FLAME SYNTHESIS OF COMPOSITE CARBON BLACK-FUMED SILICA NANOSTRUCTUREDPARTICLES

Simultaneous synthesis of SiO2/C nanostructured powders is investigate d in a premixed flame aerosol reactor by combustion of acetylene and S iCl4. The powders are found to be composed of SiO2 either encapsulated in or partially covered by carbon black. The effect of fuel equivalen ce ratio (phi) on carbon black yield and specific surface area is pres ented. High phi means fuel-rich flames that result in finer fumed sili ca though the specific surface area of the composite powder remains vi rtually unchanged with phi. The presence of silica enhances the carbon black yield 2-3 times. Applying external electric fields across the f lame allows synthesis of nanostructured powders with closely controlle d specific surface area and composition. Making composite powders perm its application of much higher electric fields than with pure carbon b lack before field breakdown. Increasing the electric field intensity d ecreases the specific surface area of the product powder in contrast t o that of electrically assisted flame synthesis of pure silica and oth er oxides. (C) 1998 Elsevier Science Ltd. All rights reserved.