Fabrication of electrochemically stable fluorinated nano-carbon film compared with other fluorinated carbon materials

We fabricated electrochemically stable fluorinated nano-carbon film that had an sp² and sp³ hybrid nanocrystalline structure formed using the electron cyclotron resonance (ECR) sputtering method. This fluorinated ECR (F-ECR) nano-carbon film prepared with a short CF₄ plasma treatment has a high fluorine content (F/C:0.20) and a low oxygen content (O/C:0.02) on its surface and retains its original morphology. This F-ECR nano-carbon is capable of a lower capacitance current, and a wider potential window than untreated ECR nano-carbon. The electron transfer rates at an F-ECR electrode are as high as those of untreated carbons for , whereas they are much slower than those of untreated ECR nano-carbon for Fe^2+/3+ and owing to its selective sp² fluorination. These slow electron transfer rates for Fe^2+/3+ and are maintained during potential cycles due to its robust nanocrystalline structure. In contrast, these slow electron transfer rates were easily recovered for fluorinated glassy carbon under same condition. Furthermore, a smaller fluorination effect was observed for polycrystalline boron-doped diamond owing to the low reactivity of its sp³ bonds. Our ECR nano-carbon film is suitable for the effective fabrication of a fluorinated surface while maintaining a relatively active electrochemical interface and excellent stability.     

Cathodic performance of LiMn1−xMxPO4 (M = Ti, Mg and Zr) annealed in an inert atmosphere

To improve the cathodic performance of olivine-type LiMnPO₄, we investigated the optimal annealing conditions for a composite of carbon with cation doping. Nanocrystalline and the cation-doped LiMn_1−xM_xPO₄ (M = Ti, Mg, Zr and x = 0, 0.01, 0.05 and 0.10) was synthesized in aqueous solution using a planetary ball mill. The synthesis was performed at the fairly low temperature of 350 °C to limit particle size. The obtained samples except for the Zr doped one consisted of uniform and nano-sized particles. The performance of LiMnPO₄ was much improved by an annealing treatment between 500 and 550 °C with carbon in an inert atmosphere. A small amount of metal-rich phosphide (Mn₂P) was detected in the sample annealed at 900 °C. In addition, 1 at.% Mg doping for Fe enhanced the rate capability in our doped samples. The discharge capacity of LiMn_0.99Mg_0.01PO₄/C was 146 mAh/g at 0.1 mA/cm² and 125 mAh/g even at 2.0 mA/cm².     

Arsenic leaching from mulch made from recycled construction and demolition wood and impacts of iron-oxide colorants

Mulch made from recycled construction and demolition (C&D) wood has been reported to contain elevated levels of arsenic from inadvertent inclusion of chromated copper arsenate (CCA)-treated wood. Such mulch is also commonly colored with iron oxide, a compound known to bind arsenic. The objectives of this study were to quantify the releases of arsenic from mulch made from C&D wood, to evaluate the impacts of an iron-oxide colorant in potentially decreasing arsenic leaching rates, and to evaluate the relative significance of additional variables on leachate concentrations. Atotal of 3 sets of mulch samples (0%, 5%, or 100% CCA-treated wood) were prepared containing a sample either with or without colorant addition. Each sample was subjected to two tests: a field leaching test and the Synthetic Precipitation Leaching Procedure (SPLP). Results showed that arsenic concentrations in the field leachate from the 0% treated wood mulches were consistently low (<0.003-0.013 mg/L) whereas leachates from 5 and 100% treated wood mulches were characterized by higher arsenic concentrations (0.059-2.23 mg/L for 5%; 0.711-22.7 mg/L for 100%). The mass of arsenic leached from the field samples during the 1-year monitoring period was between 10 and 15% of the initial mass of arsenic. The colorant reduced the leaching of arsenic by more than 20% for the field leachate and 50% for the SPLP leachate, on average. However, the study showed that the effect may not last for long periods. Besides colorant addition other factors were observed to affect the amount of arsenic leached from contaminated mulch. These include the proportion of CCA-treated wood in the mulch, time, and pH of rainfall.     

