Page 103 - Materials Chemistry, Second Edition
P. 103
90 2 Solid-State Chemistry
a
20μ
b c
40.0
50.0 nm
Height (nm) 0
25.0 nm
−40.0
0 0.25 0.50 0.75 1.00
200 nm mm
0.0 nm
20
100.002 nm Load (mN) 15
10
0.8
5
0.2 0.6
0.4 0.4 0
0 5 10 15 20
0.6 0.2 Displacement (nm)
mm
0.8
Figure 2.58. Examples of indentation processes to determine surface hardness. Shown are (a) Vickers
indentation on a SiC–BN composite, (b) atomic force microscope images of the nanoindentation of a
silver nanowire, and (c) height profile and load–displacement curve for an indent on the nanowire.
Reproduced with permission from Nano Lett. 2003, 3(11), 1495. Copyright 2003 American Chemical
Society.
layers, and weak interactions among molecules in neighboring layers (e.g., graph-
ite), a cleavage plane (c.f. slip planes, discussed earlier) is created where little force
is needed to separate the crystal into two units (Figure 2.59a, b). Since the cleavage
planes are parallel to crystal faces, the fragments formed upon cleavage will retain
the symmetry exhibited by the bulk crystal. Whereas cleavage describes the forma-
tion of a smooth piece of the original crystal when subjected to an external stress,