In Situ Study of Structure–Activity Relationship between Structure and Tribological Properties of Bulk Layered Materials by Four-Ball Friction Tester

[Image: see text] Encouragingly, a lot of research studies have demonstrated that two-dimensional (2D) nanosheets applied as an additive in oils show preferable friction-reducing and wear resistance performance. However, the current issue was that an elusive way could be adopted to probe the structure–activity relationship between the structure and tribological properties of bulk layered materials due to the structural evolution during friction testing. In this study, we studied the structure–activity relationship between the structure and tribological properties of bulk layered materials (graphite, h-BN, WS(2), and MoS(2)) by an in situ four-ball friction tester. The morphological and structural changes of the layered materials after in situ four-ball-milling were detected by a series of characterizations. This study revealed the friction-induced nanostructural evolution behaviors of bulk layered materials by a four-ball mode.