Showing papers in "Ieej Transactions on Fundamentals and Materials in 2015"

High-speed Underfilm Corrosion Imaging using a Terahertz Camera

Abstract: Nondestructive, two-dimensional distribution measurement of rusting under opaque anticorrosion coating was carried out, using a terahertz camera, a quantum cascade laser, and a galvanic scanner. The measurement speed of the present method was found to be 11 times faster than the conventional raster scanning method based on time-domain spectroscopy. A signal-to-noise ratio exceeding 102 was confirmed for both systems, which enables the detection of minor rusting.

Complex permittivity spectra of various insulating polymers at ultrawide-band frequencies

Abstract: SUMMARY Nowadays, trials to use even higher frequencies are pursued to realize high-speed wireless communications. In order to respond to such a trend, dielectric properties of insulating polymers at high frequencies have to be clarified, although the importance of clarifying low-frequency properties is still very high, especially for use as high-voltage insulators. In this regard, complex permittivity spectra from 10 mHz to 4.0 THz were obtained for various insulating polymers. The spectra obtained in the very wide frequency range are important, because they can be a valuable database and they provide various pieces of important information on dielectric characteristics.

Properties of Space Charge Distributions and Conduction Current in XLPE and LDPE under DC High Electric Field

Abstract: SUMMARY Space charge behavior and conduction current in polyethylene under dc stress were investigated. One of the reasons for the different breakdown property in cross-linked polyethylene (XLPE) from that in low-density polyethylene (LDPE) may be based on the existence of cross-linking by-products in XLPE. Furthermore, a thermal history in cross-linking process for XLPE may also cause of the difference. It is generally accepted that the existence of the cross-linking by-products increase the conduction current in XLPE under dc stress. It is also said that an anneal treatment in air atmosphere may affect to the electrical properties under dc stress. Therefore, we investigated the effect of the cross-linking by-products and the anneal treatment on space charge behavior and conduction current in polyethylene under dc stress. In our research, it is thought that the increasing dissipation power in XLPE is the cause of the breakdown in it under dc stress. Therefore, to calculate the dissipation power in the bulk of test sample, we measured the space charge distribution and the external circuit current simultaneously. Based on the results, we discussed the reason of the difference of the space charge properties in XLPE and LDPE focusing on the cross-linking by-products and the oxidation of the test samples.

Surface Modification of PTFE Using Low Energy Nitrogen Ion Irradiation:—Improvement in Adhesive Strength on Modification of Deep Modifying Layer—

Abstract: Polytetrafluoroethylene PTFE has the best properties as a material of high-frequency PC board. However, it has low adhesion force for using cabling material. In order to improve adhesion force, we studied on surface modification of PTFE by using nitrogen ion irradiation. As a result, peel strengths of PTFE improved up to 900 N/m to amount of treatment time. On the other hand, surface energy did not increase. From here onward, improved peel strengths on modified surface could be forecasted because of a change that is binding state of modified layer. The compositions of surface on samples after peel test were analyzed so as to prove the hypothesis. As a result, adhesive/PTFE system occurred to destruction in deep portion of modified layer. Moreover, binding of oxygen could be existed with long treatment time. Therefore, it was suggested that the brittle layer of deep modifying layer needs to be modified for the improvement of adhesive strength.

Removal of ethylene and by-products using packed bed dielectric barrier discharge with Ag nanoparticle-loaded zeolite

Abstract: SUMMARY Ethylene gas was decomposed using packed-bed type dielectric barrier discharge (PBDBD) plasma reactor to keep freshness of fruits. The ethylene gas was diluted with gas mixture of nitrogen, oxygen, and carbon dioxide as simulated gas in the transportation container. The PBDBD plasma was generated by a pulse switching power supply, which consisted of MOS-FET switching devices, capacitors, and pulse transformers. The Ag nanoparticle-loaded zeolite as catalyst has high activity and good performance for reduction of ozone and oxidizing carbon monoxide at room temperature. The Ag nanoparticle-loaded zeolite pellets enhanced ethylene removal efficiency and reduced ozone and carbon monoxide produced by the plasma treatment. It was confirmed that the carbon monoxide in the gas simulated dry air composition was oxidized using Ag nanoparticle-loaded zeolite with plasma treatment.