The effects of HCO3, Cl, and SO42- on copper as a candidate material for overpacking for geological disposal of high level radioactive wastes are studied at 303 K in dissolved oxygen(DO)- controlled, ground-water simulating aqueous solutions by using a cyclic polarization curve method.Two types of polarization curve were determined: Type A in which free corrosion proceeds in the active dissolution mode, and Type P in which passivation takes place in a potential domain characterized by a potential that corresponds to Eb, the potential at which the passivated film is broken. Polarization dependence on DO was also determined: when only HCO3 is present, a Type A curve results for DO < 0.5 ppm when HCO3 = 10 – 300 ppm, transiting to a Type P curve when HCO3 > 3,000 ppm; when DO < 15ppm, however, a Type P results for HCO3 ≤ 10 ppm; when either Cl− or SO42- coexists with HCO3, HCO3 promotes passivation while Cl- and SO42- promote active dissolution, the influence of Cl− being greater than that of HO42- if HCO3 content is constant. The presence of either CI or SO42 over 100 ppm makes the curve Type A irrespective of DO, both species shifting Eb toward the less noble direction.The constant potential test shows that the passivated film of copper is easily broken if Cl− is present.
The capabilities of TiO 2 -coated materials for the inactivation and removal of algae were investigated. As supports for TiO 2 , non-woven fabric and Ni foam were chosen. To evaluate the ability of noble metal cocatalyst additions to facilitate the photocatalytic algal inhibition of TiO 2 -coated materials, Pd nanoparticles were deposited on non-woven fabric-supported TiO 2 by photoelectrochemical deposition. The fabric-supported Pd/TiO 2 showed higher inhibition activity for algal growth compared to the fabricsupported TiO 2 without Pd. In addition, Ni foam-supported TiO 2 also showed high inhibition activity, both in laboratory-scale tests and open-air tests. Therefore, TiO 2 -coated materials with suitable coating methods such as the use of cocatalysts or large surface area can substantially inhibit algal growth. The ability of the TiO 2 -coated materials to inhibit algae correlated well with their activity for the photocatalytic decolorization of methylene blue, suggesting a nonspecific mechanism in the breakdown of cellular structures.
This paper describes a study of corrosion behavior of a mild steel as a candidate of the high-level nuclear waste package in the geological disposal situations, conducted to establish a model for estimating the corrosion allowance requirement to achieve the 1,000 year lifetime for the package. In several series of galvanostatic tests, the maximum penetration depth and the depth distribution were measured for each specimen with a sophisticated ultrasonic inspection technique. The Gumbel distribution model was successfully used in analyzing each set of data for the maximum penetration depth. Relations among the average penetration depth, the maximum penetration depth, and the corrosion allowance requirement were discussed.
We prepared β-FeSi2 thin-films by using a Pulsed Laser Deposition (PLD) method and succeeded to observe photoluminescence (PL) around 1.5 μm corresponding to β-FeSi2 band from the long-time and high-temperature annealed β-FeSi2 thin-films. The β-FeSi2 thin-films were ablated on Si(111) substrates heated at 550°C. After ablation, long-time and high-temperature thermal annealing was performed in order to improve the crystal-quality. Annealing times were 5, 10, 20 and 40 hrs, and annealing temperature was kept at 900 °C. Crystallinity was evaluated by an X-ray diffraction (XRD) measurement. We have observed eminent improvement on crystal-quality of β-FeSi2 thin-films. Annealed samples show (220) or (202) X-ray diffraction signals of β-FeSi2 and the full width at half maximum (FWHM) of these peaks were 0.27° although the thickness of the samples decreased with annealing time. Thermal-diffusion of Si atoms was observed from substrate to thin-films. Fe atoms in the ablated thin-films also diffused into the substrate. The relationship between the thickness of β-FeSi2 thin-films and the thermal-diffusion were investigated with rutherford backscattering (RBS) measurement. Maximum photoluminescence intensity around 1.5 μm was observed from the thickest β-FeSi2 thin-film with only 5 hrs annealing.
A three-dimensional, non-isothermal, and unsteady numerical model considering liquid water transport inside a gas diffusion layer (GDL) has been developed to investigate its effect on cell performance. Liquid water in GDL had extremely wide size distributions, as visualized by synchrotron X-ray. It was assumed that liquid water in GDL form droplets with different diameters, which would affect the thermal conductivity and diffusion coefficient. On the other hand, liquid water in the flow channel should not be discounted as it has larger liquid water mass compared with that in GDL. In this paper, the impact of liquid water in the flow channel and droplets in GDL on the steady and unsteady responses of proton exchange membrane fuel cells (PEMFC) power generating characteristics was discussed. It was found that liquid water in the entire system has a significant influence on voltage responses.
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