New Estimations of Surface Properties for Tribological Studies by Neutron Reflectometry

Tribological phenomena usually occur at a solid surface or an interface of solids. To carefully examine a tribological phenomenon, information on the state at the surface or the interface must be tried to be gotten from different angles. Estimations of the state, however, are generally considered to be difficult because there are few methods suit for adequately picking up the information on profiles and/or properties of the only nearest region to the surface. Especially for the case that the target is at the interface of metals, the estimation is more difficult because a standard electron beam cannot penetrate into either of the metal. The authors have, accordingly, developed a new estimation method applying a ‘neutron reflectometry’ to such a metal surface or a metal-metal interface. The reflectometry is suitable for analysis of vertical structures of the nearest regions to a surface as less than 1 μm. In addition, since a neutron beam can penetrate into many kinds of common metals, the estimation by the neutron reflectometry can be useful even for the metal-metal interface. In this paper, we report some results obtained by some of several basic experiments on neutron reflectometry. Surface profiles and ultra-thin film thickness of PFPE lubricant at a metal surface and/or a metal-metal interface were estimated in the study.