Characterization Techniques in Nanotechnology …
55
materials. For the Vickers microhardness testing, a well-polished, pointed, squarebased pyramidal diamond is utilized as the indenter, and HV is calculated by using
Equation:
HV =
K P
l 2
(14)
where K is 1.854, P is the applied load (Kg), and l is the average length of the
diagonal (mm).
In contrast, the Knoop microhardness testing employs a well-polished, rhombicbased pyramidal diamond as the indenter. This indenter produces a diamond-shaped
indentation where the ratio of long to short diagonals is 7:1. Contrary to the Vickers
microhardness test, the Knoop hardness number (HK) can be evaluated by dividing
the applied load with the projected area of the indentation. Hence, HK is measured
using the same equation above, where L is the length of the longer diagonal and the
constant K is equal to 14.229.
3.1.3 Nanoindentation
The hardness property of materials at nanoscales has been of great interest in recent
times due to the rapidly evolving field of nanotechnology. For this reason, the emergence of nanoindentation technique, which is an extension of microhardness test, has
taken the place of conventional hardness measurements to meet the requirements for
the investigation of new materials. Nanoindentation technique, otherwise referred to
as depth-sensing indentation technique, was first proposed and developed by Oliver
and Pharr (1992). This technology relies on the theory of contactelasto-mechanics.
Based on the load–displacement data retrieved from the tests, both the Young’s
modulus and hardness can be obtained from the slope of the initial portion of the
unloading curve as well as the ratio of the peak load to the projected contact area of the
indent, respectively. Meanwhile, not only hardness and elastic modulus can be evaluated from the loading–unloading curve, but also information such as viscoelasticity,
creep, fracture toughness, strain-hardening effect, residual stress, phase transition,
and dislocation movement can be obtained (Qian and Zhao 2018).
A typical MTS Nanoindenter XP and its schematic diagram are shown in Fig. 30a
and b, respectively. Details of the operating principle is available elsewhere (Qian and
Zhao 2018). Figure 30c is an example of Young’s moduli and hardness obtained from
nanoindentation experiments. Based on the load-indentation (Fig. 30c) and Oliver
and Pharr (1992) approach, the modulus-indentation (Fig. 30d) and the hardnessindentation (Fig. 30e) curves for ten different positions on each sample indicate that
the Young’s modulus differs slightly across the films (Asafa et al. 2013a, b). The
elastic modulus as a function of indentation depth for nanoporous zeolite thin films
is also in Fig. 30f (Chow et al. 2015).
55
materials. For the Vickers microhardness testing, a well-polished, pointed, squarebased pyramidal diamond is utilized as the indenter, and HV is calculated by using
Equation:
HV =
K P
l 2
(14)
where K is 1.854, P is the applied load (Kg), and l is the average length of the
diagonal (mm).
In contrast, the Knoop microhardness testing employs a well-polished, rhombicbased pyramidal diamond as the indenter. This indenter produces a diamond-shaped
indentation where the ratio of long to short diagonals is 7:1. Contrary to the Vickers
microhardness test, the Knoop hardness number (HK) can be evaluated by dividing
the applied load with the projected area of the indentation. Hence, HK is measured
using the same equation above, where L is the length of the longer diagonal and the
constant K is equal to 14.229.
3.1.3 Nanoindentation
The hardness property of materials at nanoscales has been of great interest in recent
times due to the rapidly evolving field of nanotechnology. For this reason, the emergence of nanoindentation technique, which is an extension of microhardness test, has
taken the place of conventional hardness measurements to meet the requirements for
the investigation of new materials. Nanoindentation technique, otherwise referred to
as depth-sensing indentation technique, was first proposed and developed by Oliver
and Pharr (1992). This technology relies on the theory of contactelasto-mechanics.
Based on the load–displacement data retrieved from the tests, both the Young’s
modulus and hardness can be obtained from the slope of the initial portion of the
unloading curve as well as the ratio of the peak load to the projected contact area of the
indent, respectively. Meanwhile, not only hardness and elastic modulus can be evaluated from the loading–unloading curve, but also information such as viscoelasticity,
creep, fracture toughness, strain-hardening effect, residual stress, phase transition,
and dislocation movement can be obtained (Qian and Zhao 2018).
A typical MTS Nanoindenter XP and its schematic diagram are shown in Fig. 30a
and b, respectively. Details of the operating principle is available elsewhere (Qian and
Zhao 2018). Figure 30c is an example of Young’s moduli and hardness obtained from
nanoindentation experiments. Based on the load-indentation (Fig. 30c) and Oliver
and Pharr (1992) approach, the modulus-indentation (Fig. 30d) and the hardnessindentation (Fig. 30e) curves for ten different positions on each sample indicate that
the Young’s modulus differs slightly across the films (Asafa et al. 2013a, b). The
elastic modulus as a function of indentation depth for nanoporous zeolite thin films
is also in Fig. 30f (Chow et al. 2015).