Dispersants for silicon carbide in water—A comparative study

Abstract

The stabilization of silicon carbide (SiC), in aqueous solutions, is well studied in the literature and many suitable dispersants have previously been suggested. Dispersants include tetramethylammonium hydroxide (TMAH), 1 polyvinylpyrrolidone (PVP) combined with polyacrylic acid 2 or the biodegradable polyaspartic acid, 3 polyethylenimine (PEI) with 4 and without citric acid, 5,6 and various modifications of polyacrylates, 7 and polymethacrylates. 8 Good stabilization, without the use of a dispersant, has also been reported for alkaline environments. 9 Normally, these studies are, however, focused on a single or very few dispersants and the comparison between results in different publications are not straight forward, because, the surface properties are sensitive to the powder polymorph, the synthesis procedure, possible pretreatments, the particle size distribution, and the supplier of the raw material. The wide range of available analysis techniques, which is used to assess the suspension stability, further complicates such a direct comparison. The complexity is further increased by differences in dispersant polymer chain lengths, degree of polymer branching, and solid loading as exemplified with the measurement of zeta-potential in a PEI-based system. 10 Despite all these uncertainties, some general results can be extracted: The SiC powder has IEP in the pH range from 2 to 4 and a very negative zeta-potential, suitable for electrostatic stabilization, can be obtained when using alkaline conditions. 9,11 A