Compatibilizing effect of a maleic anhydride functionalized SEBS triblock elastomer through a reaction induced phase formation in the blends of polyamide6 and polycarbonate—III. Microscopic studies on the deformation mechanism

Microscopic studies on the deformation mechanism of the blends of polyamide6 (PA6) and polycarbonate (PC) compatibilized with triblock copolymer of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) functionalized with maleic anhydride (SEBSgMA) were carried out. As described in our previous paper, significant improvement of mechanical properties of this blend series can be achieved by the use of the combination of SEBSgMA and unmodified SEBS (unSEBS) as compatibilizers. Especially, when the composition of the blends of PA6/PC is and the total amount of added SEBS is 20 phr, drastic enhancement of the impact strength and of the elongation at break in the tensile stress-strain tests can be achieved by varying the ratio of SEBSgMA to unSEBS. The encapsulation by SEBS on the PC domains gradually become incomplete as the increase of the ratio of unSEBS to SEBSgMA and then the mechanical properties can be maximized. We observed the deformed zone of the specimens loaded to the tensile stress-strain tests and to the Izod impact tests using transmission electron microscopy (TEM) in order to find out the origin of this enhancement of the mechanical properties. It has revealed that voids tend to be generated at the PA6/PC interface easily due to the incompletion of the encapsulation achieved by the use of the combination of SEBSgMA and unSEBS, and thereby the local shear yielding of the matrix is promoted to dissipate the tensile and the impact energy. © 1997 Elsevier Science Ltd.     

Out-of-plane quasiparticle dynamics of the cuprate superconductors belowT c in microwave region

We have investigated the anisotropic quasiparticle conductivity in the superconducting state for microwave frequencies in YBa₂Cu₃O_7– (YBCO) and La_2–xSr_xCuO₄ (LSCO) with several hole concentrations. Common features were found for YBCO and LSCO. That is, in underdoped materials, the strong two dimensional nature was found to be retained even below T_c. On the other hand, in optimally doped and overdoped materials, the anisotropy decreases rapidly below T_c. In particular, in YBCO, it is suggested that the c-axis transport becomes coherent below T_c.     

Enhancement of Thermoelectric Properties in Surface Nanostructures

The thermoelectric properties of TiN/MgO surface nanostructures have been determined using first-principles calculations based on the nonequilibrium Green’s function (NEGF) method. Through structural modification of the surfaces at the atomistic level, we find that the metallic TiN thin-film layer becomes semiconducting with a small bandgap, which enhances the Seebeck coefficient, while the electrical conductivity remains high at room temperature. Hence, a much larger thermoelectric figure of merit is obtained compared with bulk. These findings indicate the possibility of designing thermoelectric devices with surface nanostructures.     

Magnetic properties and surface crystallization induced by selective oxidation in Fe-B-Si amorphous alloy

The relationship between the annealing atmosphere and the magnetic properties of Fe_78.5B₁₃Si_8.5 amorphous alloy has been studied, showing that annealing in nitrogen, argon, hydrogen and air significantly improved the iron loss of the amorphous ribbon, giving much better results than annealing in an H₂ + H₂O atmosphere. A boron-depletion zone with the alloy composition O to 3 mol % B and 9 to 11 mol% Si was detected by Auger electron spectroscopy under the oxide film formed during annealing in H₂ + H₂O. The iron crystalline phase is formed only on the ribbon surface after annealing in H₂ + H₂O. A mechanism is proposed explaining the deleterious effect of annealing in the H₂ + H₂O, whereby the H₂O in this atmosphere selectively oxides boron in the amorphous alloy to form a B₂O₃ film and the boron-depletion zone, and the alloy in this zone is then crystallized into -Fe. This surface crystalline layer induces out-of-plane magnetic anisotropy in the amorphous alloy ribbon (which was observed by transmission Mössbauer spectroscopy) and thus deterioration of the iron loss.     

Gradient-index rod lens with high N.A

new gradient-index lens with high numerical aperture has been fabricated by a new ion-exchange technique. In this treatment, a glass rod doped with a highly polarizable ion (dopant A) is immersed into KNO3 salt doped with a medium polarizability ion (dopant B). Dopant B penetrates into the rod and modifies the refractive-index profile of the lens. This new lens has 0.6 N.A. and gives a 1.18-micron spot diam in the light-focusing system. This lens gives good results also in a light source coupling system and is useful in microoptic devices.     

