Stress Corrosion Cracking of Inconel 600 and Incology 800 in 50% NaOH at 140℃ under Slow Strain Rate Condition

Stress Corrosion Cracking (SCC) behaviour of Inconel 600 and Incoloy 800 in aerated 50%. NaOH at 140℃ was investigated using a slow strain rate method under electrochemically controlled potentials. The susceptibility to cracking and the mode of cracking were changed depending upon the applied potential and heat-treatment. SCC occurred in a primary active-passive transition region and a secondary passive region at a strain rate of 4×10^ min^. The former region : only intergranular cracking took place in both alloys for sensitized materials but not in solution annealed specimens, except for Inconel 600 which showed slight intergranular cracking. The latter region : SCC was found in both alloys and there was not so much difference in the susceptibility between annealed and sensitized materials. Transgranular cracking occurred around 0V (SCE) and intergranular cracking became predominant at a higher or lower potential than 0V. The mechanism of the SCC and the relationship between these results and earlier work were discussed

Surface-Activated Amorphous Alloy Fuel Electrodes for Methanol Fuel Cell

Amorphous alloy electrodes for electrochemical oxidation of methanol and its derivatives were obtained by the surface activation treatment consisting of electrodeposition of zinc on as-quenched amorphous alloy substrates, heating at 200-300℃ for 30 min, and subsequently leaching of zinc in an alkaline solution. The surface activation treatment provided a new method for the preparation of a large surface area on the amorphous alloys. The best result for oxidation of methanol, sodium formate and formalin was achieved by using the surface-activated amorphous palladium-base alloys. The activity is varied with heat treatment temperature in the surface activation treatment, and metallic and metalloid additives. The beneficial alloying elements were phosphorus, nickel, platinum, rhodium and ruthenium

Corrosion Behavior of Amorphous Nickel-Valve Metal Alloys in Boiling Concentrated Nitric and Hydrochloric Acids

The corrosion behavior of amorphous nickel-base alloys containing titanium, zirconium, niobium, tantalum and/or phosphorus in boiling 9 N HNO_3 solutions with and without Cr^ ion and in a boiling 6 N HCl solution was investigated. In boiling 9 N HNO_3 solutions alloys containing 20 at% or more tantalum were immune to corrosion, maintaining the metallic luster, and Ni-40～60Nb alloys showed low corrosion rates of the order of μm/year. In the boiling 6 N HCl solution only tantalum-containing alloys were immune to corrosion although a higher tantalum content was required in the 6 N HCl solution in comparison with 9 N HNO_3 solutions. Protective surface films on the Ni-Nb and Ni-Ta-(P) alloys were composed exclusively of NbO_2(OH) and TaO_2(OH). Consequently, the corrosion resistance is not provided unless alloys contain elements, the passive film of which is highly stable in these aggressive boiling acids, such as tantalum

The Corrosion Behavior of Sputter-Deposited Magnesium-Valve Metal Alloys

An attempt was made for preparation of magnesium alloys with valve metals, such as titanium, zirconium, niobium and tantalum whose melting points far exceed the boiling point of magnesium. These alloys became single phase solid solutions in wide composition ranges, but were crystalline in contrast to the fact that other alloys with valve metals such as nickel-, copper-and aluminum-base alloys were amorphous in wide composition ranges. The alloys containing sufficient amounts of valve metals showed high corrosion resistance due to spontaneous passivation in 1 M HCl at 30℃. The high corrosion resistance was attributed to the formation of passive oxyhydroxide films in which valve metal cations were remarkably concentrated. However, because of crystalline alloys and because of the presence of active magnesium, their corrosion resistance is lower than that of valve metals

CO_2 Methanation Catalysts Prepared from Amorphous Ni-Valve Metal Alloys Containing Platinum Group Elements

The amorphous Ni-valve metal (Ti, Zr, Nb and Ta) alloys containing a few at% of platinum group elements were activated by immersion into hydrofluoric acid and used for hydrogenation of carbon dioxide at 100-300℃. This surface activation led to formation of nanocrystalline surface alloys with high surface area, and to surface enrichment of platinum group elements on the titanium-, niobium- and tantalum-containing alloys, but not on the zirconium-containing alloys. The surface of the latter alloys was mainly composed of nickel. The activity and selectivity for methane formation on the titanium-, niobium- and tantalum-containing alloys were significantly affected by the difference in the platinum group elements; the ruthenium- and rhodium-containing alloys showed higher activity and selectivity for methane formation while the platinum-containing alloys exhibited the lowest activity for methane formation and produced mainly carbon monoxide. The zirconium-containing alloys showed the one order of magnitude higher activity for methanation of carbon dioxide in comparison with the titanium-, niobium- and tantalum-containing alloys and produced exclusively methane independent of platinum group elements contained. The alloying with zirconium seems very important to prepare the alloy catalysts having the extremely high activity

