Fabrication of micro-scale fracture specimens for nuclear applications by direct laser writing
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.236
Fabrication of micro-scale fracture specimens for nuclear applications by direct laser writing 1, 2
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Mike P.C. Taverne , Xu Zeng , Katrina A. Morgan , Ioannis Zeimpekis , Chung-Che Huang , Ying-Lung D. Ho , Mahmoud 1 1, Mostafavi , Anton Shterenlikht * 1
Department of Mechanical Engineering, University of Bristol, Bristol, BS8 1TR, UK
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Department of Electrical and Electronic Engineering, University of Bristol, Bristol BS8 1UB, UK
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Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK
* E-mail: [email protected]
ABSTRACT
The structural integrity of nuclear fission and fusion power plant components is the focus of this research. The state of the art is using micro scale specimens milled with a focussed ion beam (FIB). Because of their very low volume such specimens can be lab tested, even when irradiated to low or medium level of activity. This offers a possibility of testing multiple specimens to investigate stochastic effects, e.g. effects of irradiation on the shift of the ductile to brittle transition. However, FIB milled specimens suffer from Ga contamination, to the degree that the validity of fracture data obtained on such specimens is questionable. We propose to use nano-additive manufacturing as an alternative to FIB for making micro scale fracture specimens. A combination of two-photon polymerization and electrodeposition and sputtering was used to manufacture microscale Brazilian disk fracture specimens (CBD), which are free from Ga and thus better suited for the study of irradiation effects on structural integrity. In this study Ni CBD specimens were made with 30 μm diameter and up to 13 μm thickness. The slot width varied between 1 μm to 2.9 μm width the corresponding slot length of between 7.5 μm and 8 μm. Consecutive FIB characterization shows that the specimens have polycrystalline microstructure with sub-μm grains. The work is ongoing making W CBD specimens and on reducing the slot width and using chemical vapor deposition fabrication.
INTRODUCTION Recently, considerable efforts have been dedicated to micromechanical testing of small scale specimens whose microstructure can be characterized by various advanced techniques such as scanning electron microscopy [1], high resolution transmission electron microscopy [2], atom probe tomography [3], and X-ray nano-tomography [4]. This is because such small-scale tests can be ion implanted or neutron irradiated but still handled in laboratory conditions due to their small volume even if the samples show low to medium levels of activity. The currently accepted method for fabricating micro-specimens is micro-milling micro-pillars or micro-cantilever beams, which undergo compression or bend loading by using a nano-indenter. The milling is carried out by focused ion beams (FIB). The process, although extremely versatile, is known to induce damage and material alterations to the specimens; these include: Ga contamination [5], Ga s
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