Dielectric Behaviour of Ice Microcrystals Dispersed within Suspensions: A DTC Study

Abstract

The dielectric properties of water-in-oil (W/O) suspensions have been studied by means of the depolarization thermocurrent (DTC) method in the temperature range of 85-250 K. Two predominant peaks have been observed at about 140 and 225 K. Evidence has been obtained that the peak at 140 K and the dielectric absorption observed by many investigators at sub-zero temperatures in the kHz frequency range are due to the same relaxation mechanism.

Evolution with time of the dielectric properties of dispersed ice microcrystals

“…The mechanism of the extrinsic generation of Bjerrum defects can, in general, be different in the different forms of ice. In the case of dispersed ice microcrystals it is generally accepted that the extrinsic defects that generate Bjerrum defects must be physical defects within the lattice of the ice particles, whose concentration is high due to supercooling breakdown [4,6]. It is also possible that extrinsic Bjerrum defects originate in significant numbers at the interfaces.…”

“…The bending over occurs at temperatures which depend on the quality of the samples [15]. Dispersed ice microcrystals, on the contrary, are characterized by a temperature-independent value of W down to -150 ~ [6]. It is interesting to note that ice samples with high content of disturbance produced either by very rapid crystal growth or from the high-pressure polymorphs Ice II and IX behave, in this respect, similar to ice dispersions [14,15].…”

“…In a series of papers we studied the dielectric properties of dispersed ice microcrystals by means of the thermally stimulated depolarization current (TSDC) method [6][7][8][9]. Several aspects of the relaxation attributed to dipolar absorption in the ice microcrystals were studied in detail in an attempt to contribute to deeper understanding of the mechanism at the molecular level.…”

“…Our interest in the dielectric properties of water-in-oil emulsions and dispersions of ice microcrystals is twofold: it has been proved that a better understanding of the dynamics of water molecules in ice can be achieved by studying different forms of ice [14,15], including dispersions of ice microcrystals [6][7][8][9]. On the other hand, these relatively simple and easy to manipulate systems may serve as models for more complicated systems, such as food emulsions and tissue.…”

“…The circles represent the best (least-squares) fit of the theoretical equation for the depolarization current density in the case of a single Debye mechanism obeying the Arrhenius equation to the experimental data. Details of the fitting procedure are given in [6]. The figure shows that the peak temperature T~ decreases and the departure from single-relaxation-time behaviour increases in the sequence A), B), C).…”