Fig. 4

Transmission Electron Microscope images of wear material from experiment 101 (brightfield). a Quartz grain (Q) with rough fractured surface (white arrow). Clumps of amorphous silica particles (as) surround quartz grain. b Chips of crystalline quartz (top selected area electron diffraction pattern) and rounded clumps of amorphous particles (middle selected area electron diffraction pattern). At the scale of this image, nearly all amorphous silica grains are composites of smaller particles and fragments. c Broken fragments of striated plates composed of amorphous nanoparticles. Sharp slip surface composed of gradationally increasing packing density of particles toward slip surface (white arrows). Fragments are floating in loosely packed amorphous nanopowder. d Wear powder of rounded to elongate particles with grain size 10−100 nm that show no crystal structure (bottom selected area electron diffraction pattern)