Solvent free mechanochemical synthesis of MnO2 for the efficient degradation of Rhodamine-B

MnO₂ nanorods were synthesized by mechanochemical processing with subsequent heat treatment and their photocatalytic activity was studied on the decolourization of aqueous solution of Rhodamine B at different pH levels. A solid state redox reaction 2KMnO₄ + MnCl₂ → 3MnO₂ + 2KCl + O₂ was activated during mechanical milling. Excess KCl salt was added in the starting powder mixture to prevent agglomeration of MnO₂ nanoparticles. The milling resulted in the production of amorphous MnO₂ nanoparticles with a high surface area of 204 m² g^?1. Crystalline MnO₂ nanorods of diameters about 15–20 nm were produced by heating the as-milled powder at 350 °C for 1 h in air. Amorphous MnO₂ nanoparticles showed higher degradation rate of Rhodamine B than crystalline MnO₂ nanorods under simulated sunlight. The degradation rate was higher under acidic conditions. This work demonstrates the potential for cost effective, green and scalable synthesis of MnO₂ nano-catalysts for environmental applications.     

Very high temperature annealing effect on amorphous carbon films grown on refractory oxide substrates by pulsed laser deposition

We have carried out very high temperature heat treatment at 1400–2700 °C of about 10 nm-thick amorphous carbon thin films deposited on refractory substrates MgO, Al₂O₃, and yttria-stabilized zirconia (YSZ) using pulsed laser deposition techniques. After the annealing, a few nanometer scale sp² crystallization of the films and a large corrugation with a height of more than 1 μm were observed by Raman spectroscopy analysis and optical/atomic force microscopes, respectively. The corrugation is probably caused by the formation of gases at the film/substrate interface during the heat treatment.     

Steam gasification of coal cokes in an internally circulating fluidized bed of thermal storage material for solar thermochemical processes

A laboratory-scale prototype windowed internally circulating fluidized-bed reactor made of quartz sand and coal coke particles was investigated for steam gasification using concentrated Xe-light radiation as the energy source. The quartz sand was used as a chemically inert bed material for the fluidized bed, while the coal coke particles functioned as the reacting particles for the endothermic gasification reaction. The advantages of using quartz sand as the bed material for the directly irradiated gasification reactor are as follows: (1) The bed height is maintained at a constant level during the gasification. (2) The quartz sand functions as a thermal transfer/storage medium inside the reactor. The gasification performances such as the production rates of CO, H₂, and CO₂; carbon conversion; and light-to-chemical energy conversion were evaluated for the fluidized-bed reactor with a thermal transfer/storage medium (quartz sand). The effects of using the bed material (quartz sand) on the gasification performance are described in this paper.     

Preparation of poly(thiophene-alt-pyrrole) bearing chiral LC group

ABSTRACT

Preparation of poly(thiophene-alt-pyrrole bearing mesogen) was carried out with Migita–Kosugi–Stille coupling type polycondensation with an aid of Pd(0) complex catalyst. The resultant polymer shows lyotropic liquid crystallinity with good film-forming property. The smectic fan-shaped texture is maintained after completion of evaporation of solvent from the polymer solution. The cast film having liquid crystal (LC) order shows light emission function upon irradiation of excitation light at 460 nm. The polymer shows LC domain emission. Mechanical orientation allows to yield LC domain aligned film with band structure. Chiral mesogenic side chain induces π-conjugated main chain helicity from distance in molecular level.     

Iterative Learning Control Using Adjoint Systems and Stable Inversion

In this paper, we investigate iterative learning control (ILC) for non‐minimum phase systems from a novel viewpoint. For non‐minimum phase systems, the magnitude of a desiredinput obtained by ILC using forward‐time updating and Silverman's inversion are too large because of the influence of the unstable zeros. On the other hand, stable inversion constructs a bounded desired input by using non‐causal inverse for non‐minimum phase systems. In this paper, we first clarify that ILC using an adjoint system achieves the desired input defined by stable inversion. Hence, ILC using an adjoint system is an effective method for the control of non‐minimum phase systems with uncertainty. However, a useful convergence condition of ILC using an adjoint system was not achieved. Next, we develop a simple convergence condition in the frequency domain.     

Regeneration characteristics of desiccant rotor with microwave and hot-air heating

Microwave heating, because of its advantages of direct and rapid heating of materials, has the potential to be employed as a novel regeneration method of desiccant rotors in humidity conditioners. We proposed a combined regeneration process, which combines microwave heating and conventional hot-air heating. The system is expected to achieve high heating rate during an initial regeneration period by assisting water desorption using the additional energy of the microwave. In this study, the regeneration characteristics of a desiccant rotor were experimentally investigated under conditions of microwave heating, hot-air heating, and combined heating at various microwave powers and hot-air temperatures. The effectiveness of the combined regeneration was evaluated in terms of the regeneration ratio, the initial regeneration rate, the temperature distribution in the rotor, and finally in terms of the energy consumption. It was demonstrated that combined heating was effective at leveling non-uniform temperature distribution in the rotor. Combined heating achieved higher ratios and initial rates in regeneration compared to just microwave and hot-air heating. This result was obviously attributed to the additional input of microwave energy, resulting that average rotor temperature increased by microwave absorption of rotor. Moreover, it was also effective for enhancement of regeneration to level the temperature distribution in the rotor by combination of two heating methods with different heating mechanisms. Both the initial regeneration rate and the equilibrium regeneration ratio for combined heating were found to increase as the microwave power increased. A linear relationship was observed with respect to microwave power. From the viewpoint of energy consumption, it may be possible to apply combined and microwave heating to humidity control systems that switch between adsorption and regeneration in short cycle times, if the conversion and absorption efficiencies of the microwave are significantly improved.     

