Combined XRF, XRD, SEM-EDS, and Raman Analyses on Serpentinized Harzburgite (Nickel Laterite Mine, New Caledonia): Implications for Exploration and Geometallurgy

International audienceDifferent techniques have been combined to determine the crystallography and the chemical composition of serpentinized harzburgite sampled in a drill core coming from the lower part of the New Caledonia ophiolite. Specifically, this serpentinized harzburgite is the common bedrock of most of the nickel laterite mines in New Caledonia. Most of the minerals present in serpentinized harzburgite were analyzed by Raman spectroscopy and XRD. In this study, Raman spectroscopy has been applied for the first time to estimate the nickel content in lizardite, forsterite, talc, and goethite. The analyses confirm that the major serpentine minerals show two varieties: (1) Ni-bearing lizardite and (2) Ni-free lizardite. Furthermore, Ni-rich forsterite, enstatite, Ni-rich talc, sepiolite, periclase (MgO), and quartz were detected. Additionally, Raman spectroscopy evidence minor phases not detected by XRD: anatase, rutile, pyrite, hematite, chromite, magnesiochromite, and Ni-rich goethite. Our results show that the Ni substitution is only present in lizardite exhibiting turbostratic-stacking disorder. This finding has potential for being used as an exploration tool using short-wave-infrared spectroscopy online or as a portable instrument, and for defining geometallurgical parameters for processing these complex ores

Highlighting non-uniform temperatures close to liquid/solid surfaces

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Insight into the mechanism of carbon steel corrosion under aerobic and anaerobic conditions

We particularly focused our study on identifying the corrosion products formed at 30 °C on carbon steel under aerobic and anaerobic conditions and on following their evolution with time due to enhanced microbial activity under environmental and geological conditions. The nature and structural properties of corrosion products were investigated by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), X-ray diffraction (XRD) and confocal micro-Raman spectroscopy. Structural characterisation clearly showed the formation of iron oxides (magnetite and maghemite) under aerobic conditions. Under anaerobic conditions, the first corrosion product formed on the steel surface was nanocrystalline mackinawite, which was then followed by a fast transformation process into the pyrrhotite phase, and the Raman spectrum of monoclinic pyrrhotite was proposed for the first time. Finally, this study also shows that in the context of geological disposal of radioactive waste, the corrosion of carbon steel containers in anoxic and sulphidogenic environments sustained by sulphate-reducing bacteria may not be a problem notably due to the formation of a passive layer on the steel surface

Impact of a sulphidogenic environment on the corrosion behavior of carbon steel at 90 °C

The influence of sulphide ion concentration on the behavior of carbon steel in a synthetic solution at 90 °C has been investigated using the methods of weight loss, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), confocal micro-Raman spectroscopy and X-ray diffraction (XRD). Corrosion batch experiments were conducted at 90 °C for 1 month with steel coupons immersed in Na2S solutions. Weight loss measurements revealed that the corrosion layer resistance is strongly dependent on both the sulphide concentration and the physicochemical properties of the corrosion products. In the absence of sulphide ions, a magnetite (Fe3O4) corrosion product layer was formed on the steel coupon, while in presence of sulphide ions (1 mg l−1), we observed the formation of a less protective mackinawite corrosion layer. At higher sulphide concentrations (5-15 mg l−1), highly protective pyrrhotite and pyrite are formed, inhibiting the steel corrosion process. Thus, it has been suggested that the formation of pyrite and/or pyrrhotite could be a promising strategy to protect against carbon steel corrosion in sulphidogenic media

Optimization of ZnSe–SiO2 nanostructures deposited by radio-frequency magnetron sputtering: Correlations between plasma species and thin film composition, structural and microstructural properties

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Determination of porosity of mesoporous silica thin films by quantitative X-ray reflectivity analysis and GISAXS

International audienceThe determination of the porosity of mesoporous silica thin films by X-ray Reflectivity (XR) is reported. The total porosity is deduced from the total reflection plateau and a quantitative analysis involving the calculation of the XR curves by the matrix technique allows to distinguish between micro and meso porosities of the films. Two mesostructured films, in which the surfactant was removed by washing, were investigated. In combination with Grazing Incident Small Angle X-ray Scattering (GISAXS), the surface area of the mesopores is ascertained, thereby providing a complete analysis of the porosity in thin films by X-ray scattering methods

Multiple Glass-Transition temperatures in Thin Supported Films of Isotactic PMMA as Revealed by Enhanced Raman Scattering

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Synthesis, physical and semiconducting properties of SnS2 prepared by chemical route

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Evidence of oxygen content heterogeneity in TSMTG YBa2Cu3O7 − δ/Y2BaCuO5 composites by micro-Raman spectrometry

International audienceThe homogeneity of the oxygen content of TSMTG-YBa2Cu3O7 − δ/Y2BaCuO5 composites has been investigated by micro-Raman spectrometry. The Y123 compound has been found to be very sensitive to the laser power, but a laser power of 0.04 mW has been shown to not to be harmful for the samples, even after 2 h of irradiation. Raman spectra have shown that the oxygen content of YBa2Cu3O7 − δ/Y2BaCuO5 ceramics is not homogeneous at the micrometer scale. In addition, no monotonic decrease of the oxygen content is observed from the periphery to the core of the sample, confirming that the oxygen uptake is not strictly controlled by a diffusion process