Michael Moody
Professor of Materials
+44 1865 273693
My interests are focused upon enabling materials research at the nanoscale via the microscopy techniques of atom probe tomography (APT) and field ion microscopy (FIM). APT is a technique capable of material characterisations at the atomic-scale, in which each atom is identified chemically and located in three-dimensions with very high accuracy. Hence, it is a technique rapidly rising in prominence. The Atom Probe Group in the Department of Materials at the University of Oxford is interested and active in all areas of this research across a broad range of material systems.
In particular, I am developing a variety of new analytical techniques to improve the three dimensional reconstructions generated by APT and the subsequent atom-by-atom analysis of the resulting data. I am interested in applying these techniques to the characterisation of a wide variety of systems to inform materials research projects.
Selected Publications
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Using alpha hulls to automatically and reproducibly detect edge clusters in atom probe tomography datasets
2020|Journal article|Materials Characterization -
Nanoscale analysis of ion irradiated ODS 14YWT ferritic alloy
2020|Journal article|Journal of Nuclear Materials© 2019 Elsevier B.V. In this work, the nanoscale microstructure of an advanced oxide dispersion strengthened (ODS) 14YWT ferritic alloy (SM13 heat) with nominal composition Fe–14Cr–3W-0.4Ti-0.3Y2O3 (wt. %) has been characterized by atom probe tomography (APT) before and after ion irradiation with 70 MeV Fe9+ ions at 450 °C to a total dose of 21 dpa. A detailed solute cluster analysis of APT data reveals that, in the manufacturing process, larger nanoparticles form in or close to the grain boundaries respective to those inside grains. The evolution of the nanoparticles after irradiation seems to be related to their location, as a higher increase in the number density and in the Y:Ti ratio is observed for the nanoparticles in or close to grain boundaries. APT analysis also shows Cr, W and C segregation to grain boundaries enhanced by the irradiation. A previous study of this same alloy before and after irradiation reports that the mechanical properties do not seem to be affected, but the microstructure was not investigated to confirm. The present work confirms little microstructural evolution after irradiation in this 14YWT alloy, indicating tolerance at the given irradiation conditions. -
Decoration of voids with rhenium and osmium transmutation products in neutron irradiated single crystal tungsten
2019|Journal article|Scripta Materialia© 2019 High temperature, neutron irradiated single crystal tungsten, with a post irradiation composition of W - 1.20 ± 0.11 at.%Re - 0.11 ± 0.05 at.%Os - 0.03 ± 0.01 at.%Ta was characterised using a combination of Atom Probe Tomography (APT) and Scanning Transmission Electron Microscopy (STEM). APT showed that within nanoscale clusters of Re/Os, the atomic density was above the theoretical limit. Complimentary High Angle Annular Dark Field (HAADF) imaging shows that some clusters contain voids at their centre which are leading to APT aberrations and enhancing the atomic density. High resolution Energy Dispersive X-ray (EDX) spectroscopy shows that voids are decorated with a shell of rhenium with a small osmium cluster to one side. -
Observation of internal oxidation in a 20% cold-worked Fe-17Cr-12Ni stainless steel through high-resolution characterization
2019|Journal article|Scripta Materialia© 2019 Elsevier Ltd It is often assumed that internal oxidation cannot occur at temperatures below 400 °C. However, in the present work, internal oxidation was observed in a 20% cold-worked Fe-17Cr-12Ni stainless steel (SS) after exposure to simulated primary water of a pressurized water reactor at 340 °C and not in a similarly tested sample without prior cold-work. The formation of discrete Cr-oxide precipitates and the role of cold-work are discussed. The internal oxidation model is also proposed as a plausible stress corrosion cracking mechanism of Fe-17Cr-12Ni SS at that temperature. -
Observing hydrogen in steel using cryogenic atom probe tomography: A simplified approach
2019|Journal article|International Journal of Hydrogen Energy -
Atom Probe Tomography of Au-Cu Bimetallic Nanoparticles Synthesized by Inert Gas Condensation
2019|Journal article|JOURNAL OF PHYSICAL CHEMISTRY C -
Fast modelling of field evaporation in atom probe tomography using level set methods
2019|Journal article|JOURNAL OF PHYSICS D-APPLIED PHYSICSfield evaporation, atom probe tomography, FEM-BEM coupling, level set method, boundary element method, finite element method -
Radiation-induced segregation in W-Re: from kinetic Monte Carlo simulations to atom probe tomography experiments
