Surface transformation of carbon nanotube powder into super-hydrophobic and measurement of wettability

Super-hydrophobic carbon nanotube (CNT) powders were formed by NF3 glow-discharge plasma at low-pressure and their surface free energies were directly determined from the contact angles with probe liquids using the Owens–Wendt plotting. The cushion made of plasma-treated CNT powders revealed super-hydrophobicity (contact angle > 153°), regardless of kinds of probe liquids and treatment-time. The surface free energy of the NF3 plasma-treated CNT powders decreased drastically from 82.6 to 0.12 mJ/m2. The plasma treatment using fluorinated compound gases may be useful for dispersing, separating, and cutting CNTs since CNTs have tendency to aggregate in bundles and poor solubility.