In situ tests for measuring cracks using a crack-detector

Bulletin of Engineering Geology and the Environment - A crack-detector using the ultrasonic pulse method has been developed for borehole measurements. The results obtained fromin situ tests are as...     

Low-temperature ductility of an electron-beam-welded molybdenum sheet predoped with a small amount of carbon

The mechanical properties of unwelded and electron-beam-welded sintered molybdenum sheets, in which carbon was doped or not, were examined by means of a tensile test at temperatures from ?100 to 80°C. Scanning electron microscopy was applied to determine the fracture mode of the specimen and to observe the distribution of precipitates over grain boundaries. The results indicated that a small amount of pre-doped carbon was effective on the improvement in the low-temperature ductility of the welded specimen as well as that of the unwelded one. Such effects are reasonably explained in terms of the enhancement of the crack propagation stress in the fused zone of the weldment.     

Structure and electrochemical properties of carbon films prepared by a electron cyclotron resonance sputtering method

This paper describes the characterization, electrochemical properties, and applications of carbon films prepared by the electron cyclotron resonance (ECR) sputtering method. The ECR-sputtered carbon film was deposited within several minutes at room temperature. The optimized sputtering conditions significantly change the film structure, which includes many more sp3 bonds (sp3/sp2 = 0.702) than previously reported film (sp3/sp2 = 0.274)1 with an extremely flat surface (0.7 A). The ECR-sputtered carbon films exhibit excellent electrochemical properties. For example, they have nearly the same potential window in the positive direction as that of high-quality, boron-doped diamond (moderately doped, 10(19)-10(20) boron atoms/cm3)2 and an even wider potential window in the negative direction with a low background current, high stability, and suppression of fouling by electroactive species without pretreatment. The electron-transfer rates at ECR-sputtered carbon films are similar to those of glassy carbon (GC) for Ru(NH3)(6)(2+)/(3+) and Fe(CN)(6)(3-)/(4-), whereas they are much slower than those of GC for Fe2+/3+, dopamine oxidation, and O2 reduction due to weak interactions between electroactive species and the ECR-sputtered carbon film surface. Such a response can be attributed to the ultraflat surface and low surface O/C ratios of ECR-sputtered carbon films. ECR-sputtered carbon film is advantageous for measuring biochemicals with high oxidation potentials because of its wide potential window and high stability. Highly reproducible and well-defined cyclic voltammograms were obtained for histamine and azide ions with a peak potential at 1.25 and 1.12 V vs Ag/AgCl, respectively. The film is very stable for continuous voltammetry measurements in 10 microM bisphenol A, which usually fouls the electrode surface with oxidation products.     

Electrochemical surface plasmon resonance measurement in a microliter volume flow cell for evaluating the affinity and catalytic activity of biomolecules

We developed an electrochemical surface plasmon resonance flow cell for the simultaneous measurement of the binding affinity and catalytic activity of bifunctional biomolecules. These measurements will be useful for evaluating the performance of such biomolecules as ribozyme and abzyme. The simultaneous measurements were performed on a gold surface modified with a multilayer consisting of poly-l-lysine and poly(styrene sulfonate) assembled with the layer-by-layer method using an enzyme-labeled monoclonal antibody as a model compound. We obtained the amount of immunocomplex formation from the surface plasmon resonance angle shift value by injecting the compound into the flow cell containing the multilayer modified with tumor necrosis factor-alpha. Then we compared this surface plasmon resonance result with that for the in situ electrochemical oxidation of p-aminophenol formed by the catalytic reaction of labeled enzyme on the same gold film. We were able to obtain a high correlation coefficient of 0.999 between the two responses. This is because the compound could be captured with high stability with a less than 3% coulometric response decrease in the catalyzed product in the multilayer whose thickness was easily controllable. In addition, we were able to measure the catalytic activity by coulometry and thus avoid the effect of peak broadening. We also report that the dephosphorylation activity of a bound compound could be estimated from the measurement results and an equation.     

Effects of surface flow control on fluid flow phenomena and mixing time in a bottom blown bath

The intensity of mixing in a molten metal bath stirred by bottom gas injection can be represented by the mixing time. According to previous water model experiments, the mixing time is known to be dependent on the operational variables such as the bath diameter, bath depth, location of a bottom nozzle, and gas flow rate. It is not easy to control the former three variables during processing, and the dependence of the mixing time on the gas flow rate is weak. In this study, the possibility of changing the mixing time drastically due to the control of the surface flow in the bath is examined. Three kinds of boundary conditions were imposed on the bath surface, and the relation between the fluid flow phenomena resulting from the surface flow control and the mixing time was investigated. The mixing time was found to be significantly influenced by the surface flow control. In particular, when the surface flow was suppressed by bringing a circular cylinder into contact with the bath surface, the mixing time became very long.     

