The plasma jet in the vacuum plasma spray process presents characteristics such as supersonic flow, expanded jet dimensions, and a smaller decay rate for jet velocity and temperature that are distinctly different than in atmospheric plasma spray. In this work, a 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 SPVPS process is explored. Yb2O3 coatings are deposited by a radial injection of Yb(NO3)3 solution in the anode of an F4-VB torch operating under a pressure of 150-250 mbar. Solution precursor atmospheric plasma spray (SPAPS) is also applied to deposit superhydrophobic Yb2O3 coatings for comparison with the SPVPS process. The wetting behaviors of the coatings are characterized by water contact angle measurement, water rolloff test, and dynamic water impact test. The experimental setup, plasma jet characteristics, interactions of solution droplets and plasma, microstructure and wetting behaviors of coatings in the two distinct processes are compared and discussed.

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