Nanoindentation - 3 Nanoindentation 3.1 Introduction...

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3 Nanoindentation 3.1 Introduction Hardness and elasticity measurements of solid materials have a long history. Macro- and microhardness have been of major importance for industrial pur- poses. However, indentation hardness is of particular interest for nanotech- nology and nanoscience as the materials damage is much more restricted. Therefore, the underlying effects can be explored and numerous materials properties are revealed and provide new unprecedented knowledge in various branches of science including daily life. While the theory of microindenta- tion appears well developed and the physics of the process seems to be suf- Fciently described for isotropic materials [1] the reasons for the differences between nano- and microindentation were not known and could therefore not be treated in [1]. ±urthermore, various effects in terms of chemical or crystallographic phenomena, including anisotropy, are less understood not to speak of the nanoscopic or molecular basis. As basic differences between nano- and microindentation have not recently been acknowledged or included in the physical treatment it is important to treat the topic in this book also on a more empirical and quantitative basis. Therefore not only selected model sys- tems but as much chemical diversity in the materials as possible are treated in order to Fnd more general relationships. 3.2 Equipment The distinction between nano- and microindentation is made at a penetration depth of about 200 nm. There are marked differences in these techniques, and nanoindention instruments provide linear load facilities in the range of 20 µ N up to 10 mN (usually two regions of calibration), whereas the microindentation instruments span the mN range up to about 4 N. Commercial load-controlled
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178 3 Nanoindentation nanoindentation instruments are available with height resolution of less than a tenth of a nm and force resolution of less than a nN. A detailed description of useful speciFcations of nanoindentation instruments is given in [1]. Some popular commercial brands include the Nano Test R ± , TriboIndenter R ± ,Nano Indenter R ± , Nano-Hardness Tester R ± ,andUM IS R ± . Acoustic detectors may be added for the detection of cracking, Fssuring, phase transformation, and slippage beneath the indenter. Depth control instruments at ultralow load for atomistic investigations are not yet of commercial standard [2] (see Sect. 3.9). Modern commercial nanoindenters such as for example the TriboScope R ± with TriboIndenter R ± of Hysitron, Inc. apply a constant loading rate through a ca- pacitive force and displacement transducer to a more or less sharp indenter tip and avoid the so-called zero error by a preload procedure according to ISO 14577. Preferably, the indented surface is Frmly mounted on an A±M stage (for example of a Nanoscope III), which allows for direct measurement of the initial surface (roughness) and of the Fnal impression obtained using the same indenter tip (though with some tip sample convolution). Separate A±M
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This note was uploaded on 08/21/2008 for the course EMA 6510 taught by Professor Dempere during the Fall '08 term at University of Florida.

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Nanoindentation - 3 Nanoindentation 3.1 Introduction...

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