Solid State Phenomena Vols. 124-126

Abstract: Thermal properties of PEEK/silicon carbide(SiC) and PEEK/carbon fiber(CF) were investigated from ambient temperature up to 200°C measured by laser flash method. Thermal conductivity was increased from 0.29W/m-K without filler up to 2.4 W/m-K with at 50 volume % SiC and 3.1W/m-K with 40 volume % carbon fiber. Values from Nielsen theory that predicts thermal conductivity of two-phase system were compared to those obtained from experiment.

Abstract: Nanocomposites of conducting polymers of polyaniline (PANI), poly(oethoxyaniline) (PEOA) and polypyrrole (PPy) with clay prepared via either in-situ emulsion polymerization or solvent intercalation were investigated especially for electrorheological fluid (ER) application. Internal structures of these nanocomposites were examined via wide angle X-ray diffraction (WAXD), and transmission electron microscope (TEM). The intercalated nanostructures analyzed via WAXD and TEM were correlated with the electrical property change originated from the nanoscale interaction between clay and conducting polymer. Moreover, their ER behaviors were measured via rotational rheometer with external electric field controller.

Abstract: The electrochemical recycling of cofactors during enzymatic biocatalysis has long been acknowledged as a potentially powerful technology in fine chemical synthesis. Major obstacle for this approach is that cofactors only in the immediate vicinity of the electrode surface are productive. This problem further causes high overpotential at electrode surfaces leading to undesired side reactions producing enzymatically-inactive dimer and isomer of cofactor. So far, several attempts had been made to address these problems by focusing on surface modifications, which explored to retain the enzyme and/or cofactor close to the working electrode including electrode deposition and membranes surrounding the electrode. In this work, we demonstrate a new concept of cofactor regeneration by using ‘electronically-conductive’ sol-gel hybrid materials. When conductive hybrid gels were added to the reaction medium, we found that cofactor could be efficiently recycled throughout the whole reactor system leading to high yield of product, which was unattainable with conventional technologies.

Abstract: Composite laminates help to lighten components because they have the advantage of higher strength-to-weight ratio. So, they have come to be utilized as parts of advanced areas. An NDE technique for stacking orientation determination would be very beneficial because of layup orientation influence to the laminate stiffness. In this study, an investigation of shear wave ultrasonic technique was carried out in order to detect stacking orientation error for quasi-isotropy composite laminates. During testing, the most significant problem is that the couplant conditions do not remain the same because of changing the viscosity of the couplant. Therefore, the design and use of a shear wave transducers would greatly aid in alleviating the couplant problem. A pyramid with an isosceles triangle with two 45o was made of aluminum to generate shear waves using two longitudinal transducers based on ultrasonic-polarized mechanism. Also, the signal splitter was connected to the pulser jack on the pulser/receiver and to the longitudinal transducers. The longitudinal transducers were mounted with mineral oil and the shear transducer was mounted on the bottom as a receiver with burnt honey. It is found that the shear wave was generated at a maximum and a minimum based on the ultrasonic-polarized mechanism. To apply this method into a practical inspection tool, the quasi-isotropy composite laminates were nondestructively evaluated for detecting error of the laminates.

Abstract: Supercritical impregnation of eicosane into polyester fiber was experimentally examined. Polyester fiber was bound on the cylindrical stainless steel net inside high pressure cylinder and was impregnated with supercritical eicosane solution. After an hour under supercritical condition, the system was expanded to atmospheric pressure and impregnated polyester fiber was obtained. Eicosane was successfully impregnated into the polyester fiber even at temperature below it’s glass transition(Tg), and the impregnated fiber showed high energy storage and release capacity around the melting point of eicosane.

