1 research outputs found
Source of Electrofreezing of Supercooled Water by Polar Crystals
Polar
crystals, which display pyroelectricity, have a propensity
to elevate, in a heterogeneous nucleation, without epitaxy, the freezing
temperature of supercooled water (SCW). Upon cooling, such crystals
accumulate an electric charge at their surfaces, which creates weak
electric fields, –1, that are thousands
of times lower than necessary for inducing homogeneous ice nucleation.
By performing comparative freezing experiments of SCW on the same
surfaces of three different polar crystals of amino acids, we demonstrate
that preventing the formation of charge at these surfaces, by linking
the two hemihedral faces of the polar crystals with a conducting paint,
reduces the temperature of freezing by 2–5 °C. The temperature
of ice nucleation was found to be correlated with the amount of the
surface charge, thus implying that the surface-charge-induced interactions
affect the interfacial water molecules that trigger freezing at a
higher temperature. This finding is in contrast to previous hypotheses,
which attribute the enhanced SCW freezing to the effect of the electric
field or capture of external ions or particles. Possible implications
of this mechanism of freezing are presented