Size dependence of the dissociation process of spherical hydrate particles via microsecond molecular dynamics simulations

Abstract

The dissociation process of spherical sII mixed methane-propane hydrate particles in liquid hydrocarbon was investigated via microsecond-long Molecular Dynamics simulations. A strong dependence of the melting temperature on the particle...

Clathrate Adhesion Induced by Quasi-Liquid Layer

“…Third, the decrease in the capillary force upon approaching the temperature of the dissociated region can be explained by the rapid thickening of the QLL. In general, QLL thickens as the temperature increases , and leads to an increasing radius r . Finally, low adhesive forces in the low-temperature region are explained by a vanishing or discontinuous QLL.…”

“…However, the origin of adhesion forces for clathrate surfaces is poorly understood. Recently, it was reported that clathrate surfaces are not rigid solids but covered by an intrinsic nanometer-thick quasi-liquid layer (QLL) due to surface premelting. − However, to what extent the QLL affects the adhesion force of clathrate surfaces was not understood. Therefore, we carry out force measurements and theoretical modeling to find out how the QLL affects the adhesion of clathrate surfaces to other solid surfaces.…”

Surface Science in the Research and Development of Hydrate-Based Sustainable Technologies

“…In-depth analysis of the force-versus-distance curve in Figure b indicated that the thickness of this QLL is around 10 nm at −4 °C . This experiment-derived thickness of the QLL is significantly thicker than that of subnanometer observed in simulations. − Similar discrepancies are observed for the studies of ice surfaces, for which the reported thickness depends largely on the methods employed (Figure ). Hence, quantifying the thickness of the QLL remains an intrinsic challenge (discussed in the Prospects and Challenges section).…”

“…Maeda et al indicated that interfacial premelting of hydrate surfaces is a thermodynamically favorable process. , Computer simulations have enabled a close look at the temperature-dependent premelting layer on hydrates and ice (Figure ). − Some properties of the QLL such as diffusion coefficient and interfacial tension can be estimated based on computer simulations. − A question of fundamental importance is how the surface premelting affects the specific surface free energy (γ sv ) of hydrates. Maeda et al was the first research group attempting to estimate γ sv of hydrates using a semiempirical method .…”

“…Molecular dynamics simulations showed that the premelting happens at a few outmost water layers and yields to a subnanometer QLL (Figure ). − Nguyen et al measured the interaction between a silica microsphere and a tetra-butyl ammonium bromide (TBAB) hydrate surface utilizing atomic force microscopy (AFM) . They found that the interaction between a silica microsphere and a silicon wafer surface (as a reference system) is dominated by a van der Waals (vdW) force (Figure a) described by Equation . − Where, the negative sign indicates an attractive force, A is a physical constant (Hamaker constant) specific to the two materials and the medium, R is the radius of the sphere, and D is the closest distance between the sphere and the surface.…”