T. Isshiki et al., HIGH-RESOLUTION TRANSMISSION ELECTRON-MICROSCOPY OF LAYER STRUCTURE AND STACKING-FAULTS IN TUNGSTEN DISULFIDE LUBRICANTS, Wear, 170(1), 1993, pp. 55-61
Tungsten disulphide crystals used as lubricants have been studied by h
igh resolution transmission electron microscopy (HRTEM). Theoretical c
alculation of the HRTEM image using the multislice method shows that t
he WS2 [2110BAR] images can distinguish between the W and S columns al
ong the incident electron beam and enable one to determine not only th
e crystal structure but also the fault structure. Observation of a WS2
[2110BAR] crystal, prepared by grinding, discloses stacking faults an
d an array of edge dislocations whose extra planes are single S-W-S la
yers, revealing the stacking sequence of W and S layers, and also the
stepwise structure of its (0001) surfaces as a result of the shear str
ain. The lubrication mechanism for solid lubricants such as WS2 and Mo
S2 is interpreted microscopically in terms of the crystallography on t
he basis of the observation.