The effect of particle solubility on the strength of nanocrystalline agglomerates: Boehmite

Nanosized powders readily agglomerate during processing and handling. The strength of the interparticle bonds can dramatically affect the strength of the agglomerates and subsequent consolidation. This paper focuses on the origin of agglomerate strength for <10 nm sized boehmite (γ-AlOOH) powders. The agglomerate strength of boehmite gel is (= 23 MPa) more than three times higher than ethanol-dispersed boehmite agglomerate. Based on a series of experiments, it is demonstrated that solubility of the nanomaterials is largely responsible for increased agglomerate resistance to deformation and powder consolidation. A model is presented to explain how agglomerate strength increases as a result of the enhanced solubility of nanosize particles and precipitation of the solute at particle contacts during drying.