Wazo Komatsu

Synergetic effect of oxide catalysts with different dopents on catalytic activity: I. Nickel oxide and zinc oxide for carbon monoxide oxidation

Abstract The catalytic activity of pure, doped nickel oxide, and mixtures of nickel oxides with different dopents was investigated by the reaction of carbon monoxide oxidation. The incorporation of lithium ions in the oxide enhanced the activity and the addition of indium lowered the activity. The activity of mixtures increased to several times greater than would be predicted by simple additive effect of single doped catalysts. For zinc oxide, the incorporation of lithium or indium ions, respectively, decreased or increased the activity. Mixtures of zinc, oxides with different dopents were also more active than expected from the simple additive effect. The mechanism of the enhanced activity of mixtures was discussed from the viewpoint of synergetic action of doped catalysts with different Fermi levels.

Kinetics of sintering at a constant rate of heating

従来, 提出されている初期焼結の速度式から, 一定速度で昇温した場合の速度式 (1) を理論的に導出した.log(ΔL/L0)1/m-loglog A+Bt/A=logK-E/R(A+Bt) (1)この式の妥当性を検討するため, ZnO, NiOおよびFe2O3の焼結を昇温法でおこなった. 収縮の測定には差動偏位測定器を用い, また焼結過程での錠剤断面の状態を調べるために走査型電子顕微鏡などを用いて観察した. この結果, 粉体が球状に近い場合, 実験データーはきわめてよく式 (1) によってあらわされ, 式 (1) のプロットからえられる見掛けの活性化エネルギーが文献値とよく一致することを示した.

Phase Transformation and Toughening in MgO Dispersed with ZrO2

Transformation of tetragonal ZrO2 to monoclinic ZrO2 has widely been used to increase the toughness of ceramic materials. The materials being used as a matrix include cubic ZrO2,1,2,3 α-alumina,4 β”-alumina,5 ZnO,6 Si3N4,7 etc. For the toughening of alumina one can use either monoclinic ZrO2 or tetragonal ZrO2. The results of most of the works indicated that the enhancement of toughness was greater when the tetragonal ZrO2 was dispersed in the matrix.8 This is, of course, due to the fact that stress induced transformation is responsible for the toughening.