Geochemical fingerprints of brannerite (UTi 2 O 6 ): an integrated study
AbstractBrannerite (UTi2O6) is among the major uranium-bearing minerals found in ore deposits, however as it has been long considered as a refractory mineral for leaching it is currently disregarded in ore deposits. Brannerite is found in a variety of geological environments with the most common occurrences being hydrothermal and pegmatitic. On the basis of scanning electron microscopy observations coupled with electron probe micro-analyses and laser ablation inductively-coupled plasma mass spectrometer analyses, this study describes the morphological features and the major- and trace-element abundances of brannerite samples from five hydrothermal and five pegmatitic localities across the w…
Direct synthesis of pure brannerite UTi2O6
International audience; A new method based on the precipitation of uranium(IV) and titanium(IV) hydroxide precursors was developed to prepare pure brannerite UTi2O6 samples. In fact, U(IV) dissolved in HCl (6 mol L−1) was mixed to Ti (IV) alkoxyde before a basification step with an excess of NH4OH to obtain a highly reactive nanometric (U,Ti)(OH)4 powder. The obtained powder was then dried under vacuum, pressed into pellets and finally fired at 1300 °C. This method led to the formation of pure brannerite in contrast to previous reported protocols, which showed the formation of impurities such us UO2 and TiO2. The refined unit cell parameters of UTi2O6 led to a = 9.8113(2) Å, b = 3.7681(1) Å…
La recherche publique en France en 2019 : Diagnostic et propositions du Comité national
Projet porté par le Comité National du CNRS.; Dans le contexte de la préparation d’une loi de programmation pluriannuelle de la recherche, ce document présente la contribution du Comité national de la recherche scientifique à l’analyse de la situation de la recherche publique en France, de son évolution récente (depuis la loi LRU de 2008) et de ses perspectives, ainsi qu’un ensemble de propositions qui ont été finalisées et ont fait l’objet d’une approbation solennelle lors de la session plénière du Comité national organisée à Paris le 4 juillet 2019.
An XRD, TEM and Raman study of experimentally annealed natural monazite
The healing of radiation damage in natural monazite has been experimentally studied in annealing experiments using XRD, TEM, Raman microprobe and cathodoluminescence analysis. The starting material was a chemically homogeneous monazite from a Brazilian pegmatite with a concordant U–Pb age of 474 ± 1 Ma and a U–Th/He age of 479 Ma. The monazite shows nm-scale defects induced by radioactive decay. The Xray pattern of the unheated starting material revealed two distinct monazite ''phases'' A and B with slightly different lattice parameters. Monazite A shows sharp reflections of high amplitudes and slightly expanded lattice parameters (1% in volume) compared to a standard monazite. Phase B exhi…