W. Richard Bowen and Nidal Hilal 4

4.8 CHARACTERIsATION OF METAL sURFACEs 129
TAbLE 4.6 surface Characteristics Obtained from AFM Images.
Surface Area Ra (nm) RMS (nm) Average height (nm) Maximum range (nm)
(a) 38.3 49.5 361.1 726.6
(b) 124.3 170.1 785.4 1407.5
FIgURE 4.24 SEM image of a CaCO 3 crystal mounted as a probe on the apex of an
AFM cantilever.
images. Table 4.6 shows surface characteristics obtained from such
AFM images.
The differences in the roughness average (Ra) and root mean square
roughness (RMS) show that the statistical variation in height of the
individual points in each image becomes greater from sample (a) to (c),
whilst the average height and maximum range show that the magnitude
of the variations in height, and hence size, of the surface features is much
greater from sample (a) to (c).
Adhesion measurements were taken with a CaCO 3 crystal, Figure 4.24,
at five different points on the sample surface, with a total of approximately
100 measurements per sample, and mean adhesion values were calculated.