It is known that chemical reactions can be coupled to mechanical stresses, but the underlying fundamental understanding of this coupling is still limited. For example, the effect of the applied stress on the rate of chemical reactions is often described by phenomenological theories, such as the Eyring model. However, the physical interpretation of parameters in such models (i.e., the activation volume) has been elusive and large discrepancies have been reported for nominally the same materials systems.<br/><br/>Here, I will discuss new insights into mechano-chemical coupling at surfaces and interfaces brought in through atomistic simulations. Specifically, we discovered that in addition to the typically assumed contributions to mechano-chemical coupling from the electronic changes and bond stretching right at the reactive sites, the contribution from the deformation of the surrounding bulk region can play an important and sometimes dominant role. One example is interfacial reactions in tribological contacts where we found that the relative contributions to mechano-chemical coupling from the surface and from the solid depend on the stiffness of these regions and on the contact geometry. Different contact geometries in experiments could explain the variation in activation volumes reported in literature for the same materials systems. We developed an analytical theory that captures the relative contributions of surface and bulk to the activation volume. In the second example, we demonstrate that stiffness of the solid plays also an important role in corrosion. The effect of bulk stiffness on surface reactions will be demonstrated by considering corrosion of amorphous SiC in water and air. Our results imply that tuning of bulk stiffness by modifying stoichiometry can provide an effective method for controlling chemical reactions at surfaces and thus the rate of environmental degradation of materials.<br/><br/>Finally, I will discuss how chemical reactions at interfaces can impact friction forces by modifying the contact area of tribological contacts. This phenomenon is termed as chemical creep and it describes a process in which chemical bonding at the interface exerts additional adhesive force at the interface, which in turn significantly increases the contact area. Our study shows that interfacial chemistry and contact mechanics are intimately coupled to each other and that static contacts are not truly static, but instead evolve in time.

Coupling between surface reactions and deformation of the underlying material

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.