Density Fluctuations of Carbon Dioxide in Cylindrical Nanopore

It is important to understand the phase behavior of carbon dioxide in nanoporous structure, which could determine the pore shape and size distribution during a foaming process. In this work, we study the density fluctuations of carbon dioxide in a cylindrical nanopore by using classical density functional theory. It is found that the density fluctuations in solvophobic nanopore could exceed its bulk value by two orders of magnitude. The thickness of the layer with large density fluctuation is more than 3 nm to the wall. With decreasing the solvophobicity, the density fluctuation in nanopore could still be large with a decreased thickness of large fluctuation layer. The large density fluctuations happen only at the liquid side nearby the predrying line. These results are useful for the foaming process to manufacture porous material with a uniform pore shape and narrow size distribution.