In flight treatment of metallurgical silicon powder by RF thermal plasma: elaboration of hydrogenated silicon deposit on a substrate

A plasma deposition process of metallurgical grade silicon powders was used in order to combine purification and deposition processes onto different kinds of substrate with a high deposition rate ( approximate to 100 mum min(-1)). The calibrated silicon particles, previously (50 < circle divide < 120 mum) are injected axially in the plasma and dragged by a carrier gas flow. Laser doppler gramilometry (LDG) analysis has been undertaken in order to measure the residence time tau of the particles in the plasma which is approximately 12 ins for 30-cm-long trajectories and an evaporation rate close to 30%. The decrease in particle size is due to the melting and evaporation reactions, which lead to the purification process. EDX and ICP analyses show that under optimised experimental conditions, dense and pure silicon deposits are obtained on a ceramic substrate. (C) 2002 Elsevier Science B.V. All rights reserved.