Microscopic observations of formation processes of clathrate-hydrate films at an interface between water and carbon dioxide

The formation processes of clathrate-hydrate film are observed at the interface between water and carbon dioxide using microscspy. After a certain induction period, the hydrate him propagates from nucleation points along the interface. A second him propagation is sometimes observed immediately after the primary propagation, which illustrates the molecular distribution near the interface. The dendrite growth following the film coverage of the interface in both phases suggests that the hydrate him grow mainly in the water phase. The propagation rates are determined from video images and are found to depend on the supercooling. This result and the bubble formation on the hydrate film following him propagation indicate that the rate-determining process is mainly heat diffusion from the reaction sites. A him thickness of 0.13 mu m is estimated using the heat diffusion model. (C) 1999 Elsevier Science B.V. All rights reserved.