Measurement And Analyses Of The Characteristic Time Of Trabslation And Rotation Degrees Of Freedom In Structural Glass Systems

The glass transition has been one of the core issues in the field of condensed matter physics, and the experiment measurements and theoretical researches of glass system relaxation time with tremendous change in the order of 15 from 10-12 seconds to 103 seconds in a relatively narrow temperature range is one of the key issues to explore the glass transition mechanism. At present stage, the researchers usually employ several techniques to obtain the relaxation time in a wide range, but only the rotational degree of freedom is measured. Recently, by introducing ion probe in structural glass systems, our group devised a method that can get translational and rotational relaxation time of structural glass systems, in 11 orders form10-11 seconds to 1 second, in a measurement of dielectric loss spectrum of ion probe and structural glass system. However, since only two kinds of samples were measured and the data of some parameters are insufficient, the experimental laws summarized in previous studies have low credibility. Thus, on the one hand, the method needs to be verified in more systems; on the other hand, to improve the reliability of the experimental results and summarize experimental laws, the number of measured parameter data should be increased further. This work has great value to study the dynamics of glass system.This paper, to obtain the characteristic time of liquid translational and rotational degrees of freedom of n-butanol and 1, 3-butanediol, two structural glass systems rarely studied before, magnesium chloride and sodium hydroxide are used as probes respectively. And the results further verify the feasibility of the method. Then the dielectric spectrums of one structural glass systems(incorporation of different kinds and concentrations of ion probe glycerol) been studied previously by our group are measured and analyzed in the heating and cooling processes with extending frequency range and more frequencies. At last, the characteristic time of translation and rotation in the low temperature region is compared and the temperature dependent activation energies are analyzed. The findings of the dielectric spectroscopy experiments are as follows:1) The temperature dependent complex dielectric constants of 1,3- butanediol and n-butanol doped different concentrations ions as probe are measurd in the frequency range of 1Hz-106 Hz with the rate of 1.5K/min and the temperature ranges are 123K-353 K and 113K-283 K for two samples respectively. Then the characteristic time of translational and rotational degrees of freedom of the samples in the larger time range can be obtained. The results shows that the method above is effective to measure 1,3-butanediol and n-butanol.2) The complex dielectric constants of glycerol doped sodium chloride is measured with 29 frequency points in the range of 1Hz-107 Hz and the rate of 0.5K/min in the temperature range of 123K-353 K. And the characteristic time of translational degrees of freedom is get from imaginary part of complex dielectric constants of ions. At the same time, the glycerol relaxation time within the frequency range of 1MHz-3GH at the temperature of 296 K is measured. The characteristic time of translational degrees of freedom and rotational relaxation time gained from different kinds and concentrations ion probe are in accordance with each other.3)By the investigation on the characteristic time of the translational and rotational degrees of glycerol and 1,3-butanediol, the relationship between translational and rotational degrees of freedom in the cryogenic temperature area are analyzed, and the results indicate that the translational and rotational degrees of freedom are coupled together in the higher temperature region. As the temperature decreases, the translational and rotational degrees of freedom of the system appeared decoupling, which is more obvious in the lower temperature.4) By the analysis of the characteristic time of the translational degrees of glycerol, propylene carbonate and 1,3-butanediol, the relationship between activation energy(E) and temperature(T) has been investigated. The results indicate that the activation energy decreases with temperature increasing and E and 1/T is approximately an exponential relationship in the measurement of temperature region. The fragility factors of propylene carbonate is larger, and which of glycerol and 1,3-butanediol( m=54.8) are moderate, but the activation energy with temperature of them have the similar change trends.The paper selects the glycerol, propylene carbonate, 1,3-butanediol and n-butanol as experimental samples doping different concentrations ions as probe, so the conclusions obtained have certain representativeness and universality, which verify the feasibility of obtaining the characteristic time of the translational degrees of liquid at larger time range by ion probe in an experiment process. At last, the decoupling phenomena of the translation and rotation degree at low temperature range and the relationship of the activation energy with temperature are analyzed. This paper further verify the reliability of the results and will provide more reference to study fluid dynamics.