An in-situ TEM Nanoindenter System with 3-axis Inertial Positioner
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An in-situ TEM nanoindenter system with 3-axis inertial positioner M.S. Bobji, C.S. Ramanujan, R.C. Doole, J.B. Pethica, B.J. Inkson1 Department of Materials, University of Oxford, Oxford, OX1 3PH, U.K. 1 Dept. of Engineering Materials, University of Sheffield, Sheffield, S1 3JD, U.K. ABSTRACT To quantify the mechanical properties and deformation behaviour of sub-micron wires, an in-situ nanoindenter system is being developed for a TEM. The miniaturized displacement controlled nanoindenter fits inside a side entry specimen holder. For coarse positioning, a novel 3-axis inertial positioner has been developed. This positioner has a range of 5mm with a 300 nm resolution. The fine displacements are generated by means of a tube piezo and the force is measured using a fibre optic interferometer.
INTRODUCTION Materials with sub-micron grain sizes and defect distributions behave very differently from bulk materials. A high proportion of atoms in un-bulk-like sites such as grain and phase boundaries significantly alter bulk intrinsic deformation modes such as the initiation and propagation of dislocations and localised yield at cracks. Examples of beneficial mechanical properties, which can be obtained by the use of nanostructured materials, include the manifold increase in strength of metals such as Cu and Al with the reduction in grain size and the vastly improved ductility of nanocrystalline ceramics [1-6]. It is important to understand the mechanical properties of the materials at smaller scales in order to design and develop nanometer scale machines. In order to understand and improve the mechanical behaviour of materials at the nanometer level, it is necessary to have a sub-micron mechanical properties probe. Nanoindentation [7] introduced the ability to observe a complete cycle of loading and unloading of sub-micron volumes. This means that much more than just hardness can be determined. Parameters such as elastic modulli, creep response, visco-elastic effects can be quantitatively measured. To observe the nanoindentation deformation in a transmission electron microscope (TEM) [8,9], we have developed a nanoindenter with a novel 3-axis inertial positioner and a force sensor to do in-situ experiments. With this, we aim to unite the strain observing abilities of TEM [8,9] with the stress determining abilities of nanoindentation.
TEM NANOINDENTER DESIGN The nanoindenter has been designed to fit inside a side-entry specimen holder that can be used in JEOL 2010 and JEOL 3000 microscopes. All the moving parts are within the vacuum
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side of the holder, which means that a vacuum of less than 2x10-7 mbar can be easily achieved. The indenter consists of a 3-axis micro-positioner, a 4-quadrant piezo tube for fine positioning, a fibre optic interferometer based force sen
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