Overview: Homogeneous nucleation from the vapor phase—The experimental science

Abstract

Homogeneous nucleation from the vapor phase has been a well-defined area of research for ∼120 yr. In this paper, we present an overview of the key experimental and theoretical developments that have made it possible to address some of the fundamental questions first delineated and investigated in C. T. R. Wilson’s pioneering paper of 1897 [C. T. R. Wilson, Philos. Trans. R. Soc., A 189, 265–307 (1897)]. We review the principles behind the standard experimental techniques currently used to measure isothermal nucleation rates, and discuss the molecular level information that can be extracted from these measurements. We then highlight recent approaches that interrogate the vapor and intermediate clusters leading to particle formation, more directly.

Dynamical aspects of nanoparticle formation by wire explosion process

“…The phase transformation from vapour to solid takes place through the formation of stable nuclei. Critical size of the nucleus, r C on which growth occurs is given as equation (14) as (Wyslouzil and Wolk 2016),…”

“…where, s Metal is the surface tension of solid vapour interface, v Metal is the molar volume of the molten metal, m D is chemical potential given by -RTln(S), T is temperature and S is saturation ratio. Activation energy (DG rc ) for the formation of r C in classical homogeneous nucleation is given as (Wyslouzil and Wolk 2016),…”

Crystals creeping out of cracks

“…The formation of condensates can occur from pure vapor in a process termed homogeneous nucleation, or it may be catalyzed by a substrate onto which the condensates nucleate heterogeneously. Homogeneous nucleation of droplets from the vapor often requires very high saturation S L , that is, a high vapor phase partial pressure P G relative to the bulk phase liquid vapor pressure P L (bulk) (4). This behavior is a result of the fact that the very small initial clusters that form during nucleation are in the nanometer size range and, thus, they have very large surface-to-volume ratios.…”

Mass spectrometry of aerosol particle analogues in molecular beam experiments

“…The aerosol formation can be probed by special experimental arrangements directly in the macroscopic nozzle [43][44][45][46][47][48][49] or in post-nozzle flows. [50][51][52] The aerosol probing can be performed by different techniques ranging from X-ray and neutron scattering 49,53 to VUV ionization mass spectrometry. 50,52,54 Such experiments enable direct experimental observation of the onset of the aerosol nucleation.…”