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This work shows that after creating certain dual scale roughness structures by femtosecond laser irradiation different metal alloys initially show superhydrophilic behavior with complete wetting of the structured surface. However, over time, these surfaces become nearly superhydrophobic with contact angles in the vicinity of 150 degrees and superhydrophobic with contact angles above 150 degrees. The contact angle hysteresis was found to lie between 2 and 6 degrees. The change in wetting behavior correlates with the amount of carbon on the structured surface. The explanation for the time dependency of the surface wettability lies in the combined effect of surface morphology and surface chemistry.

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Gas hydrate formation was studied in a new apparatus designed to accommodate three different size volume beds of silica sand particles. The sand particles have an average diameter equal to 329 μm. The hydrate was formed in the water, which occupied the interstitial space of the water-saturated silica sand bed. A bulk gas phase was present above the bed (gas cap). Gas uptake measurements were carried out during experiments at constant temperature. More than 74.0% of water conversion to hydrate was achieved in all experiments conducted with methane at 4.0 and 1.0 °C. An initial slow growth was followed by a rapid hydrate growth rate of equal magnitude for nearly all experiments until 43-53% of water was converted to hydrate. During the third and final growth stage, the final conversions were between 74 and 98% and the conversion dynamics changed. Independent verification of hydrate formation in the sand was achieved via Raman spectroscopy and morphology observations in experiments using the same sand/water system.