Molecular simulation of the effects of humidity and of interfacial Si- and B-hydroxyls on the adhesion energy between glass plates

ES Savoy and FA Escobedo, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 465, 233-241 (2016).

DOI: 10.1016/j.jcis.2015.11.024

Adhesion energies for sub-micron particles cannot be accurately calculated with macro-scale theories, in part because heterogeneities in surface morphology and chemistry play a significant role. Atomistic models have been used previously to quantify adhesion energies in wet environments for pure silica surfaces. To extend such modeling to more complex glass materials, we adopt a more comprehensive amorphous glass potential, and use a simplified approach to define the interaction between the hydroxylated surface and SPC/E water. We compute adhesion energies for pure SiO2, and 90 mol% SiO2 + 10 mol% B2O3, in dry and humid conditions. We find that the addition of B2O3 reduces adhesion, due to multiple effects which result in reduced hydrogen bonding. At high RH, the water between the plates forms a clear liquid bridge, whereas at the lowest RH, the water connects in chains of hydrogen bonded molecules that form and break during the adhesion process, so that capillary forces do not come into play. We also find that for under-hydroxylated pure SiO2 surfaces, a transitional state which may be found after heating or during glass formation, adhesion energies are the highest. (C) 2015 Elsevier Inc. All rights reserved.

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