Philip Withers, Professor of Materials Science at the University of Manchester, shares his experiences and research results with ZEISS microscopes
”I’m a materials scientist so I’m interested in, for example, how the microstructure of engineering materials gives rise to their outstanding properties,” explains Philip Withers. Until now it has only been possible to study their microstructure in 2D or in 3D by destructive serial sectioning. Yet by being able to visualize the microstructural evolution of materials in 3D and over a wide range of scales, it is possible to more fully understand their performance and the accumulation of damage under realistic service conditions. Withers adds: “By understanding how damage accumulates over time, or as a function of load, or environment, we can develop safer and higher performing materials.”
Correlative Microscopy, made by ZEISS
ZEISS offers innovative technologies for these applications. Thanks to high-resolution X-ray microscopes (XRM), microstructures can now be visualized in 3D non-destructively and as well over time using time-lapse imaging. The ZEISS microscopy portfolio also covers a large variety of length scales by integrating different systems – this is a one-of-a-kind technology which lets microscopes ‘speak’ to each other. Withers sees this technology as vital for his research: “There are very few ways to study both engineered and natural materials microstructures over 8 or 9 orders of magnitude. ZEISS systems enable us to perform correlative tomographies, revealing important aspects about the relationship between microstructural evolution and performance.”
A breakthrough in 3D materials science
Lab-based X-ray diffraction contrast tomography (LabDCT) is a new technology for the ZEISS XRM Versa product family. As the very first customer for one of these systems, Withers’ research team was able to map the crystallographic grain structure of a beta titanium alloy at the beginning of 2016 – a world first. Through a routine application of this new technique, he would like to improve materials’ performance, e.g. by controlling grain growth of metals and ceramics during sintering of powders to form 3D components.
Withers has been working with ZEISS systems since 2008, and he has a total of four X-ray and two electron microscopes from ZEISS within his facility. Withers’ research has already been honored with the most prestigious award in UK higher education: the University of Manchester was presented with the Queen’s Anniversary Award in 2014 for ‘New techniques in x-ray imaging of materials critical for power, transport and other key industries.’ 2016 has been as good year for Withers. He was elected a Fellow of the Royal Society, and it has been announced he will become the first Regius Professor of Materials as part of the Queen’s 90th Birthday celebrations. Further, he is establishing the Sir Henry Royce Institute for Advanced Materials aiming to strengthen the connection between first-rate science and industrial applications: “The work we’re doing together with ZEISS in the field of microscopy plays an important role in achieving this goal.”
Breaking new ground together
Withers says: “The primary reason we opted to collaborate with ZEISS was the high level of technical competency. We wanted to pioneer new techniques and push boundaries. ZEISS offered us this opportunity to work hand in glove to see things that just couldn’t be seen before.”
Complete Interview with Philip Withers, Professor of Materials Science at the University of Manchester (UK) and Director of the University’s Imaging Facility.
Can you tell us briefly about your overall research aims and key initiatives at the University of Manchester?
Well, primarily we’re interested in the relationship between microstructure and material properties. I’m a material scientist myself, and so I’m interested in how the structure of engineering materials gives rise to outstanding properties – whether they be man-made engineering materials or bio materials which have been engineered through natural selection to achieve a particular set of properties. What X-ray imaging enables us to do is to obtain those structures in 3D and to obtain them non-destructively. Non-destructively is good in itself, because many materials are difficult to section or difficult to prepare. The wonderful thing about X-ray imaging is that often you have to do very little to prepare the sample. This allows you to look at very fragile samples or samples that have a great historical or archival value without destroying them. Since you can take one 3D image and then another 3D image, X-ray imaging enables you to collect images over time so that you can study how the microstructure might give rise to certain properties over time.
3D material science is one of your core research thrusts. Can you comment on how ZEISS products enable progress in this area and what role correlative microscopy plays?
Well at an engineering level, often the behavior of a material and the lifetime of a material are determined by how defects nucleate and grow. And so if we can understand how defects grow, starting with a small nucleus and moving from a propagation phase to ultimate failure, then we can engineer those materials to slow down the rate of the nucleation of the defects or even remove the defects in the first place by improving manufacturing. We can then move to much safer and higherperforming materials with longer lifetimes. One really unique feature of the ZEISS instruments available is the ability to have large working distances in X-ray imaging. You offer X-ray imaging systems that can look on the millimeters and centimeter scale. But you also have very high resolution electron microscopes that enable us to study the same microstructure but at a much finer scale. For example: we can identify a crack in a component and then, through a series of different instruments, study how the crack nucleated at the nanometer scale. It’s very rare that you can follow microstructures over eight or nine orders of magnitude. This is one really unique feature of ZEISS instruments. One other thing that you offer us, which we very rarely get from X-ray imaging machines, is large working distances and phase contrast for looking at materials of low contrast. Phase contrast is usually only obtainable at a synchrotron but is not so easy to obtain in the lab.
