NanoLAB Triboprobe: Characterizing Dynamic Wear, Friction and Fatigue at the Nanoscale
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NanoLAB Triboprobe: Characterizing Dynamic Wear, Friction and Fatigue at the Nanoscale A J Lockwood1, J Wedekind2, R S Gay1, J J Wang1 M S Bobji3, B Amavasai2, M Howarth2, G Möbus1 and B J Inkson1 1 Department of Engineering Materials, The University of Sheffield, Sheffield, S1 3JD, UK 2 MMVL, Sheffield Hallam University, Sheffield, S1 1WB, UK 3 Department of Mechanical Engineering, Indian Institute of Science, Bangalore, 560 012, India ABSTRACT In-situ transmission electron microscopy (TEM) has developed rapidly over the last decade. In particular, with the inclusion of scanning probes in TEM holders, allows both mechanical and electrical testing to be performed whilst simultaneously imaging the microstructure at high resolution. In-situ TEM nanoindentation and tensile experiments require only an axial displacement perpendicular to the test surface. However, here, through the development of a novel in-situ TEM triboprobe, other surface characterisation experiments are now possible, with the introduction of a fully programmable 3D positioning system. Programmable lateral displacement control allows scratch tests to be performed at high resolution with simultaneous imaging of the changing microstructure. With the addition of repeated cyclic movements, both nanoscale fatigue and friction experiments can also now be performed. We demonstrate a range of movement profiles for a variety of applications, in particular, lateral sliding wear. The developed NanoLAB TEM triboprobe also includes a new closed loop vision control system for intuitive control during positioning and alignment. It includes an automated online calibration to ensure that the fine piezotube is controlled accurately throughout any type of test. Both the 3D programmability and the closed loop vision feedback system are demonstrated here. INTRODUCTION The development of micro- and nano-scale devices with moving parts, such as micro/nanoelectromechanical systems (MEMS/NEMS) and magnetic storage devices, requires knowledge and understanding of their tribological properties and wear resistance. As the size of device components shrink, an increasing percentage of a component’s volume is contained in the outermost 10 nm, so assessment of the tribological properties and failure mechanisms of these surface layers is incredibly important, and requires dedicated high resolution dynamical test methods. Significant progression has been made over the last ten years in the development of TEM stages to study the nanoscale properties of materials using nanoprobes [1-4]. Typically, manipulators have been incorporated into TEM holders to allow probes to be moved around and into contact with specimens in the microscope. Here we have developed new functionality for combined scanning probe microscopy (TEMSPM) which allows a miniaturized probe inside a TEM to do cyclic motion in three dimensions with precise control of the 3D position, speed and number of cycles [5-6]. By bringing the TEM probe into contact with a nanostructure under an electron beam, it is possible to observ
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