Maiko Nishibori

Resistive oxygen sensor using ceria-zirconia sensor material and ceria-yttria temperature compensating material for lean-burn engine.

Temperature compensating materials were investigated for a resistive oxygen sensor using Ce0.9Zr0.1O2 as a sensor material for lean-burn engines. The temperature dependence of a temperature compensating material should be the same as the sensor material; therefore, the Y concentration in CeO2-Y2O3 was optimized. The resistance of Ce0.5Y0.5O2-δ was independent of the air-to-fuel ratio (oxygen partial pressure), so that it was confirmed to function as a temperature compensating material. Sensor elements comprised of Ce0.9Zr0.1O2 and Ce0.5Y0.5O2-δ were fabricated and the output was determined to be approximately independent of the temperature in the wide range from 773 to 1,073 K.

Catalyst Combustors with B-Doped SiGe/Au Thermopile for Micro-Power-Generation

A micromachined thermoelectric (TE) power generator with a ceramic catalyst combustor operating at room temperature (RT) has been developed. A thermopile of 20 thin-film couples of B-doped Si0.8Ge0.2/Au and a Pt-loaded alumina ceramic thick-film catalyst combustor were integrated on a thin dielectric membrane, which was fabricated by bulk-Si wet etching. We have demonstrated a successful power generation of 0.26 µW using the micro-TE-generator with a fuel gas flow of 3 vol. % H2 in air, 1000 ccm, at RT.

Development of highly sensitive mechanoluminescent sensor aiming at small strain measurement

This paper was focused on the elasticoluminescence (ELS) characteristics, especially a response to small strain (below 1000 μst), of mechanoluminescence (ML) sensor using strontium aluminate doped with small amount of europium (SrAl2O4:Eu) synthesized by different methods. By using nitrate decomposition method as a synthetic method of SrAl2O4:Eu, the response to small strain of the ML sensor was enhanced in comparison with using a conventional solid-state reaction method. Based on SEM observation and thermoluminescence (ThL) measurement, we proposed a hypothesis that the sensing characteristic of small strain affect the plate-like shape of SrAl2O4:Eu grain and/or shallower carrier trap levels formed by nitrate decomposition method.

Solvent free oxidative coupling polymerization of 3-hexylthiophene (3HT) in the presence of FeCl3 particles

A solvent free oxidative coupling reaction of 3-hexylthiophene (3HT) within a nanocavity is reported. It is found that 3HT can be encapsulated in nanocavities larger than 1 nm, which corresponds to the size of the molecule. In this case, the side reaction at the 4-position in 3HT is regulated.

Solvent-free, improved synthesis of pure bixbyite phase of iron and manganese mixed oxides as low-cost, potential oxygen carrier for chemical looping with oxygen uncoupling

Abstract Chemical looping with oxygen uncoupling (CLOU) is the tendency of releasing gaseous oxygen of an oxygen carrier upon heating, which is the key property for the efficient and cleaner combustion of solid fuels for their wide exploitation for thermal power applications. The solvent-free, improved synthesis method was developed for the synthesis of pure bixbyite, FeMnO3 (Ia3̅, a=b=c=0.94 nm) as a low-cost, oxygen carrier by exposing of the abundantly available precursors (Fe3O4 and MnO) under inert- or reduction- atmosphere followed by air at 900°C. The bixbyite FeMnO3 showed the enhanced, stable multi-cycle CLOU performance than that of the physical mixture and it is converted into FeMn2O4 after the complete exhaustion of reactive oxygen under CLOU conditions. FeMnO3 showed the uniform elemental distribution of Fe, Mn and O, which facilitate the regeneration in air upon heating for multi-cycle performance. 3.2 wt.% of reactive oxygen can be obtained compared to the mass of FeMnO3 which is almost equal to the theoretical value under CLOU conditions. The lattice of FeMnO3 is altered linearly above 100°C with the increase of temperature, however; without the decomposition of the bixbyite phase and it was reinstated virtually upon cooling in air.

Preparation of High-Density Polymer Brushes with a Multihelical Structure

It is well-known that a mixture of isotactic and syndiotactic polymethyl methacrylate (PMMA) forms a stereocomplex consisting of a multihelical structure in which an isotactic chain is surrounded by a syndiotactic chain. Here, we report the basic structure of the stereocomplex formed when the syndiotactic PMMA chains are tethered to a silicon substrate and form a high-density polymer brush. The influence of geometric confinement was investigated by preparing the high-density polymer brushes on a flat and spherical substrate. In both cases, mixing the untethered isotactic PMMA with the grafted syndiotactic PMMA led to the formation of a stereocomplex with a multihelical structure. Static contact angle measurements showed a hindered surface mobility at the outermost surface of the polymer brush, indicating that the stereocomplex forms a crystalline structure. A syndiotactic polymer brush with substituted fluoroalkyl groups was prepared to increase the contrast for grazing incidence wide-angle X-ray diffraction (GIWAXD) measurements. The GIWAXD results verified that the stereocomplex forms a crystalline structure oriented perpendicular to the substrate with a relatively low degree of orientation.

