Wetting of Liquids Inside Carbon Nanotubes

As discussed earlier, infiltration of molten metals and salts was used to prove that CNTs were indeed hollow, soon after their discovery in the early 1990s. Renewed interest in the wetting and filling behavior of CNTs with low-molecular-weight fluids, such as water. 

This first group of results has raised novel questions that are now being answered through experiments and simulations (see Fig. 10.7) How do the water molecules arrange themselves within the nanotube, and what is their phase What happens to the water molecules when the surface chemistry of the carbon wall is changed (from hydrophobic to hydrophilic) Do all these aspects have an effect on the flow of water inside small (sub-10 nm in diameter) CNTs  

Many of the discrepancies between numerical and experimental results concerning liquid behavior inside CNTs discussed above can be attributed to the presence of surface defects or functionalities on the tube walls, or to the structure of the tube walls. 

Systematic analysis of the effects of surface chemistry and structure on the wettability of CNTs has shown that it is possible to control their wettability from hydrophobic to hydrophilic. An 

Similar experiments on the contact angle of water on CNTs films annealed at temperatures ranging from 670°C to 2,000°C in high vacuum have shown an increase from 40° to 80° due to graphitization of the carbon structure.  

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