| Abstract
| - We report the first direct measurement of surface hydrophilicity−hydrophobicity in multiwall carbonnanotubes (MWNTs) by analyzing the binary solvent adsorption excess isotherms of freshly oxidized aswell as thermally annealed MWNT samples. Heat-induced changes in the sample morphology are monitoredby XRD and N2 adsorption isotherms, the hydrophilic−hydrophobic surface ratio is calculated from ethanol−cyclohexane adsorption excess isotherms. The surface fractal dimension and the dimension of the capillarycondensation are also determined. Results obtained from these independent methods correlate well witheach other. The character of the MWNT surface gradually turns from hydrophilic (no treatment) intohydrophobic (12 h in N2 at 1673 K) upon heating. The suggested method appears to be a feasible, reliable,fast, and economic technique of characterizing MWNT surface properties.
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