Search for and analysis of composition and structure of submicron-size particles in geological and environmental samples

摘要

A technique combining SR XRF, XRF mapping, μ-XRF, and μ-XAFS for search for microparticles in different matrices and determination of particle size, as well as analysis of their composition and structure, has been developed at Budker Institute of Nuclear Physics. The technique is based on comprehensive examination of sample with gradually increasing the spatial resolution and constricting the study area for locating the desired microparticle. The beam size for preliminary studies ranges from 1 mm to 100 μm in height and 10 mm in width. The next stage is examination using X-ray optics (polycapillary lenses) with single-lens and confocal schemes. The apparatus function of each lens is measured, which enables controlled variation of the focal spot size from 10 μm to 70 μm. This multifacet technique was tested on search for and study of micro-inclusions of light platinum group metals (Ru and Pd) in Bushveld (South Africa) Intrusive Complex samples. An area with high concentration of Pd has been found. The particle sizes (～50 μm) have been identified. A localized particle was studied using the μ-XAFS method. The forms of Pd state in the particle have been established; their structural parameters (interatomic distances and coordination numbers) have been determined.