Michitaka Ohtaki

A mixed oxide (Zn1−xAlx)O exhibits promising thermoelectric properties attaining a dimensionless figure of merit ZT of 0.30 at 1000 °C, which value is much superior to other oxides and quite comparable to conventional state-of-the-art thermoelectric materials. The addition of a small amount of Al2O3 to ZnO results in a large power factor of 10–15×10−4 W/mK2, showing a marked increase in the electrical conductivity while retaining moderate thermoelectric power. A large product of the carrier mobi

Rapid progress in thermoelectric performance of oxide materials has been conducted virtually exclusively in Japan, resulting in more than 10 times increase in the ZT values of oxides within the last two decades. This has caused a revolutionary change in the guiding principles of thermoelectric materials research, in which oxide materials had been disregarded as a potential candidate until early 1990s. Promising oxide thermoelectric materials having been discovered include CaMnO3-based perovskite

Thethermoelectric properties of mixed oxides In2O3·MOx(MOx= Cr2O3, Mn2O3, NiO, ZnO, Y2O3, Nb2O5 SnO2) are investigated in terms of the thermoelectric materials at high temperature. The Seebeck coefficients,S, of all the samples have negative values, and those of In2O3·SnO2 and In2O3·ZnO increase linearly with temperature, attaining values of –90 and –210 µV K–1 at 1000 °C, respectively. The electrical conductivities, σ, of these oxides are significantly high. The power factor S2σ of the oxides h

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of polymer support on the substrate selectivity of covalently immobilized ultrafine rhodium particles as a catalyst for olefin hydrogenationMichitaka Ohtaki, Makoto Komiyama, Hidefumi Hirai, and Naoki ToshimaCite this: Macromolecules 1991, 24, 20, 5567–5572Publication Date (Print):September 1, 1991Publication History Published online1 May 2002Published inissue 1 September 1991https://doi.org/10.1021/ma00020a014RIGHTS & PERMISSIONSArticle Views2

Abstract Ultrafine particles of platinum were prepared as stable aqueous dispersions by a photoreduction method in the presence of soluble protective polymers. By use of the protective polymer with methyl acrylate residues as a reactive group, the polymer-protected ultrafine platinum particles were successfully immobilized onto crosslinked polymer supports with amino groups. The present immobilization was attributed to the formation of amide bonds by the reaction of methyl acrylate residues in t

Abstract Rhodium(III) ions in an aqueous solution were successfully photoreduced by ultraviolet light irradiation. In the presence of a soluble polymer or a surfactant as a protective agent, the stable dispersions of ultrafine metal particles of rhodium were prepared. Besides, the photoreduction proceeded on irradiation with visible light in the presence of ethanol or 2-propanol.

The thermoelectric properties of sintered bodies of NaCo2O4, which is so far the most promising p-type candidate for oxide thermoelectric material, are investigated in terms of their sintering conditions. Double-step sintering, for which single-phase NaCo2O4 obtained by calcination and sintering with addition of 10% excess of Na each time is re-ground and sintered again, is revealed to attain a marked improvement in the thermoelectric performance of the oxide. The improvement is due to increase

Thermoelectric properties of Al-doped ZnO (Zn0.98Al0.02O) with nanosized pore (nanovoid) structure were investigated. Nanovoids were formed by using monodisperse polymethylmethacrylate (PMMA) particles of 150, 425, and 1800 nm in average diameter as a void forming agent (VFA). Whereas the thermal conductivity of the samples sintered with the 150 nm PMMA particles of 5–10 wt % was efficiently suppressed, the magnitude of the suppression was almost the same as that of the electrical conductivity,