Raman Spectroscopic Studies on the Formation Mechanism of Hydrous-Zirconia Fine Particles

The Raman spectra of hydrous-zirconia fine particles produced by the hydrolysis of various ZrOCl₂ solutions were investigated. The Raman spectra of hydrous zirconia synthesized at HCl concentrations below 1 mol/L were similar to those of monoclinic, crystalline ZrO₂; those of hydrous zirconia synthesized at HCl concentrations greater than 1 mol/L showed a crystal structure change. The line width of the Raman bands increased with increasing H⁺ ion concentration. Analyzing the relationship between Raman band width and particle size revealed that the primary particle size of hydrous zirconia was controlled by the H⁺ and Cl⁻ ions, because these ions interfered with the polymerization in a hydrolysis reaction. Based on the experimental results, the formation mechanism for primary particles of hydrous zirconia was determined.     

Synthesis of High Density and Transparent Forsterite Ceramics Using Nano-Sized Precursors and Their Dielectric Properties

Forsterite (Mg₂SiO₄) ceramics were prepared using Mg(OH)₂ and SiO₂ as precursors, and the effect of powder characteristics of Mg(OH)₂ on calcination and sintering was investigated. The use of highly dispersed Mg(OH)₂ powder (HD powder) resulted in a lower calcination temperature. Forsterite powder of high homogeneity and small particle size prepared from the HD powder enabled synthesis of high-density forsterite ceramics by ordinary sintering without applying external pressure. Moreover, transparent forsterite ceramics were successfully synthesized through addition of excess Mg to the precursors to compensate for Mg evaporated during the sintering process. Subsequent dielectric measurements revealed that the transparent forsterite ceramics had a very low dielectric loss (tan δ<10⁻⁴).     

Evaporation characteristics of multi-component fuel

The maximum liquid phase penetration and evaporation behavior was investigated by using simultaneous measurement for mie-scattered light images and shadowgraph ones. The objective of this study was to analyze effect of variant parameters and fuel properties on evaporation behavior, and to investigate liquid phase penetration for the single- and multi-component fuels. The experiments were conducted in a constant-volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector. It was observed that: liquid phase length is influenced by fuel properties. High-boiling point fuel within the multi-component fuel controls liquid phase length.     

Syntheses of group 4 transition metal complexes bearing 2-pyridinethiolate ligands and their catalytic activities for ethylene polymerization

Titanium bis(2-pyridinethiolate) complexes, Ti(6-R-SPy)₂(NMe₂)₂ (6-R-SPy = 6-R-2-pyridinethiolate, 3a: R = H; 3b: R = Me; 3c: R = Ph; 3d: R = C₆H₄-4-Me; 3e: R = C₆H₄-4-t-Bu; 3f: R = C₆H₃-3,5-Me₂), and the titanium bis(2-pyridinolate) complexes, Ti(6-Ph-OPy)₂(NMe₂)₂ (6-Ph-OPy = 6-phenyl-2-pyridinolate, 8) were prepared by treating Ti(NMe₂)₄ with 2 equiv. of 6-R-2-pyridinethiol or 6-Ph-2-pyridinol. The cis-configuration of the diamido moieties in the pseudo octahedral geometry was elucidated by X-ray crystallography for 3a. Reaction of M(NMe₂)₄ (M = Ti, Zr) with 4 equiv. of 2-pyridinethiol cleanly gave tetrakis(pyridinethiolate) complexes, M(6-H-SPy)₄·THF (6: M = Ti; 7: M = Zr). The triangular dodecahedral geometries of 6 and 7 were also revealed by X-ray crystallography. These complexes catalyzed ethylene polymerization upon activation with MAO (methylaluminoxane) or MMAO (modified MAO). The catalytic activities of titanium bis(6-aryl-pyridinethiolate) systems were found to be remarkably higher than that of titanium bis(6-methyl-pyridinethiolate) system. Among the complexes synthesized in this study, Ti[6-(C₆H₃-3,5-Me₂)-SPy]₂(NMe₂)₂ (3f)/MMAO showed the highest activity (1200 kg/Ti-mol h atm) for ethylene polymerization at 60 °C under atmospheric pressure. In contrast, the activity of the corresponding 6-aryl-pyridinolate system 8/MMAO was rather low (9.3 kg/Ti-mol h atm). Both the N-S chelating structure and the bulky aryl substituents are essential for the high activities of the 6-aryl-pyridinethiolate complexes.     

