Examination of the role of oxygen in the photografting of methacrylic acid on a polyethylene film with a mixed solvent consisting of water and organic solvents

The photografting of methacrylic acid (MAA) on a linear low‐density polyethylene film (thickness = 30 μm) under air and nitrogen atmospheres was investigated at 60°C in mixed solvents consisting of water and an organic solvent, with xanthone as a photoinitiator. The organic solvents used were acetone, methanol, tetrahydrofuran, and dioxane. A maximum percentage of grafting occurred at a certain concentration of the organic solvent in the mixed solvent. This was observed for the systems under both air and nitrogen. The grafting reaction under air exhibited an induction period, but the rate of grafting after the period was greater than that under nitrogen. The formation of poly(ethylene peroxide)s by photoirradiation seemed to be a factor for the accelerated photografting under air. On the basis of attenuated total reflection infrared spectroscopy and scanning electron microscopy of the grafted film, the MAA‐grafted chains of the sample prepared under air tended to penetrate more deeply inside the film than those of the sample prepared under nitrogen. The resulting grafted films exhibited a pH‐responsive character: the grafted films shrank in an acidic medium but swelled in alkaline medium. This was evaluated from measurements of dimensional changes in the grafted films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 992–998, 2003     

Development of a fast neutron radiography converter using wavelength-shifting fibers

A fluorescent converter for fast neutron radiography (FNR) comprising a scintillator and hydrogen-rich resin has been developed and applied to electronic imaging. The rate of the reaction between fast neutrons and the converter is increased by thickening the converter, but its opaqueness attenuates emitted light photons before they reach its surface. To improve the luminosity of a fluorescent converter for FNR, a novel type of converter was designed in which wavelength-shifting fibers were adopted to transport radiated light to the observation end face. The performance of the converter was compared with that of a polypropylene-based fluorescent converter in an experiment conducted at the fast-neutron-source reactor YAYOI in the University of Tokyo.     

Reexamination of grain-boundary sliding by diffusion

Steady-state sliding of grain boundaries is discussed by taking into account the change in the potential energy of an applied stress, when the sliding occurs by diffusional accommodation. The present analysis enables us to derive the sliding rates at boundaries of various shapes in a simple manner without knowing local stress fields. Sliding rate of a boundary containing second phase particles is also derived by similar calculations. The results are compared with previous calculations by other investigators, and it is found that the resultant expressions for the sliding rates are essentially identical to those derived from more complex analyses.     

Development of cable fault location method using fiber optic distributed temperature sensor

When ground-fault problems occur on a cable line, immediate fault location and restoration are required. Therefore, various new methods to locate the fault point instantaneously have been investigated to replace such conventional methods as the Murray loop method and the pulse radar method [1]. These methods require a long time to locate the fault point. One possible fault location method is to sense the temperature rise following a ground fault using a fiber optic distributed temperature sensor. Application of this method was found feasible through sensing the temperature rise at a ground-fault test using a thermocouple as a temperature sensor with test cables [4]. A power/optical composite cable was prepared experimentally and after verifying its thermal mechanical performance, the temperature rise at an incidence of a fault was determined and the anticipated performance was demonstrated in a ground-fault test. This article describes the outline of the test.     

Formation of dityrosine and other fluorescent amino acids by reaction of amino acids with lipid hydroperoxides

Formation of fluorescence by the reaction of various amino acids with lipid hydroperoxides,i.e., linoleic acid 13-monohydroperoxide, methyl linoleate 13-monohydroperoxide and phosphatidylcholine hydroperoxide, in the presence of methemoglobin was investigated. Two types of fluorescence were produced: fluorescent dityrosine (3,3′-dityrosine) from tyrosine, and unidentified fluorophores with α- and ε-amino groups of various amino acids. While the former was stable after treatment with borohydride, the latter fluorophores were readily destroyed. The rate of dityrosine formation was rapid, and the yield of dityrosine was dependent on the concentrations of tyrosine and the lipid hydroperoxides. Butylated hydroxytoluene and tocopherol inhibited the formation of dityrosine, but did not affect the formation of fluorophores on the amino groups. Dityrosine appears to be formed by radical reaction of the lipid hydroperoxides, while the other fluorophores seem to be created by nonradical mechanisms.     

