Carbon and fumed silica particles are routinely made on an industrials scale. Carbon particles are used as a reinforcement for elastomeres (tires), adsorbents (activated carbon) and have potential applications as catalyst supports. Among other applications, silica particles also reinforce rubber, significantly increasing its strength by forming silica networks within the rubber structure. The combination of carbon black and silica particles is more effective at reinforcing rubber than carbon black alone. Carbon black and fumed silica are also precursors for production of SiC and opaque silica aerogels. In these applications, it is typical to mix solid carbon and silica particles and hope that the final product would be a uniform composite. However since both silica and carbon particles are made by flame aerosol process it may be more efficient to make the composite in a single process. This may minimize the need for solid powder mixing and possible segregation and inhomogeneity in the final product. From a scientific point of view, the synthesis of composite carbon black -fumed silica particles is very interesting as silica sintering is favored at high temperatures while coalescence of carbon particles is favored at low temperatures when the carbon particles are young and contain some hydrogen atoms.Here carbon and silica-carbon particles are made by combustion of acetylene and SiCl 4 in a premixed flame in the presence of electric fields created by plate electrodes across the flame. The effect of fuel equivalence ratio(EQR) and applied electric potential is studied as the latter appear to facilitate synthesis of nanoparticles with closely controlled characteristics (Vemury and Pratsinis, 1995).In the absence of electric fields, the flame appearance is similar for all EQRs: A narrow gap is seated between the burner mouth and the most luminous region of the flame. The brightness decreases with any further increase of the height above this luminous area. At the tip of the flame sooting is observed. The size of the gap between the burner face and the luminous zone is decreasing and less sooting is observed as the oxygen supply is increased and the EQR is decreased. This makes the flame brighter indicating higher temperatures with decreasing EQR. These observations are in good agreement with studies of acetylene-oxygen, propane-oxygen and toluene/air flames. By changing the oxygen flow-rate from 208 to 243 c.cm/min the specific surface area (SSA) decreases from 235 to 120 sq.m/g corresponding to EQR of 3.6 and 4.2, respectively. Assuming agglomerates of non-porous, uniform spherical particles and neglecting the neck area, the average (Sauter) primary particle diameter d p ranged from 13 to 28 nm assuming carbon density of 1.8 g/c.cm. Smaller carbon particles are formed in the less fuel rich flames that exhibit higher temperatures favoring soot oxidation. Assuming that all carbon atoms will be converted to carbon particles, the maximum amount of 0.35 g/min of the latter can be formed corresponding to a process yield equal to one. The yield is 0.03 for EQR=3.6 and increases to 0.066 for EQR=4 while it does not change very much for larger EQRs. Low EQRs result in higher temperatures enhancing soot oxidation. Higher EQRs on the other hand favor surface growth and particle inception rates increasing, thus, the process yield.Microscopic analysis indicated that the carbon particles, in general, are agglomerates. Some of the agglomerates have short chains looming in various directions. In the fuel richer flames (EQR = 4) most of the particles are large, but few of them are very small. Particles formed in the less fuel rich flames (EQR = 3.6) seem to have a more uniform particle size. The micrographs suggest a primary particle diameter of 16 nm, which is in very good agreement with BET (14.1 nm). The less fuel rich flames are hotter, thus promoting oxidation of the soot and, therefore, favoring the disappearance of the smaller particles and the reduced size of the remaining ones.In the absence of an electric field the flame shows a straight shape. For a potential larger than 2 kV, the flame is increasingly tilted towards the negatively charged electrode in good agreement with Payne and Weinberg (1959) who investigated ethylene rich premixed and diffusion flames influenced by electric fields. The SSA of carbon particles increased from 130 sq.m/g in the absence of an electric field to 250 sq.m/g for + 5 kV and to as much as 275 sq.m/g for a potential of - 5 kV. The corresponding particle sizes are 26 nm in the absence of an electric field, 13 nm for a positive and 12 nm for a negative potential of 5 kV. On the other hand, the yield decreases with increasing potential across the flame. Lower yields may well result from higher flame temperatures and from incomplete soot formation due to shorter residence times in the reaction zone. This assumption is further confirmed by the observation that the flames are more luminous in the presence of strong electric fields indicating higher temperatures and thus, electric fields may increase the flame temperature. Microscopic analysis indicated that when an electric field is applied, particles still form agglomerates, although the amount of small primary particles decreases and the size of the remaining ones seems to be less than in the absence of electrical fields. Also the diameter of the larger particles is smaller in the presence than in the absence of electric fields. These changes may result from particle charging resulting in reduced coagulation rates and electrostatic dispersion, but also from an increase of the flame temperature, which favors soot oxidation.Making silica-carbon particles reduced the luminosity of the flame but nearly tripled the soot yield. It appeared that these flames exhibited lower temperatures and that the newly formed silica particles served as seed nuclei for soot formation by surface growth accelerating and increasing the amount of carbon to precipitate as soot rather than escape as CO or CO 2 . Applying external electric fields across the flame allowed synthesis of composite powders with closely controlled specific surface area and composition at the expense of soot yield. Making composite powders permitted application of higher electric fields than with pure carbon particles before field breakdown. Increasing the electric field intensity reduced the carbon content of the product powder and decreased its specific surface area in contrast to that of electrically-assisted flame synthesis of pure silica (Vemury and Pratsinis, 1996). Electric fields remove particles from the flame at oxygen rich areas where accelerate their oxidation and decreasing their specific surface area. This may be attributed to in-situ soot oxidation on fumed silica resulting in local sintering.