Figure 2

0°–30° SEM image: (a) overall image of Black Spot 1; (b, c) enlarged view of Black Spot 1; (d) overall drawing of Black Spot 2; (e, f) enlarged drawing of Black Spot 2.
0°–30° SEM image: (a) overall image of Black Spot 1; (b, c) enlarged view of Black Spot 1; (d) overall drawing of Black Spot 2; (e, f) enlarged drawing of Black Spot 2.