Strong correlation between y'/x and superconductivity of Nax(H3O)zCoO2 y'H2O

Abstract

We prepared single-phase Nax(H3O)zCoO2·y'H2O with varying amount of Br2 volume in acetonitrile, and examined the Na + content (x), H3O + content (z), H2O content (y') and Tc. By changing the amount of Br2 during preparation, the amount of x in Nax(H3O)zCoO2·y'H2O was controlled from 0.282 to 0.359. It was found that superconductivity is not correlated with Co valence but with y'/x, that is, the coordination number of Na + with H2O, and secondly with x/x+z, that is, the ratio of Na + ion in the (Na + + H3O + ) site, suggesting that shielding effect of Nax(H3O)zCoO2·y'H2O governs superconductivity.

Influences of Al2O3 grain size on high-temperature oxidation of nano-Ni/Al2O3 composites

“…Al 2 O 3 materials thus exhibit poor toughness that restricts their application. In order to increase their toughness, dispersion of non-oxide phases such as Ni, NiAl, Co and SiC in Al 2 O 3 matrix were proposed [1][2][3][4]. On the other hand, the presence of the non-oxide phases gives the materials the self-healing function that occurs at high temperatures in the air [2,[5][6][7].…”