Layered liquid-liquid flow in microchannels having selectively modified hydrophilic and hydrophobic walls

When two immiscible liquids make contact in a microchannel, the flow pattern is affected by the affinity between channel walls and liquids. In this study, microchannels (200 μm in width and 200 μm in depth) having a T-shaped bifurcation point were fabricated on PMMA plates. The inner walls of the microchannels were modified in a zone-selective manner to be either hydrophilic or hydrophobic, based on verification accomplished via a laser interference fringe technique. The microchannel was placed horizontally, and water and octane were introduced into the upper-side channel (hydrophilic) and into the lower-side channel (hydrophobic), respectively. The experimental results showed that water and octane formed a stable layered flow, and the two liquids were virtually completely separated at the T-shaped section, even when static pressure was intentionally applied to the outlets. CFD simulation, using FLUENT 6.3 software, was performed to explain the role of zone-selective modification of microchannel walls.     

Electrochromism of nickel oxide thin film with polymer gel electrolyte

Polymer gel electrolytes were investigated for an electrochromic device (ECD) using nickel oxide thin film. Poly(ethylene oxide) (PEO) derivatives were cross‐linked and swelled in KOH–aqueous solution giving a hydrogel electrolyte. The ECD containing the uniformly cross‐linked hydrogel showed good result in electrochromic switching performance. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1305–1308, 2002     

Surface condition of Si implanted GaAs revealed by the noncontact laser/microwave method

The surface recombination of GaAs which has a heavily doped surface layer formed by Si implantation and subsequent annealing has been investigated using the noncontact laser/microwave evaluation method. The experimental results of the samples implanted with doses ranging from 1.0 × 10¹¹ to 3.9 × 10¹² cm⁻² at an energy of 100 keV indicate that the effective surface recombination velocity decreases with dosage because of the heavily doped layer formed after the annealing. On the other hand, the results of the samples implanted with a dose of 3.9 × 10¹² cnr⁻² at energies raging from 50 to 180 keV indicate that the effective surface recombination velocity increases with energy. This is mainly due to the decrease in the peak carrier concentration in the heavily doped layer.     

Residual impurities in GaN/Al2O3 grown by metalorganic vapor phase epitaxy

Residual impurities in GaN films on sapphire (A1₂O₃) substrates grown by two-step metalorganic vapor phase epitaxy (MOVPE) have been investigated. We have mainly investigated the incorporation of carbon into the GaN films with GaN buffer layers on A1₂O₃ during MOVPE growth, comparing trimethygallium (TMGa) and triethygallium (TEGa) as the typical gallium precursors. The films were characterized by secondary ion mass spectroscopy analysis, photolu-minescence, and Hall measurements. The carbon, hydrogen, and oxygen concentrations increase with decreasing growth temperature in using TMGa. Especially the carbon concentration increases with decreasing a V/III ratio, for both TMGa and TEGa. There is about two times more carbon in the GaN films grown using TEGa than those using TMGa. The carbon from TMGa mainly enhances the D-A pair emission (∼378 nm), which shows the carbon makes an acceptor level at nitrogen sites in GaN. On the other hand, the carbon from TEGa enhances a deep emission (∼550 nm), which shows the carbon makes not only an acceptor level but deep levels at interstitial sites in GaN. The carbon impurities originate from methyl radicals for TMGa, or ethyl radicals for TEGa. It is supposed that, in the case of TEGa, the carbon impurities are not always located at nitrogen sites, but are also located at interstitial sites because of the C-C bonding in ethyl radicals.     

Kinematic analysis and planning for form closure grasps by robotic hands

A new approach to the planning of form closure grasps by robotic hands is presented. The form closure grasp is to constrain a rigid workpiece by surrounding the object surface with mechanical fingers so that the object motion is geometrically constrained in all directions. First, kinematic conditions for the form closure grasp are obtained for workpieces with smooth surfaces, and are extended those one comprising edges and vertices. An efficient algorithm for examining the form closure grasp conditions is then developed by applying linear programming techniques. A computer-assisted planning system is also developed for the synthesis of grasping points as well as for the design of grippers. Fingertip locations are determined so as to accomplish the form closure grasp, given the geometry of a workpiece. A couple of examples demonstrate the usefulness of the method.     

