DETERMINATION OF URANIUM AND THORIUM SURFACE DISTRIBUTION IN GEOLOGICAL SAMPLES: COMPARISON OF TABLETOP MACRO AND MICRO-XRF SCANNING.

This paper describes the identification and quantification of uranium, thorium and other chemical elements in a low-grade uranium ore, using macro and micro-X-ray fluorescence scanning. The result of such scanning is their surface distribution determined in flat samples. The basic parameters of both setups are described. The investigation was focused mainly on the improvement of the lateral resolution in the laboratory tabletop macro-XRF and its comparison with micro-XRF scanning. A standard reference material NIST 610 was used as a homogeneous reference silicate material of a known composition. The measurements have demonstrated how the macro-XRF with a quite wide X-ray beam can be competitive with the micro-XRF scanning. The capabilities of both devices were established, utilizing measurements of selected uranium-bearing sediments samples, from the Brevniste deposit in the Czech Republic.

A novel route of colloidal chemistry: room temperature reactive interactions between titanium monoxide and silicon monoxide sols produced by laser ablation in liquid resulting in the formation of titanium disilicide.

In spite of advanced research on functional colloidal inorganic nanoparticles and their reactivity, room temperature reactive interactions between two different colloids have remained challenging so far. Laser ablation of titanium monoxide and silicon monoxide in ethanol and water allows the generation of TiO-derived and SiO-derived colloidal nanoparticles which were characterized for their stability, size distribution and zeta potentials with dynamic light scattering and after evaporation of solvent examined for their morphology, chemical and phase composition by scanning electron microscopy, Raman spectroscopy, high resolution transmission electron microscopy and electron diffraction and small angle X-ray scattering. Aqueous and ethanolic TiO-derived colloids consist of anatase and monoclinic TiO, while ethanolic SiO-derived colloids are composed of crystalline and amorphous Si, nanocrystalline Si and SiO2 and aqueous SiO-derived colloids contain, in addition to these phases, a high pressure form of cristobalite. Simple room temperature mixing of ethanolic TiO- and SiO-derived colloids allows the formation of TiSi2, which is a case of so far unreported room temperature reactive interactions between two colloidal species. All colloids absorb solar light and act as photocatalysts for methylene blue degradation. These findings present a challenge for further search for feasible room-temperature reactions between distinct colloidal particles and open the potential for green synthesis of other desirable and hardly achievable phases.