Hydrophobicity and adhesion of aggregated diamond particles

Diamond powders with high hydrophobicity are prepared by etching graphite plates using a hydrogen/argon (H${}_2$/Ar) plasma. The morphology and size of the diamond powders are found to vary with the proportion of Ar in H${}_2$ from 0% to 50%. Wettability is measured using water contact angle (WCA) measurements giving values between 129.7° and 146.9°. The high hydrophobicity can be ascribed to the aggregated structure of the as-grown diamond powders. To check this assumption, the aggregated diamond powders are separated into individual particles by mechanical grinding; then, the WCAs of separated as-grown diamond powders and commercial dispersed diamond powders are compared. The separated diamond surfaces show the lower WCAs of 99.68° and 96.96°. The surface of the aggregated diamond powders also exhibits high adhesion to water. The diamond surface grown in 2% Ar suspends 40 μL of water under a tilt angle of 180°. Such aggregated diamond powders are promising for no-loss liquid transportation. (© 2020 Wiley-VCH GmbH)