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Magnesiochromite as most likely or chromite after cluster average analysis and comparison with mineral database. The identification as diamond should be ignored as it is based on overlapping spectral regions without any features.
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We identify and characterize the rock forming mineral using a newly installed, state of the art Scanning Electron Microscope integrated with Micro-Raman Spectrometer (SEM-Raman) at Physical Research Laboratory, Ahmedabad, India. The characteristic raman shifts (wave numbers) enable us acquiring the structural information and chemical fingerprint fo...
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... and 610 cm -1 are rather weak, poorly defined and belong to E g and F 2g respectively. We could observe that the most prominent the 685cm -1 which 1 is produced by the bonds of (Cr 3+ , Fe 3+ , Al 3+ )O 6 octahedra is present sample (Fig.3). The correlation between A 1g and chromite chemical composition can be expressed as polynomial function [3]. ...
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Despite intensive studies on the effect of grain morphology, that results from Selective Laser Melting (SLM) fabrication, on the mechanical properties of Inconel-718 (IN718), there is a lack of insight into its effect on the alloy’s oxidation behavior. This work compared the oxidation of IN718 alloy manufactured by SLM (SLM-IN718) with that of a cast-rolled commercially available sample (Comm-IN718) when heating to 900°C. Our results showed that the passivating chromia layer that forms on Comm-IN718 was resistant to rupture because it is a thin oxide layer with a favorable distribution of internal stress due to the alloy’s well-defined quasi-honeycomb primary grain morphology. In comparison, SLM-IN718 had a poorly defined grain morphology, with two distinct length-scales best described as dendritic structures. This morphology resulted in the formation of a thicker oxide scale without favorable distribution of the stress into the alloy grain boundaries. This led to the rupture of the passivation layer. These findings give us a new insight into how the primary microstructure of Inconel alloys can affect their oxidation behavior by affecting the stress distribution within surface oxide films. We are the first to show that morphology characteristic control plays a key role in improving Inconel oxidation.
To determine the chemical composition of minerals on planetary surfaces from spectroscopic data, it is required to establish the link between mineralogy, spectroscopy and chemical composition of rock forming minerals on Earth. To meet this requirement, we performed integrated mineralogical and spectroscopic (Visible-Near Infrared and micro Raman) characterisation of chromite from the chromitite layer in the mantle section of the Nidar ophiolite complex, SE Ladakh, J&K, India. Chromite commonly occurs as monominerallic chromitite layers (up to 1 meter wide) and disseminated grains within the dunites and harzburgites. The Cr2O3 content is generally high (>60 wt%) and chemically homogeneous across the grains. The X-ray Diffraction (XRD) analyses show highest peak intensity at ∼36° 2θ, followed by other diagnostic peaks for chromite. Micro-Raman of chromite yields very strong diagnostic Raman active vibrational modes at 685 cm−1 (A1g), followed by 520 cm−1 (F2g(2)). The other peaks, viz. 446 cm−1 and 610 cm−1 are rather weak and correspond to Eg and F2g, respectively. VNIR (0.4μ to 2.4μ) reflectance spectroscopy of chromite suggested strong absorption near 2 μm and could be useful to quantify the chemical composition (especially Cr2O3, Al2O3 and Cr#). We found a good correlation of VNIR absorption and chemical composition of chromite (e.g. band positions versus Al2O3 and Cr# are well within 95% correlation interval). The intense Raman peak at 685 cm−1 corresponds to higher Cr content. This study, therefore, implies a significant understanding in determination of mineral chemistry (especially Chromites) by VNIR and micro Raman spectroscopy, which could be a useful tool for the future planetary exploration.
