Thermophoresis Velocity of SiO₂ Ultrafine Particles in a Flame [Translated]^†

Abstract

Thermophoresis of ultra•-fine SiO:-particles formed in a flame was experimental~\' investigated by setting an adhering surface perpendicular to a flame axis. The fo!!owing results v•.:ere obtained. I) Near the adhering surface, the number density of particles is considered to increase up to almost twice that in a flame. This is because the approaching velocity of particles decreased to about half of its original value keeping the cross sectional area of the flolt"ing region constant. 2) The therrnophoresis velocity was I. 0~ I. 4cmj s. 3) A particle diameter corresonding to the thermophoresis velocity is 0. 4-0. 8,u m, which is larger than a particle diameter measured in a flame. that is, 50~ 60nm. 4) Particles are considered to adhere to each other in the vicinity of the swface. 5) A main mechanism of particle adhesion is thermophoresis, and the effect of inertia can be neglected.