Thermophoresis: The mass transfer mechanism in modified chemical vapor deposition

Abstract

The mass transfer of particulates of silica and germania is characteristic of the MCVD process for preparing optical fiber preforms. Here, after considering a number of alternatives, it is suggested that the dominant mechanism of mass transfer is thermophoresis, i.e., diffusion due to a large temperature gradient. Analytical arguments are given which support this assertion and compare favorably with experiments carried out in a MCVD apparatus.