The Electrocatalytic Oxidation of Ethylene and Methane, and Reduction of Oxygen on Gas-Diffusion Electrodes Made of Amorphous Nickel-Valve Metal-Platinum Group Metal Alloys

Exploratory work has been done on the performance of electrocatalytic reduction of oxygen and anodic oxidation of ethylene and methane on the gas-diffusion electrodes prepared from amorphous alloys containing one atomic percent platinum group elements. Gas-diffusion electrodes were made by coating the mixture of catalysts prepared by immersion in 46% HF from melt-spun ribbon shaped amorphous alloys, carbon black, polytetrafluoroethylene and sugar, and subsequent baking in nitrogen gas. The electrode made of catalyst prepared from amorphous nickel-niobium alloy containing platinum and ruthenium was the most active for electrocatalytic reduction of oxygen. For electro-oxidation of ethylene and methane, amorphous nickel-value metal alloy containing only platinum possesses higher activity in comparison to the electrode made of platinum black powder

Corrosion Behavior of Amorphous Nickel-Base Alloys in a Boiling Concentrated Sodium Hydroxide Solution

application/pdfPolarization curves were measured in a boiling 50% NaOH solution, and the specimen surface was analyzed by X-ray photoelectron spectroscopy. A combined addition of chromium and molybdenum to amorphous nickel-phosphorus alloys significantly enhances the corrosion resistance. Addition of copper and lead are also effective in improving the corrosion resistance. The surface film formed on amorphous nickel-base alloys consists mainly of hydrated nickel oxyhydroxide. Chromium is concentrated in the alloy surface immediately under the surface film when nickel-base alloys containing chromium are immersed or polarized anodically at potentials close to the corrosion potential.紀要類(bulletin)673229 bytesdepartmental bulletin pape

Fast WDM provisioning with minimal probing: the first field experiments for DC exchanges

We propose an approach to estimate the end-to-end GSNR accurately in a short time when a data center interconnect (DCI) network operator receives a service request from users, not by measuring the GSNR at the operational route and wavelength for the End-End optical path but by simply applying a QoT probe channel link by link, at a convenient wavelength/modulation-format for measurement. Assuming connections between coherent transceivers of various frequency ranges, modulators, and modulation formats, we propose a new device software architecture in which the DCI network operator optimizes the transmission mode between user transceivers with high accuracy using only standard parameters such as Bit Error Rate. In this paper, we first experimentally built three different routes of 32 km/72 km/122 km in the C-band to confirm the accuracy of this approach. For the operational end-to-end GSNR measurements, the accuracy estimated from the sum of the measurements for each link was 0.6 dB, and the wavelength-dependent error was about 0.2 dB. Then, using field fibers deployed in the NSF COSMOS testbed (deployed in an urban area), a Linux-based transmission device software architecture, and coherent transceivers with different optical frequency ranges, modulators, and modulation formats, the fast WDM provisioning of an optical path was completed within 6 minutes (with a Q-factor error of about 0.7 dB).Comment: 9 pages, 11 figures, 3 table

Status of 48Ca double beta decay search in CANDLES

We study a strategy to reduce veto-time in the search for neutrino-less double-beta decay (0υββ) with CANDLES-III system. We develop a new likelihood analysis and apply it to our new Run010 data. We show that we can increase the un-vetoed live-time by 11.8%. Thanks to this improvements, We expect to increase a limit on the life-time of 0υββ by a factor of three by analyzing both Run009 and Run010 data

Stress Corrosion Cracking of Amorphous Iron Base Alloys

The stress corrosion cracking behaviour at room temperature of amorphous Fe-Cr-Ni-P-C alloys subjected to constant strain rates was studied in some acidic solutions containing Cl- ions. Hydrogen embrittlement of the alloys occurred in the potential region lower than -300 mV relative to the corrosion potential in acidic solutions regardless of Cl- concentration. In the passive potential region no embrittlement was observed during tests in neutral NaCl solutions and in acidic solutions with low concentrations of Cl- ions. Only when tensile stress was applied to the specimen in relatively strong acidic solutions containing a certain amount of Cl- ions, fracture stress decreased in this potential region. The lowering of the fracture stress can also be attributed to hydrogen embrittlement