The Formation and Decay of an Unstable State of a Suspension of Hydrophobic Nanoporous Particles under Rapid Compression

The study of non-wetting liquid transport in a nanoporous medium is stimulated by the possible use of this process to absorb or accumulate mechanical energy. The filling of nanopores of suspended particles with a non-wetting liquid under decay of the unstable state, when the pressure increase rate is much higher than the rate of volume change, is studied. Based on the new experimental data and a theoretical model of the interacting modes of the spontaneous filling and filling under rapid compression, a picture of the percolation transition and a mechanism of liquid transport under such conditions are proposed. It is shown that a new dynamic filling threshold P0 is reached. It is shown that the filling of the porous medium is the result of the slow mode of impact compression when the fast mode of spontaneous filling is continuously adjusted to the slow mode on a small time scale. The theoretical model of the interacting modes is based on the solving of a system of kinetic equations for the distribution functions f(n,t) and F(n,t) clusters of filled pores under rapid compression, respectively. It is shown that filling at P=const corresponds to the non-dissipative transport of liquid on a time scale smaller than the characteristic filling time. The proposed model quantitatively describes the experimental data. So, the response of suspension to impact is characterized by the positive feedback.

Possible approach to estimating the dispersion interaction in powder systems

In this paper, we present the results of testing the algorithm for calculating the Hamaker constant proposed by the authors as characteristics of the dispersion interaction according to experimental data obtained by studying the composition of fine powders of basalt and polymineral sand. For this purpose, based on a number of assumptions, the concept of an analogue Hamaker constant is introduced, which is an experimentally determined quantity.This parameter is recommended to be used when choosing the quantitative ratio of powder raw materials as a criterion for assessing the maximum possible van der Waals effect of dispersion interaction. An assumption was made about the presence of a constant characteristic of a thin film wetting the analyzed surface. Moreover, this thin film has a contact angle of the transition region “film-bulk phase”, the value of which is determined by the nature of the surface and the properties of the wetting liquid. The contact angle of the transition region can be an additional quantitative criterion for the selection of materials that are compatible in nature.