Shift of redox potential and kinetics in Lix(MnyFe1−y)PO4

The relatively high redox potential in the olivine-type LiMPO₄ (M = Mn, Fe, Co, Ni) materials has largely been explained by the M–O–P inductive effect which increases the ionic character of transition metal atoms. Here, we identify the additional perturbative effect that slightly but systematically shifts the redox potential. The substitution of iron by manganese in the olivine LiMPO₄ framework raises both of the Fe³⁺/Fe²⁺ and Mn³⁺/Mn²⁺ redox potentials by ∼0.1 V. The overall volume expansion upon Mn substitution in the whole Li_x(Mn_yFe_1−y)PO₄ system possibly increases the average metal-oxide bond length and hence the ionicity of each transition metal. The voltage shift in a single cell is small but should be significant in a larger-scale battery where there exist a large number of series connections. The kinetic shift for each of the Fe³⁺/Fe²⁺ and Mn³⁺/Mn²⁺ redox reactions is also investigated.     

Synthesis and properties of poly(phenylacetylene)s with pendant imino groups

Summary Polymerization of phenylacetylenes containing imino groups with a variety of transition metal catalysts was investigated. The monomers employed were N-(4-ethynylbenzylidene)aniline (1), N-(3-ethynylbenzylidene)aniline (2), N-(4-ethynylbenzylidene)-2,6-diisopropylaniline (3), N-(4-ethynylbenzylidene)-4-hexylaniline (4), N-(4-ethynylbenzylidene)butylamine (5), and N-(4-ethynylbenzylidene)octylamine (6). All of the monomers smoothly polymerized with [(nbd)RhCl]₂-Et₃N to give polymers in excellent yields, whereas no polymerization took place with W, Mo, and Fe catalysts. The produced polymers were orange to red solids and soluble in common organic solvents except for poly(1). UV-vis spectra of the polymers indicated that the main chains possess a similar degree of conjugation to that of poly(phenylacetylene). However, the stability of polymer backbone toward oxidative cleavage in solution remarkably improved, which is contributed by the electron-withdrawing character of imino groups. Received: 24 August 1999/Accepted: 29 September 1999     

Ambient pressure synthesis of La2LiHO3 as a solid electrolyte for a hydrogen electrochemical cell

The capability of La₂LiHO₃ as a H⁻ conductive solid electrolyte has recently been demonstrated, which has suggested the possibility of developing electrochemical devices based on H⁻ conduction. However, the performance of La₂LiHO₃ as a solid electrolyte has not yet been fully clarified. In this study, we prepared La₂LiHO₃ sintered pellets by a conventional solid-state reaction with LiH flux under ambient pressure and characterized the crystal structure and thermal stability (to moisture, ambient air, and oxygen) by neutron and X-ray diffraction measurements. The produced sintered pellets exhibited an activation energy of 69.2 kJ/mol, which is consistent with the value of the sample synthesized by the high-pressure method. The gas-sealing properties of the sintered La₂LiHO₃ pellets as the H⁻ conductive solid electrolyte were confirmed by measuring the electromotive force using a hydrogen concentration cell.     

Application of photoluminescence microspectroscopy: a study on transfer of uranyl and europium ions on dry silica gel plate

ABSTRACT

When water contacts with porous materials, water and chemical species dissolved in the water transfer into the inside of the porous materials. Here, to study the transfer of uranyl and europium ions on a dry silica gel plate, we dropped a small amount of aqueous solution (~0.5 μL) dissolving the two ions on a dry silica gel plate, and the distributions of the two ions spread on the silica gel plate were observed by photoluminescence microspectroscopy. Photoluminescence images of uranyl and europium ions clearly show that when uranyl ion coexists in the solution, europium ion transfers in a larger area compared to uranyl ion. It can be interpreted that the larger-area distribution of europium ion is caused because uranyl ion is preferentially adsorbed to silica gel and the uranyl adsorption disturbs the adsorption of europium ion. The coexistence of uranyl ion may influence the mobility of other ion species.