Bubble-loop complexes induced by helium irradiation and effect of pre-irradiation and post-irradiation of hydrogen in reduced-activation ferritic/martensitic steel

In the present work, the synergistic effect of high concentration hydrogen and helium on the dislocation loops and bubbles as well as their correlations in reduced-activation ferritic/martensitic (RAFM) steels is investigated. Such an effect was transmuted from 14?MeV neutron irradiation and has been one of the most challenging issues for RAFM steels for future fusion reactors. After low dose (0.18?dpa) high concentration (5000 appm) single-ion helium irradiation at 723?K, very large dislocation loops were observed, and the majority of bubbles were inside dislocation loops, forming bubble-loop complexes. These bubble-loop complexes defects were also present in hydrogen/helium and helium/hydrogen sequential-ion irradiated steels. Pre-irradiated hydrogen ion effectively inhibited the later growth of loops induced by helium post-irradiation, and the higher the ratio of hydrogen to helium fluence, the greater the effect of inhibition. At high fluence of hydrogen pre-irradiation, the structure of bubble-loop complexes disappeared. On the other hand, hydrogen post-irradiation promoted the growth of loops induced by helium pre-irradiation, and the higher the ratio of hydrogen to helium fluence, the greater the effect of promotion. The mechanisms for hydrogen/helium synergistic effects are discussed.     

Mesoporous titania films investigated by positron annihilation based on a slow positron beam

Tunable mesoporous titania (TiO₂) thin films were synthesized via a sol-gel method using an amphiphilic triblock copolymer F38 as the structural template. The dependence of crystalization, pore morphology and interconnectivity of TiO₂ films on the weight ratio of F38 was studied by wide-angle X-ray diffraction, field emission scanning electron microscopy and Doppler broadening of positron annihilation radiation spectroscopy based on a slow positron beam. By loading more F38, the crystallization of TiO₂ films is enhanced, accompanied by a decrement in oxygen vacancies/grain boundaries. Smaller and isolated mesopores are formed in the films prepared with F38 less than 15?wt%. The pore percolation occurs when the weight ratio of F38 is up to 20?wt% and larger and interconnected worm-like pores are formed.     

Annealing studies of Ti/Al multilayer film by slow positron beam

Single detector and coincidence Doppler broadening (CDB) spectroscopy measurements using slow positron beam were carried out to study as-deposited and annealed Ti/Al multilayer films. The changes of the film structure and defects in each layer by heat treatment have been investigated through the analysis of Doppler broadening lineshape variation. The coincidence Doppler broadening measurements revealed that Ti is the dominant diffusion species during the alloying process of Ti/Al by high temperature annealing. These results highlight the potential of slow positron beam in characterizing the vacancy-type defects evolution and mechanism of interlayer diffusion in Ti/Al multilayer film.     

Synergistic effect of iodide ions on the corrosion inhibition of steel in 0.5 M H2SO4 by new chalcone derivatives

The effect of addition of 4′,4-dihydroxychalcone (P₁), 4-aminochalcone (P₂) and 4-bromo, 4′-methoxychalcone (P₃) on the corrosion of steel in 0.5 M sulphuric acid has been studied by weight loss measurements, potentiodynamic and EIS measurements. We investigate the synergistic effect of iodide ions on the corrosion inhibition of steel in the presence of chalcone derivatives. The corrosion rates of the steel decrease with the increase of the chalcones concentration, while the inhibition efficiencies increase. The addition of iodide ions enhances the inhibition efficiency considerably. The presence of iodide ions increases the degree of surface coverage. The synergism parameters S_Θ and S_I, calculated from surface coverage and the values of inhibition efficiency, in the case of chalcone derivatives are found to be larger than unity. The enhanced inhibition efficiency in the presence of iodide ions is only due to synergism and there is a definite contribution from the inhibitors molecules. E (%) obtained from the various methods is in good agreement. Polarisation measurements show also that the compounds act as cathodic inhibitors.