Papers by Keyword: Ionic Radius

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Authors: Masahiko Morinaga, M. Yoshino, A. Shimode, K. Okabayashi, H. Nakamatsu, R. Sekine
Abstract: The electron density distributions in a series of metal oxides are calculated using the DV-Xα molecular orbital method. It is found that the logarithm of the electron density, logρ(r), decreases with the distance, r, from the oxygen nucleus, while keeping a constant slope relevant to oxygen atom. The magnitude of the slope is about 15.75 for O-1s electrons, and about 6.61 for O-2s, 2p electrons, being nearly close to the respective values of 16 and 8, expected from the radial distribution functions of hydrogen-like atom containing only one electron. The extent of the region for the O-2s, 2p electrons changes with metal species in the oxides, but the slope remains unchanged. Furthermore, it is shown that the nature of the chemical bonding is well represented in log (ρ minZ-3) vs. 2(Z/n) rminb plots, where ρmin is the minimum electron density, rmin is the distance r at ρmin, Z is the atomic number, and n is the principal quantum number.
77
Authors: Yorinobu Takigawa, Yukihisa Naka, Kenji Higashi
Abstract: The effect of cation ion dopant on phase transformation of zirconia bioceramics is evaluated by ageing in hot water. The phase transformation progresses with time in all specimens. However, the transformation behavior is much different depending on the dopant. The transformation is promoted when the 1 mol% of pentavalent element is added to 3mol% yttria stabilized zirconia (3Y-TZP). In contrast, the transformation is suppressed when the bivalent element is added. In case that the tetravalent element is added, the transformation is promoted if the ionic radius of the element is larger than that of zirconium, and the transformation is suppressed if the element with smaller ionic radius than zirconium ion is added. This result indicates that the ionic radius and the valency of ions are important factors to control the phase stability in zirconia.
97
Authors: Tetsuhiko Onda, Kenji Okazaki, Hisayuki Suematsu, H. Yamauchi, Motozo Hayakawa
471
Authors: Yukihisa Naka, Yorinobu Takigawa, Kenji Higashi
Abstract: The effect of cation dopant on tetragonal to monoclinic (t-m) phase transformation of zirconia is examined, which causes the degradation of zirconia in vivo. The transformation behavior is much different depending of the dopant. The transformation is promoted when the pentavalent element is added. In contrast, the transformation is suppressed when the bivalent element is added. In case the tetravalent element is added, the transformation is promoted if the ionic radius of the element is larger than that of zirconium, and that is suppressed if the element with smaller ionic radius is added. The valence and the ionic radius of dopant must be important factors for the phase stability of zirconia.
1231
Authors: J.H. Zhang, Hai Feng Liu, Wei Sun, H.Y. Lu, D.X. Tang, Jian Meng
Abstract: The relationship between structure, ionic radius and electronegativity and solubility of the various rare-earth elements in Mg was studied. It is found that light RE(La-Sm, Eu, Yb) have more complicated phase relation with Mg but the heavy RE(Gd-Lu, Sc) have the similar crystal structure with magnesium. Also it is found that the less electronegativity difference between Mg and RE is, the more solubility limit of RE in Mg is. The fact of the RE solubility decreased in magnesium with lowering temperature suggests that there is a possibility of Mg supersaturated solid solution formation and it will decomposition during aging. According to the rule, an megnesium alloy with higher strength feature was developed. Their mechanical properties are UTS 347MPa, YTS 290MPa and elongation 12.5% at room temperature.
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