2019|Journal article|European Physical Journal B© 2019, The Author(s). Abstract: A viable fusion power station is reliant on the development of plasma facing materials that can withstand the combined effects of high temperature operation and high neutron doses. In this study we focus on W, the most promising candidate material. Re is the primary transmutation product and has been shown to induce embrittlement through cluster formation and precipitation below its predicted solubility limit in W. We investigate the mechanism behind this using a kinetic Monte Carlo model, implemented into Stochastic Parallel PARticle Kinetic Simulator (SPPARKS) code and parameterised with a pairwise energy model for both interstitial and vacancy type defects. By introducing point defect sinks into our simulation cell, we observe the formation of Re rich clusters which have a concentration similar to that observed in ion irradiation experiments. We also compliment our computational work with atom probe tomography (APT) of ion implanted, model W-Re alloys. The segregation of Re to grain boundaries is observed in both our APT and KMC simulations. Graphical abstract: [Figure not available: see fulltext.]. -
A multi-technique study of “barrier layer” nano-porosity in Zr oxides during corrosion and hydrogen pickup using (S)TEM, TKD, APT and NanoSIMS
2019|Journal article|Corrosion Science© 2019 We have used (S)TEM, TKD, NanoSIMS and APT to study nano-porosity in the oxide grown on deuterated Zr-1.0Nb and Zr-2.5Nb alloys. A detailed analysis of “barrier layer” nano-porosity by TEM and TKD has revealed that the oxide grain structure is much more disorganised and the nano-porosity network better developed in the rapidly oxidising post-transition alloy. Direct observations of the trapped deuterium (D) distributions from NanoSIMS analysis also shows much more penetration of the oxide layer post-transition. APT analysis shows that there is Fe and D segregation to some of the oxide grain boundaries with occasional evidence of porosity containing trapped D and H. We conclude that interconnected porosity would offer a dominant pathway for the transport of hydrogenic species to the metal substrate during the aqueous corrosion of zirconium alloys in service. -
A Nanoscale Investigation of Carlin-Type Gold Deposits: An Atom-Scale Elemental and Isotopic Perspective
2019|Journal article|Economic GeologyCarlin-type gold deposits are one of the most important gold mineralization styles in the world. Despite their economic importance and the large volume of work that has been published, there remain crucial questions regarding their metallogenesis. Much of this uncertainty is due to the cryptic nature of the gold occurrence, with gold occurring as dispersed nanoscale inclusions within host pyrite rims that formed on earlier formed barren pyrite cores. The small size of the gold inclusions has made determining their nature within the host sulfides and the mechanisms by which they precipitated from the ore fluids particularly problematic. This study combines high-resolution electron probe microanalysis (EPMA) with atom probe tomography (APT) to constrain whether the gold occurs as nanospheres or is dispersed within the Carlin pyrites. APT offers the unique capability of obtaining major, minor, trace, and isotopic chemical information at near-atomic spatial resolution. We use this capability to investigate the atomic-scale distribution of trace elements within Carlin type pyrite rims, as well as the relative differences of sulfur isotopes within the rim and core of gold-hosting pyrite. We show that gold within a sample from the Turquoise Ridge deposit (Nevada) occurs within arsenian pyrite overgrowth (rims) that formed on a pyrite core. Furthermore, this As-rich rim does not contain nanonuggets of gold and instead contains dispersed lattice-bound Au within the pyrite crystal structure. The spatial correlation of gold and arsenic within our samples is consistent with increased local arsenic concentrations that enhanced the ability of arsenian pyrite to host dispersed gold (Kusebauch et al., 2019). We hypothesize that point defects in the lattice induced by the addition of arsenic to the pyrite structure facilitate the dissemination of gold. The lack of gold nanospheres in our study is consistent with previous work showing that dispersed gold in arsenian pyrite can occur in concentrations up to ~1:200 (gold/arsenic). We also report a method for determining the sulfur isotope ratios from atom probe data sets of pyrite (±As) that illustrates a relative change between the pyrite core and its Au and arsenian pyrite rim. This spatial variation confirms that the observed pyrite core-rim structure is due to two-stage growth involving a sedimentary core and hydrothermal rim, as opposed to precipitation from an evolving hydrothermal fluid.
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