Decomposition of ammonia with iron and calcium catalysts supported on coal chars

Decomposition of NH₃ to N₂ with Fe and Ca catalysts supported on brown coal chars has been studied with a cylindrical quartz reactor from a viewpoint of hot gas cleanup. The catalyst is prepared by pyrolyzing a brown coal with Fe or Ca ions added. In the decomposition of 2000 ppm NH₃ diluted with He at 750 °C and at a space velocity of 45,000 l/h, 2-6 wt% Fe catalysts are more active than not only 6 wt% Ca catalyst but also 8 wt% Fe catalyst loaded on a commercial activated carbon. The transmission electron microscope observations show that fine iron particles with the sizes of 20-50 nm account for the higher catalytic performances. When reaction temperature is increased to 850 °C, all of Fe and Ca catalysts on the chars achieve complete decomposition of NH₃. The co-feeding of H₂ with 2000 ppm NH₃ improves the performance of the 2% Fe catalyst at 750 °C, but contrarily the coexistence of syngas (CO/H₂=2) deactivates it remarkably, whereas the addition of CO₂ to syngas restores the catalytic activity of the Fe to the original state without syngas. The powder X-ray diffraction and temperature programmed desorption measurements strongly suggest that the Fe and Ca catalysts promote NH₃ decomposition through cycle mechanisms involving the formation of N-containing intermediate species and the subsequent decomposition to N₂.     

Gibbs Energy Change of Carbothermal Nitridation Reaction of γ-AlON and Its Thermodynamic Stability

In order to determine the standard Gibbs energy change of carbothermal nitridation reaction of γ-aluminum oxynitride spinel, γ-AlON, the equilibrium N₂–CO gas compositions coexisting with γ-AlON, aluminum nitride (AlN), and graphite have been measured by means of gas chromatography at elevated temperatures. From the results obtained, the standard Gibbs energy change has been determined at temperatures ranging from 1912 to 2002 K , where γ-AlON is expressed as Al_{(64+ x )/3} V _{(8− x )/3}O_{32− x} N _x ( V : vacancy). Moreover, the thermodynamic stability in the homogeneous phase region of γ-AlON has been evaluated by a thermodynamic model of γ-AlON together with the experimental results.     

Role of a surfactant in the electrical potential oscillation across a liquid membrane

Electrical potential oscillation across a liquid membrane of a water/octanol/water system, in which a surfactant and ethanol are present in one of the waters, and electrical potential between octanol and aqueous phases of the octanol/water system were measured. On using sodium dodecyl sulfate (SDS) as the surfactant, potential oscillation was initiated with a sudden potential change toward the more negative potential. The upper potential (E_A,SDS) and lower potential (E_B,SDS) of the first oscillation were affected by the electrolyte added to the aqueous phase containing no previous surfactant. With hexadecyltrimethylammonium bromide (CTAB) as the surfactant, direction of the pulse was opposite that when using SDS. The lower potential (E_A,CTAB) and upper potential (E_B,CTAB) of The first oscillation were affected by the electrolyte. For instance, E_A,SDS and E_B,CTAB were greatly affected by halide ion size. In contrast, E_A,CTAB and E_B,SDS were only slightly affected by this parameter. The effects of the electrolytes on E_A,SDS and E_B,SDS were essentially the same as those on potentials at the interface between the octanol and aqueous phases of the octanol/water system in the absence of SDS (E_C,SDS) and presence of SDS (E_D,SDS), respectively. The effects of electrolytes on E_A,CTAB and E_B,CTAB were also basically the same as those on the potentials at the interface between the octanol and aqueous phases of the octanol/water system in the absence of CTAB (E_C,CTAB) and presence of CTAB (E_D,CTAB), respectively. Potential oscillation thus appears quite likely due to the repetitive formation and destruction of the surfactant layer adsorbed on the octanol/water interface.     

Effect of Sintering Additives on Superplastic Deformation of Nano-Sized β-Silicon Nitride Ceramics

The effect of sintering additives on superplastic deformation of nano-sized β-Si₃N₄ ceramics has been studied by compression tests at 1500°C. The sintering additives were (i) Y₂O₃+Al₂O₃; (ii) Y₂O₃+MgO; and (iii) Y₂O₃. Nano-sized Si₃N₄ ceramics with different sintering additives had similar microstructures. For the first two sintering additives, the stress exponents were determined to be ∼2 at a lower stress region and ∼1 at a higher stress region, where the strain rate was dependent on sintering additives only at the higher stress region, and was independent at the lower stress region. Nano-ceramics with Y₂O₃ additives had only one region, which had a stress exponent of ∼1 within the stress range that we studied. The results could be explained by the different deformation mechanisms at the higher and lower stress regions and the influence of viscosity of liquid phase on the transition stress.     

Novel Catalytic Properties of Rh Sulfide for the Synthesis of Methanol from CO + H2 in the Presence of H2S

Rh sulfide yielded 800 gkg-cat^–1h^–1 of methanol at 593 K and 5.1 MPa from CO + H₂ (syngas) even in the presence of H₂S 100 ppm in concentration. The obtained space-time yield of methanol was comparable with that obtained with a commercial Cu/Zn/Al catalyst at a conventional reaction condition (523 K and 5.1 MPa) from a feed containing both syngas and CO₂.     