Possibility of Thermal Protection in Earth Re-entry Flight by MHD Flow Control with Air-Core Circular Magnet

The possibility of thermal protection in an earth re-entry flight by the magnetohydrodynamic (MHD) flow control with an air-core circular magnet producing about 1 T or less on the wall surface of a space vehicle is examined by r-z two-dimensional numerical simulations. The present study adopts a hemisphere with a radius of 1.0 m as the nose shape of a space vehicle. The numerical results show that aerodynamic heating can be reduced by the MHD flow control with an air-core circular magnet, and also that the maximum wall heat flux and the effect of the MHD flow control become prominent with the magnitude of coil current and the flight altitude. Furthermore, it is found that there is an optimum magnet size to maximize the effect of MHD flow control under constant exciting magnetic energy, and also the optimum size gets reduced with the decrease in the flight altitude. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Measurement of Young’s Modulus and Poisson’s Ratio of Thermal Barrier Coating Based on Bending of Three-Layered Plate

Thermal barrier coatings (TBCs) are used to protect the hot sections of gas turbine engines and airplane engines. A TBC system comprises a substrate, bond coat, and TBC topcoat. The development of an accurate method for determining the Young’s modulus and Poisson’s ratio of TBC using a multilayered specimen is of importance. In this study, we applied the bending theory of a laminated plate to a three-layered material and proposed models to determine the Young’s modulus and Poisson’s ratio of the TBC layer using the bending strain of the TBC system specimen. Three methods were developed by utilizing (i) the coating biaxial strain, (ii) substrate biaxial strain, or (iii) coating and substrate biaxial strains. Subsequently, we determined appropriate dimensions of the specimen and span by using three-dimensional finite element analysis, and numerically verified the usefulness of the three proposed methods. However, the Young’s modulus and Poisson’s ratio determined using the multilayered specimen with a substrate are sensitive to experimental errors. Therefore, we evaluated the sensitivity of the three proposed methods to experimental error, and we determined the most insensitive method among them. Finally, we experimentally demonstrated the usefulness of this method.     

Durable Ultraflexible Organic Photovoltaics with Novel Metal‐Oxide‐Free Cathode

Flexible and stretchable organic photovoltaics (OPVs) are promising as a power source for wearable devices with multifunctions ranging from sensing to locomotion. Achieving mechanical robustness and high power conversion efficiency for ultraflexible OPVs is essential for their successful application. However, it is challenging to simultaneously achieve these features by the difficulty to maintain stable performance under a microscale bending radius. Ultraflexible OPVs are proposed by employing a novel metal‐oxide‐free cathode that consists of a printed ultrathin metallic transparent electrode and an organic electron transport layer to achieve high electron‐collecting capabilities and mechanical robustness. In fact, the proposed ultraflexible OPV achieves a power conversion efficiency of 9.7% and durability with 74% efficiency retention after 500 cycles of deformation at 37% compression through buckling. The proposed approach can be applied to active layers with different morphologies, thus suggesting its universality and potential for high‐performance ultraflexible OPV devices.     

Ultrathin Organic Electrochemical Transistor with Nonvolatile and Thin Gel Electrolyte for Long‐Term Electrophysiological Monitoring

Skin‐based electrical‐signal monitoring is one of the basic and noninvasive diagnostic methods for observing vital signals that contain valuable information about the dynamic status of the inner body. Soft bioelectronic devices are developed for the acquisition of high‐quality biosignals by taking advantage of their inherent thin and soft bodies. Among these devices, the organic electrochemical transistor (OECT) is a promising local transducing amplifier because of its key advantages, such as low operating voltage, high transconductance, and biocompatibility. However, the transistor's direct electrolyte‐gated operation limits its ability to measure biosignals only when the electrolyte exists. Here, an ultrathin OECT‐based wearable electrophysiological sensor based on a thin (≈6 µm) and nonvolatile gel electrolyte is reported, which can operate on dry biological surfaces. This sensor can measure biopotentials with a high mechanical stability and high signal‐to‐noise ratio (24 dB) even from dry surfaces of the human body and also shows stable performance during long‐term continuous monitoring and multiple reuse in a test that lasted more than a week.     

Real-time ball-position measurement using multi-view cameras for live football broadcast

Multimedia Tools and Applications - We developed a robust ball-position-measurement system that can be used for actual football games. It measures the positions of a ball by integrating tracking...