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Powders and divided solid materials are widely represented as finished or intermediary products in industries as widely varied as foodstuffs, cosmetics, construction, pharmaceuticals, electronic transmission, and energy. Their optimal use requires a mastery of the transformation process based on knowledge of the different phenomena concerned (sintering, chemical reactivity, purity, etc.). Their modelling and understanding need a prior acquisition of sets of data and characteristics which are more or less challenging to obtain. The goal of this study is to present the use of different physico-chemical characterization techniques adapted to uranium-containing powders analyzed either in a raw state or after a specific preparation (ionic polishing). The new developments touched on concern dimensional characterization techniques for grains and pores by image analysis, chemical surface characterization and powder chemical reactivity characterization. The examples discussed are from fabrication process materials used in the nuclear fuel cycle.

The production of thermal barriers using High Power Plasma Spraying (HPPS) requires both optimal spraying conditions and control over the stability of the manufacturing process. One way in which to reach these two goals is to undertake a métallographie inspection of a polished section of the pieces which are manufactured. This entails systematic, reproducible appraisals so as to follow the evolution of the measured magnitudes. The present article shows the approach adopted to optimize a metallographie inspection station. The goal is to use it as a rapid and economical line control tool based on the principal of a quality control approach.

Powders and divided solid materials are widely represented as finished or intermediary products in industries as widely varied as foodstuffs, cosmetics, construction, pharmaceuticals, electronic transmission, and energy. Their optimal use requires a mastery of the transformation process based on knowledge of the different phenomena concerned (sintering, chemical reactivity, purity, etc.). Their modelling and understanding need a prior acquisition of sets of data and characteristics which are more or less challenging to obtain. The goal of this study is to present the use of different physico-chemical characterization techniques adapted to uranium-containing powders analyzed either in a raw state or after a specific preparation (ionic polishing). The new developments touched on concern dimensional characterization techniques for grains and pores by image analysis, chemical surface characterization and powder chemical reactivity characterization. The examples discussed are from fabrication process materials used in the nuclear fuel cycle.

Abstract: The Fe-U system is one of the binaries of the U-Fe-Zr-O quaternary system that is important for a safe nuclear program. A new thermodynamic assessment of Fe-U is presented, taking into account some recent thermodynamic measurements: enthalpy of formation and of melting as well as heat capacities for both intermetallic compounds Fe2U and FeU6. The calculated phase diagram and thermodynamic data generally agree very well with the experimental values. The calculated temperature of the peritectic transformation [FeU6 ↔ liquid + bcc-U] is equal to 1104 K, which is higher than in the previous assessments, but in agreement with Labroche’s value. However, the experimental melting enthalpy of FeU6 is not reproduced by the present set of thermodynamic parameters.

The fibre-matrix interfacial zone formed during the isothermal/isobaric chemical vapour infiltration processing of SiC fibres (ex-polycarbosilane)/boron nitride/SiC matrix composites has been analysed by TEM/electron energy loss spectroscopy, Auger electron spectroscopy, and secondary ion mass spectroscopy. In the composites, the boron nitride interphase (deposited from BF3-NH3) is made of turbostratic boron nitride, almost stoichiometric but containing some oxygen (less than 5 at %). The boron nitride layer stacks are randomly orientated except in the very vicinity of the fibre surface where they lie almost parallel to the substrate. The long chemical vapour infiltration treatment at 1000 °C used to infiltrate the SiC matrix acts as an annealing treatment for the metastable ex-polycarbosilane fibres which gives rise to the growth of an SiO2/carbon amorphous double layer at the boron nitride/fibre interface. Deflection of microcracks arising from the failure of the brittle SiC-matrix occurs at the boron nitride/SiO2 interface considered to be the weaker link in the matrix/boron nitride interphase/SiO2/carbon/fibre sequence. It is suggested that the combination of the boron nitride layered interphase and SiO2/carbon fibre decomposition products might play an important role in determining the propagation path of microcracks in the fibre/matrix interfacial zones and could be responsible, at least to some extent, for the non-brittle behaviour of such composites.

Analysis parameters for an electron microprobe are numerous, and the accuracy of the quantitative analysis is very sensitive to the selection of these experimental conditions. The expert system intends to optimize the choice of each analysis parameter as well as to automate the phases of a quantitative analysis on all kinds of materials. To summarise, the aim of the expert system is to simplify the procedures, improve the accuracy of results and control the analysis time. The figure 1 illustrates the various stages of the expert system.The starting point of the expert system is an interactive questionnaire concerning the sample,( ie, what is already known), and about the expectations on the analysis,( ie, the accuracy of the results and/or the duration of the analysis required by the operator). Then, the expert system performs a semi-quantitative analysis on the sample. Based on the acquisition of a wavelength qualitative spectrum, this method is a way to obtain the sample composition in a short time with the advantages of the WDS system, and with a reasonable accuracy.

Electron diffraction was observed in 1928 by Kikuchi. In electron diffraction, diagrams characteristic of the crystal lattice and the phase orientation are formed. Consequently, Venable, then Dingley recently developed electronic diffraction coupled with scanning electron microscopy. Their approach enables micrometric scale examination of a specimen obtained by simple metallographical preparation (polished surface). Since the 1980’s, this technique has benefited from strong technological and computerized development which have led to the sale of the first systems under the name of Electron Backscatter Diffraction (EBSD). Niobium is used in the cast industry of uranium to refine it (getter function). The strong affinity of niobium for carbon leads indeed to the formation of small precipitates of niobium carbides. Whereas carbon cannot be detected by EDS because of its high absorption by the niobium (absorption coefficient μ=29000), hardness measurement indicates the presence of carbides (HV30= 2000), but without further information on the nature of those carbides.