The Effects of Three Types of Deflocculants and the Increase in the pH on the Rheological Behaviour of Nano Carbon/SiC Suspensions

In this study, the rheological behavior of nano carbon black/SiC suspension with different amounts of three deflocculants (Dispex G40, Dispex N40 and CMC) has been investigated. The weight ratio of silicon carbide to carbon black was 1:0.4, a volume ratio of 1:0.6. Rheological behavior of these suspensions has been investigated as a function of pH alone, and at various concentrations of the deflocculants, with and without the addition of alkali. 45 volume percent silicon carbide/carbon black suspensions cannot be fully deflocculated using alkali alone. However, DispexG40, N40 and CMC are all effective in the complete deflocculation of these suspensions. The addition of alkali enhances the deflocculating power of CMC and Dispex G40, reducing any existing yield stress to zero. However, it would appear that Dispex N40 is desorbed when the pH is increased as rapid coagulation of the system is apparent, arising from a reduction in the repulsive forces. The rheological behavior of two component suspensions containing deflocculants show similar trends to those obtained for carbon black suspensions.