High-accuracy experimental determination of photon mass attenuation coefficients of transition metals and lithium fluoride in the ultra-soft energy range.

In the field of quantitative X-ray analysis techniques, such as electron probe microanalysis, precise knowledge of fundamental parameters is crucial. Especially, the accurate determination of photon mass attenuation coefficients is essential to perform correct elemental quantification. While the widely used databases offer agreement for the hard X-ray range, significant differences arise for lower photon energies. Furthermore, addressing the uncertainties of the tabulated data, which can be of several hundreds of percent, is of urgent need. Driven by recent advances in analytical techniques in the low energy range including investigation of materials containing lithium, the interest in a reliable set of photon mass attenuation coefficients is steadily increasing. In this study, we experimentally determine photon mass attenuation coefficients for lithium fluoride, aluminium, and different transition metals in the extreme low energy range from 40 eV to a several hundreds of eV. This high-precision experimental determination allows a comparison with the existing data tables. We observe differences that turn out to be significant, especially around the absorption edges.

A Simple Approach for Thickness Measurements Using Electron Probe Microanalysis.

A simple and fast method for thickness measurements using electron probe microanalysis (EPMA) is described. The method is applicable on samples with a thickness smaller than the electron depth range and does not require any knowledge of instrumental parameters. The thickness is determined by means of the distance that electrons travel inside the sample before crossing through it. Samples are first deposited on a substrate that, when reached by the transmitted electrons, produces an X-ray signal. The measured characteristic X-ray line intensity of the substrate is later used to determine the energy of transmitted electrons, which is proportional to the distance that electrons travel inside the sample. The study was performed on spherical K411 glass particles and cylindrical particles of U­Ce oxide with a size ranging from 0.2 to 4 µm. The measured thicknesses of all the studied particles showed good agreements with the real values. Although the method is only validated on particles with usual shapes, it can be applied to determine a local thickness of thin samples with irregular morphologies. This can help solving multiple issues in analysis with EPMA of non-bulk samples exhibiting complex geometries. Three dimensional microscopic imaging could also find a good utility in the described method.

Characterization of the Chemical Composition of Uranium Microparticles with Irregular Shapes Using Standardless Electron Probe Microanalysis and Micro-Raman Spectrometry.

We describe an approach enabling the identification of the elemental composition of uranium microparticles with undefined geometry using standardless quantitative electron probe microanalysis (EPMA) and micro-Raman spectrometry (MRS). The standardless procedure is based on a ZAF peak-to-background quantitative method in combination with Monte Carlo simulations. The experimental X-ray spectra were measured with an energy-dispersive spectrometer attached to a scanning electron microscope. To account for the X-ray intensity loss due to the transmission of electrons in microparticles with irregular shapes, a method was developed enabling the determination of an apparent thickness of the particle by means of the mean distance that electrons travel inside the particle before being transmitted. Size effects were further taken into account by using peak-to-background ratios and performing simulations on a particle with a thickness equal to the apparent thickness. To assess the validity of the standardless procedure in EPMA, weight fractions were determined for NIST homogeneous spherical microparticles of K411 glass and compared to certified ones. The correction of size effects was achieved and lead to accurate quantitative results with absolute relative deviations less than 9%. The model used for the determination of the apparent thickness was validated on the set of spherical K411 particles and enabled us to conduct quantifications on irregularly shaped uranium microparticles. The chemical composition of uranium particles was further investigated using MRS which enabled us to verify the reliability of the results obtained by the standardless approach.

Characterization of palladium species after γ-irradiation of a TBP-alkane-Pd(NO3)2 system.

The γ-irradiation of a biphasic system composed of tri-n-butylphosphate in tetrapropylene hydrogen (TPH) in contact with palladium(ii) nitrate in nitric acid aqueous solution led to the formation of two precipitates. A thorough characterization of these solids was performed by means of various analytical techniques including X-Ray Diffraction (XRD), Thermal Gravimetric Analysis coupled with a Differential Scanning Calorimeter (TGA-DSC), X-ray Photoelectron Spectroscopy (XPS), InfraRed (IR), RAMAN and Nuclear Magnetic Resonance (NMR) Spectroscopy, and ElectroSpray Ionization Mass Spectrometry (ESI-MS). Investigations showed that the two precipitates exhibit quite similar structures. They are composed at least of two compounds: palladium cyanide and palladium species containing ammonium, phosphorous or carbonyl groups. Several mechanisms are proposed to explain the formation of Pd(CN)2.