| A number of theories have been developed to explain heterogeneous nucleation. However, none of them perfectly predict or accurately explain all of the results from nucleation experiments. Gaps between observed nucleation phenomena and the theory still exist.; The first objective of this study is to investigate factors affecting heterogeneous nucleation: chemical properties of nuclei and condensing vapor materials. Next, a new approach was taken to help reduce the discrepancies between theory and measurement using the chemical properties based on their nucleation activities. This approach takes account of the chemical interactions between the nuclei and the condensing vapor in the heterogeneous nucleation mechanism as well as the supersaturation ratio and particle radius upon which almost all of the previous theories have concentrated for nucleation and/or particle growth.; A series of experiments were performed to examine the approach. Carbon particles were generated by combustion and used as nuclei. Nucleation of dibutyl phthalate (DBP), octadecane, octadecanol, and octadecanoic acid on these particles has been measured. These compounds have similar physical properties such as boiling point and supersaturation ratio at given conditions. However, they have different chemical properties such as dipole moment and polarizability, which are the factors of interest of this study, because they have different functional groups; ketone, alcohol, and carboxilic acid are for DBP, octadecanol, and octadecanoic acid, respectively while octadecane is an aliphatic hydrocarbon.; Using a modified turbulent mixing condensational nuclei counter (TMCNC), heterogeneous nucleation of the vapors with carbon particles was studied. The nucleation and growth were measured with a scanning mobility particle sizer (SMPS) system. The measured size distributions were converted to nucleation rates. Then, the experimental results were compared with Fletcher's (1958) well-known heterogeneous nucleation theory.; Differences between theory and experiment were observed as expected. The new approach using chemical interactions, dipole/dipole, dipole/induced-dipole, and induced-dipole/induced-dipole interactions among the nuclei and vapors, were applied to the comparison of the experiments with Fletcher's theory. When interaction energy ratio to Fletcher's Gibbs free energy for a given condition converges for a vapor, the Fletcher's theory predicts the observed experimental results well. When this ratio deviates from a constant value, or varies with partial vapor pressure and particle size, the theory shows poor prediction. The interaction terms used for the comparison of the experimental and theoretical heterogeneous nucleation were included in estimating particle growth and unexpected new particle generation in the condensing process. |
