Search publications of the members of the Royal Belgian institute of natural Sciences
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Raman Micro - Spectroscopy as a Tool to Characterise Cobalt — Manganese Layered Oxides (Heterogenite - Asbolane – Lithipophorite), Study on Crystalline and Amorphous Phases from the DRC (Democratic Republic of the Congo)
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Study of the spectro-chemical signatures of cobalt-manganese layered oxides (asbolane–lithiophorite and their intermediates) by Raman spectroscopy.
- In this study, Raman micro spectroscopy is applied to investigate two manganese oxides: lithiophorite [(Al,Li)Mn4+O2(OH)2] and asbolane [(Ni,Co)xMn4+(O,OH)4.nH2O], along with their intermediates (“Asbolane-Lithiophorite Intermediates”: ALI). These oxides typically incorporate variable concentrations of Co, Ni, Cu and Li. They represent a group of economically interesting phases that are difficult to identify and characterize with classical X-ray diffraction techniques. We show that Raman micro spectroscopy is useful to the investigation of those phases, but they require to be tested in very low laser power conditions to avoid sample degradation (e.g. 0.2mW 532nm). We propose reference Raman spectroscopic signatures for lithiophorite, asbolane and ALI phases. These spectra are mainly composed of two spectral domains, the first one is located between 370-630 cm-1 and the second one between 900-1300 cm-1. We then assess the impact of their highly variable chemistry on their Raman peak positions, intensities and FWHM using a semi-systematic curve-fitting method profiled for these phases.
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Stratochip, a dual balloon high-altitude platform: controlled altitude flight experiments and potential applications in geosciences.
- A high-altitude dual balloons system, the 'Stratochip', was designed at the Geological Survey of Belgium to serve as a development platform to carry measurement and earth observation equipments, in altitudes comprised between 1000 and 25000m. These working altitudes far exceed the range of current motor powered unmanned aerial vehicules, with a higher weight carrying capacity (up to 10-15kg). This platform is built around a two helium balloons configuration, than can be released one by one at a target altitude or location, allowing a partially controlled drift of the platform. Using a 'nowcasting' meteorological model, updated by flight telemetry, the predicted path can be refined live to follow and retrieve the equipment in a predicted landing area. All subsystems (balloon cut-off devices, flight controller, telemetry system) have been developed in-house. Three independent communication channels, designed to work at extremely low temperature (up to -60° C) ensure a continuous tracking until landing. A calibrated parachute is used to control the safe descent of the equipment. Several flight tests have been performed in Belgium to control the meteorological model accuracy for wind predictions (model based on National Oceanic and Atmospheric Administration data). Those tests demonstrated the capability of the platform to maintain its altitude in a predicted path, allowing using the platform for new types of atmospheric studies and affordable high-altitude remote-sensing applications (i.e. sub-meter resolution stereo imagery).
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Heterogenite vs asbolane: a mineralogical study of cobalt oxides from the DRC (Democratic Republic of the Congo)
- The largest cobalt ore reserves are located in DRC, the Democratic Republic of Congo. Most of cobalt is observed as black cobaltic oxide minerals: heterogenite [HCoO2] and asbolane [(Ni,Co)2-xMn(O,OH)4.nH2O] which are hardly differentiable since they exhibit similar macroscopic habit and textures. These minerals are frequently observed in similar environment (oxidized horizon of ore deposits) and they are commonly poorly-crystallized limiting their study with XRD. Their chemical composition is also not very well-constrained since they exhibit significant chemical substitutions with cations as Cu, Co, Ni, Mn. Our observations on a set of heterogenite and asbolane samples from DRC combined with samples from other localities shows that each phase, even under an amorphous form, can be readily distinguished by Raman microspectrometry. This technique is therefore attractive during ore deposit characterization campaigns or during the follow-up extraction operations where it is important to distinguish the main constituting Co-phase(s). The main advantage of this technique is its speed since no sample preparation is required during the collection Raman spectra that usually last few tens of seconds. The method provides information at a mum-scale and several points are thus required to fully characterize ore batches composed of different mineralogical phases. Our petrographical observations show also that asbolane and heterogenite mineralogical phases can coexist at a mum-scale as two distinct phases into 'heterogenite' ore. The distinction between heterogenite and asbolane from our sample set can also be conducted on a chemical base showing that heterogenite represents the richer Co-phase with variable Cu concentrations. By contrast, only Mn traces are usually observed in heterogenite minerals from DRC except in few samples, but always in lower concentration than in asbolane. The latter shows variable Mn/(Mn+Co) ratio between 0.85 and 0.3 and the decrease of this value is related to enrichment into Cu.
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A new Cambrian black pigment used during the late Middle Palaeolithic discovered at Scladina Cave
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The shaping of Brussels‘ urban landscape: an interdisciplinary perspective
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MOnitoring en MOdellering van het cohesieve sedimenttransport en evaluatie van de effecten op het mariene ecosysteem ten gevolge van bagger- en stortoperatie (MOMO). Activiteitsrapport (1 juli 2014 - 31 december 2014).
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Ant differential response to nutrient addition in an Andean forest.
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Spatio-temporal variation of ant distribution among ground layers in an Andean tropical forest.
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Arboreal ant mosaics meltdown with elevation.
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Arthropod distribution in tropical rainforests: contribution of horizontal, vertical and seasonal gradients to species diversity.
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Focus Stacking: a low budget semi-automated approach allowing high quality mass digitization.
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Integrating micromorphology and archaeobotany to unravel the function of an archaeological structure. The example of the site of Petite Rue de Bouchers (Brussels, Belgium)
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From individual diet determination to food web disentanglement: the use of stable isotopes and fatty acids in the study of ant trophic ecology.
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Arboreal ant mosaics meltdown along an elevational gradient in Papua New Guinea.
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Étude interdisciplinaire du paysage médiéval de la vallée de la Senne à Bruxelles : le site de petite rue des Bouchers
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Facing complexity: archaeobotany and Dark Earth. Towards an integration of botanical and geoarchaeological data
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A remarkable new species of Paraphamartania Engel from Portugal (Diptera, Asilidae)
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Use of digital photogrammetry for the study of unstable slopes in urban areas: Case study of the El Biar landslide, Algiers
- Recent developments in remote sensing techniques provide powerful tools for geomorphological studies. The geometric and kinematic characterization of landslides are key factors in understanding the mechanisms of movement. The purpose of this publication is to show the potential of digital photogrammetry in the spatiotemporal study of landslides in urban areas. The case study focuses on the landslide of El Biar in Algiers. Comparison of digital elevation models generated following an established methodology shows the morphological evolution of the site. Orthophotos are used to measure surface displacements. The analysis of horizontal displacements between 1995 and 2007 shows that the landslide of El Biar can be divided into two zones: a peripheral zone moving at an average speed of about 5 cm per year and a central zone moving at an average speed of about 10 cm per year. Comparing the results with those obtained by traditional survey methods shows a remarkable consistency, thus validating the techniques used. This study demonstrates that digital photogrammetry, when combined with geological and geotechnical data, can improve the characterization and understanding of landslides mechanisms, and thus help defining mitigation solutions.
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Chromosome evolution in pseudoxyrhophiine snakes from Madagascar: a wide range of karyotypic variability
