Nanometric Si-Based Oxide Powders: Synthesis by Laser Spray Pyrolysis and Characterization

摘要

The versatility of the laser synthesis method has been improved during the last few years. In this paper we present the synthesis of amorphous, nanosized Si/C/O powders obtained via ultrasonic injection of aerosol droplets into the beam of a high-power tunable CO_2 laser, using (CH_3)_xSi(OC_2H_5)_(4-x) (0 ≤ x ≤ 3) and hexamethyldisiloxane as alkoxysilane precursors. All these precursors strongly absorb the CO_2 laser emission between 9 and 11 μm. The addition of precursors containing Al or Ti in tetraethoxysilane (x = 0) leads to Si,Al or Si,Ti oxide composite powders. The evolution of the powders (chemical composition, crystallization, morphology) during heat treatment under air, argon or nitrogen is studied by infra-red absorption, thermogravimetric analysis, transmission electron microscopy and X-ray diffraction. Silica powders with specific surface area up to 500 m~2 g~(-1) are obtained when heating in air.