Deposition of uranium oxide following the reduction in weak acid solution using Electrochemical Quartz Crystal Microbalance (EQCM)

Ouchi, Kazuki; Otobe, Haruyoshi; Kitatsuji, Yoshihiro; Yamamoto, Masahiro

ECS Transactions, 75(27), p.51 - 57, 2017/01

https://doi.org/10.1149/07527.0051ecst

We investigated the deposition of U(IV) following a valence change of U as electrodeposition using an electrochemical quartz crystal microbalance (EQCM). When measurements of the reduction of U(VI) in a weak acid solution were performed, deposits of U(IV) were observed on the electrode surface. From deposition rates, pH dependence of them, and oxidation potentials of deposits, we proposed the following deposition mechanism. The deposition is divided into the three phases; First, in the induction phase, U(IV) produced by the disproportionation forms U(IV) hydroxide nucleus. Next, in the growth phase, U(IV) deposits begin to grow. In this phase, the deposits catalyze the reduction of U(V) to U(IV), resulting an increase of the reduction current. Finally, in the transformation phase, U(IV) hydroxide species transform into U dioxide having more stable state.

Pitting potential of zircaloy-2 in artificial seawater under -ray irradiation

Motooka, Takafumi; Komatsu, Atsushi; Tsukada, Takashi; Yamamoto, Masahiro

ECS Transactions, 53(21), p.25 - 32, 2013/05

https://doi.org/10.1149/05321.0025ecst

Effects of tritiated water on passivation behavior of SUS304 stainless steel

Oyaizu, Makoto; Isobe, Kanetsugu; Yamanishi, Toshihiko

ECS Transactions, 50(50), p.63 - 69, 2013/00

https://doi.org/10.1149/05050.0063ecst

The effects of tritiated water on the passivation behavior of SUS304 stainless steel were electrochemically studied by anodic polarization measurements and diachronic measurements of open circuit potential with changing tritium concentration and dissolved oxygen concentration as parameters in the electrolyte of 1N sulfuric acid solution, where the passivation inhibitory effects by tritiated water could be clearly observed. As a result, it was found that the passivation would be proceed with two steps. The effects of tritiated water could be observed in both of two steps; delay in the first step and deceleration in the second step. From these results, it was suggested that the passivation inhibitory effect might be promoted by further oxidation and sequential dissolution of Cr by radiolysis products.

PFG-NMR and SANS studies in cation exchange membranes based on sulfonated polyphenylene multiblock copolymers

Yoshida, Miru*; Zhao, Y.; Fujita, Masahiro*; Ohira, Akihiro*; Takeoka, Yuko*; Koizumi, Satoshi*; Rikukawa, Masahiro*

ECS Transactions, 50(2), p.1045 - 1053, 2012/10

https://doi.org/10.1149/05002.1045ecst

Conductometric analysis for the formation of poly(vinylidene fluoride)-based ion track membranes

Yamaki, Tetsuya; Nuryanthi, N.*; Koshikawa, Hiroshi; Asano, Masaharu; Sawada, Shinichi; Hasegawa, Shin; Maekawa, Yasunari; Voss, K.-O.*; Trautmann, C.*; Neumann, R.*

ECS Transactions, 35(24), p.1 - 12, 2011/05

https://doi.org/10.1149/1.3643329

Our focus has been placed on ion track membranes of poly(vinylidene fluoride) (PVDF), a type of fluoropolymer, because of their superior chemical, mechanical and ferro-electric properties. The aim of this study is to investigate the formation of the PVDF track membranes in more detail by electrolytic conductometry. Interestingly, application of a higher voltage to the conductometry cell as well as irradiation with a higher-LET beam promoted track etching up to breakthrough probably because electrophoretic migration of dissolved products occurred out of each pore.

Gate stack technologies for SiC power MOSFETs

Watanabe, Heiji*; Hosoi, Takuji*; Kirino, Takashi*; Uenishi, Yusuke*; Chanthaphan, A.*; Ikeguchi, Daisuke*; Yoshigoe, Akitaka; Teraoka, Yuden; Mitani, Shuhei*; Nakano, Yuki*; et al.

ECS Transactions, 41(3), p.77 - 90, 2011/00

https://doi.org/10.1149/1.3633023

XAFS analysis of unpyrolyzed CoPPyC oxygen reduction catalysts for Anion-Exchange Membrane Fuel Cells (AMFC)

Asazawa, Koichiro*; Yamamoto, Kazuya*; Yamada, Koji*; Tanaka, Hirohisa*; Matsumura, Daiju; Tamura, Kazuhisa; Nishihata, Yasuo; Atanassov, P.*

ECS Transactions, 33(1), p.1751 - 1755, 2010/10

https://doi.org/10.1149/1.3484664

CoPPyC were analyzed with X-ray adsorption fine structure (XAFS) measurements. Acid-treated CoPPyC (CoPPyC-AT) has higher activity than PPyC for oxygen reduction reaction. From the analysis of EXAFS of Co, CoPPyC electrocatalysts as synthesized consist of two peaks. The peak around 1.6 was assigned to Co-N and/or Co-O shells. The second peak around 2.6 was assigned to Co-O-Co shells originated from cobalt hydroxide. CoPPyC-AT showed only one peak of assigned to Co-N and/or Co-O, and it indicates that cobalt hydroxide is removed by acid treatment. It is clear that a coexistence of cobalt and nitrogen in CoPPyC-AT shows specific performance, and pyrolysis is not necessary to make correlation of Co-N.

