Properties of CaCl2 hydrate with an inorganic powder. Part 1.—Electrical conductivity of CaCl2·nH2O (n= 6.00–7.35) with α-Al2O3 powder

Abstract

Electrical conductivity and its temperature dependence have been measured for mixtures of α-Al₂O₃ powder and CaCl₂·nH₂O (n= 6.00–7.35) with liquid content 17.1–42.9 vol.%. The influence of the solid surface on electric conduction and phase transition in the liquid phase is discussed. Plots of the logarithm of the electrical conductivity, ln σ, vs. reciprocal temperature, 1/T, showed an abrupt change of slope at a temperature, T_t, the deflection point. The value of T_t appears to correspond to the end-point of the melting of the hydrate. The value of T_t decreased as the liquid phase decreased and as n increased. The activation energy for the electrical conductivity, ΔE_a, decreased with increase in the apparent average thickness of the liquid phase up to 30–40 nm, after which ΔE_a became constant. These results show that the thickness of the liquid layer which exists on, and is influenced by, the solid phase is ca. 30–40 nm. In this region, the melting point of the hydrate melt tends to be lowered and this change contributes to the electric conduction of hydrate at temperatures below the melting point.