Improving the mechanical properties of isosorbide copolycarbonates by varying the ratio of comonomers

Polycarbonates were synthesized by transesterification polymerization of isosorbide, bisphenol A, and diphenyl carbonate in the presence of n‐BuSn(?O)OH as the catalyst. The polymers were prepared by varying the ratio of the two monomers. The polymers exhibited good thermal stability, rigidity, and strength. The storage moduli for the polymers were 2.6 to 3.2 GPa at 25°C and increased with increasing isosorbide content. The dynamic mechanical analysis indicated that the storage moduli (E′) of the polymers are constant to higher temperatures than that of bisphenol A polycarbonate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Picoliter volume glass tube array fabricated by Si electrochemical etching process

Fabrication process for picoliter volume SiO₂ glass tube array partially embedded in Si wafer was developed. As a template for the glass tubes, macropore array was formed at the surface of n-Si(1 0 0) wafer by photo-assisted electrochemical etching process. The area-selective formation of the array was achieved by applying Au/Cr micropatterns formed at the back-side surface of the substrate as the shade mask, which controls the illumination condition to optimize the etching reaction conditions. Subsequently, surface of the macropores was wet-thermally oxidized to form glass layer, and the bulk Si region was removed by alkaline etching, remaining the “glass tubes”. As a result of complete removal of the bulk Si, released glass tubes were obtained. By partial removal of the bulk Si part, the glass tubes were exposed, fixed in the remaining Si substrate in the form of well-ordered array. It was confirmed that the depth, the exposed region and the wall thickness of each glass tube were controllable by adjusting the parameters such as the duration of the Si electrochemical etching, the alkaline etching and the wet-thermal oxidation, respectively. In order to demonstrate microreaction in the glass tube, aqueous rhodamine B solution was injected into the tubes and excitation light was irradiated to them. As a result, the fluorescence of rhodamine B was clearly detected, confirming the applicability of the glass tubes for various kinds of devices and systems such as microreactors.     

Molecular simulation for adsorption of chlorinated hydrocarbon in zeolites

Equilibrium and isosteric heat of adsorption for the system of chloroform and USY-type zeolite were studied. The USY-type zeolite (PQ Co., SiO₂/Al₂O₃=70) was used both as a pure crystalline powder and as granulated particles with binder. Chloroform was reagent grade. The adsorption equilibria were measured using a gravimetric method and were expressed as isotherms. A chromatographic method (i.e. pulse response of chloroform through the USY column with helium carrier) was used to get the initial slope of the isotherms. In the simulation, the GCMC method was used to calculate amounts adsorbed for various conditions. FF parameters were confidently applied. And modified structure model was effective for simulation. This paper was presented at The 5th International Symposium on Separation Technology-Korea and Japan held at Seoul between August 19 and 21, 1999.     

Water Vapor Adsorption and Desorption on Materials Hydrothermally Solidified from Clay Minerals

Water vapor isotherms were examined and ¹H-magic-angle spinning nuclear magnetic resonance (¹H-MAS NMR) analysis was conducted to determine the amount of water vapor adsorbed and desorbed on hydrothermally solidified materials derived from clay minerals. The amount of water vapor adsorbed and desorbed decreased with increasing mesopore volume of the materials, which disagreed with the estimation obtained using the Kelvin equation. Water vapor was physisorbed on alumina-like sites in the materials. An increase in the binding energy between water vapor and the materials led to an improvement in the water vapor adsorption–desorption properties of materials.     

In Vivo Electrophysiology of Peptidergic Neurons in Deep Layers of the Lumbar Spinal Cord after Optogenetic Stimulation of Hypothalamic Paraventricular Oxytocin Neurons in Rats

The spinal ejaculation generator (SEG) is located in the central gray (lamina X) of the rat lumbar spinal cord and plays a pivotal role in the ejaculatory reflex. We recently reported that SEG neurons express the oxytocin receptor and are activated by oxytocin projections from the paraventricular nucleus of hypothalamus (PVH). However, it is unknown whether the SEG responds to oxytocin in vivo. In this study, we analyzed the characteristics of the brain–spinal cord neural circuit that controls male sexual function using a newly developed in vivo electrophysiological technique. Optogenetic stimulation of the PVH of rats expressing channel rhodopsin under the oxytocin receptor promoter increased the spontaneous firing of most lamina X SEG neurons. This is the first demonstration of the in vivo electrical response from the deeper (lamina X) neurons in the spinal cord. Furthermore, we succeeded in the in vivo whole-cell recordings of lamina X neurons. In vivo whole-cell recordings may reveal the features of lamina X SEG neurons, including differences in neurotransmitters and response to stimulation. Taken together, these results suggest that in vivo electrophysiological stimulation can elucidate the neurophysiological response of a variety of spinal neurons during male sexual behavior.     

