UC Merced

Continuum mechanics models for contacting surfaces assume a constant interfacial energy, or work of adhesion, between materials. Recent studies have challenged this assumption, instead demonstrating that stress-dependent chemical reactions across the interface modify the work of adhesion. Here, we perform 77 adhesion tests on diamond–silicon contacts using in situ transmission electron microscopy and atomistic simulations to quantify how the adhesion changes as a function of applied pressure. The results show a sevenfold increase in the work of adhesion (from approximately 1 to 7 J/m2) with an increase in the mean applied pressure from 0 to 11 GPa, where the most significant increase occurs above 5 GPa. We rule out alternative explanations for the changing work of adhesion, such as electron-beam artifacts, bulk shape change by inelastic deformation, and time-dependent processes such as creep. Therefore, these results confirm the presence of stress-driven chemical reactions in the contact and quantify the resulting change in the adhesion of these materials with applied pressure.