Fabrication of superhydrophobic ceramic coatings via a novel solution precursor vacuum plasma spray process

The plasma jet in the vacuum plasma spray process presents unique properties such as supersonic flow, expanded jet dimensions, and a smaller decay rate for jet velocity and temperature than in atmospheric plasma spray. In this work, a novel solution precursor vacuum plasma spray (SPVPS) process is described, which combines vacuum plasma spray with solution precursor as the feedstock. The deposition of superhydrophobic ceramic coatings via the novel SPVPS process was explored. Ytterbium oxide coatings were deposited by radial injection of ytterbium nitrate solution into a F4-VB torch operating under a pressure of 150-250 mbar. Solution precursor atmospheric plasma spray (SPAPS) was also applied to deposit superhydrophobic ytterbium oxide coatings for the comparison with SPVPS process. The wetting behaviors of the coatings were characterized by water contact angle measurement, water roll-off test and dynamic water impact test. The experimental setup, plasma jet properties, interactions of solution droplets and plasma, microstructure and wetting behaviors of coatings in the two distinct processes are compared and discussed.