Dielectric Breakdown Characteristics of Frozen Sodium Chloride Solutions at Low Temperatures

In this study, the potential use of ice as a cryogenic material with low environmental impact was investigated. To this end, NaCl solutions containing 0–4.50 mol/l NaCl were frozen in a freezer at −80°C, and their AC breakdown strength (Fb) and durometer hardness were measured in a liquid nitrogen (LN 2 ) environment. To investigate the effect of ions in ice on electrical insulation, a similar experiment was conducted using HCl. The results revealed that (1) the average Fb decreased with increasing NaCl concentration up to 2.57 mol/l and subsequently increased up to 4.50 mol/l. (2) The durometer hardness of the frozen NaCl sample increased with increasing NaCl concentration in the range of 0.56–4.50 mol/l. (3) Fb increased at low temperatures, but exhibited greater variability. (4) The durometer hardness of frozen NaCl and HCl samples increased with increasing solution concentration (0.001–0.1 mol/l), with no significant differences observed between them. (5) At each solution concentration, the Fb of frozen HCl samples was higher than that of frozen NaCl samples, and Fb increased with increasing concentration in both cases.