Effect of polycarbonate–poly(methyl methacrylate) graft copolymer as a modifier improving the surface hardness of polycarbonate

With the use of macromonomers that have a dicarboxyl group, polycarbonate–poly(methyl methacrylate) (PC–PMMA) graft copolymers were prepared, and the relationship between the length of PMMA branches and Vickers hardness of the graft copolymer was investigated. With the use of the PC–PMMA graft copolymer as a modifier to improve the surface hardness of PC, Vickers hardness of PC/PC–PMMA blend polymers was examined. PC/PC–PMMA blend polymers are more transparent than PC/PMMA blend polymers. PC/PC–PMMA blend polymers are superior in Vickers hardness to PC/PMMA blend polymers, although the content of PMMA in PC/PC–PMMA blend polymers is smaller than that of PC/PMMA blend polymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2774–2779, 2002; DOI 10.1002/app.10252     

Photocatalytic decomposition of NO on titanium oxide thin film photocatalysts prepared by an ionized cluster beam technique

Transparent TiO₂ thin film photocatalysts were prepared on transparent porous Vycor glass (PVG) by an ionized cluster beam (ICB) method. The UV‐VIS absorption spectra of these films show specific interference fringes, indicating that uniform and transparent TiO₂ thin films are formed. The results of XRD measurements indicate that these TiO₂ thin films consist of both anatase and rutile structures. UV light (λ > 270 nm) irradiation of these TiO₂ thin films in the presence of NO led to the photocatalytic decomposition of NO into N₂, O₂ and N₂O. The reactivity of these TiO₂ thin films for the photocatalytic decomposition of NO is strongly dependent on the film thickness, i.e., the thinner the TiO₂ thin films, the higher the reactivity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photocatalytic decomposition of N2O on Cu+/Y-zeolite catalysts prepared by ion-exchange

Insitu characterization of Cu⁺/Y-zeolite catalysts and their photocatalytic reactivities for the decomposition of N₂O into N₂ and O₂ have been investigated by means ofin situ photoluminescence, XAFS, and ESR techniques along with an analysis of the reaction products. It was found that Cu(I) ions included within the nanopores of Y-zeolite exist as the [Cu(I)--Cu(I)] dimer species as well as the isolated Cu(I) monomer species, their ratio being much dependent on the SiO₂/Al₂O₃ ratio of Y-zeolite. UV irradiation of these Cu⁺/Y-zeolite catalysts in the presence of N₂O led to the photocatalytic decomposition of N₂O into N₂ and O₂ at temperatures as low as 275 K. The electronically excited state of Cu(I) ion (3d⁹4s¹ state) plays a vital role in the photocatalytic decomposition of N₂O into N₂ and O₂. The photocatalytic reactivity of these Cu⁺/zeolite catalysts was found to be strongly affected by the local structure of the Cu(I) ions which could easily be modified by changing the SiO₂/Al₂O₃ ratio of Y-zeolite. The isolated linear 2 coordinated Cu(I) monomer species formed on Y-zeolite having a moderate SiO₂/ A1₂O₃ ratio exhibited a high photocatalytic reactivity for the direct decomposition of N₂O into N₂ and O₂, clearly showing the importance of the coordinative unsaturation of the active sites.     

Interaction of nylon 6-clay surface and mechanical properties of nylon 6-clay hybrid

We synthesized nylon 6-clay hybrid materials using four types of clay minerals, montmorillonite, saponite, hectrite, and synthetic mica. The mechanical properties of their injection molded specimens were measured according to ASTM. Nylon 6-clay hybrid using montmorillonite was superior to the other hybrids in mechanical properties. This might result from the difference in the interaction between nylon molecules and silicates in the hybrids. To clarify this hypothesis, we synthesized intercalated compounds of the clay minerals with glycine as the model of the hybrids, and analyzed the interaction using ¹⁵N cross polarization magic angle spinning (CP/MAS) NMR spectroscopy. The ¹⁵N-NMR result reveals that the positive charge density on the nitrogen of the intercalated compound based on montmorillonite was largest in all the intercalated compounds. It was suggested that montmorillonite interacted strongly with nylon 6 by ionic interaction. This ionic interaction was one of the reasons why these hybrid materials had superior mechanical properties. © 1995 John Wiley & Sons, Inc.