J. Phys. Chem. 1083, 87, 4037-4039
Our results in Table I verify these predictions. This verification provides more evidence that our model for the interpretation of the low-temperature peak in pure ice is valid and that the low-temperature DTC peak in ice emulsions is due to dipolar absorption in ice. Wand TM in ice emulsions immediately after freezing are higher than the corresponding values in macroscopic pure ice (Table I). A possible explanation of this behavior is that a higher activation energy is needed for the motion of the orientational defects in the ice microcrystals of the emulsions than in macroscopic pure ice, because of the higher concentration of physical defects in the former. If this explanation is true, then the evolution with time to lower W and TM has to be attributed to the decrease of the concentration of physical defects in the ice microcrystals in the course of time. On the other hand, Boneds put forward a theoretical model for the interpretation of the evolution with time of the dielectric behavior of macroscopic poiycrystalline pure ice12 and ice emulsion^.^ However, his model is a general one for a solid-solid transformation. It is not specific for ice and not at the molecular level. We think that the question of the interpretation of the evolution with time of the dielectric behavior of ice emulsions is still open. Results for CP = 0.65 and 2-h preservation at -1 "C are not shown in Table I, since the DTC peak appears then to be a double peak. Measurements in an ice emulsion with @ 0.50 showed the same result. We have no explanation for this behavior as yet. At all events, from both microscopic observation and DTC measurements in our emulsions after freezing and subsequent thawing, it can be excluded that this behavior is due to a possible damage (e.g., coalescence) of the emulsions. We note that the reported ac measurements in ice emulsions at advanced states of e v ~ l u t i o nare ~ . ~confined to CP < 0.50. It is also
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noteworthy in this connection that the dielectric relaxation profiles computed numerically by Hanai et d.16in a theory of interfacial polarization in W/O emulsiom show at higher concentrations (@ > 0.60) remarkable deviations from those in a single relaxation type and look in some particular cases like the composite behavior of two kinds of a single relaxation mechanism. Also the DTC peak for CP = 0.40 at advanced stages of evolution (Figure 2) cannot be satisfactorily described by eq 1. Our result is consistent with the qumerical result obtained by Clausse,13namely, that if the dielectric 'relaxation in macroscopic ice is assumed to be described by a single relaxation time (the Cole-Cole plot is a semicircle with its center on the 6' axis), then the dielectric relaxation in ice emulsions cannot be described by a single relaxation time. It is described by a continuous distribution of'relaxation times about a mean value (the Cole-Cole plot is an arc of a circle with its center below the t' axis).
Conclusion Summarizing,we have obtained more evidence that the low-temperature DTC peak in dispersions of ice micrcrystals in oil is due to dipolar absorption in ice, (a) by comparing the characteristics of this peak at advanced states of evolution with time with those of the low-temperature DTC peak in macroscopic pure ice, (b) by comparing the results of ac measurements by other investigators in ice emulsions at advanced states of evolution with those in macroscopic pure ice, and (c) by investigating this peak with different kinds of electrodes. Registry No. Water, 7732-18-5. (16) T. Hanai, Y. Kita, and N. Koizumi, Bull. Inst. Chem. Res. Kyoto Uniu., 58, 534 (1980).
Neutron Diffraction Studies and CRN Model of Amorphous Ice M. R. Chowdhury, J. C. Dore, Physics laboratory, University of Kent, Canterbury, Kent, GT2 7NR, England
and D. 0. Monlague' Physics Department, Willamette University, Salem, Oregon 97301 (Received: September 14, 1982; I n Final Form: December 1, 1982)
Neutron diffraction measurements have been made of vapor-deposited amorphous D20ice at 10 K. The pair correlation function obtained from the measurements is found to be in good agreement with the continuous random hydrogen-bonded network predictions of Boutron and Alben. There is strong orientational correlation between adjacent molecules which may be modeled as a tetrahedral unit comprising five molecules. This basic unit is present as a regular feature in the ice Ih lattice but is disordered in the amorphous phase. Spatial correlations extend to -20 A but it is only in the low r value region (