A behavioral model for optically powered OCT endoscope with a micro electrostatic vertical‐comb optical scanner

This paper presents a novel device architecture for optically actuated microelectromechanical systems (MEMS) endoscopes for optical coherence tomography (OCT) measurement. A 10‐mW infrared light beam at a wavelength of 1.5 µm is transferred through the single‐mode fiber to provide a scanning MEMS mirror with the drive voltage (maximum 11 V) by exciting a photovoltaic cell, while also providing with a secondary light beam at a wavelength of 1.3 µm for the OCT measurement. An electrostatic vertical comb‐drive optical scanner (1.5 mm × 2.0 mm × 0.5 mm) has been developed by using the deep reactive ion etching (DRIE) of a silicon‐on‐insulator (SOI) wafer. The design of the scanner module is discussed, along with the experimental results of electrostatic operation. An equivalent circuit model for the optical scanner is developed to explain the behavior of the optically powered actuation mechanism, including the hysteresis loop in the frequency response and the voltage dependence of oscillating angle (mechanical peak ±3.2°/7 V around the resonance frequency of 250 Hz). OCT measurement of a tissue is demonstrated to reconstruct the cross‐sectional image of a fingerprint at a resolution of lateral 40 µm × vertical 8 µm and penetration depth of 2.5 mm. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A PSS‐Free PEDOT Conductive Film Supported by a Hierarchical Nanoporous Layer Glass

The importance of transparent conductive film is increasing due to its use in applications such as touch‐panel devices. Although indium tin oxide is widely used because of its high conductivity and transparency, conductive polymers are being studied as alternative materials that avoid the use of rare metals and the brittleness associated with existing systems. Polyethylene dioxythiophene (PEDOT)/polyethylene sulfonic acid (PSS) is drawing a lot of attention due to its well‐balanced conductivity, transparency, film formability, and chemical stability. The nonconductive PSS reportedly covers the conductive PEDOT. The PSS shell provides carrier and film‐formability to PEDOT but is also a barrier that hinders electrical conductivity. Therefore, the PEDOT film formability is explored supported by a substrate without the addition of PSS. The “hierarchical nanoporous layer glass” holds the PSS‐free PEDOT with its nanopores to form a homogeneous, transparent film. The PSS‐free PEDOT film thus achieves transparency of over 85% and resistivity of below 500 Ω sq^?1.     

Pore-scale visualization of gas trapping in porous media by X-ray CT scanning

Entrapment of the non-wetting phase in porous media has been observed in a variety of fields such as petroleum engineering, geological storage of carbon dioxide, and remediation of ground water. We investigated gas trapping in porous media from a microscopic point of view. High-resolution, three-dimensional images of pore structure and trapped gas bubbles in Berea sandstones were obtained using a micro-focused X-ray CT scanner. We used vertical and horizontal Berea sandstone cores, 8 mm in diameter and 15 mm long. Based on the three-dimensional image analysis, the statistical distribution of the trapped gas volume was estimated. Trapped bubbles have a pore-network scale size and distribute over several pores. In the case of the vertical core, the porosity fluctuates along the flow direction due to the layered structure. The residual gas saturation also fluctuates with porosity along the flow direction. The higher gas saturation in porous layers at the end of gas injection results in a higher trapped gas saturation compared to dense layers. On the other hand, in dense layers the gas saturation at the end of gas injection is almost the same as residual gas saturation. Therefore, most of the gas injected into the dense layers would be trapped. In the case of the horizontal core, the gas saturation at the irreducible water condition is lower than that for the vertical core, because the injected gas selectively passes through the more permeable layers. However, the residual gas saturation is 29.2% for the horizontal core, which is comparable with that for the vertical core (30.9%). Finally, the effect of capillary number on stability of trapped gas bubbles has been estimated. Trapped gas bubbles are stable against the increased flow rate up to a capillary number of 1.0×10^?5.     

Co-continuous monolithic titania prepared by organic polymer monolith as pore template

We achieved preparation of co-continuous titania based monolithic materials using several organic polymer monoliths as pore templates. Firstly, the organic polymer monoliths that had well controlled structures were prepared, and filled the pores of polymer monolith with tetra-n-butyl titanate (titan monomer). The following hydrolysis of the titan monomer resulted in titanium dioxide. The polymer monolith was removed by calcination at elevated temperature. We carefully studied the utility of polymer monolithic template, filling method of the titan monomer, and calcination conditions to realize co-continuous titania monolith. In addition, by the change of domain size (size of a skeleton + size of through a pore) of template, we were able to control domain size of the resulting titania monoliths.