Ground-State Copper(III) Stabilized by N-Confused/N-Linked Corroles: Synthesis, Characterization, and Redox Reactivity

Stable square planar organocopper(III) complexes (CuNCC2, CuNCC4, and CuBN) supported by carbacorrole-based tetradentate macrocyclic ligands with NNNC coordination cores were synthesized, and their structures were elucidated by spectroscopic means including X-ray crystallographic analysis. On the basis of their distinct planar structures, X-ray absorption/photoelectron spectroscopic features, and temperature-independent diamagnetic nature, these organocopper complexes can be preferably considered as novel organocopper(III) species. The remarkable stability of the high-valent Cu(III) states of the complexes stems from the closed-shell electronic structure derived from the peculiar NNNC coordination of the corrole-modified frameworks, which contrasts with the redox-noninnocent radical nature of regular corrole copper(II) complexes with an NNNN core. The proposed structure was supported by DFT (B3LYP) calculations. Furthermore, a π-laminated dimer architecture linked through the inner carbons was obtained from the one-electron oxidation of CuNCC4. We envisage that the precise manipulation of the molecular orbital energies and redox profiles of these organometallic corrole complexes could eventually lead to the isolation of yet unexplored high-valent metal species and the development of their organometallic reactions.

Bis-Copper(II)/π-Radical Multi-Heterospin System with Non-innocent Doubly N-Confused Dioxohexaphyrin(1.1.1.1.1.0) Ligand

A contracted doubly N-confused dioxohexaphyrin(1.1.1.1.1.0) complex consisting of two paramagnetic copper metals and open-shell π-radical ligand was synthesized as a new multi-heterospin motif. X-ray spectroscopy supported the divalent character of the inner copper centers, and electron paramagnetic resonance and magnetometric studies suggested the presence of unpaired d electrons strongly antiferromagnetically coupled with π-radicals delocalized on the macrocycle. The 25 π non-innocent dioxohexaphyrin ligand allowed the facile interconversion between antiaromatic 24 π and aromatic 26 π species, respectively, upon redox reactions.

Improved catalytic activity of PrMO3 (M = Co and Fe) perovskites: synthesis of thermally stable nanoparticles by a novel hydrothermal method

A novel and simple hydrothermal synthesis method using metal cyano complex precursors was demonstrated to synthesize nano-sized PrCoO3 and PrFeO3 perovskites. It was possible to achieve significantly improved catalytic properties, but more importantly with thermal stability and purity of perovskite phases in their nanoparticle form. These materials were characterized by means of X-ray powder diffraction, FE-SEM, HR-TEM as well as H2-TPR analysis, and evaluated for their catalytic activity towards CO oxidation reaction. Both the nanoperovskites were able to retain their morphology achieved through hydrothermal treatment, even after high temperature calcination. The catalytic activity of these materials was also compared with conventionally synthesised materials using a solid state method, as well as those reported in the literature. The superior catalytic activity of the PrCoO3 catalyst for CO oxidation over the PrFeO3 catalyst is mainly because of its better redox properties and may also be due to preferential adsorption of CO on PrCoO3 perovskite at low temperature. However, the marked improvement in catalytic activity for both nanoperovskites was primarily due to their improved surface area and better reducibility, which can be attributed to their nanoform. It appears possible to control the particle size as well as the shape of perovskites using this improved synthesis method, while more importantly, it was possible to reduce sintering and agglomeration of perovskites. While the method has potential to apply for synthesis of several other mixed oxide materials in nanoform, it will be important to investigate other physical properties of such thermally stable nanoperovskites.

Thermoelectric gas sensors of different catalyst oxides and heater metals

Thermoelectric hydrogen sensors with different catalyst oxides, Pt-Al2O3 and Pt-CeO2 have been prepared, and their gas sensing properties are investigated in the air and N2 flow. In air, the relationship between the sensor output and the gas concentration is a linear indicating the combustion only depends on the gas concentration in air. In N2 atmosphere, where the oxygen gas content of N2 source cylinder is below the industrial standard of 50 ppm, the sensor output shows also a linear relationship with the gas concentration, but depressed signal level. The microheater of the thermoelectric sensor has been prepared by the co-sputtering of tungsten and platinum to enhance the high temperature stability. The temperature coefficients of the Pt-W alloy multilayer heater were lowered to a half of the level of Pt.