Effect of APC addition on stability of nanosize precursors in sol-gel processing of SiC nanopowder

Dispersion characteristics of a sol were assessed in terms of surface charge, particles size and rheological measurements. TEOS and phenolic resin were used as silicon and carbon sources, respectively, for preparing SiC nanopowder. APC was used as a dispersant agent. APC significantly increased the surface charges of the particles in intermediate pH and moreover as an acidic agent shifted pH to lower values. DLS measurements indicated more stability and controllable size of particles in the presence of APC. At pH < 4, size of particles was measured to be less than 10 nm. Rheometry measurements for sol showed that the viscosity increased and stability of particles decreased in intermediate pH. Electrokinetic measurements were used to determine adsorption specific free energy (Delta G degrees(sp)) between surface sites and adsorbing dispersant. Results showed a negative amount (-1.57 RT) that indicates a favorable interaction between particle surface and dispersant. FTIR of the dried gel powder indicated that (Si-O-C) bonds were formed due to hydrolysis and condensation reactions. XRD studies showed that the synthesized powder which was heat treated in 1500 degrees C for 1 h consists of beta-SiC phase. SEM observations showed that the beta-SiC particles agglomerated with a particle size less than 100 nm.TEM analysis indicated a semi-spherical morphology and mean size of 30-50 nm for beta-SiC particles. (c) 2010 Elsevier B.V. All rights reserved.