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Superlubricity of molybdenum disulphide

1993; American Physical Society; Volume: 48; Issue: 14 Linguagem: Inglês

10.1103/physrevb.48.10583

1095-3795

Jean‐Michel Martin, C. Donnet, Th. Le Mogne, Thierry Épicier,

Adhesion, Friction, and Surface Interactions

We have studied the atomistic origins of the ultralow friction coefficient of a molybdenum disulphide (${\mathrm{MoS}}_{2}$) coating in ultrahigh vacuum conditions. A friction coefficient in the ${10}^{\mathrm{\ensuremath{-}}3}$ range is associated with friction-induced orientation of ``easy shear'' basal planes of the ${\mathrm{MoS}}_{2}$ crystal structure parallel to the sliding direction. In addition to this basal plane orientation, an orientation disorder around the c axis is observed, indicating that frictional anisotropy during intercrystallite slip could be at the origin of the vanishing of the friction force. Experimental HRTEM lattice fringe imaging of ${\mathrm{MoS}}_{2}$ wear particles clearly show the existence of characteristic Moir\'e patterns. We have simulated TEM lattice fringe images of a [0001] ${\mathrm{MoS}}_{2}$ crystal and produced rotational Moir\'e patterns by superimposing two such images. A qualitative agreement between experimental and simulated Moir\'e patterns is demonstrated, which gives credence that ultralow friction of ${\mathrm{MoS}}_{2}$ in high vacuum can be attributed to a superlubric situation, by frictional anisotropy of sulphur-rich basal planes during intercrystallite slip.