Microprocesses of Agglomeration, Hetero-coagulation and Particle Deposition of Poorly Wetted Surfaces in the Context of Metal Melt Filtration and Their Scale Up

Abstract

AbstractIn this chapter the fundamental principles of the interaction of poorly wetted particles with interfaces of particles and bubbles are investigated in a water-based model system in which the similarity of poor wettability of non-metallic inclusions by molten metal and the poor wettability of silanized metal-oxide-particles by water is utilized. Capillary forces, the presence of nanobubbles and absorption of gas layers accompany the decreased wettability and lead to strong attractive forces. The combined effect of wettability and surface roughness is analyzed in detail, employing a variety of Atomic Force Microscopy techniques, as well as theoretical modeling of capillary forces and retarded van der Waals Forces for layered substrates. These concepts are extended to investigate particle-bubble interactions at different approach velocities by Colloidal Probe Atomic Force Microscopy and analysis by the Stokes-Reynolds-Young–Laplace model. The influence of temperature effects on the particle–particle interaction is investigated by High Temperature Atomic Force Microscopy. Additionally, the suitability of different interaction potentials for the Molecular Dynamics simulation of sintering alumina nanoparticles is accessed. Macroscopic agglomeration and hetero-coagulation experiments in a baffled stirred tank provide an insight into the dynamics of agglomeration and hetero-coagulation at for the metal melt filtration typical inclusion concentrations and wettability states.