Powder Technology, Vol.376, 199-208, 2020
Direct observation of heterogeneous condensation on micron particles with uniform surface
Heterogeneous condensation events play an important role in the atmospheric environment and pre-technique for fine particle removal. In present work, superhydrophobic/partide surfaces were prepared and applied to achieve the direct observation of heterogeneous condensation on uniform particle's surface by an environmental scanning electronic microscope (ESEM). It indicates that heterogeneous condensation site on a single particle is randomly distributed. However, when the particles are connected together, heterogeneous condensation always occurs at the interface of particles. It shows that the interface between particles is favorable for nucleation process. This is because the Gibbs free energy barrier of critical cluster formed at the particle interface is smaller than that at other sites. Basing on the experimental and critical free energy calculation results, the evolution of heterogeneous condensation on particles is inferred. It shows that the initial stage and critical supersaturation of heterogeneous condensation on two or more particles are the same. (C) 2020 Elsevier B.V. All rights reserved.