Hydrogen embrittlement and corrosion fatigue of corroded bridge wires

Cables of old suspension bridges and stays of cable-stayed bridges often suffer from steel corrosion. Corroded galvanized steel wires on different corrosion levels were produced at laboratories, and their mechanical properties and remaining strength were investigated. Actual tensile strength of corroded wires did not decrease with corrosion levels, whereas elongation decreased sharply after the zinc layer was partly depleted and the steel started to corrode. As the accumulated amounts of diffusive hydrogen of corrosion level-2 wires-with and without added tension-were almost the same and less than 0.2 ppm, the applied tension of steel wires did not affect the amount of diffusive hydrogen which was well below the critical concentration of 0.7 ppm to cause brittleness. This indicates that hydrogen embrittlement is unlikely to occur. Fatigue tests showed that fatigue strength did not change when only the galvanized layer was corroded, but it significantly decreased after corrosion of the steel below the galvanized layer progressed. Fatigue strength further lowered when the steel wire was cyclically stressed under wet environments when compared with the fatigue strength under dry environments. The broken wires of an old suspension bridge were also investigated. The fracture surface was similar to that caused by corrosion fatigue rather than hydrogen embrittlement. It was estimated that the wires were fractured by the mixed effects of corrosion, cyclic stresses and hydrogen.     

Lithium isotope effect accompanying electrochemical insertion of lithium into gallium

Lithium has been electrochemically inserted from a 1:2 (v/v) mixed solution of ethylene carbonate (EC) and methylethyl carbonate (MEC) containing 1 M LiClO₄ or from dimethyl sulfoxide (DMSO) containing 1 M LiCl into gallium, and the lithium isotope fractionation accompanying the insertion has been observed. The lighter isotope was preferentially fractionated into gallium, which was in accordance with the theory of the equilibrium isotope fractionation arising from molecular vibrational quantum effects. The single-stage lithium isotope separation factor ranged from 1.015 to 1.025 at 25 °C. It was independent both of the kind of electrolyte solution and of the chemical composition of the Li–Ga alloys formed within the experimental range studied and within experimental uncertainty.     

Creep damage assessment of 10Cr-1Mo-1W-VNbN steel forging through EBSD observation

10Cr-1Mo-1W-VNbN steel forging was observed through TEM (Transmission Electron Microscope), SEM (Scanning Electron Microscope) with EBSD (Electron BackScattering Diffraction) pattern method and tested through nano-indentation tester to investigate the microstructural change during creep damage process. Long-term creep rupture and interrupted creep test samples were investigated and effective damage parameters were selected. Dislocation substructure through TEM thin foil method showed increasing block/lath width especially near grain boundary according to creep damage accumulation and the same feature was observed through EBSD IPF mapping more clearly and easily. Area averaged KAM (Kernal Average Misorientation) KAM_ave was shown to be effective for evaluating dislocation microstructural changes during creep. Nano-indentation tests were conducted at the same position in EBSD measurement, which showed a good correlation between hardness value and the square root of KAM_ave. The differential equation of dislocation density with creep time was applied to estimate the relationship between averaged KAM_ave and time through the relationship between hardness and dislocation density. The creep damage estimation curves were obtained by the integrated form of the equation. As the KAM_ave showed an apparent drop against time fraction in the primary creep stage near grain boundary followed by almost constant trend for later stage. The statistical distribution of KAM_ave during creep damage process suggested the localized recovery of dislocation substructure near grain boundary.     

Characterization of self-standing Ti-containing porous silica thin films and their reactivity for the photocatalytic reduction of CO2 with H2O

Self-standing porous silica thin films with different pore structures were synthesized by a solvent evaporation method and used as photocatalysts for the photocatalytic reduction of CO₂ with H₂O at 323 K. UV irradiation of these Ti-containing porous silica thin films in the presence of CO₂ and H₂O led to the formation of CH₄ and CH₃OH as well as CO and O₂ as minor products. Such thin films having hexagonal pore structure exhibited higher photocatalytic reactivity than the Ti-MCM-41 powder catalyst even with the same pore structure. From FTIR investigations, it was found that these Ti-containing porous silica thin films had different concentrations of surface OH groups and showed different adsorption properties for the H₂O molecules toward the catalyst surface. Furthermore, the concentration of the surface OH groups was found to play a role in the selectivity for the formation of CH₃OH.     

Photoelectrochemical reaction of biomass-related compounds in a biophotochemical cell comprising a nanoporous TiO<Subscript>2</Subscript> film photoanode and an O<Subscript>2</Subscript>-reducing cathode

Photoelectrochemical decomposition of bio-related compounds such as ammonia, formic acid, urea, alcohol, and glycine by a biophotochemical cell (BPCC) comprising a nanoporous TiO₂ film photoanode and an O₂-reducing cathode generating simultaneously electrical power was investigated. The bio-related compounds studied were all photodecomposed by the present BPCC when they were either liquid or soluble in water. It was shown that ethanol exhibits similar characteristics both under 1 atm O₂ and air as studied by cyclic voltammograms. Although the present BPCC utilizes only UV light, a solar simulator at AM 1.5G and 100 mW cm⁻² light intensity gave also moderate photocurrent–photovoltage (J–V) characteristics with about 2/5 of the short circuit photocurrent (J _sc) values (J _sc) of that under a Xe lamp irradiation at the intensity of 503 mW cm⁻². It was demonstrated that varieties of bio-related compounds can be used as a direct fuel simultaneously for photodecomposition and electrical power generation. The charge transport processes in the BPCC operation were analyzed using glycine by an alternating current impedance spectroscopy, showing that the charge transfer reactions on the photoanode and the cathode surfaces compose the major resistance for the cell performance.     

Evaluation of risk and benefit in thermal effusivity sensor for monitoring lubrication process in pharmaceutical product manufacturing

In the process design of tablet manufacturing, understanding and control of the lubrication process is important from various viewpoints. A detailed analysis of thermal effusivity data in the lubrication process was conducted in this study. In addition, we evaluated the risk and benefit in the lubrication process by a detailed investigation. It was found that monitoring of thermal effusivity detected mainly the physical change of bulk density, which was changed by dispersal of the lubricant and the coating powder particle by the lubricant. The monitoring of thermal effusivity was almost the monitoring of bulk density, thermal effusivity could have a high correlation with tablet hardness. Moreover, as thermal effusivity sensor could detect not only the change of the conventional bulk density but also the fractional change of thermal conductivity and thermal capacity, two-phase progress of lubrication process could be revealed. However, each contribution of density, thermal conductivity, or heat capacity to thermal effusivity has the risk of fluctuation by formulation. After carefully considering the change factor with the risk to be changed by formulation, thermal effusivity sensor can be a useful tool for monitoring as process analytical technology, estimating tablet hardness and investigating the detailed mechanism of the lubrication process.     

Energy-Saving Sintering of Electrically Conductive Powders by Modified Pulsed Electric Current Heating Using an Electrically Nonconductive Die

Sintering of Cu and thermoelectric Ca₃Co₄O₉ was tried using a modified pulsed electric current sintering (PECS) process, where an electrically nonconductive die was used instead of a conventional graphite die. The pulsed electric current flowed through graphite punches and sample powder, which caused the Joule heating of the powder compact itself, resulting in sintering under smaller power consumption. Especially for the Ca₃Co₄O₉ powder, densification during sintering was also accelerated by this modified PECS process.