Dielectric properties of woven fabric glass fiber reinforced polymer-matrix composites in the THz frequency range

Electromagnetic wave transmittances of plain woven fabric glass fiber reinforced epoxy matrix composite (PW-GFRP) and eight-harness-stain fabric glass fiber reinforced polyimide matrix composite (8H-GFRP) with 1.0 mm thickness were measured in a terahertz (THz) frequency range. The transmittance values for both composites are nearly zero at a frequency of 1.0 THz. The real parts of the complex dielectric constant, ε′(ω) are 4.45 and 3.87 for PW-GFRP and 8H-GFRP, respectively, in the frequency range from 0.2 to 1.0 THz, and they are almost frequency independent. Conversely, the imaginary parts of the dielectric constant, ε′′(ω) for both composites linearly increases with increase of the frequency from 0.13 to 0.37 for PW-GFRP, and from 0.12 to 0.33 for 8H-GFRP.     

Deposition of DLC film with adhesive W-DLC layer on stainless steel and its tribological properties

Tribological properties of a diamond-like carbon (DLC) coating with an adhesive tungsten-containing DLC (W-DLC) layer were investigated. The coatings were deposited onto AISI316L steel substrates and Si wafers using plasma enhanced chemical vapor deposition and tungsten co-sputtering of the metal target. Methane and argon gases were used as the precursor of the coatings. In this study, three types of coatings were evaluated: DLC/W-DLC on AISI316L (DLC-1), DLC/W-DLC on Si wafer (DLC-2), and DLC on Si wafer (DLC-3). The structural characterizations were performed by transmission electron microscopy and tapping mode atomic force microscopy. At the boundary between the W-DLC layer and the AISI316L substrate, microscopic decohesion or delamination was not observed. The surface roughness of the DLC-1 coating was greater than that of the DLC-2 coating. This feature was derived from the surface roughness of the initial surface of the AISI316L substrate. Friction tests were performed using a rotation-type ball-on-flat configuration tribometer. The observed friction of the DLC-1 coating was unstable compared with the DLC-2 or DLC-3 coatings. This was due to wear debris which had risen to the friction surface resulting in unstable friction on the DLC-1 coating. During the friction studies, the top DLC layer was removed from the adhesive W-DLC layer because the adhesive strength at this part was not enough. In order to achieve the low and stable friction of the DLC coating with the W-DLC layer on AISI316L, it is necessary to improve the smoothness of the surface and the adhesion between the DLC coating and the W-DLC layer.     

Structural analysis and transistor properties of hetero-molecular bilayers

We examined the film morphologies and transistor properties of hetero-molecular bilayer consisting of N, N’-dioctyl-3, 4, 9, 10-perylenedicarboximide (PTCDI-C₈) and quaterrylene. First, the structure and carrier conduction of PTCDI-C₈ films were studied, followed by an analysis of the carrier accumulation process in a PTCDI-C₈/quaterrylene hetero-bilayer transistor. Based on the displacement current measurement (DCM), we stress the potential of the hetero-bilayer for tuning carrier accumulation like carrier doping techniques in field-effect transistors.     

Microstructural analysis of the stir zone of Al alloy produced by friction stir spot welding

The present study applied friction spot joining (FSJ), which was recently developed as a lap joining technique of Al alloys, to two sheets of Al alloy 6061, 1 mm in thickness, and then examined the microstructural feature in the weld. The weld had the nugget-shaped stir zone around the exit hole of the probe, and the stir zone exhibited the equiaxed grain structure having finer grain size than that of the base material. The crystallographic texture analysis using electron backscattered diffraction method suggested that the material movement occurred along the rotating direction of the welding tool in the wide region including the stir zone. In the periphery of the nugget-shaped stir zone, which was characterized as the region having the finer grain size than that of the stir zone interior, any inclusions and precipitates were not found in the SEM scale. The weld was softened around the weld centre. The softening could be explained by dissolution and/or growth of the strengthening precipitates due to thermal cycle of FSJ.     

The unique flow of polypropylene at the weld line behind an obstacle in injection molding

In this article, a weld line placed behind an obstacle in an injection‐molded plaque made of metallic mold‐in‐color polypropylene (PP) was investigated. A broad uneven glossy section was visually observed along the weld line after the v‐notch weld disappeared. Although disk‐shaped metallic pigments were oriented parallel to the wall according to laminar flow, the pigment particles at the weld behind the obstacle were ordered vertically at the center of the depth direction. In PP molded without pigment, a black line was observed at the same position in the metallic weld. Based on a measurement of the crystal structure, the black line was caused by the rapid cooling of molten PP. Elongational flow occurred along the weld line after the diminishing v‐notch weld. The unique flow ordered the pigments obliquely at the advancing flow front and disturbed the subsequent flow of hot PP which transferred heat to the crystallizing mass. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Mesophase structure discovered through in-situ X-ray measurement in drawing process of poly(ethylene 2,6-naphthalene dicarboxylate) fiber

The structure development in the continuous laser-heated drawing process of poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) fiber was analyzed by in-situ X-ray diffraction measurement. Because of the rapid and uniform laser heating, and the resultant steady-state nature of the necking-drawing, the structure development after the on-set of necking could be measured in the time resolution of several hundred microseconds. We found for the first time the temporal appearance of meridional (001′) diffraction at several milliseconds after the on-set of necking indicating that the mesophase structure similar to the one reported for poly(ethylene terephthalate) was also formed in the initial stage of fiber structure development of PEN. The d-spacing of the (001′) diffraction 1.230 ± 0.003 nm was shorter than the c-axis lengths of both α and β crystals.     

Effects of veterinary drugs on beta-hexosaminidase release from rat basophilic leukemia cells (RBL-2H3)

Little is known about the effects of residual veterinary drugs on the allergic reaction, except for the antigenicity of antibiotics and synthetic antimicrobials. Therefore, 59 kinds of veterinary drugs were investigated for their effects on the IgE receptor-mediated beta-hexosaminidase release from RBL-2H3 cells as an index of immediate allergic reaction. We found that the antibiotics chlorotetracycline, doxycycline, monensin, the synthetic antimicrobial pyrimethamine and the steroid hormone testosterone inhibited beta-hexosaminidase release. Most of the veterinary drugs showed no action, though the ionophores lasalocid, salinomycin and the steroid hormone hexestrol promoted beta-hexosaminidase release from injured cells. Based on the residual levels of these drugs and the frequencies of detection in actual food samples, it seems unlikely that these drugs have any immediate allergic effect in practice.     

Determination of free fatty acids in milk and dairy products by reversed-phase HPLC with fluorescence detection

A highly sensitive HPLC with fluorescence detection was developed for the determination of free fatty acids (FFAs) in milk and dairy products. For this purpose, the FFAs were extracted from small amounts of milk (1.0 mL), cheese (0.5 g) and butter (0.5 g) using Sep-Pak cartridge columns, and then derivatized to 9-anthrylmethyl esters with 9-anthryldiazomethane (ADAM). Good separations of the ADAM derivatives of 16 FFAs (C4-C18) that exist in milk, cheese and butter, which permitted quantitative estimation of their individual FFAs, were achieved by HPLC on a C18 column (Cadenza CD-C18, 150 x 3 mm i.d.) using gradient elution with methanol and water. The acid values calculated from the contents of individual FFAs were in good agreement with those obtained by the conventional titration method. These results demonstrate that the present HPLC method is simple, sensitive and precise, and could be utilized widely for determination of the FFAs in milk and dairy products.