3. Thermophoresis, photophoresis, diffusionphoresis phenomena

3.1 Thermophoresis

First observed by Tyndall, thermophoresis is the phenomenon whereby aerosols are repelled by very hot bodies. So, when there is a temperature gradient in a gas, particles move in the direction of decreasing temperatures. The modulus of the thermophoresis force depends on the properties of the gas and aerosols, and the temperature gradient. The first theories were established by Einstein in 1929 and Epstein in 1924, and later by various authors. Thermophoresis is applied in thermal precipitators