Order-disorder transition of micellar aqueous solution of hydrophobically modified polyethyleneglycol (C12E25)

Aggregation behavior of hydrophobically modified ethyleneglycol oligomer, poly(ethylene glycol) monododecyl ether (C12E25), in aqueous solution has been studied in wide ranges of concentration and temperature by means of light scattering, X-ray scattering, and linear-viscoelastic measurements. C12E25 forms stable micelles in dilute solution. It is found that the micellar solution exhibits the sol-gel transition accompanied with disorder-to-order structural transition as increasing concentration at lower temperatures, or with decreasing temperature at higher concentrations. The transition concentration is located around 30 wt% irrespective of temperature, while the transition temperature is about 56 °C independent of concentration. In the gel region, the micellar particles form a long-range order structure of body-centered cubic lattice.     

Influence of film structure on gas barrier properties of SiOxNy films

SiO_xN_y thin films were deposited on PET substrates by dc magnetron sputtering under various nitrogen gas flow ratios, and the influence of the nitrogen gas flow ratio on the gas barrier performance was examined on the basis of local structure of SiO_xN_y. The surface morphology of the films was evaluated by FE-SEM and AFM observations. The local structure of SiO_xN_y was determined by FT-IR analysis and measurement of refractive index. No obvious macro-defects, such as pinholes, were observed in the films and the surface morphology of all samples was similar. The film density increased with increasing nitrogen gas flow ratio during the deposition process. However, the gas barrier performance decreased with increasing nitrogen gas flow ratio. On the basis of FT-IR analysis, it was determined that the structure of the SiO_xN_y film was a random bonding model (RBM) structure and an increase in the nitrogen gas flow ratio caused an increase in hydrogen termination in the Si-O-N network. The degradation of gas barrier performance at a high nitrogen gas flow ratio is due to the discontinuous Si-O-N network caused by the hydrogen termination.     

Kinetic study on the surface treatment of a Zr0.9Ti0.7Ni1.1Co0.1Mn0.6V0.2 electrode with a boiling alkaline solution

The effect of surface treatment of Zr_0.9Ti_0.1Ni_1.1Co_0.1Mn_0.6V_0.2 alloy electrodes with a boiling 6 M KOH solution for different periods of time was discussed quantitatively by comparison of exchange current density measured by micropolarization method and charge-transfer resistance measured by ac impedance method. The initial activation, exchange current density and charge transfer resistance were greatly improved by increasing alkali treatment time. In particular, the alkali treatment for 2 h showed sufficient electrocatalytic activity and activation effect. The alkali treatment was effective for the progress of the pulverization as well as the removal of the surface Zr-oxide layer. Additionally, the increase in the Ni component on the alloy surface as a result of the alkali treatment was responsible for the above improvement.     

Characteristics of laminated tape insulation in high vacuum at cryogenic temperature

A composite insulation system of laminated tape and high vacuum is newly proposed for a superconducting bus-line cable operated at relatively low voltage. Its breakdown characteristics were investigated using model cable specimens with different kinds of laminated tapes such as semisynthetic paper, polypropylene film, and kraft paper of insulation thickness less than 1 mm. First, ±dc, ac, and —Imp breakdown stresses of the semisynthetic papers were investigated. +dc breakdown stress was 21.7 kV/mm for a specimen of insulation thickness 1 mm and −dc breakdown stress was 41.5 kB/mm, so that the remarkable polar effect was observed. ac breakdown stress was 18 kV/mm. Also, the ratio of −Imp breakdown stress was about 3. Furthermore, ac breakdown stresses of other tapes were investigated, but remarkable differences among their stresses were not observed. Most of the specimens were broken from the “butt gap” between tapes. To understand this cause, measurements of the partial discharge were carried out. It was found that the inception stress of partial discharge of butt gap located just on the conductor was about 20 kV/mm, not dependent on the kind of tape. This value is much lower than the breakdown stress of the same length of vacuum gap. Therefore, it is considered that the trigger of the breakdown of this insulation system is the surface discharge along the edge of the butt gap. © 1998 Scripta Technica, Inc. Electr Eng Jpn, 121(3): 20–26, 1997     

The field test of a cable internally cooled with fire resistant oil

Tricresyl phosphate (TCP), a phosphate ester with fire-resistant and insulating properties, is proposed as a cable cooling medium. A field test was performed with a 275 kV internally-oil-cooled, oil-filled (OF) power cable system using TCP, and it was ascertained that the cable system meets requirements for ease of installation, cooling characteristics, and long-term stability of the cable and the long-term stability of the cable and the TCP. The series of tests has demonstrated the practicality of the cable system