Troisiéme Conférence Européenne sur les Matériaux et les Procédés Avancés
J. Phys. IV France 03 (1993) C7-1481-C7-1484
Nanosized Si/C/N composite powders formed by laser-aerosol couplingN. HERLIN, O. CROIX, M. CAUCHETIER, M. LUCE and E. MUSSET
CEA-DSM-DRECAM, Service des Photons, Atomes et Molécules, CE Saclay, 91191 Gif-sur-Yvette cedex, France
Recently it has been shown that ultrafine preceramic Si/C/N powders in the nanometric range can be obtained by combining the ultrasonic injection of a liquid precursor with the CO2 laser irradiation. At the CEA the first experiments were conducted with hexamethyldisilazane - (CH3)3SiNHSi(CH3)3 - (or HMDS) as the precursor. The aerosol droplets formed by the Pyrosol process are carried out with a flow of argon or argon - ammonia mixture into the beam of a high powered industrial continuous wave CO2 laser. At laboratory scale up to 100cm3/hr of liquid are displaced with a conversion efficiency (liquid → powder) of about 45%. The chemical composition is controlled by varying the synthesis conditions. The C/N atomic ratio changes from 3 (under argon) to 0.35 (under argon + ammonia). The as-formed powders are amorphous, monodispersed and nanosized (<100nm). The effect of heating under nitrogen atmosphere has been studied by various diagnostics (chemical analysis, BET, XRD).
© EDP Sciences 1993