Theoretical and experimental characterization of wettability of various nanolens arrayed polymer surfaces replicated with nanodimpled aluminum mold insert

Various types of polymer surfaces with a nanolens array, which has an entrant shape with a low aspect ratio, were fabricated and the wettability of the fabricated surfaces was evaluated in both theoretical and experimental ways. The nanolens array was replicated on three different polymer surfaces of polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), and polymethylmethacrylate (PMMA) by means of replica molding and hot embossing with a nanodimpled aluminum mold that was manufactured by a chemical oxidation process. From the theoretical and experimental evaluations of the wettability it was found that the measured contact angles were very similar with the theoretically estimated ones and also the hydrophilicity and hydrophobicity of the hydrophilic PMMA and hydrophobic PDMS, respectively, surfaces were reinforced by the nanolens array within the Wenzel wetting state.     

Computational Analysis of Oxide Ion Conduction in Orthorhombic Perovskite Structured La0.9A0.1InO2.95 (A = Ca,Sr and Ba)

Oxide ion conduction in orthorhombic perovskite structured oxides, La_0.9A_0.1InO_2.95 (A = Ca, Sr and Ba) is analyzed using molecular dynamics simulation. Factors influencing oxide ion conductivity of the compositions considered are analyzed using radial distribution function, bond energies between dopant and oxide ions, and the diffusion path. It is known that perovskite oxides with smaller ion size mismatch between host and dopant ions have higher electrical conductivities. However, exceptions exist, such as a La_0.9A_0.1InO_2.95 (A = Ca, Sr and Ba) system, where high electrical conductivities occur with large ion size mismatches. Based on this study, a dopant with smaller ion than host ion results in the formation of strong ionic bonds with oxide ions, suggesting that the A‐site dopant should be larger than the host ion for forming weaker O–A bonds. Consequently, the trade‐off between ion size mismatch and O–A bond needs to be considered for enhancing oxide ion conductivity of perovskite oxides.     

Simple fabrication of a Pd-P film on a polymer membrane and its catalytic applications

Composites were prepared by a surface activation by aerosol deposition of Pd nanoparticles (Pd nano seeds) on a poly(tetrafluoroethylene) membrane and subsequent Pd-P film formation by electroless deposition. Activation of the membrane processed by an ambient Pd spark discharge and subsequent fixation of the spark produced Pd nano seeds. Characterizations for electroless Pd-P films indicated that P entered into the crystal lattice of Pd and formed an alloy. The fabricated composites were applied to catalytic applications of formic acid oxidation (FAO) and toluene conversion (TC). The composite catalysts from the simple activation had more stable performances of FAO and TC than those from the conventional Sn-Pd activation, and their better performances might have originated from better purity due to the simple activation that only introduced pure Pd nano seeds.     

Development of an auto-welding system for CRD nozzle repair welds using a 3D laser vision sensor

A control rod device (CRD) nozzle attaches to the hemispherical surface of a reactor head with J-groove welding. Primary water stress corrosion cracking (PWSCC) causes degradation in these welds, which requires that these defect areas be repaired. To perform this repair welding automatically on a complicated weld groove shape, an auto-welding system was developed incorporating a laser vision sensor that measures the 3-dimensional (3D) shape of the groove and a weld-path creation program that calculates the weld-path parameters. Welding trials with a J-groove workpiece were performed to establish a basis for developing this auto-welding system. Because the reactor head is placed on a lay down support, the outer-most region of the CRD nozzle has restricted access. Due to this tight space, several parameters of the design, such as size, weight and movement of the auto-welding system, had to be carefully considered. The cross section of the J-groove weld is basically an oval shape where the included angle of the J-groove ranges from 0 to 57 degrees. To measure the complex shape, we used double lasers coupled to a single charge coupled device (CCD) camera. We then developed a program to generate the weld-path parameters using the measured 3D shape as a basis. The program has the ability to determine the first and final welding positions and to calculate all weld-path parameters. An optimized image-processing algorithm was applied to resolve noise interference and diffused reflection of the joint surfaces. The auto-welding system is composed of a 4-axis manipulator, gas tungsten arc welding (GTAW) power supply, an optimized designed and manufactured GTAW torch and a 3D laser vision sensor. Through welding trials with 0 and 38-degree included-angle workpieces with both J-groove and U-groove weld, the performance of this auto-welding system was qualified for field application.     

