Aleksey M. Kaverin

Nucleation in superheated liquid argon–krypton solutions

We report nucleation-rate measurements in metastable liquid argon–krypton solutions at pressures of 1.0 and 1.6 MPa over a wide temperature and concentration range. These measurements were performed with the use of a superheated liquid lifetime measurement method. The experimental results are compared with the homogeneous nucleation theory data both using a macroscopic (capillary) approach and taking into account the dependence of critical bubble surface tension on interface curvature. The size effect in nucleation is considered in the framework of the Van-der-Waals, Cahn–Hilliard method. The experimental data indicate that the homogeneous nucleation theory quantitatively describes the kinetics of a first order phase transition in binary solutions of simple liquids if the size effect is taken into account and nucleation rates are J≳106 m−3 sec−1. At J≲106 m−3 sec−1 there is initiated nucleation. A diffusion spinodal of a solution is approximated. The attainable superheating temperature data are presented.

Surface tension at the boundaries of helium-argon and neon-argon solutions at 108–140 K

The capillary constant was measured and surface tension determined for helium-argon and neon-argon solutions by the differential version of the capillary rise method over the temperature range 108–140 K at pressures up to 4 MPa. The adsorption of helium and neon in interfacial solution layers was calculated.

Heterogeneous Vapor Bubble Nucleation on a Rough Surface

Vapor bubble nucleation on a microrough surface wetted by a volatile, incompressible liquid has been analyzed. The work of formation of a critical nucleus in a surface cavity has been evaluated. Concave sites of a surface with negative curvature can decrease the height of the activation barrier for the formation of a critical nucleus. The average density of the nucleation sites has been evaluated for a surface whose (small) deviation from a plane is specified by a Gaussian random function.

Attainable superheat of argon-helium, argon-neon solutions.

The method of lifetime measurement has been used to investigate the kinetics of spontaneous boiling-up of superheated argon-helium and argon-neon solutions. Experiments were made at a pressure of p = 1.5 MPa and concentrations up to 0.33 mol% in the range of nucleation rates from 10 (4) to 10 (8) s (-1) m (-3). The homogeneous nucleation regime has been distinguished. With good agreement between experimental data and homogeneous nucleation theory in temperature and concentration dependences of the nucleation rate, a systematic underestimation by 0.25-0.34 K has been revealed in superheat temperatures over the saturated line attained by experiment as compared with theoretical values calculated in a macroscopic approximation. The revealed disagreement between theory and experiment is connected with the dependence of the properties of new-phase nuclei on their size.

Superheating of liquid xenon in metal tubes

The method of measuring the lifetime has been used to investigate the kinetics of spontaneous boiling-up of superheated xenon in copper tubes. In experiments the temperature dependence of the mean lifetime has been determined at pressures of 1.48 and 1.98 MPa. The data obtained have been compared with homogeneous nucleation theory. It has been found that experimental values of the attainable superheating temperature and the derivative (partial differential ln J/partial differential T)p are systematically lower than their theoretical values. A description of experimental data in the framework of heterogeneous nucleation theory has shown that for the agreement of theory and experiment with the use of a macroscopic model of nucleation on a smooth surface it is necessary to take the value of the equilibrium contact angle theta0 equal to 70 degrees, which is not a characteristic for a xenon-metal system. Taking into account the contribution of the energy of the three-phase contact solid wall-liquid-gas in a microscopic nucleation model makes it possible to reconcile heterogeneous nucleation theory and experimental data at a contact angle theta0 close to zero, with the linear tension taken equal to -6 x 10(-12) J/m and the microscopic contact angle theta* approximately 57 degrees. The number of weakened sites, on which bubbles may form, is always smaller than the number of molecules adjacent to the solid wall.

Surface tension of dimethyl ether in the temperature range 120–214 K

The capillary constant a2 was measured by the differential capillary method of surface tension measurement. The surface tension σ of dimethyl ether was calculated. The experiments were performed both above the triple point temperature (Tt = 131.66 K) and below it in the range in which the coexisting liquid and gas are metastable. Equations that approximate the temperature dependences of a2 and σ were suggested. The excess surface entropy and energy were determined. The surface entropy had a maximum at T ≈ 190 K.

Attainable superheating of liquid n-butane

Temperatures of the attainable superheating of liquid n-butane have been determined at pressures from 0.4 to 2.0 MPa in the range of nucleation rates J = 104–108 s−1 m−3. The data obtained have been compared with classical nucleation theory (CNT). At J > 106 s−1 m−3, satisfactory agreement between theory and experiment has been noted in both the value of the limiting superheating and the slope of the temperature dependence of the nucleation rate. It is shown that temperatures of the attainable superheatings of hydrocarbons of the methane series satisfy the one-parameter similarity. The possibility of manifestation of heterogeneous nucleation in experiment is discussed.