Comparisons of Two Models for the Simulation of a DC Arc Plasma Torch

The hypothesis of local thermal equilibrium (LTE) in thermal plasma has been widely accepted. Most of the simulation models for the arc plasma torch are based on the hypothesis of LTE and its results indicate good validity to mimic the pattern of plasma flow inside a plasma torch. However, according to the LTE hypothesis, electrical conductivity near electrodes is significantly lower because of the low gas temperature. Consequently, it is difficult for electrical current flows to pass between the anode and cathode. Therefore, the key subject for a model concentrating on the LTE assumption is to deal with the low electrical conductivity near the electrodes. In this study, two models determining the electrical conductivity at the vicinity of the electrodes with two different assumptions were used to calculate the flow patterns inside a non-transferred DC arc plasma torch. Gas temperature, velocity, voltage drop, and heat energy of the plasma arc were compared between the two models. The results indicated that the plasma arc inside the plasma torch fluctuates, as simulated by both models. It seems that the model can obtain comparable accuracy with the experimental results if the plasma gas electrical conductivity is determined by nominal electron temperature.     

Development of novel temperature-stable Al2O3–TiO2-based dielectric ceramics featuring superior thermal conductivity for LTCC applications

A new composition was developed using sintering to improve the dielectric properties of low-temperature co-fired alumina (LTCA) containing CuO–TiO₂–Nb₂O₅–Ag₂O. By substituting some alumina with rutile TiO₂, the second-phase compound could be changed from AgNbO₃ to the rutile phase. Further, low-temperature sintering at temperatures below 960 °C was possible, suppressing Al₂TiO₅ formation during firing. The dielectric characteristics, particularly the temperature coefficient of the resonant frequency (τ_f) and Q × f values, were improved without significantly reducing the sinterability and thermal conductivity. The dielectric properties of the developed 88Al₂O₃–12TiO₂-based ceramic were ε_r: 14.7, τ_f: +0.8 ppm/K, and Q × f: 13,383 GHz (at ～10 GHz) at a firing temperature of 940 °C. The thermal conductivity was 18.5 W/mK, which is the highest value for reported temperature-stable low-temperature co-fired ceramics (LTCCs). These results provide one of the key technologies for the practical application of LTCCs with superior thermal conductivities.     

Preparation and mechanical properties of polystyrene–clay hybrids

Polystyrene–clay hybrids (PSCHs) were prepared by melt blending a styrene vinyloxazoline copolymer with organophilic clay. In the PSCHs, the silicate layers of the clay were delaminated and dispersed homogeneously to the nanometer level. The moduli of the PSCHs were higher than that of the PS copolymer. For example, the tensile modulus of the PSCH with 5 wt % clay was 1.4 times higher compared to that of the PS copolymer. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3359–3364, 1999     

Influence of a fiber-network microstructure of paper-structured catalyst on methanol reforming behavior

A novel microstructured catalyst that consists of Cu/ZnO catalyst powders and ceramic fibers was successfully prepared using pulp fibers as a tentative matrix by a papermaking technique. As-prepared material, called a paper-structured catalyst, possessed porous microstructure with layered ceramic fiber networks (average pore size ca. 20 μm, porosity ca. 50%). In the process of methanol autothermal reforming (ATR) to produce hydrogen, paper-structured catalysts demonstrated both high methanol conversion and low concentration of undesirable carbon monoxide as compared with catalyst powders and pellets. The catalytic performance of paper-structured catalysts depended on the use of pulp fibers, which were added in the paper-forming process and finally removed by thermal treatment before ATR performance tests. Confocal laser scanning microscopy and mercury intrusion analysis suggested that the tentative pulp fiber matrix played a significant role in regulating the fiber-network microstructure inside paper composites. Various metallic filters with different average pore sizes, used as supports for Cu/ZnO catalysts, were subjected to ATR performance tests for elucidating the pore effects. The tests indicated that the pore sizes of catalyst support had critical effects on the catalytic efficiency: the maximum hydrogen production was achieved by metallic filters with an average pore size of 20 μm. These results suggested that the paper-specific microstructures contributed to form a suitable catalytic reaction environment, possibly by promoting efficient diffusion of heat and reactants. The paper-structured catalyst with a regular pore microstructure is expected to be a promising catalytic material to provide both practical utility and high efficiency in the catalytic gas-reforming process.     

Enhancement of the thermoelectric figure of merit in p- and n-type Cu/Bi-Te/Cu composites

The resultant thermoelectric properties of welded Cu/Bi-Te/Cu composites were measured at 298 K as a function of relative thickness x of Bi-Te compound by changing the interval s between two thermocouples and compared with those calculated as a function of x by treating it as an electrical and thermal circuit. These composites were prepared by welding with eutectic solder of Pb-Sn, after one end surface of the as-grown p- and n-type Bi-Te ingots were plated with Ni. It was found that the observed ZT of composites has a local maximum at an optimum x even when s was changed, as in the case of Cu/Bi-Sb/Cu and Ni/Bi-Sb/Ni composites with various relative thicknesses. Appearance of a local maximum in ZT is owing to the barrier thermo-emf generated by a sharp temperature drop at the interface between Bi-Te compound and copper. It may be caused by the separation of non-equilibrium carriers at the interface between them. The observed maximum ZT values at 298 K of the p- and n-type composites reached surprisingly great values of 1.53 and 1.66 at x=0.98, which correspond to about twice as large as those of commercially utilized Bi-Te compounds. This enhancement of ZT is available for generators, but may be not utilizable as a Peltier module. The composite materials were thus found to be utilizable as useful means of further increase in ZT of macroscopic bulk materials.