Synthesis, structure, and properties of superhydrophobic nickel-PTFE nanocomposite coatings made by electrodeposition

The objective of the current research is to create multifunctional metal matrix composite coatings that are able to provide high strength as well as high water repellency by electrodeposition of nanocrystalline nickel matrix with embedded polytetrafluoroethylene (PTFE) particles. The study of the co-deposition process demonstrated that the amount of PTFE co-deposited is highly dependent on the concentration of PTFE particles in the electroplating bath. A very high fraction of co-deposited PTFE was achieved (69 vol.%) using a concentration of 30 g/L of PTFE particles in the plating bath. The contact angle of the surface greatly increased when the PTFE content increased over 50 vol.%. At 69 vol.% PTFE the coatings had a contact angle of 152°. Saccharin was added to the electroplating bath in an attempt to refine grain size. Using transmission electron microscopy, the average grain size of the nickel matrix without saccharin was determined to be 27 nm for the coating containing 69 vol.% PTFE. However, no nickel grain size reduction was observed when saccharin was added as it was found that the composite samples already had a very fine grain structure likely due to the use of cetyltrimethylammonium bromide (CTAB) as a PTFE particle dispersant. The addition of saccharin provided no additional hardening of the composite while the wetting angle was greatly decreased at concentrations greater than 0.1 g/L.