Morphological Investigations of Methane−Hydrate Films Formed on a Glass Surface

Methane clathrate formation on water films without previous hydrate formation history was studied. It was found that hydrates form in two layers, each with a clearly distinct morphology. As the clathrate aged, this difference in morphology tended to disappear. Higher driving forces produced smaller hydrate grains and smoother surfaces than lower driving forces within the water film. The converse was true for hydrate formed on the periphery. A third hydrate layer growing outside of the original water boundary was also observed. For the first time, it was shown that this growing front could induce nucleation by creating a “bridge” between segregated water droplets. Hydrate reformation was also studied and it was found that it proceeded in a manner different than that of a system without previous clathrate formation history. For reformation, nucleation occurred within the film and a circular hydrate front(s) advanced toward the periphery of the water film with uniform morphology.