It has been well accepted that polyacrylic acid (PAA) is an effective dispersant for metal diborides (such as ZrB2) in aqueous media. However, when dispersing HfB2 powder, the dispersing effect is reduced significantly. In this work, a second dispersant, ammonium citrate, was used to resolve this problem. It was found that a PAA-ammonium citrate binary dispersant system could effectively enhance the zeta potential, increase the PM adsorption content, and improve the stability of HfB2. The apparent viscosities of the suspensions were also investigated. Results showed that the PAA-ammonium citrate binary dispersant system was effective for improving the dispersion of HfB2 particles in aqueous media. (C) 2013 Elsevier B.V. All rights reserved.