Synthesis and Characterization of Diepoxyalkenes Derived from (3Z,6Z,9Z)-Trienes: Lymantriid Sex Pheromones and Their Candidates

All stereoisomers of three diepoxyalkenes derived from (3Z,6Z,9Z)-trienes with a C₂₁, C₁₉, or C₁₈ straight chain, lymantriid sex pheromones and their candidates, were synthesized by MCPBA oxidation of optically active epoxyalkadienes. Their chromatographic behaviors were examined with GC and LC equipped with achiral and chiral columns. Detailed inspection of the mass spectra of these epoxides indicated the following diagnostic ions for determining the chemical structures: m/z 128, 167, M-87 and M-85 for (Z)-cis-3,4-cis-6,7-diepoxy-9-enes; m/z 111, M-125 and M-69 for (Z)-cis-6,7-cis-9,10-diepoxy-3-enes; and m/z M-125 and M-139 for (Z)-cis-3,4-cis-9,10-diepoxy-6-enes. Mass chromatographic analysis that monitored these fragment ions revealed the existence of a new pheromonal compound with a C₂₁ chain in an extract from virgin females of a lymantriid species, Perina nuda F. The three diepoxyalkenes were converted into the corresponding DMDS adducts, which showed characteristic ions from fragmentation between the two thiomethyl groups, reflecting the position of an original double bond.     

Identification of Epoxyhenicosadiene and Novel Diepoxy Derivatives as Sex Pheromone Components of the Clear-Winged Tussock Moth Perina nuda

Four EAG-active components (A–D) were found in the solvent extract of virgin females of the clear-winged tussock moth, Perina nuda. The most abundant component (B, ca. 250 ng/female) was identified as (3Z,6S,7R,9Z)-6,7-epoxyhenicosa-3,9-diene by GC-MS analyses of the extract, chemical derivatization, and comparative chiral HPLC. Minor components also elucidated were (3Z,9Z)-cis-6,7-epoxyicosa-3,9-diene, (A); (3R,4S,6S,7R,9Z)-3,4-6,7-diepoxyhenicos-9-ene, (C); and its 3S,4R,6S,7R isomer, (D); with amounts of 0.4, 5, and 8 ngt/female, respectively. Component B showed weak attractiveness to male moths in the field. The attractiveness was significantly enhanced by addition of component(s) C and/or D. No males were captured with either the antipode of component B or its mixtures with the minor components. In this field test, noctuid Hypocala rostrata males were also attracted with the synthetic P. nuda pheromone.     

Modeling of hydrogen embrittlement in single crystal Ni

A large-scale molecular dynamics simulation by the embedded atom method was carried out on hydrogen embrittlement of a single crystal containing 1,021,563 nickel atoms. The details of the deformation in the specimen were identified by a new method of the deformation analysis. Plenty of slip deformation occurred around the crack tip and in the bulk of the hydrogen-free specimen. Hydrogen embrittlement was most serious in the specimen hydrogen-charged in the notched area. Serious embrittlement was also observed in the specimen hydrogen-charged in the slip planes, in which dislocation emission was localized at the crack tip and enhanced on the planes where hydrogen atoms were located. It is considered that the fracture process is due to the hydrogen-enhanced decohesion mechanism.     

NMR Measurements of a possible New Quantum Phase in 2D 3He

No Heading A monolayer of ³He adsorbed on graphite surface preplated with a monolayer of ⁴He constitutes an ideal model system for studying strongly correlated two-dimensional fermions. The system behaves as a fluid phase at low densities and as the density is increased, accompanied by a Mott localization, it approaches the 4/7 registered phase. Recent heat-capacity measurements suggest that before the Mott transition, there exists an intermediate hole-doped Mott localized phase. We started new NMR measurements focusing on this novel phase to verify its existence and characteristics. We measured the static magnetization of the system down to 10 mK as a function of density. The magnetization data continuously intervene the fluid phase and the 4/7 phase, and support the above mentioned scenario.PACS numbers: 67.70+n, 67.55.–s, 67.80.Jd, 71.10.Ay.     

Advances in Biological Liquid Crystals

Biological liquid crystals, a rich set of soft materials with rod‐like structures widely existing in nature, possess typical lyotropic liquid crystalline phase properties both in vitro (e.g., cellulose, peptides, and protein assemblies) and in vivo (e.g., cellular lipid membrane, packed DNA in bacteria, and aligned fibroblasts). Given the ability to undergo phase transition in response to various stimuli, numerous practices are exercised to spatially arrange biological liquid crystals. Here, a fundamental understanding of interactions between rod‐shaped biological building blocks and their orientational ordering across multiple length scales is addressed. Discussions are made with regard to the dependence of physical properties of nonmotile objects on the first‐order phase transition and the coexistence of multi‐phases in passive liquid crystalline systems. This work also focuses on how the applied physical stimuli drives the reorganization of constituent passive particles for a new steady‐state alignment. A number of recent progresses in the dynamics behaviors of active liquid crystals are presented, and particular attention is given to those self‐propelled animate elements, like the formation of motile topological defects, active turbulence, correlation of orientational ordering, and cellular functions. Finally, future implications and potential applications of the biological liquid crystalline materials are discussed.