Sensing-based risk mitigation control of hydrogen dispersion and accumulation in a partially open space with low-height openings by forced ventilation

This paper presents the real-time sensing-based risk-mitigation control of hydrogen dispersion and accumulation in a partially open space with low-height openings by forced ventilation. In the partially open space we previously considered (Matsuura et al., Int J Hydrogen Energy, 35(10), p. 4776–4786 (2010)), a hydrogen buoyant plume is subjected to cross flows during forced ventilation, and hydrogen travels over a long distance in the lower part of the space, which enhances the hydrogen concentration there. On the basis of those results, we alternatively propose in this paper a new partially open space that permits the almost vertical rising of hydrogen from a leak source, and exhausts, by forced ventilation, hydrogen temporarily accumulated near the roof. We first describe computational geometries and scenarios, mathematical models and numerical procedures.     

Zeta potential of alumina powders with different crystalline phases in simulated body fluids

The zeta potential of alumina (Al₂O₃) powder with different crystalline phases, prepared by heat treatment of boehmite, was measured in simulated body fluids in order to discuss the mechanism on in vivo formation of a calcium and phosphorus (CaP)-rich layer on bone cement containing δ-Al₂O₃-based bead powder. γ, δ, and θ-Al₂O₃ powders were obtained by heat treatment of boehmite powder at 600 °C, 900 °C, and 1025 °C, respectively. It was found that δ-Al₂O₃ gave a negative zeta potential in an acidic simulated body fluid, whereas γ-Al₂O₃ and θ-Al₂O₃ gave a positive potentials. During the bone fracture healing process, acidic conditions are maintained at the site of fracture for several days. Consequently, it is speculated that the negative surface potential of δ-Al₂O₃ in an acidic body fluid, similar to the fracture site, might be responsible for the in vivo formation of the CaP-rich layer on the overlying bone cement, given that the negatively charged surface of δ-Al₂O₃ would attract calcium ions from the surrounding body fluid, thereby facilitating the formation of the CaP-rich layer.     

Processing of Al/SiC composites in continuous solid–liquid co-existent state by SPS and their thermal properties

Silicon carbide (SiC)-particle-dispersed-aluminum (Al) matrix composites were fabricated in a unique fabrication method, where the powder mixture of SiC, pure Al and Al–5mass% Si alloy was uniquely designed to form continuous solid–liquid co-existent state during spark plasma sintering (SPS) process. Composites fabricated in such a way can be well consolidated by heating during SPS processing in a temperature range between 798 K and 876 K for a heating duration of 1.56 ks. Microstructures of the composites thus fabricated were examined by scanning electron microscopy and no reaction was detected at the interface between the SiC particle and the Al matrix. The relative packing density of the Al–matrix composite containing SiC was higher than 99% in a volume fraction range of SiC between 40% and 55%. Thermal conductivity of the composite increased with increasing the SiC content in the composite at a SiC fraction range between 40 vol.% and 50 vol.%. The highest thermal conductivity was obtained for Al–50 vol.% SiC composite and reached 252 W/mK. The coefficient of thermal expansion of the composites falls in the upper line of Kerner’s model, indicating strong bonding between the SiC particle and the Al matrix in the composite.     

Excitons in organic-inorganic hybrid compounds (CnH2n + 1NH3)2PbBr4 (n = 4, 5, 7 and 12)

Thin films of microcrystalline (C_nH_2n + 1NH₃)₂PbBr₄ (n = 4, 5, 7 and 12) have been prepared by a modified spin-coating method, and the effect of the number of carbon atoms of the alkyl chain length (n) on optical properties has been investigated. Absorption spectra reveal that (C_nH_2n + 1NH₃)₂PbBr₄ films show stable excitons with a binding energy of a few hundred meV. The excitonic structure of (C_nH_2n + 1NH₃)₂PbBr₄ varies with the number of carbon atoms. The lowest-energy exciton splits into a few fine-structure levels at low temperature. (C_nH_2n + 1NH₃)₂PbBr₄ films (n = 5, 7 and 12) show not only singlet excitons but also triplet excitons at low temperature, while (C₄H₉NH₃)₂PbBr₄ films show only singlet excitons. The intersystem crossing from excited singlet state to triplet state plays an important role in the relaxation process of excitons.     

