eV For Stage Research Articles

Thermal recovery characteristics of neutron-irradiated high-copper weld (Linde 80)

The recovery activation energy, the order of reaction and the characteristic recovery rate constant were determined by isochronal (573–823 K) and isothermal (723 K and 775 K) annealing experiments on specimens made from a broken half of a surveillance weld specimen (fluence: 1.21 × 10 23 n/m 2, E ≥ 1 MeV, Cu: 0.29 wt%) to investigate the recovery characteristics of a high copper weld of neutron-irradiated reactor pressure vessel (RPV). Vickers microhardness tests were conducted to trace the recovery behavior after heat treatments. The results were analyzed in terms of recovery stages, behavior of responsible defects and recovery kinetics. It was shown that recovery occurred through two annealing stages (stage I: 673–753 K, stage II: 753–823 K) with recovery activation energies of 2.68 eV and 2.83 eV for stage I and II, respectively. The isothermal hardness recovery at 723 K and 775 K coincided with the ratio of the characteristic rate constant for each recovery stage. The order of reaction was 2 for both recovery stages. The recovery activation energies of present specimens are approximately equal to that of copper diffusion in α-iron in the presence of vacancies, suggesting that recovery may occur through the diffusion of copper atoms. The present results strongly support the copper precipitate coarsening model.

Electronic and Lattice Modes of Graphite-Cocl2

ABSTRACTReflectivity measurements on graphite-CoCl2 intercalation compounds between 0.06 eV and 2.0 eV for stages 3 and 5 show sharp Drude edges and superimposed interband structure. Stage 5 shows structure near 0.4 eV and 0.55 eV while stage 5 shows structure between 0.12 eV and 0.55 eV. The observed number of interband transitions is equal to the stage index which is consistent with a recently proposed kz-axis zone-folding model of the electronic energy bands. In addition to the electronic optical transitions, features associated with lattice vibrations are observed in the spectra. In particular, the graphite-like IR mode near 1580 cm–1 is clearly resolved in the intercalation compounds. A reflectivity minimum and splitting of this vibrational mode is observed for both stages 3 and 5 of graphite-CoCl2.

The electronic structure of ferric chloride intercalated graphite

Abstract The electronic excitation spectrum in energy and momentum space of stage 1 and stage 2 FeCl 3 intercalated graphite has been measured from 0.2 to 287 eV by high resolution (0.1 eV) electron energy loss spectroscopy. The dispersion of intra- and interband plasmons was measured and the dielectric function ϵ( q, E ) computed by a Kramers-Kronig analysis of the energy loss data. Critical points in the dielectric function and the interband plasmon dispersion indicate that the carbon π bands are only weakly perturbed. A tight binding model of the carbon π bands is used to compute ϵ( q, E ) and the intraband plasmon dispersion thus providing an accurate measure of the amount of charge transfer. In addition, the spectrum of excitations of carbon 1S core states to empty carbon 2P states directly probes the new states which appear after intercalation and provides a direct measurement of Fermi level lowering in intercalated graphite. Charge transfer per intercalant layer is constant in the various compounds and with respect to pure graphite the Fermi level has been lowered by 0.9 and 0.7 eV in stage 1 and stage 2 FeCl 3 -graphite, respectively.