Effect of Composition on the Oxygen Tracer Diffusion in Transparent Yttrium Aluminium Garnet (YAG) Ceramics

The grain boundary structure and oxygen tracer diffusion in transparent yttrium aluminum garnet (YAG) ceramics varying from 2% excess of Y₂O₃ to 0.5% excess of Al₂O₃ were studied. The characterization of the specimens is as follows: (i) For the Y₂O₃-excess specimen, a second phase (yttrium aluminum perovskite: YAP) containing silicon in the grain boundary was found, (ii) For the Al₂O₃-excess specimen, both aluminum-rich particles (alumina) and a silicon-rich segregant layer were observed in the grain boundary. The volume diffusion of the oxygen tracer is little influenced by the excess composition. In contrast, the grain boundary diffusion of the oxygen tracer is suppressed in the Y₂O₃-excess specimens, compared to Al₂O₃-excess specimens. These differences are thought to result from the chemical reaction between the second phase and the intergranular liquid phase during the sintering.     

Microbial degradation of cyanobacterial cyclic peptides

Bacterial strain B-9 possesses hydrolytic enzymes capable of degrading microcystins (MCs) and nodularin that are toxic cyclic peptides produced by cyanobacteria. In the present study, the degradation activities of the cell extract of B-9 against non-toxic cyanobacterial cyclic peptides other than the MCs and nodularin were investigated, and the degradation products were analyzed by liquid chromatography/ion trap tandem mass spectrometry (LC/ITMS). It was confirmed that B-9 could also degrade these cyanobacterial cyclic peptides by hydrolysis of their peptide bonds. These results indicated that this bacterium possesses a very unique hydrolytic activity that can degrade structurally different cyclic peptides and that this may be effective for the detoxification of hazardous cyclic peptides.     

Liquid-liquid transition without macroscopic phase separation in a water-glycerol mixture

The existence of more than two liquid states in a single-component substance and the ensuing liquid-liquid transitions (LLTs) has attracted considerable attention because of its counterintuitive nature and its importance in the fundamental understanding of the liquid state. Here we report direct experimental evidence for a genuine (isocompositional) LLT without macroscopic phase separation in an aqueous solution of glycerol. We show that liquid I transforms into liquid II by way of two types of kinetics: nucleation and growth, and spinodal decomposition. Although liquid II is metastable against crystallization, we could access both its static and dynamical properties experimentally. We find that liquids I and II differ in density, refractive index, structure, hydrogen bonding state, glass transition temperature and fragility, and that the transition between the two liquids is mainly driven by the local structuring of water rather than of glycerol, suggesting a link to a plausible LLT in pure water.     

Fabrication of dielectric nanocubes in ordered structure by capillary force assisted self-assembly method and their piezoresponse properties

Ordered structures of barium titanate (BT) nanocubes, strontium titanate (ST) nanocubes and BT/ST nanocubes mixture were directly fabricated on Si and Pt-coated Si substrates using a capillary force assisted assembly method. The morphology of self-assembled structures was observed using field emission scanning electron microscopy (FE-SEM) and scanning probe microscopy (SPM). It was revealed that nanocubes were arranged with various degrees of ordering to develop multilayer and monolayer regions at the surface of substrates. The elemental mapping of the structure consisting of the nanocubes mixture was also investigated by transmission electron microscopy (TEM) with an energy dispersive X-ray spectroscopy (EDX). It was revealed that BT and ST nanocubes coexisted homogeneously in the structure and had possibility to be arranged in order to each other. The piezoresponse properties obtained by scanning probe microscopy (SPM) indicated that the hetero-interface between BT and ST nanocubes would introduce anomaly in piezoelectric properties.     

Capacitance distribution of Ni-Nb-Zr-H glassy alloys

Capacitance distribution of {(Ni(0.6)Nb(0.4)(1-x)Zrx}(100-y)-Hy (x = 0.30, 0.35, 0.40, 0.45 and 0.50, 0 < or = y < or = 20) glassy alloy ribbons was carried out by ac impedance analysis at frequency of 1 kHz, in terms of a distributed constant equivalent circuit. The capacitance can be represented by oblique contour lines. The highest capacitance (1-11 microF) could be found near the point when x = 0.40, y = 10, which is a composition occurring room-temperature Coulomb oscillation, while capacitance of the composition (x = 0.35, y = 4) occurring ballistic transport was around 0.8 microF. The capacitance difference would be explained by an effect of hydrogen localization derived from morphology of distorted Zr-centered icosahedral Zr5Ni5Nb3 clusters and ideal Ni-centered clusters. The electrocapillarity equation showed that the specific capacitance between two electrodes increases parabolic with decreasing the distance, as a polarized glutinous liquid.