GAS PRESSURE IN NANOSCALE PORES

10.25712/ASTU.1811-1416.2024.04.007

Abstract

Thermodynamic models of inhomogeneous media are adapted for their use in the study of nanoscale systems. An analytical model of gas phase interaction with the walls of nanoscale pores and vacancy clusters in solids is proposed. The possibility of an approximate accounting of interphase interaction in the calculation of the free energy of the system and gas pressure by introducing additional summands into the equation of state is shown. For the approximate calculation of these summands, simple formulas are proposed in the present work, which allow us to estimate the adsorption correction to the free energy in nanoscale gas bubbles analytically. In this case, the interaction between gas atoms and walls is described using the Lennard-Jones potential. The developed model is used to study the states of helium, hydrogen, and argon in tungsten nanopores. It is found that the interaction with walls gives a very significant contribution to the free energy of the gas, the relative fraction of which strongly depends on the parameters of the equation of state and the interaction potential of gas molecules with walls. The analysis points to the necessity of taking into account "wall" corrections in the study of gas states. The results obtained indicate a significant contribution of the phase interaction energy to the gas free energy, even at relatively large values of pore radii of tens and hundreds of nanometers. The influence of the interaction of gas molecules with pore walls on the gas pressure is weaker. For all the cases considered, neglecting the interfacial interaction when calculating the gas pressure is possible if the pore radius is at least ten nanometers. The results obtained can be useful in the study of gas pressure in nanopores of solids, for example, in the problems of surface plasma chemistry, controlled thermonuclear synthesis, and powder metallurgy.