Grain boundary plasticity plays a critical role in deformation of nanocrystalline materials. However, it was unclear how strength of these materials depended upon grain boundary properties. Ultra nanocrystalline diamond was used as a model material in which the plastic deformation was mainly located at the grain boundaries and the dislocation processes were not active. It was discovered that hardness and yield stress had a simple functional dependence upon the stress required for grain boundary sliding. These results on hydrogenated ultra-nanocrystalline diamond demonstrated that phenomena from the field of nanoscale friction can be utilized to understand the deformation of nanocrystalline materials.

Strength of Ultrananocrystalline Diamond Controlled by Friction of Buried Interfaces. Y.Mo, D.Stone, I.Szlufarska: Journal of Physics D, 2011, 44[40], 405401