Kinetic Model for the Sublimation of a Solid and Evaporation of Colloidal Particles from a Solid Substrate

Abstract

A kinetic approach, based on a first passage time analysis, is proposed to study sublimation. A surface located molecule/particle is considered to perform a chaotic thermal motion in a potential field created by its pairwise interactions with all other molecules of the solid. For the normal (to the surface) motion of the surface molecule this field represents a potential well from which the molecule escapes during sublimation. The mean time necessary for this escape can be determined by solving the Smoluchowski equation for the single molecule distribution function in a potential well wherein the molecule performs its chaotic motion. Knowing this time, one can determine the rate of evaporation of molecules/particles from the surface. The method is applied to two kinds of sublimation. One is the "molecular" sublimation of a solid during which its molecules evaporate from its free surface. The other is the emission of nanoparticles from a solid substrate on which they are adsorbed. Both the substrate and nanoparticles can be coated with thin films which allow one to control the rate of particle emission at a given temperature. The effect of various parameters of the system on the process is studied numerically.

Mechanistic and Kinetic Insight into Spontaneous Cocrystallization of Isoniazid and Benzoic Acid

“…The crystallites no longer exhibit the distinct crystal habit characteristic to isoniazid and particle surfaces after milling appear rougher, indicating that surface defects may form during milling. A higher density of such defects after milling increases the sublimation rate of a compound. As benzoic acid tends to sublime, its vaporization behavior after milling (30 Hz, 5 min) was observed using an optical microscope (Figure S5 in Supporting Information).…”

Impurity Partitioning During Colloidal Crystallization

“…Colloidal crystals, periodic arrays of colloidal particles, have attracted great interest in a large number of fields because of their potential application in functional devices, such as photonic crystals . In addition, colloidal crystals are also useful for modeling diverse physical phenomena, e.g., glass transition, nucleation, and sublimation. , Although the interactions between atoms and between colloidal particles are different, it has been recognized that some of the behaviors of colloidal systems follow the classical theory of atomic systems, , and hence, the study of colloidal systems provides us with precious information about those processes that are difficult to experimentally detect for atomic systems due to the atomic spatial/time scale.…”