Fuel-cell performance of multiply-crosslinked polymer electrolyte membranes prepared by two-step radiation technique

Yamaki, Tetsuya; Sawada, Shinichi; Asano, Masaharu; Maekawa, Yasunari; Yoshida, Masaru*; Gubler, L.*; Alkan Grsel, S.*; Scherer, G. G.*

ECS Transactions, 25(1), p.1439 - 1450, 2009/10

https://doi.org/10.1149/1.3210700

A multiply-crosslinked polymer electrolyte membrane was prepared by the radiation-induced co-grafting of styrene and a bis(vinyl phenyl)ethane (BVPE) crosslinker into a radiation-crosslinked polytetrafluoroethylene (cPTFE) film. We then investigated its hydrogen/oxygen fuel-cell performance at 60 and 80C in terms of the effect of radiation and chemical crosslinking. At 60C, all the membranes initially exhibited similar performance, but only the cPTFE-based membranes were durable at 80C, indicating the necessity of radiation crosslinking in the PTFE main chains. Importantly, cell performance of the multiply-crosslinked membrane was found high enough to reach that of a Nafion112 membrane. This is probably because the BVPE crosslinks in the graft component improved the membrane-electrode interface in addition to membrane durability. After severe OCV hold tests at 80 and 95C, the performance deteriorated, while no significant change was observed in ohmic resistivity. Accordingly, our membranes seemed so chemically stable that an influence on overall performance loss could be negligible.

Bias temperature instability characterization of advanced gate stacks

Fujieda, Shinji*; Terai, Masayuki*; Saito, Motofumi*; Toda, Akio*; Miura, Yoshinao*; Liu, Z.*; Teraoka, Yuden; Yoshigoe, Akitaka; Wilde, M.*; Fukutani, Katsuyuki*

ECS Transactions, 6(3), p.185 - 202, 2007/00

https://doi.org/10.1149/1.2728797

In order to find how bias temperature instability occurs in advanced gate stacks, we will review experimental results of our investigation on SiO, plasma-nitrided SiON, HfSiON and HfSiON with Ni-silicide electrodes. It thus seems that we need to clarify and control the chemical and physical influences on the insulator bulk and the insulator/Si interface caused by newly incorporated materials and process technologies, in order to ensure the reliability of bias temperature instability for advanced gate stacks.

Effect of Fe/Si ratio on epitaxial growth of FeSi on Ge substrate

Kumano, Mamoru*; Ando, Yuichiro*; Ueda, Koji*; Sado, Taizo*; Narumi, Kazumasa; Maeda, Yoshihito; Miyao, Masanobu*

ECS Transactions, 11(6), p.481 - 485, 2007/00

https://doi.org/10.1149/1.2778405

The effects of the Fe/Si ratios on molecular beam epitaxy (MBE) of FeSi on Ge substrate have been investigated in a wide range of growth temperatures (60300 C). From XRD measurements, it was found that FeSi layers were epitaxially grown on Ge(111) substrates at 60200 C under the stoichiometric (Fe:Si = 3:1) and non-stoichiometric (Fe:Si = 4:1) conditions. From RBS measurement, it was found that atomic mixing of Fe and Ge at FeSi/Ge interfaces began at a growth temperature of 300 C. In the case of MBE under the stoichiometric condition, the crystallinity of FeSi is significantly improved compared to the non-stoichiometric condition. As a result, very low was obtained in a wide temperature (60200 C) under the stoichiometric condition. From the transmission electron microscopy measurements, it was shown that high-quality DO3-type FeSi/Ge structures with atomically flat interfaces were realized at a low temperature (200 C) under the stoichiometric condition.

Nano-structure controlled polymer electrolyte membranes for fuel cell applications prepared by ion beam irradiation

Yamaki, Tetsuya; Kozone, Yuichi; Hiroki, Akihiro; Asano, Masaharu; Kubota, Hitoshi*; Yoshida, Masaru

ECS Transactions, 3(1), p.103 - 112, 2006/00

https://doi.org/10.1149/1.2356129

Fluoropolymer-based electrolyte membranes for water electrolyzers and fuel cells were prepared by using heavy ion beams from the cyclotron accelerator. The preparation method for these so-called "nano-scale structure-controlled membranes" involves (1) the swift heavy ion irradiation of polyvinylidene fluoride films and subsequent chemical etching to obtain cylindrical pores with a diameter of 100 nm, and (2) the filling of proton-conducting polymer chains into the etched pores by -ray-induced graft polymerization. The proton transport only in the thickness direction was observed for the resulting membranes with controlled ion exchange capacities, indicating the formation of one-dimensional straight proton-conducting pathways parallel to the ion-beam incident axis. The membranes exhibited a lower water uptake and reduced methanol permeability compared to commercially-available Nafion probably due to the restricted structures.