Neutron Reflectometry under High Shear in Narrow Gap for Tribology Study

Abstract

Abstract A parallel-face narrow gap viscometer was installed in the energy-resolved neutron reflectometer to investigate the change in interfacial structure under high shear. The viscometer was designed to operate with high shear rate while maintaining a µm-order constant gap between two parallel faces. When the base oil without any additives was sandwiched in the gap of viscometer, the neutron reflectivity profiles without and with the rotation of viscometer was the same. This result shows that correct measurements were performed regardless of whether the upper specimen was rotated or not. On the other hand, when the base oil containing polymethacrylate-type additive was sandwiched in the gap, both the thickness and density of adsorbed additive layer in shear field became lower than that in stay condition. The results demonstrate that the proposed method can be used to analyse the structural changes in the adsorbed layer formed by the additive on the surface. Such approaches with the combination of neutron reflectometer and narrow gap viscometer are promising for near-future tribology studies.