Some experimental findings in compression-after-impact (CAI) tests of CF/PEEK (APC-2) and conventional CF/epoxy flat plates

Compression-after-impact (CAI) tests have been conducted for quasi-isotropic thick plates with 48 plies by using the NASA method and on plates with 32 plies by using the SACMA method. Specimens are made of CF/PEEK (APC-2) and conventional CF/epoxy for the NASA plates and CF/epoxy for the SACMA plates. In the NASA CAI tests, the sequence of delamination buckling and its propagation is clearly revealed through various experimental techniques. One major technique is moiré topography, and the other is thermo-mechanical stress analysis with a high-accuracy infrared sensor. The arrest of delamination propagation just before catastrophic failure due to high fracture toughness is clearly captured by the moiré camera. This behavior provides good CAI values of CF/PEEK. The initial buckling properties of the delaminated region by the impact are then extensively discussed. Numerical predictions of initial buckling stress have been obtained by modelled geometry of the delaminated region simplified from its precise structure clarified by ultrasonic C-scanning. They agree fairly well with the experimental results. The in-plane stress distribution in the delaminated region before initial buckling is measured by an infrared stress graphic system. This compared favorably with finite element predictions. Two types of symmetric buckling modes with respect to the central plate surface, twin and single peak ones, are experimentally captured.     

The cause of the uneven carbonization process in wet coal charging in coke oven chamber

In the case of the wet coal charging process in coke oven chamber, it is known that the coking process is uneven and a local carbonization delay occurs. The reason was investigated through a laboratory-scale experiment and a quantitative estimation. A partial carbonization test in a test coke oven replicated the uneven plastic layer and local carbonization delay. It was revealed that most of the gas generated in the uncarbonized coal layer results from the evaporation of condensed water and that steam can break through the plastic layer in a test coke oven. Moreover, the order estimation implied that steam that generates in the uncarbonized coal layer and breaks through the plastic layer has sufficient heat capacity to cool the heating wall and delay the carbonization. It was also shown that the steam pressure peak measured in a commercial coke oven is much lower than the estimated steam pressure in this study assuming steam not breaking through the plastic layer. The above-mentioned results and quantitative investigation strongly support the ‘steam breaking through the plastic layer’ theory proposed by Dr. Rohde that an uneven carbonization process is caused by vaporized coal moisture breaking through the plastic layer at definite, unforeseeable points, which results in cooling of the wall by the steam flow.     

NiCoFe/C cathode electrocatalysts for direct ethanol fuel cells

A direct ethanol fuel cell (DEFC), which is less prone to ethanol crossover, is reported. The cell consists of PtRu/C catalyst as the anode, Nafion^® 117 membrane, and Ni–Co–Fe (NCF) composite catalyst as the cathode. The NCF catalyst was synthesized by mixing Ni, Co, and Fe complexes into a polymer matrix (melamine-formaldehyde resins), followed by heating the mixture at 800 °C under inert atmosphere. TEM and EDX experiments suggest that the NCF catalyst has alloy structures of Ni, Co and Fe. The catalytic activity of the NCF catalyst for the oxygen reduction reaction (ORR) was compared with that of commercially available Pt/C (CAP) catalyst at different ethanol concentrations. The decrease in open circuit voltage (V_oc) of the DEFC equipped with the NCF catalysts was less than that of CAP catalyst at higher ethanol concentrations. The NCF catalyst was less prone to ethanol oxidation at cathode even when ethanol crossover occurred through the Nafion^®117 film, which prevents voltage drop at the cathode. However, the CAP catalyst did oxidize ethanol at the cathode and caused a decrease in voltage at higher ethanol concentrations.