Fig. 2: Wear tests of the tungsten/graphite contact.
From: Robust structural superlubricity under gigapascal pressures
a, b Experimental setup (a) and OM image (b) of the tungsten/graphite contact. c, d OM (c) and AFM (d) images of the graphite substrate after sliding tests. The testing procedure includes 3 steps of (1) sliding the tungsten tip under the pressure of 3.74 GPa within Region I, (2) elevating the pressure to 5.07 GPa and move the tip from Region I to Region II through Trace I, and (3) sliding the tip under the pressure of 5.07 GPa within Region II. The sliding velocity and sliding amplitude are 10 μm/s and 30 μm, respectively. The test was stopped once obvious wear of graphite was in-situ observed by OM, or the number of sliding cycles reached 104 (corresponding to a total sliding distance of 0.6 m). e, f Magnified views of the step edge indicated by yellow and cyan dashed boxes in d. Source data are provided as a Source Data file.
