Lab profile: Philip Withers, University of Manchester

Lab name Henry Moseley X-ray Imaging Facility

Group leader Philip Withers

Location Henry Royce Institute for Advanced Materials, University of Manchester

Further information www.royce.ac.uk,
www.mxif.manchester.ac.uk

X-ray image probing the interior of a Li coin cell showing the manganese oxide cathode attached to the positive (uppermost) battery terminal. [16]

X-ray diffraction contrast tomography (colors) and attenuation CT (B&W) imaging allow tracking of the grain orientations and grain growth in a copper powder compact as it sinters towards full density. (Courtesy S.M. McDonald, Zeiss, and Xnovo.)

3D rendering of damage around a 3.175mm hole in a [45°/90°/-45°/0°]S carbon fiber epoxy composite after fatigue at 60% of the ultimate tensile strength until 50% loss in stiffness. [17]

Painted Lady chrysalis at 16 days development showing anatomy such as the limbs, mouthparts, and cuticle. (Courtesy T. Lowe, P.J. Withers after [10].)

(a) 3D rendering and tomographic slice through a velociraptor claw; (b) central slice through an image-based finite element model of the von Mises stresses in the (repaired) claw confirm that it was strong enough to hook their claws into their prey. [13]

Advanced imaging and characterization techniques can give scientists an unparalleled insight into a range of objects and materials from jet engines to a butterfly chrysalis, from meteorites to velociraptors, from bioscaffolds for tissue engineering to bread. These insights can help understanding of how structure forms and gives rise to specific properties, as well as how degradation occurs under realistic service conditions in real time.

Philip Withers, within the School of Materials at the University of Manchester, is the first Regius Professor of Materials in the UK and Chief Scientist for the Henry Royce Institute for Advanced Materials. He has dedicated his career to this kind of multiscale imaging and characterization, with the scope of his research traversing a huge range of unusual topics, as well as more traditional materials science challenge such as establishing processing-microstructure-property relationships and the behavior of materials in demanding environments.

After receiving his Ph.D. in Metallurgy and then lecturing at Cambridge, Withers joined Manchester University to take up a chair in 1998. He was elected to the Royal Academy of Engineering in 2005 and became a Fellow of the Royal Society in 2016. His imaging facility was awarded the Queen’s Anniversary Award for Higher Education in 2014 for outstanding innovation, excellence, and impact.

Philip Withers talked to Materials Today about his current research and future plans.

Can you describe your group?

My group has recently become part of the newly established Henry Royce Institute for Advanced Materials, which is a £300m project with its hub in Manchester and spokes at the Universities of Liverpool, Leeds, Sheffield, Cambridge, and Oxford, Imperial College, the National Nuclear Labs, and Culham Centre for Fusion Energy. This national center is opening up our facilities for collaborative research and innovation and allowing us to link up closely with industry to accelerate the discovery and development of new materials systems to address a range of global challenges.

How many staff currently makes up your group?

Along with Drs. Tim Burnett, Brian Connolly, and Prof. Bob Cernik, we have a team of about 40 post-docs and PhD students. In addition, hundreds of scientists and industrial users come and use our imaging facilities from within the University, nationally, and from all over the world through the Royce Institute. One of the things I love about my job is that we have people from many different fields working alongside one another applying similar analysis methods across a very wide range of materials, for example studying the pore structure in materials as diverse as batteries [1], bioscaffolds, rocks [2], and even bread [3].

What are the major themes of research in your group?

The highly penetrating nature of x-rays (and neutrons) means that we can study materials behavior in situ and in operando under demanding environments including ultra high temperature materials [4] and thermal barrier coatings [5] or follow novel manufacturing processes such as the additive manufacture of metals [6]. We can undertake time-lapse experiments at frame rates from 1000 per second [6] to experiments that evolve over months or years [7] looking in particular at advanced materials for the aerospace, nuclear, and oil and gas sectors. We are also developing new techniques such as 3D grain imaging [8] and color imaging (moving from B&W X-ray images to images that can discriminate different elements).

How and why did you come to work in these areas?

Originally, I was fascinated by why materials fail and I was one of the first to use penetrating neutron and synchrotron X-ray beams to measure the distribution of stresses in order to understand the degradation processes at work. Just as important as the internal stresses are defects and cracks, which led me to become excited by the high-resolution images, we can obtain in three dimensions (3D) using X-ray computed tomography (CT). One of the main advantages of X-ray CT is that a 3D image can be reconstructed non-destructively, which means that it is possible to study valuable artifacts that cannot be destroyed, or to apply the technique multiple times to track the evolution of structure over time (sometimes called 4D (3D+time) imaging) through a manufacturing process, during service life, aging or repair, for example.

This has led me to apply X-ray imaging to study all manner of things from resolving that ancient Egyptian iron beads are made from meteorites [9] to watching what goes on inside a chrysalis during pupation of a butterfly [10], from probing sub-surface corrosion in pipeline steels over long timescales [11] to the fast failure of composites used in wind turbines [12], from image-based modeling of veloceraptors [13] to materials that can heal themselves [14].

What facilities and equipment does the lab have?

In Manchester, we are lucky to have one of the largest collection of X-ray imaging CT scanners in the world, each tailored for in situ and in operando studies of materials stretching from objects 50 cm in size down to imaging of sub-millimeter sized samples at 50 nm. Uniquely, these facilities lie alongside a suite of electron microscopes that enables us to image the same sample over nine orders of magnitude in length scale. In particular, within the Royce we have automated serial mechanical sectioning, ultramicrotomy, and focused Ga⁺ and Xe⁺ plasma ion beams alongside chemical mapping techniques such as X-ray photoelectron spectroscopy (XPS), electron probe microanalysis (EPMA), and energy-dispersive X-ray spectroscopy (EDX) enabling us to create massive multimodal datasets automatically.

Do you have a favorite piece of kit or equipment?

I am still fascinated by the 3D images we can collect using X-ray CT scanners. Advances in imaging technology mean that each year new phenomena are being opened up to imaging.

What do you think has been your most influential work to date?

It is always difficult to pick out a single piece of work since much of it is driven by industrial challenges. For example, the research we did on controlling residual stresses caused by inertia welding is very important in terms of ensuring the structural integrity of aero engine disk assemblies [15]. Our work on correlative tomography [11], however, is very pleasing because it brings together microscopy and characterization across a range of scales and modalities on the same sample to build up a rich multiscale picture of materials behavior. I think correlative microscopy will become increasingly important and routine in the future.

What is the key to running a successful group?

I think the two key aspects are having a vision about which you are passionate and developing a team-working culture. This is especially important for challenge-based research because doing new science often requires contributions from mathematicians, physicists, chemists, materials scientists, instrument scientists, engineers, and biologists. I am a strong adherent of ‘measure what you value, don’t just value what you can measure’.

How do you plan to develop your group in the future?

I am really interested in the possibilities of machine learning, alongside high-throughput combinatorial methods, to accelerate the development of new materials systems. This requires a ‘fast design, make, test, and break culture’. As a materials scientist, I think materials microstructures are key, but to incorporate microstructures into such learning requires new methods to digitize or ‘fingerprint’ them. In this respect, I am aiming to develop our capabilities in automated and massive collection of 2D, 3D, and 3D+time digitized datasets to empower machine-learning and physics-based understanding of materials and their iterative development.

Key publications

Lab profile: Philip Withers, University of Manchester

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