The surface chemical properties and wettability of carbon nanofibers（CNFs）synthesized by CVD were studied by wicking kinetic measurements. The influence of the microstructure, preparation conditions and the surface modification of the CNFs on their wettability in different solvents were investigated. Results indicated that the preparation conditions such as catalyst composition, and especially the carbon source, have an obvious effect on the surface properties and wettability of CNFs. CNFs from Fe/γ- Al2O3 and C2H4 has the worst wettability in water, while CNFs from Ni/γ- Al2O3 and CO has the best wettability in cyclohexane. Measurement of contact angle in cyclohexane, acetone, ethanol and water showed that interaction between the CNF surface and the solvent changed significantly with the solvent used. The contact angles of CNFs from Fe/γ- Al2O3 and CO in water, acetone and ethanol relative to that in cyclohexane (in which the contact angle is arbitrarily set to 0°), are 81.6°，45.2°，24.8° respectively. It is believed that a small polarity of the CNF surface leads to its higher wettability in a non-polar solvent such as cyclohexane than in polar solvent such as water. The nature of the CNF surface groups and the wettability of CNFs in different solvents could be tailored by different surface modifications. Treatment in concentrated nitric acid increased the CNF wettability both in water and in cyclohexane, while treatment in hydrogen peroxide decreased the CNF wettability in both solvents. Interestingly, thermal treatment in argon increased the CNF wettability in water, but decreased it in cyclohexane.
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