Abstract: Thin foil hot press process was used to fabricate metal/intermetallic compound laminate composites to induce self-propagating high-temperature (SHS) reaction between different pure metal sheets. In the present study, Ni/Ni-aluminide and Ti/Ti-aluminide laminate composites were fabricated through diffusion bonding, reaction synthesis and post-heat treatment of alternatively stacked pure Ni/Al and Ti/Al foils, respectively. Thick intermetallic layers of NiAl and TiAl3 were formed by a self-propagating high-temperature synthesis (SHS) reaction, and thin continuous layers of Ni3Al and TiAl were formed by a solid-state diffusion. Also, Ni/Ni-aluminide//Ti/Ti-aluminide laminate composite, considered as a functionally gradient material, was manufactured from stacked foils of pure Ni, Ti and Al in order of Ni/Al/Ni/.../Ni/Al /Ti/.../Ti/Al/Ti. Nb/Nb-aluminide laminate composite was manufactured with pure Nb and Al multilayered foils, consisting of fine Nb/Nb3Al/Nb2Al/NbAl3 layer structure.

Abstract: Lead magnesium niobate-lead titannate single crystal (abbreviated as PMNT) was used to fabricate PMNT/polymer 1-3-2 piezoelectric composite with different volume fractions of PMNT, by dicing single crystal PMNT along mutually perpendicular two directions on the surface and then filling polymer into grooves. The piezoelectric, dielectric and electromechanical properties of the novel composite were determined. It was demonstrated that a thickness electromechanical coupling coefficient of the composites could reach as high as 0.75 and acoustic impendence decreased to 14.9 Mrayls (lower than 30 Mrayls of PMNT). The pulse-echo waveforms of the composites without backing were also measured. It showed a -6dB bandwidth of 88% at the center frequency of 0.95MHz.

Abstract: The polymer nanotube and nanorod of polystyrene (PS) and polymethyl methacrylate (PMMA) respectively hav been synthesized by wetting process, using nanoscale AAO templates. For the AAO template formed in phosphoric acid, which has the pore diameters between 200 and 300 nm, the polymer nanotubes can be obtained. However, for the AAO template formed in oxalic acid with the pore diameters between 60 and 70 nm, polymer nanorods are obtained due to a complete filling of the pore space instead of pore wall wetting of polymer. It is indicated that the wetting behavior of polymer on the AAO template play an important role in synthesis of polymer nanotubes, and the shape and length can be controlled by anodic time for AAO template fabrication.

Abstract: Novel continuously porous alumina (25%monoclinic-Zirconia) (Al2O3-(m-ZrO2)) and tetragonal Zirconia (t-ZrO2) composites were fabricated with concentric multilayer shells of Al2O3-(m-ZrO2) and t-ZrO2 by the multi-pass extrusion process. Nanocrystaline Al2O3-(m-ZrO2)/ t-ZrO2 powders and graphite powder as a pore forming agent were mixed with polymer in extrudable form. The microstructure was tailored in the green bodies by the extrusion process with high flexibility of control. The green body was burnt-out and sintered to obtain the continuously porous ceramics. The pore diameter and pore frame thickness were around 198±10.5 μm and 158.5±10.2 μm, respectively. The pore frame region was furnished with 9 alternating shells of Al2O3-(m-ZrO2) and t-ZrO2 with uniform thickness of about 17.6±1.1 μm. The interfaces of the alternate layers were designed corrugated shape. The detailed microstructure of the porous bodies was characterized by SEM techniques.

Abstract: Poly(vinylidene fluoride) (PVDF) / multi-walled carbon nanotube (MWNT) thermoplastic composites was melt compounded in an internal mixer. The percolation level for this system in electrical conductivity clearly occured between 2 and 2.5 wt%. PVDF/MWNT thermoplastic composites exhibited an increased crystallization temperature with the loading level, at 10 wt% loading by ca. 6
. In addition, they presented a shoulder posterior to the main melting peak and an increased endpoint of the peak. In the Wide Angle X-ray Diffraction (WAXD) patterns, the incorporation of MWNT produced a larger shoulder at 2θ =20.7° with increasing the loading level, corresponding to the β-form crystal of PVDF.