title: Electric conductivity percolation in naturally dehydrating, lightly wetted, hydrophilic fumed silica powder.
abstract: In studying the dehydration of surface-moistened fumed silica Aerosil powders, we found a conductivity percolation transition at low hydration levels. Both the percolation exponent and the threshold are typical for correlated site-bond transitions in complex two-dimensional (2D) systems. The exponent values, 0.94-1.10, are indicative of severe heterogeneity in the conducting medium. The surface moisture at the percolation threshold takes on a universal value of 0.65 mg([H2O])/m(2)([silica]), independent of the silica grain size, and equivalent to twice the first hydration monolayer. This level is just sufficient to sustain a quasi-2D, hydrogen-bonded water network spanning the silica surface.
authors.affiliation: Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland.
authors.forename: Dagmara
authors.initials: D
authors.lastname: Sokolowska
authors.forename: Daniel
authors.initials: D
authors.lastname: Dziob
authors.forename: Urszula
authors.initials: U
authors.lastname: Gorska
authors.forename: Bartosz
authors.initials: B
authors.lastname: Kieltyka
authors.forename: Jozef K
authors.initials: JK
authors.lastname: Moscicki