Abstract This study is focused on understanding interaction energies for Al 2O 3 nanoparticle suspensions at high solids loadings. Among the four interaction energies: van der Waals interaction energy, electrostatic interaction energy, steric interaction energy, and depletion interaction energy, the study found that the van der Waals attraction is the dominant mechanism in destabilizing the dispersion system; the steric repulsion is a more effective stabilization mechanism than the electrostatic repulsion. The fundamental cause for an unstable suspension due to the particle–particle close contact and thus attraction at high solids loading can be overcome by increasing the particle–particle repulsion. When a dispersant is used in a suspension, the polymer chain length must be carefully selected so that the dispersant provides enough stabilization but does not compromise the maximum achievable solids loading. If an appropriate dispersant is chosen, up to 45 vol% solids loading suspension can be obtained for the Al 2O 3 nanoparticles.