Neutron and X-ray experiments at high temperature
2014 Advanced technologies, like for instance aerospace or nuclear engineering require the most exhaustive information on the behaviour of materials used at very high temperature such as ceramics, refractory alloys or molten metals. Among high temperature techniques, X-rays and more recently neutron scattering have appeared as powerful tools to get information, mainly structural, on these materials in their working conditions. High temperature devices (above 2 000 K) developed for that purpose, based on various heating techniques (induction, imaging furnaces, lasers, gas-flame heaters and principally Joule heated devices) are reviewed. Some crucial points are particularly emphasized such as : 2014 the determination of the real temperature (thermocouples and optical pyrometry) in the scattering zone hardly accessible partly due to the unavoidable thermal gradients, 2014 the chemical reactivity of the sample with its surrounding, i.e. atmosphere and sample holder. Neutrons, mainly because of their low absorption by matter, allow the work on real bulky materials and give a greater freedom in the conception of high temperature scattering devices compared to X-rays. At the present time thermal neutron high flux reactors offering a wide range of neutron wavelengths are available, and a new generation of more and more efficient multidetectors has emerged in the last decade; the data acquisition and consequently the high temperature exposure time have been notably reduced, opening a way for precise and reliable experiments in the 3 000 K range. This very high temperature domain already studied by a few other techniques can also be investigated by neutron scattering. Revue Phys. Appl. 19 (1984) 649-662 SEPTEMBRE 1984, PAGE (*) The author’s personal work has been done at the ILL (HFR Grenoble). Now with the Equipe de Physico-Chimie Moleculaire, CENG-DRF, 85X, 38041 Grenoble Cedex, France. REVUE DE PHYSIQUE APPLIQUEE. T. I9, N° 9, SEPTEMBRE 1984 45 Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/rphysap:01984001909064900
Etude par diffraction neutronique des structures de haute temperature de La2O3 et Nd2O3
Abstract The structure of the H and X high temperature forms of La 2 O 3 and Nd 2 O 3 have been solved by neutron diffraction experiments performed on the D1B multidetector powder goniometer of the I.L.L.: the hexagonal H form belongs to the P6 3 /mmc space group and the cubic X form to the Im3m space group. We propose a new crystallochemical principle which allows a coherent description of the A-low temperature form, the H and the X forms. The statistical description of the high temperature forms H and X resulting from a partial oxygen disorder can be assumed either by a static or dynamic model.
HRTEM study of orthorhombic zirconia in MgO-PSZ
High-resolution transmission electron microscopy (HRTEM) was used to study the phase of orthorhombic ZrO2 formed in magnesia partially stabilized zirconia (MgO-PSZ) during HRTEM specimen preparation. Based on the three reported crystal structures of orthorhombic ZrO2, with the space groups Pbcm, Pbc21 and Pbca, here it is shown that orthorhombic ZrO2 formed in MgO-PSZ has the Pbcm structure.