Figure 6.

SEM and energy-dispersive X-ray spectrometer (EDS) analysis after a scratch test for (a) US and (b) NT: (on the right) SEM image of scratches where the numerical scale corresponds to the length of scratches (3 mm); (in the middle) high-magnification SEM image of a selected area marked as a green square; (on the left) EDS study of the selected area; (Scan 1 and 2) line profile EDS analysis across the scratches. Image (c) demonstrates dependence of the normal force on distance and estimated values of the critical normal force at which delamination of the thorough oxide film was observed for both the US and NT.