Nanoindentation is a method of measurement of the mechanical properties of small volumes of materials using an instrumented indentation technique. Elastic modulus, hardness, fracture toughness, creep and dynamic properties such as storage and loss moduli can be measured. In this and subsequent articles, we will look at some of the issues facing the user of a nanoindentation instrument. Our purpose is to educate and inform the prospective user of this type of equipment as to what can be measured and what factors influence the results obtained.
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Figure 1. The IBIS Nanoindentation system from Fischer-Cripps Laboratories.
Locating Your Nanoindentation Instrument
Nanoindentation is concerned with the measurement of depths of penetration to sub-nm resolution and the application and measurement of forces in the uN range. To be able to do this, the instrument needs to be correctly positioned and prepared for use. In general, the laboratory conditions should be similar to those used for SEM or AFM imaging. In particular, the following points should be observed with respect to location:
- Avoid placing the instrument near windows where the sun will shine on the instrument.
- Avoid placing near open doorways or windows where there will be wind blowing on the instrument.
- Avoid placing near refrigerators, furnaces, vacuum pumps or other heavy machinery that would introduce electrical and mechanical interference.
- If the room is air conditioned, then make sure the air outlets are not directed onto the instrument since cycling off and on of the air conditioner will cause the temperature to change by an unacceptable amount.
- Avoid if possible placing the instrument near heavily trafficked areas, near doors that are often opened or closed, in a building near heavy rail and road traffic, etc.
A basement location is the ideal. The noise floor increases as the floor location increases due to building vibration. In the intended room, place the instrument near a solid support pillar or foundation – avoid placing in the middle of a suspended floor.
Thermal Equilibrium
If the instrument has been recently installed or moved, it is best to wait a day or two to allow for complete thermal equilibrium of the parts with the laboratory.
Example Installations
Some examples of good and poor installation are given here:
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Figure 2. Good installation.
Figure 2 shows a good instrument installation where the instrument is located in a small room away from other equipment, but this room has tiled floor and walls which means that acoustic noise is sufficient to show up on the displacement readings (such as if the operator talks too loudly). This installation would benefit from curtains on the walls and a carpet on the floor.
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Figure 3. Poor installation.
Figure 3 shows a poor installation where the instrument is mounted in the middle of the bench top with no solid under- support. The bench has very flimsy construction and is welded square tube with only a single upright. Fluorescent lighting is too close and will cause both electrical and thermal problems. Instrument location is near a window. This instrument will give poor results unless the initial contact force and maximum load are set fairly high.
If the instrument is poorly located, then it will be difficult to obtain accurate and reliable results. Often there is not much choice in location, and the best has to be done with what is available. Useful results can still be obtained under arduous conditions as long as the user understands what effects the conditions have on the data obtained.
Much more valuable information about nanoindentation can be found in Fischer-Cripps' free downloadable IBIS Handbook of Nanoindentation
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This information has been sourced, reviewed and adapted from materials provided by Fischer-Cripps Laboratories.
For more information on this source, please visit Fischer-Cripps Laboratories.