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Primary water stress corrosion cracking (PWSCC) of Alloy 600 remains an important degradation phenomenon in PWRs. In particular, the susceptibility to the PWSCC initiation at 290°C is of recent interest because that is one of the typical temperatures of the primary water in contact with Alloy 600 which remains in PWRs. In this paper, oxide film formed on Alloy 600 in simulated primary water at 290°C was analyzed by X-ray absorption fine structure (XAFS) measurements at the Fe K-edge. For the preparation of the oxide film, Alloy 600 was immersed in simulated primary water with dissolved hydrogen (DH) concentration of 5 or 30 ml/kg-H2O. The near edge region of the XAFS suggested that the oxide film for 5 ml/kg-H2O DH had a larger Fe3+/Fe2+ ratio than for 30 ml/kg-H2O DH. Additionally, the extended region of the XAFS revealed that Fe3+ mainly occupied the octahedral site of the spinel oxide. Previous reports indicate that an Fe3+-rich spinel oxide is less defective and protective against PWSCC initiation. Therefore, our results suggest that the lower DH concentration (5 ml/kg-H2O) could potentially mitigate the susceptibility of Alloy 600 to the PWSCC initiation at 290°C. [ABSTRACT FROM AUTHOR]

X-ray absorption spectroscopy measurements were performed for the C K-edge of Pt nanoparticles on Ar+-irradiated carbon supports in order to elucidate the origin of improved catalyst performance after the introduction of vacancies into the carbon support. We observed a change in the electronic structure at the interface between the Pt nanoparticles and the carbon support after vacancy introduction, which is in good agreement with theoretical results. The results indicated that vacancy introduction resulted in a drastic change in the Pt–C interactions, which likely affected the d-band center of the Pt nanoparticles and led to the enhancement of the oxygen reduction reaction in catalysts. [ABSTRACT FROM AUTHOR]

The ion beam-induced defects in carbon supports for platinum (Pt) nanoparticles have been found to enhance the catalytic activity. Highly oriented pyrolytic graphite (HOPG) was irradiated with 380 keV argon ions (Ar + ), and Pt nanoparticles were then deposited on it by a radio frequency (rf) magnetron sputtering method. The Pt nanoparticle size on Ar + -irradiated HOPG and the carbon structure at the interface were investigated by transmission electron microscope (TEM) and Raman spectroscopy, respectively. The observed size of Pt nanoparticles on the irradiated HOPG was larger than that on the non-irradiated HOPG. Raman spectra indicated that vacancy-like defects were formed on the HOPG surface by Ar + -irradiation at the fluences between 1.0 × 10 12 and 1.0 × 10 13 ions/cm 2 , and sp 3 defects were induced by irradiation more than 5.0 × 10 13 ions/cm 2 . These defective structures on the HOPG would promote the Pt particle growth. [ABSTRACT FROM AUTHOR]

Abstract We implanted polyimide (PI) ion-track membranes with 100 keV Ar+ to prepare a cathode for the galvanic deposition of platinum (Pt) nanocones. The surface layer of the irradiated PI films was carbonized to produce a graphitic structure at a fluence of 7.6 × 1016 ions/cm2. The carbonized surface exhibited an electric conductivity and electrochemical stability, which could be sufficient for use as a cathode. Pt nanocones were electrodeposited into the pores of the PI ion-track membrane after the implantation under the same conditions. This indicated that the Ar+ irradiation resulted in the preparation of a conductive layer on the total surface area of the ion-track membrane including the innermost regions of the pores. Highlights • Polyimide ion-track membranes were irradiated with 100 keV argon ions (Ar+). • The surface of the membranes became conductive due to carbonization. • The Ar+-irradiated surface was employed as an electrode for electrodeposition. • Platinum nanocones were electrodeposited into the pores of the membrane. [ABSTRACT FROM AUTHOR]

Abstract A glassy carbon (GC) substrate was irradiated with 380 keV argon ions (Ar+), and platinum nanoparticles (Pt NPs) were then deposited on it by a radio-frequency magnetron sputtering method. The interfacial effect of the Ar+-induced defects in the GC substrate on the size and electronic structure of the Pt NPs was investigated. The irradiation defects in the carbon support promoted the growth of the Pt NPs on the substrate, leading to a larger NP size. Density functional theory calculations revealed that the lattice vacancies in the graphitic structure lowered the position of the Pt d-band center via the interfacial charge transfer. This down-shift in the d-band center would be a reason for the higher catalytic activity, which was reported in our previous research. Highlights • The Pt nanoparticles were deposited on a 380 keV Ar+-irradiated carbon support. • The particle sizes on the irradiated and non-irradiated support were investigated. • A Pt electronic structure was modified by the irradiation defects of the carbon support. • We discussed how the Pt size and electronic structure affected the catalytic activity. [ABSTRACT FROM AUTHOR]

Abstract The chemical state and local structure of 2.6-nm-sized platinum (Pt) nanoparticles on an ion-irradiated glassy carbon (GC) substrate were investigated by X-ray absorption fine structure measurements. The partial oxidation of the Pt nanoparticles was confirmed by the peak intensity in the near-edge region of the absorption spectrum. The analysis of the extended region revealed a higher coordination number and shorter bond length of Pt–Pt compared to those of the Pt nanoparticles on the non-ion-irradiated GC. Thus, Pt nanoparticles on the ion-irradiated GC substrate were found to hold a rigid metallic coordination during the oxidation. Highlights • Pt nanoparticles were deposited on a 380 keV Ar+-irradiated carbon support. • The partial oxidation of Pt was confirmed by XANES measurements. • Pt on the irradiated support held a rigid metallic coordination during oxidation. [ABSTRACT FROM AUTHOR]