Explosive boiling of argon nanofilms in the Wenzel or Cassie state on high-temperature nanopillar-arrayed surfaces

In this work, phase change behaviors of liquid argon nanofilms in the Wenzel or Cassie state on gold nanopillar-arrayed surfaces are investigated via molecular dynamics (MD) simulations. The results show that the argon films with 4.0 and 7.0 nm thickness have lower onset temperatures of explosive boiling than that with 1.5 nm thickness. At the same wall temperature of 190 K and film thickness of 4.0 nm, evaporation only is observed for the films in the Cassie state, whereas explosive boiling is noted for the films in the Wenzel state, indicating that the Wenzel state has a lower onset temperature. The nanopillar height has significant effects on the occurrence of explosive boiling. On the nanopillar-arrayed surfaces with an intrinsic contact angle of 35°, liquid films are always in the Wenzel state, and explosive boiling occurs at a prolonged time for the surface with a larger nanopillar height of 2.040 nm, attributing to the larger energy barrier for the Wenzel-to-Cassie wetting transition. On the nanopillar-arrayed surfaces with an intrinsic contact angle of 101°, films are initially in the Wenzel state for the smaller nanopillar height of 1.224 nm; however, they transition to the Cassie state for the larger nanopillar height of 2.040 nm, leading to the prolonged explosive boiling.