Purification of steryl esters from soybean oil deodorizer distillate

Soybean oil deodorizer distillate (SODD) contains steryl esters in addition to tocopherols and sterols. Tocopherols and sterols have been industrially purified from SODD but no purification process for steryl esters has been developed. SODD was efficiently separated to low b.p. substances (including tocopherols and sterols) and high b.p. substances (including 11.2 wt% DAG, 32.1 wt% TAG, and 45.4 wt% steryl esters) by molecular distillation. The high b.p. fraction is referred to as soybean oil deodorizer distillate steryl ester concentrate (SODDSEC). We attempted to purify steryl esters after a lipase-catalyzed hydrolysis of acylglycerols in SODDSEC. Screening of industrially available lipases indicated that Candida rugosa lipase was most effective. Based on the study of several factors affecting hydrolysis, the reaction conditions were determined as follows: ratio of SODDSEC/water, 1∶1 (w/w); lipase amount, 15 U/g reaction mixture; temperature, 30°C. When SODDSEC was agitated for 24 h under these conditions, acylglycerols were almost completely hydrolyzed and the content of steryl esters did not change. However, study with a mixture of steryl oleate/trilinolein (1∶1, w/w) indicated that about 20% of constituent FA in steryl esters were exchanged with constituent FA in acylglycerols. Steryl esters in the oil layer obtained by the SODDSEC treatment with lipase were successfully purified by molecular distillation (purity, 97.3%; recovery, 87.7%).     

Recovery of sterols as fatty acid steryl esters from waste material after purification of tocopherols

Tocopherols are purified industrially from soybean oil deodorizer distillate by a process comprising distillation and ethanol fractionation. The waste material after ethanol fractionation (TC waste) contains 75% sterols, but a purification process has not yet been developed. We thus attempted to purify sterols by a process including a lipase-catalyzed reaction. Candida rugosa lipase efficiently esterified sterols in TC waste with oleic acid (OA). After studying several factors affecting esterification, the reaction conditions were determined as follows: ratio of TC waste/OA, 1∶2 (wt/wt); water content, 30%; amount of lipase, 120 U/g-reaction mixture; temperature, 40°C. Under these conditions, the degree of esterification reached 82.7% after 24 h. FA steryl esters (steryl esters) in the oil layer were purified successfully by short-path distillation (purity, 94.9%; recovery, 73.1%). When sterols in TC waste were esterified with FFA originating from olive, soybean, rapeseed, safflower, sunflower, and linseed oils, the FA compositions of the steryl esters differed somewhat from those of the original oils: The content of saturated FA was lower and that of unsaturated FA was higher. The m.p. of the steryl esters synthesized (21.7–36.5°C) were remarkably low compared with those of the steryl esters purified from high-b.p. soybean oil deodorizer distillate substances (56.5°C; JAOCS 80, 341–346, 2003). The low-m.p. steryl esters were soluble in rapeseed oil even at a final concentration of 10%.     

Effect of Surface Condition on Oxygen Self-Diffusion Coefficients for Single-Crystal Al2O3

Oxygen self-diffusion coefficients were determined for two Al₂O₃ single crystals by the isotope-exchange technique, using chemically polished and Ar -ion-milled samples. Results represented by D=562 exp[–665(kJ/mol)/RT] cm²/s are lower than those for diamond-paste-finished samples and near Reed and Wuensch's results. The oxygen diffusion coefficient determined using crushed particles and the microscopically measured ratio of surface area to volume agreed with these values     

Synthesis of Nanowire TiO2 Thin Films by Hydrothermal Treatment and their Photoelectrochemical Properties

Nanowire TiO₂ thin films were successfully prepared on Ti metal substrates by hydrothermal treatment of calcined Ti foils in 10 M NaOH. The nanowire TiO₂ thin films exhibited much larger surface area and higher photoelectrochemical performance than the TiO₂ thin films prepared on Ti metal substrates by the calcination of Ti foil. These nanowire films were shown to act as an efficient photoanodes for the photoelectrochemical water splitting reaction.