Water Network in Room-Temperature Ionic Liquid: <Emphasis Type="Italic">N,N</Emphasis>-Diethyl-<Emphasis Type="Italic">N</Emphasis>-Methyl-<Emphasis Type="Italic">N</Emphasis>-2-Methoxyethyl Ammonium Tetrafluoroborate

Crystal structures of room-temperature ionic liquid (RTIL)-H₂O mixtures are determined by the X-ray diffraction method. The RTIL is N,N-diethyl-N-methyl-N-2-methoxyethyl ammonium tetrafluoroborate, [DEME][BF₄]. At 0.9 mol pct H₂O, two kinds of superstructures occur simultaneously without a strain. Also, the volume of the unit cell is very small only at 0.9 mol pct additives. This relates to the composite domain structure, including a twin-related one, as an elastic anomaly. At other water concentrations, such an extraordinary behavior is not observable. By assuming a sublattice having an equivalent lattice constant, a water network at 1 mol pct H₂O is simulated using a Monte Carlo (MC) method. The network develops over the medium range in the simulation box.     

Reaction between magnesium ammine complex compound and lithium hydride

The possibility of using ammonia as a hydrogen carrier is examined for the reaction between magnesium ammine complex MgCl₂(NH₃)₆ and lithium hydride LiH. Sample was milled at low temperature of −40 °C to avoid decomposition of MgCl₂(NH₃)₆ during the milling. The effects of milling time, milling speed (revolutions per minute), and catalysts on hydrogen storage properties were investigated by thermogravimetry, thermal desorption mass spectroscopy, and X-ray diffraction experiments. Experimental results indicated that a milled composite of Mg(NH₃)₆Cl₂ and catalyzed-LiH desorbed the ∼100% H₂ gas even at 125 °C in a closed system. The reverse reaction also proceeded by separately cooling MgCl₂ at lower temperature than 100 °C and heating LiNH₂ at 300 °C in the closed system.     

Recycling Technology for a Recycling Society and the Consumer's Expected Consciousness: Recycling from the Viewpoint of Four Items of Home Appliances

The concept of ‘recycling’ was adopted to solve the overuse of resources by mass production and mass consumption of products in the 20th century. In the latter half of the 20th century, all companies started recycling activities slowly but positively, and some of them established their own recycling plants. This article introduces the processes through which used home appliances are made into materials (for reuse), and the machines, facilities, and methods for such reuse, as well as the results of their actual application by the study of a recycling plant. It is expected that this article would motivate the readers for recycling and to consider and feel what we, consumers, should do. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Nitrogen-doped titanium dioxide photocatalysts for visible response prepared by using organic compounds

In order to utilize visible light in photocatalytic reactions, nitrogen atoms were doped in commercially available photocatalytic TiO₂ powders by using an organic compound such as urea and guanidine. Analysis by X-ray photoelectron spectroscopy (XPS) indicated that N atoms were incorporated into two different sites of the bulk phase of TiO₂. A significant shift of the absorption edge to a lower energy and a higher absorption in the visible light region were observed. These N-doped TiO₂ powders exhibited photocatalytic activity for the decomposition of 2-propanol in aqueous solution under visible light irradiation. The photocatalytic activity increased with the decrease of doped N atoms in O site, while decreased with decrease of the other sites. Degradation of photocatalytic activity based on the release of nitrogen atoms was observed for the reaction in the aqueous suspension system.     

Microstructure and hydrogen desorption characteristics of hydrogenated ScH2–MBn (M = Mg and Ca) systems synthesized by mechanical milling

The mixtures of scandium hydride ScH₂ and metal boride MB_n, which is MgB₂ or CaB₆, were hydrogenated by mechanical milling under hydrogen pressure at room temperature. ScH₂–MgB₂ and ScH₂–CaB₆ desorbed 3.4 and 2.3 mass% of H₂, respectively, with peaks below 300 °C. The results of synchrotron radiation X-ray powder diffraction and X-ray absorption spectroscopy at the Sc K-edge indicated that ScB₂ was produced by milling. Fourier-transform infrared spectroscopy suggested that hydrogen was stored as B–H bonds in the as-milled samples. Nuclear magnetic resonance spectroscopy clarified the presence of metal borohydrides M(BH₄)₂ (M = Mg and Ca) in the as-milled ScH₂–MB_n mixtures. These results indicate that M(BH₄)₂ is synthesized by milling the ScH₂–MB_n mixtures under hydrogen pressure at room temperature, and hydrogen was desorbed from M(BH₄)₂. The by-products of M(BH₄)₂ are MgH₂ in the M = Mg case, which was observed by transmission electron microscopy, and ScB₂ in both cases.