Neutron studies of diffusion processes near a singular point in a dilute aqueous solution of ethanol

The problem considered in this work relates to the physics of liquids. Rather, to the physics of dynamic processes in liquids. The method of quasielastic scattering of slow neutrons was used to study the dynamics of molecules of the water-ethanol system as a function of concentration at a temperature of 8 °C and as a function of temperature at a concentration of X = 0.04 molar particles (mol. particl.). The overall coefficient of self-diffusion of molecules D, its single-particle Ds-p and collective Dcoll components, as well as the time of settled life of a molecule in a vibrational state t, are determined. The region of small concentrations was studied in detail, where in the vicinity of concentrations X = 0.04 mol. particl. and X = 0.2 mol. particl. two minima are found in the coefficients D and Ds-p. Time t at these concentrations increases significantly. This indicates a significant decrease in the intensity of the activation mechanism of molecular diffusion at these concentrations, which is quite possibly caused by the binding of water and ethanol molecules into complexes (clusters). Similarly, a deep minimum was found in the D and Ds-p coefficients near the temperature of 4 °С. Time t at this temperature also increases. That is, at a temperature of 4 °C, the intensity of the activation mechanism of the diffusion of solution molecules decreases. Therefore, at a concentration of X = 0.04 mol. particl. and at a temperature of 4°C, a special point exists in the water-ethanol system. However, its position does not coincide with the data on scattering light

Temperature features of molecules' dynamics in "heavy water - glycerol" solution

By the method of quasi-elastic scattering of slow neutrons, the dynamics of molecules of the solution "heavy water - glycerol" with glycerol concentration of 0.046 molar fractions has been studied in the temperature range (2 - 10) °С. The features in the temperature dependence of total self-diffusion coefficient and its one-particle component are found: at 3 °C deep minimum is observed. In this case, the residence time of the molecule of glycerol in the vibrational state increases substantially. The analysis shows that these effects are due to increase in the intensity of the clustering processes at 3 °C

Influence of coal sorbents on water molecules dynamics

The results of investigations of the effect of non- and porous sorbents on water dynamics have been discused. Characteristics of dynamics by the spectra was obtained of quasi-elastic slow neutron scattering have been calculated. The total coefficient of self-diffusion of water molecules the contributions to it from collective (Lagrange) motion and single-particle (Frankel) motion; molecule lifetime at oscillation state and length of molecule jump from one to another equilibrium center have been quantitative estimated. Nonporous sorbents don't effect on water dynamics but porous sorbents decrease total coefficient of self-diffusion at the constant value of the contribution from collective motion has been established for the condition of experiment

Self-diffusion of water molecules after contact with silicon-containing compounds

Influence of crystalline and amorphous silica on the diffusion coefficients of water molecules according to the experimental data on quasi-elastic scattering of slow neutrons is quantified. It was established that after the contact of silicon-containing compounds of natural origin chalcedony and spongolit with water, the mechanisms of its self-diffusion are significantly changed: self-diffusion is carried out only by the mechanism of continuous diffusion; the magnitude of the total self-diffusion coefficient of water molecules decreases and there is no contribution from the activation mechanism of self-diffusion by at least 24 hours after separation of the solid phase from the liquid. The pyrogenic amorphous silica has relatively little effect on the diffusion of water molecules

Quasielastic scattering of slow-neutron in water-alcohol solutions

Research of molecules dynamics of solutions “water - propyl alcohol” of different concentration at the temperature 281 K is conducted by the method of slow-neutron quasi-elastic scattering. There were experimentally exposed the feature of effective self-diffusion coefficient of molecules of the indicated solutions. Based on the time- scale hierarchy the division of selfdiffusion coefficient to one-particle and collective contributions was conducted, and the time of the molecules settled life in position of equilibrium was calculated. There were also exposed the feature of self-diffusion concentration dependence of coefficient of self-diffusion and his selfpart contribution, namely: presence of two minimums is in the areas of concentrations (0,04 ÷ 0,05) of mass fraction and (0,18 ÷ 0,22) m.c. of the alcohol and continuous character of diffusion at concentrations higher then 0,4 m.c. of the alcohol. It is shown that the indicated concentration areas correspond the certain local structures of investigational solution