize the surface compositions. New data are proposed for the binding energies of core electrons in arsenopyrite based on the fitted XPS spectra: 706.9 eV for the Fe 2p3/2 level, 161.2 eV for the S 2p level, and 40.7eV for the As 3d level. Spectroscopic analyses of the surfaces following oxidation indicated a range of iron oxides and hydroxides (Fe1−xO, Fe3O4, Fe2O3, FeOOH and Fe(OH)3), arsenic oxides (As2O3 and As2O5), sulphur and iron sulphates (FeSO4, Fe2(SO4)3). The relative proportions of the different phases present in the surface layer are related to the strength of the oxidant employed and, where relevant, the Eh/pH conditions prevalent during oxidation. The conclusions regarding the nature of the oxidation of arsenopyrite are discussed in relation to arsenopyrite extraction by flotation and leaching, and the breakdown of arsenopyrite in natural systems.

This work studied the phases in the Al corner of the Al–Mn–Be phase diagram in the as-cast state and heat-treated conditions. Metallographic investigations, X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy were used for identifying the phases. The Be contents in the identified phases were precisely determined using Auger electron spectroscopy. The results indicated that Al6Mn does not dissolve Be, whilst λ-Al4Mn dissolves up to 7 at.% Be. The average composition of the T phase, which is normally designated as Al15Mn3Be2, was 72 at.% Al, 19 at.% Mn, and 9 at.% Be. The phase with the nominal composition Be4AlMn contained more Al than Mn. The atomic ratio Al:Mn was between 1.3:1 and 2:1. The hexagonal Be-rich phase did not dissolve any Al and Mn. The icosahedral quasicrystalline (IQC) phase contained up to 45 at.% Be. The compositions of T phase, λ–Al4Mn, IQC, and Be4AlMn may vary, however, the ratio (Al + Be):Mn remained constant, and was close either to four or six indicating substitution of Al atoms with Be atoms in these phases.

In this article, the secondary electron-emission properties of both vertically and laterally inhomogeneous samples are discussed. To study the effect of surface coverage, the total electron-emission yield of tungsten and niobium samples was measured as a function of primary electron energy and oxide thickness. A method is suggested to avoid charging difficulties during AES measurements of samples that consist of both metal and various insulator parts.

Intrinsic stresses as a function of σ, the 1/e penetration depth were measured for a smooth, 1μm thick, fine grained, cylindrical post magnetron sputtered molybdenum film deposited on a vycor glass substrate in the dynamic deposition mode. Using grazing incidence diffraction and the Mo (321) reflection, lattice spacing profiles were determined for τ values from 200-4400 Å. The in-plane intrinsic stresses parallel and perpendicular to the post axis were determined employing the ϕ-integral method and assuming elastic isotropy. The results were related to the surface structure and composition profiles via atomic force microscopy (AFM) and auger electron spectroscopy (AES) respectively.