Dissolution and deagglomeration of silicon nitride in aqueous medium

Silicon nitride undergoes hydrolysis and dissolution when subjected to an a queous environment. Molecular dynamics simulations suggest that hydrolysis proceeds through nucleophilic attack of water with the formation of an inte rmediate molecular complex involving a pentacoordinated silicon, We found t hat the dissolution of an oxidized silicon nitride powder resembles that of silica; the dissolution rate could be described using a simple kinetic equ ation with a dissolution activation energy of 52 kJ.mol(-1). The deagglomer ation of a fine silicon nitride powder under mild agitation was evaluated; we show that the peptization kinetics at room temperature is dominated by t he breakup of particle-particle bonds due to hydrodynamic friction and clus ter attrition. For breakup of hard agglomerates of small particles the diss olution of interparticle necks will play an important role.