Contact Electrification of Aminosilane Treated Silica Powder

Abstract

Contact charging was measured against reference Fe powder. A blow-off apparatus which is recently developed having a unique Faraday cage structure was used for the measurement.
As the amount of aminosilane adsorbed on silica powders was increased, following were observed.
(1) the contact charge varied from (-) to (+) value.
(2) the pH value of these powders dispersed in deionized water became larger.
(3) the zeta potential varied from (-) to (+) linearly as the contact charge varied toward (+) direction.
From the above facts it is obvious that the contact charging is in close correlation with the acidity (or basicity) of the powder surfaces, the decrease in the acidity being due to the replacement of the silanol groups of the silica surface (which act as H⁺ ion doners) by the amino groups of the silane (which act as H⁺ ion accepters). These facts also suggest a general possibility that the contact charging of a fine powder can be controlled by suitable selection of both the species and number of the functional group (e. g. -NH₂) adsorbed on its surface.