Vol. 16, issue 05-06, article # 19

Abstract:

We propose to describe the diffusion of nanoparticles in a rarefied gas using kinetic theory. For this purpose, we use the interaction potential between a disperse particle and a carrier gas molecule we have constructed ourselves. The dependence of the diffusion coefficient on the radius of a particle and temperature of the carrier gas is studied. The theoretical results are compared with experimental data in detail. It has been established that the commonly used Cunningham-Millikan-Davies (CMD) correlation is inapplicable to small particles (less than 10 nm in diameter). Hence, any measurement method measuring mobility of particles or the diffusion coefficient to determine the particle size using the CMD correlation leads to a large systematic error (up to 100% and even more) in the region of small particle size. Furthermore, the CMD correlation is shown to apply adequately only in a narrow range of near-room temperatures, for which the parameters of this correlation were determined.