Atomic Force Microscopy and X‐ray Photoelectron Spectroscopy Investigation of the Onset of Reactions on Alkali Silicate Glass Surfaces

Abstract

Atomic force microscopy was used to measure forces acting on a sharp tungsten tip as it was brought into contact with silica and 30 mol% binary alkali silicate glasses. Experiments were performed in controlled atmospheres and under vacuum. Attractive forces and liquid‐layer thicknesses were found to vary markedly between the glasses, and heterogeneity was observed on the binary alkali silicates analyzed in vacuo. Air or wet carbon dioxide exposure resulted in the penetration of the tip into a soft surface layer on the alkali silicates. In addition, liquid layer formation on the alkali silicates was found to be promoted by exposure to water vapor in the order lithium < sodium < potassium. X‐ray photoelectron spectroscopy indicated that reaction between the potassium silicate surface and water vapor occurred on exposure to only 10−4 torr (1 torr = 1.33 × 102 Pa) water. Surface segregation and leaching of potassium occurred under the same conditions. Copyright © 1993, Wiley Blackwell. All rights reserved