Effects of the confinement on wall pressure, interfacial tension, and excess adsorption at the nanocylindrical wall

Abstract

In this article, a hard sphere fluid confined between two homocentric cylinders which formed a bicylindrical pore has been investigated. Our aim is investigation of the effect of an outer cylinder on the values of wall pressure, interfacial tension, and excess adsorption of fluid at a convex nanocylindrical wall, inner wall. To investigate this effect, the modified fundamental measure theory (MFMT) used. To do so at first we presented a general solution for weighted density integrals in cylindrical coordinate which is applicable for infinite and infinite lengths of cylindrical pore, bicylindrical pore, cylindrical wall, and even truncated cone. In the second step, the wall pressures, interfacial tensions, and excess adsorptions at a convex nanocylindrical wall are obtained for confined fluids in bicylindrical pores and compared with those values for bulk fluids. Our results showed that confinement leads to an oscillatory behavior for wall pressure, interfacial tension, and excess adsorption of the fluid at the wall. The reason for these oscillations lies in structural changes that occur for a fluid as a result of confinement. Variation of the type of interaction of inner wall with fluid from hard to attractive one can reverse the behavior of interfacial tension and adsorption versus size. Also in some cases, it changes their signs while the change in the type of interaction of the outer wall only leads to an increase in amplitudes of the oscillations.