Removal of PM2.5 entering through the ventilation duct in an automobile using a carbon fiber ionizer-assisted cabin air filter

This study evaluated the charging characteristics of a carbon fiber ionizer for PM2.5 and carried out particle capture laboratory tests after an ionizer was installed upstream of the media of an electret cabin air filter. When the ion concentration per particle (N_i) of the carbon fiber charger was 10⁶ ions/cm³, the average charge numbers for each particle were 1.54, 0.88, and 0.49 at 0.6, 1.2, and 1.8 m/s of face velocity, respectively (the particle charging times, τ, were 167, 83, and 56 ms, respectively). For these face velocities, the PM2.5 removal efficiencies of the filter media were 69.3%, 65.2% and 62.2%, respectively, but increased to 80.4%, 71.2% and 65.5%, respectively, when the ionizer was turned on. The carbon fiber ionizer was then installed in front of an electret cabin filter in the air conditioning system of an automobile, after which field tests were performed at a roadside area. For the same N_iτ used in the lab-scale tests, the effects of the carbon fiber ionizer on increasing PM2.5 %Reduction were mild as 9.4%, 4.0%, and 2.8% when the flow rates were at the second, fourth, and sixth levels, respectively (the face velocities were 0.6, 1.2, and 1.8 m/s, respectively). The PM2.5 %Reduction can be substantially increased by 20–21%, for a higher value of N_iτ (=1.0×10⁸ ions s/cm³), which is realized by increasing the power consumption of the carbon fiber ionizer.     

Full wafer scale nanoimprint lithography for GaN-based light-emitting diodes

A UV-imprinting process for a full wafer was developed to enhance the light extraction of GaN-based green light-emitting diodes (LEDs). A polyvinyl chloride flexible stamp was used in the imprinting process to compensate for the poor flatness of the LED wafer. Two-dimensional photonic crystal patterns with pitches ranging from 600 to 900 nm were formed on the p-GaN top cladding layer of a 2 inch diameter wafer using nanoimprint and reactive ion etching processes. As a result, the optical output power of the patterned LED device was increased by up to 44% at a driving current of 20 mA by suppressing the total internal reflection and enhancing the irregular scattering of photons at the patterned p-GaN surface.     

Surface Modification of Exfoliated Layered Gadolinium Hydroxide for the Development of Multimodal Contrast Agents for MRI and Fluorescence Imaging

A novel method for modifying the surface of magnetic‐resonance‐contrasting layered gadolinium hydroxide (LGdH) is developed providing them with water‐ and bio‐compatibility and acid‐resistance, all of which are essential for medical applications. A stable colloid of exfoliated layers is synthesized by exchanging interlayer anions of LGdH with oleate ions. The delaminated layers are successively coated with phospholipids with poly(ethylene glycol) tail groups, and their effectiveness as a contrast agent for magnetic resonance imaging (MRI) is demonstrated. The adaptability of this surface modification approach for incorporating functional molecules and fabricating a fluorescent colloid of LGdH, which has the potential utility as a multimodal probe, is also demonstrated. This result provides a novel approach for expanding the applications of layered inorganic materials and developing a new class of MRI contrast agents.     

Effect of composite coating with poly-dopamine/PCL on the corrosion resistance of magnesium

We report the use of poly(ε-caprolactone) (PCL) and poly-dopamine (PD) as a protective coating that inhibits corrosion of the underlying magnesium metal. The PD coating layer also improved the adhesion of the PCL layer, which has been found to have a significant effect on corrosion behavior. In this study, electrochemical methods were employed to investigate the corrosion behavior of Mg after applying PCL composite coatings. Potentiodynamic polarization measurements determined that the PCL coating pretreated with PD effectively inhibited metal corrosion. In addition, the coating layer with improved adhesion has shown the possibility of inhibiting metal corrosion.