Sammendrag
Interaction forces and adhesion between a silica
sphere and a flat silica surface in aqueous electrolyte
solutions were investigated by atomic force microscopy.
The forces were measured as a function of surface separation,
pH and NaCl concentration as the surfaces were
approaching each other. The adhesion force was determined
upon retraction with respect to pH, NaCl concentration
and contact time. The magnitude of the long range
repulsive force was decreasing with decreasing pH. A short
range repulsive force was observed at pH = 2, but no long
range repulsive forces were observed at this pH. Force
measurements showed that adhesion of silica surfaces in
water was obstructed by short and long range repulsive
forces. Adhesion was enhanced when both the long and the
short range repulsive force was mitigated. A maximum
adhesion force of 7.8 mN/m was measured at pH = 12.5
when the short range force vanished and the long range
repulsive force was reduced by increasing the NaCl
concentration. At pH = 12.5, the work of adhesion was
calculated to be 1.2 mJ/m2 according to the Derjaguin–
Muller–Toporov (DMT) model. Adhesion energy was
much less at pH = 2 (0.3 mJ/m2) due to persistive short
range repulsion.
sphere and a flat silica surface in aqueous electrolyte
solutions were investigated by atomic force microscopy.
The forces were measured as a function of surface separation,
pH and NaCl concentration as the surfaces were
approaching each other. The adhesion force was determined
upon retraction with respect to pH, NaCl concentration
and contact time. The magnitude of the long range
repulsive force was decreasing with decreasing pH. A short
range repulsive force was observed at pH = 2, but no long
range repulsive forces were observed at this pH. Force
measurements showed that adhesion of silica surfaces in
water was obstructed by short and long range repulsive
forces. Adhesion was enhanced when both the long and the
short range repulsive force was mitigated. A maximum
adhesion force of 7.8 mN/m was measured at pH = 12.5
when the short range force vanished and the long range
repulsive force was reduced by increasing the NaCl
concentration. At pH = 12.5, the work of adhesion was
calculated to be 1.2 mJ/m2 according to the Derjaguin–
Muller–Toporov (DMT) model. Adhesion energy was
much less at pH = 2 (0.3 mJ/m2) due to persistive short
range repulsion.