James Marrow
My research is focussed on the degradation of structural materials and the role of microstructure. A key aspect is the investigation of fundamental mechanisms of damage accumulation using novel materials characterisation techniques. This has concentrated recently on computed X-ray tomography and strain mapping by digital image correlation, together with X-ray and neutron diffraction, which I apply to studies of the degradation of Generation IV nuclear materials such as graphite and silicon carbide composites, as well as new materials for electrical energy storage
The next generation of nuclear power systems must be demonstrably safer, proliferation resistant and efficient. They will not provide power for some decades to come. Their development requires new high temperature fuels and structural materials with resistance to irradiation. This can only be achieved through fundamental understanding of materials microstructure and the mechanisms of materials ageing.
Research in engineering materials for energy generation is not a quick-fix topic. New materials take from 15-20 years to come into service, and then are expected to be in service for 40-80 years. The key physical mechanisms that determine manufactured performance, and how these properties age in service, are not very well understood, and mistakes in materials selection can have enormous financial and social implications.
Prediction is a major challenge, and deep understanding of the fundamental mechanisms of materials aging is essential to identify and avoid potential "cliff-edges" in future materials performance.
We use synchrotron tomography and also laboratory tomography in our work. You can follow some of the images we obtain on our laboratrory tomography instrument here www.instagram.com/xradia_oxford
New Research Projects Available
Selected Publications
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Comparison of ultrafine-grain isotropic graphite prepared from microcrystalline graphite and pitch coke
April 2021|Journal article|Fuel -
Assessment of the fracture toughness of neutron-irradiated nuclear graphite by 3D analysis of the crack displacement field
January 2021|Journal article|Carbon -
Corrigendum to “Unifying the Effects of in and out-of-plane constraint on the fracture of ductile materials” [Journal of the Mechanics and Physics of Solids (2020) 141, 103956] (Journal of the Mechanics and Physics of ...
January 2021|Journal article|Journal of the Mechanics and Physics of Solids© 2020 Elsevier Ltd The authors regret that Dr Ahmet Cinar's name was missed from the list of authors. We hereby correct the mistake and declare the correct list of authors are as follows: S.M. Tongea, C.A. Simpsona, A.F. Cinarb, C. Reinhardc, T. Connolleyc, A.H. Sherryd, T.J. Marrowe, M. Mostafavia a Department of Mechanical Engineering, University of Bristol, Queens Building, University Walk, Bristol, BS8 1TR, UK b Department of Mechanical Engineering, University of Sheffield, Mappin Building, Mappin Street, S1 3JD c Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE. UK d National Nuclear Laboratory, 5th Floor, Chadwick House, Warrington Road, Birchwood Park, Warrington, WA3 6AE, UK e Department of Materials Science, University of Oxford, 21 Banbury Road, Oxford, OX2 6HT, UK The authors would like to apologise for any inconvenience caused. -
Effects of polymer infiltration processing (PIP) temperature on the mechanical and thermal properties of Nextel 312 fibre SiCO ceramic matrix composites
January 2021|Journal article|Composites Part A: Applied Science and Manufacturing© 2020 Elsevier Ltd Effects of the polymer infiltration processing (PIP) temperature between 850 and 1050 °C on the mechanical and thermal properties of Nextel 312 fibre SiCO ceramic matrix composite were studied. The aim was to optimise the material system for its proposed application as a mechanical gas-seal at temperatures up to 900 °C. The microstructure and its failure behaviour at room temperature were characterised using electron microscopy (SEM, TEM), X-ray diffraction and high resolution X-ray Tomography, with mechanical testing by nano-indentation, fibre-push out and flexural bending. Thermo-gravimetric analysis quantified the thermal stability. Processing at 950 °C or above gave a combination of high effective elastic modulus, good resistance to mechanical damage from tensile strain and good thermal stability. -
Imaging Sodium Dendrite Growth in All‐Solid‐State Sodium Batteries Using 23 Na T 2 ‐Weighted Magnetic Resonance Imaging
November 2020|Journal article|Angewandte Chemie -
3D finite element modeling of water diffusion behavior of jute/PLA composite based on X-ray computed tomography
October 2020|Journal article|Composites Science and Technology -
Imaging Sodium Dendrite Growth in All-Solid-State Sodium Batteries Using 23 Na T2 -Weighted Magnetic Resonance Imaging.
October 2020|Journal article|Angewandte Chemie (International ed. in English)Two-dimensional, Knight-shifted, T2 -contrasted 23 Na magnetic resonance imaging (MRI) of an all-solid-state cell with a Na electrode and a ceramic electrolyte is employed to directly observe Na microstructural growth. A spalling dendritic morphology is observed and confirmed by more conventional post-mortem analysis; X-ray tomography and scanning electron microscopy. A significantly larger 23 Na T2 for the dendritic growth, compared with the bulk metal electrode, is attributed to increased sodium ion mobility in the dendrite. 23 Na T2 -contrast MRI of metallic sodium offers a clear, routine method for observing and isolating microstructural growths and can supplement the current suite of techniques utilised to analyse dendritic growth in all-solid-state cells. -
In situ measurement of elastic and total strains during ambient and high temperature deformation of a polygranular graphite
August 2020|Journal article|Carbon© 2020 Elsevier Ltd In situ neutron diffraction and synchrotron X-ray diffraction, combined with image correlation analysis of 2D optical and 3D X-ray tomography datasets, have been used to investigate the relationship between elastic lattice strain and total strain during deformation of Gilsocarbon (IM1-24) polygranular nuclear grade graphite. The specimens were flat-end Brazilian discs under diametral loading, such that a compressive-tensile biaxial stress state was developed in the central region. The X-ray study was at ambient temperature, and the neutron diffraction was conducted at temperatures from ambient to 850 °C. When under compression, there is a temperature-insensitive linear relationship between the total strain and the lattice strain that is measured perpendicular to the graphite basal planes. However, when under tensile stress, the total strain and elastic strain relationship is temperature sensitive: below 600 °C, the lattice tensile strain saturates with increasing total tensile strain; above 600 °C, significantly higher tensile lattice strains are sustained. The saturation in tensile lattice strain is attributed to microcracking in the graphite microstructure. Improved resistance to microcracking and damage tolerance at elevated temperature explains the increase in tensile strength of polygranular graphite. -
A 3D full-field study of cracks in a nuclear graphite under mode I and mode II cyclic dwell loading conditions
August 2020|Journal article|FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTUREScyclic loading, DVC, dwell, graphite, mode I, mode II, residual strain, strain accumulation -
Unifying the Effects of in and out-of-plane constraint on the fracture of ductile materials by using synchrotron X-ray tomography and digital volume correlation
August 2020|Journal article|Journal of the Mechanics and Physics of Solids