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Dong Liu

Dr Dong Liu
EPSRC Postdoctoral Research Fellow
1851 Exhibition Brunel Research Fellow
Junior Research Fellow at Mansfield College

Department of Materials
University of Oxford
16 Parks Road
Oxford OX1 3PH

Tel: +44 1865 273777 (reception)
Fax: +44 1865 273789 (general fax)

Summary of Interests

Materials with multiple length-scale structures are a fascinating yet critical class of material that have characteristic dimensions spanning from nano- to macro-scales. These materials have enormous potential for future use as they can display unique properties such as combinations of strength and toughness at ambient to elevated temperatures. Mechanistic understanding of the failure mechanisms in these materials at operating temperature is vital to assure the integrity of these components, from the safe operation of nuclear reactors to the extended protection of turbine blades in aero jet engines and land-based gas turbines.

My current research focuses on the mechanical testing (strength, damage and fracture including single mode and mixed-mode fracture) on a range of energy materials at multiple length-scales (micro-, meso- and macro-scale), and under extreme conditions such as neutron and proton irradiation and elevated temperatures above 1000C. The materials of interest include HOPG graphite, nuclear-grade graphites, carbon composites, MAX-phase ceramics, environmental and thermal barrier coatings, nano-structured steels and GaN-diamond composite materials for electronic devices.

Current Research Projects

An innovative, multi-scale, real-time approach to the understanding of deformation and fracture in irradiated nuclear reactor core graphites
Dr Dong Liu (EPSRC Postdoctoral Research Fellow), hosted by Professor James Marrow
The primary material of interest for this project is nuclear graphite. Nuclear graphite current serves as a neutron moderator and structural core component in the 14 operation UK Advanced Gas-cooled Reactors, and it is also a candidate material for future reactor designs such as Very High Temperature Reactors worldwide. In the irradiating and high temperature environment, nuclear graphite degrades in its microstructure, physical and mechanical properties. This project makes use of a range of cutting-edge techniques to investigate the deformation and fracture of nuclear graphites in the extreme environments. These are challenging experiments that require access to national and international large facilities (ENGIN-X, Rutherford Appleton Laboratory; ALS, Lawrence Berkeley Laboratory). In general, micro-mechanical testing on micro-metre miniature specimens prepared by focussed ion beam milling, high temperature in situ neutron diffraction combined with high temperature digital image correlation, high temperature in situ x-ray computed tomography with digital volume correlation, high temperature in situ Raman spectroscopy, and in situ electro-thermal mechanical testing combined with infrared imaging/pyrometry are adopted to characterise the deformation and fracture over multiple length-scales from nano-metre (lattice) up to centimetre range. These outcome will feed into microstructure-based computer models to forward predict the bulk behaviour and integrity of graphite components subjected to longer service. In addition to nuclear graphite, this project studies a range of other nuclear and energy materials such as MAX phase ceramics with combined properties from ceramics and metals at high temperature for the application of neutron resistant components and porous nanomaterial-based catalysts in solid oxide fuel cells, porous ceramic thermal barrier coatings for the application of turbine blades, SiC composites for high temperature nuclear applications, and the mechanical integrity of GaN-diamond based electronic devices.

1 public active projects

Research Publications

Liu, D* and Flewit, P (2017). 'Deformation and fracture of carbonaceous materials using in situ micro-mechanical testing' Carbon 114, 261–274.

Liu, D., Francis, D., Faili, F., Middleton, C., Anaya, J., Pomeroy, J.W., Twitchen, D.J., Kuball, M.* (2017). 'Impact of diamond seeding on the microstructural properties and thermal stability of GaN-on-diamond wafers for high-power electronic devices' Scripta Materialia, 128, 57–60.

Liu, D., Sun., H.R., Pomeroy, J.W., Francis, D., Faili, F., Twitchen, D.J., Kuball, M.* (2015). 'GaN-on-diamond electronic device reliability: mechanical and thermo-mechanical integrity' Applied Physics Letters, 107(25), 251902.

Marrow, T.J., Liu, D.*, Barhli, S.M., Saucedo Mora, L., Vertyagina, Y., Collins, D.M., Reinhard, C., Kabra, S., Flewit, P., Smith, D.J. (2015) 'In situ measurement of the strains within a mechanically loaded polygranular graphite' Carbon 96, 285-302.

Savija, B., Liu, D.*, Smith, G., Hallam, K.R., Schlangen, E., Flewit, P. (2015) Experimentally informed multi-scale modelling of mechanical properties of quasi-brittle nuclear graphite' Engineering Fracture Mechanics 153, 360-377.

Liu, D.*, Rinaldi, C. and Flewit, P. (2015) 'Effect of substrate curvature on the evolution of microstructure and residual stresses in EBPVD-TBC' Jornal of the European Ceramic Society, 35(9) 2563-2575.

Liu, D.*, Kyaw, S.T., Flewit, P., Seraffon, M., Simms, N.J., Pavier, M. and Jones. I.A.* (2014) 'Residual stresses in environmental and thermal barrier coatings on curved superalloy substrates: Experimental measurements and modelling, Materials Science and Engineering: A, 606, 117-126.

Liu, D.*, Lord, O., Stevens, O., Flewit, P. (2013) 'The role of beam dispersion in Raman and photo-stimulated luminescence piezo-spectroscopy of yttria-stabilized zirconia in multi-layered coatings' Acta Materialia, 61(1), 12-21.