Developing Short-Range Repulsive Potentials for Aqueous Processing of Reliable Ceramics: Fid-Bau Portal

Developing Short-Range Repulsive Potentials for Aqueous Processing of Reliable Ceramics

Lange, F. F.

Abstract Nearly all ceramics are processed with powders. Until recently, powders used for advanced ceramics were not sufficiently plastic to use shape forming technologies common for traditional ceramics based on clay. Thus, engineering shapes are generally formed either as the powder is consolidated to a high volume fraction during drypressing, or by producing plastic behavior by adding large volumes of a polymer. Both shaping methods have severe limitations in producing advanced, engineering components. It is now recognized that interparticle potentials can be manipulated to produce non-touching, weakly attractive particle networks that lead to clay-like plasticity. Short-range repulsive potentials are required for this behavior. Particle pair potentials that include a short-range repulsive potential have a potential well that defines the equilibrium separation distance, the force needed to pull the particles apart, and the interparticle ‘spring constant’. The particle pair potential that produces a weakly attractive, but non-touching network can be evaluated by rheological (elastic constant and yield stress) measurements, or by surface force measurements (SFA or AFM). Different methods to produce the short-range repulsive potentials include adding excess salt slurries initially dispersed via double-layer, electrostatic potentials and adsorbing short molecules to produce steric effects at short separation distances. At high volume fractions, consolidated bodies can be plastic provided the particles are not forced to touch one another by ‘pushing’ them into their deep potential well during pressure consolidation. The yield stress of the touching, consolidated network is generally too high causing the saturated body to fracture when stressed.