title: Nanoscale repulsive forces between mica and silica surfaces in aqueous solutions.
abstract: Nanoscale repulsive forces between mineral surfaces in aqueous solutions were measured for the asymmetric mica-silica system. The force measured with an atomic force microscope (AFM) has universal character in the short range, less than ∼1 nm or about 3-4 water molecules, independent of solution conditions, that is, electrolyte ion (Na, Ca, Al), concentration (10(-6)-10(-2)M), and pH (3.9-8.2). Notably, the force is essentially the same as for the glass-silica system. Single force curves for a mica-silica system in a 10(-4)M aqueous NaCl solution at pH ∼ 5.1 show oscillations with a period of about 0.25 nm, roughly the diameter of a water molecule, a consequence of a layer-by-layer dehydration of the surfaces when pushed together. This result provides additional support to the idea that nanoscale repulsive forces between mineral surfaces in aqueous solutions arise from a surface-induced water effect; the water between two mineral plates that are pushed together becomes structured and increasingly anchored to the surface of the plates by the creation of a hydrogen-bonding network that prevents dehydration of the surfaces.
authors.affiliation: Department of Food Engineering, University of Bio-Bio, Chillán, Chile. sacuna@ubiobio.cl
authors.forename: Sergio M
authors.initials: SM
authors.lastname: Acuña
authors.forename: Pedro G
authors.initials: PG
authors.lastname: Toledo
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D012822:Silicon Dioxide / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D012996:Solutions; D014867:Water; D012822:Silicon Dioxide; C011934:mica