You’re the world’s first customer of a new imaging modality: ZEISS LabDCT diffraction contrast tomography. This incorporates diffraction information of an X-ray microscope to obtain crystallography information. Can you share how this helps address specific problems in the material science community?
Until about 15 years ago, it was very difficult to measure grain orientations in 2D. Electron backscattered diffraction (EBSD) has totally revolutionized the imaging capabilities. Now we can easily image grain orientations, grain boundary relationships and microstructures in 2D. Performing 3D analysis has always been very laborious. We’ve had to take slices, and that’s meant that most crystallographic structures have focused on really small areas. With ZEISS LabDCT for Xradia Versa, we can actually measure crystal orientations in 3D in the laboratory for the first time. This is really important for a whole range of understandings. There are many properties that are dependent on the 3D crystalline orientations, and these have simply not been available to us on anything except a very, very small region. With ZEISS LabDCT, we can now move from imaging in 3D with EBSD in the electron microscope over regions of 50-100 microns to collecting 3D data over many millimeters. That’s two orders of magnitude. These are bigger volumes than we were able to do before, opening up a whole new range of science in materials.
You’ve been a ZEISS customer since 2008. Why did you choose ZEISS products and how has ZEISS helped enable your research ambitions?
There is a very large number of reasons why we’ve been happy to work with ZEISS. It starts with technical competency. We’re interested in innovating and being able to do new things. ZEISS enables us to work hand in glove with the company and the opportunity to pioneer and push the boundaries of what we can see. We’ve also found that the technical support is excellent, meaning that we can keep the machines running longer and therefore achieve higher throughput. We’ve had an ongoing dialog about new ways of stretching the envelope of what we can do. This has been absolutely vital to the kind of novel work that we’ve been able to do. Equally important has been the ability to integrate experiments and equipment, which has been one of our defining characteristics and ZEISS has allowed us to do that. By working alongside ZEISS, we’ve been able to see things that just people could never see before. In cases where people have only been able to take 2D images, we’ve been able to see really detailed 3D images for the first time. We’ve actually been able to see that you can time-lapse X-ray imaging. These techniques tell us some really important things about the relationship between microstructural evolution and performance. This is a very special set of insights. ZEISS makes it possible to see the unseen.
Where do you see the future of 3D microscopy? Where are the greatest challenges and opportunities?
3D imaging sounds very attractive, and of course at one level you get a lot more data. So you have to identify the right kind of problems for 3D analysis. It isn’t simply a case of 3D being better. You need to identify where analyzing microstructures in 3D really is important so that you can, for example, understand the connectivity of systems. In a 2D slice, it’s very difficult to see the connectivity of a series of cracks or to understand the connectivity of a series of pores. But in 3D that connectivity comes alive and we can understand how pores relate to one another. That’s very important, for example, in the oil industry, where we’re trying to understand the flow of liquids through porous systems. Another area is where we’re trying to archive samples. We can save that information and then share it with many other researchers. That may enable multiple groups to work on the same data sets. There are a lot of applications for 3D microstructures. I think we’re only just beginning to really learn how to characterize those microstructures and thus the connection to material properties. Once we’ve understood this relationship, we can then design new materials where the microstructure has been fashioned across the many length scales. Biology has been doing that for many millions of years. Material science in the engineering world is only just beginning to catch onto that.
While material science is your core competency, you often branch out into other complementary application areas. What is the driver for this? And how do these efforts relate to your experience in material science?
In all of these areas, understanding the relationship between microstructure and properties is important. It’s really exciting when you can take techniques that you’ve developed in one domain and see how much value they can deliver in another. It’s also fascinating in terms of delivering a lively laboratory. Having a medic sitting next to a chemical engineer, sitting next to a mathematician, sitting next to a chemical engineer leads to a very diverse scientific community. And each person brings different skills and knowhow to the table. For example: one of our first students was working with a natural history museum. She was measuring the shapes of particular types of reptile skull using 3D analysis techniques that we were able to transfer over into manufacturing. Now you’d normally expect the pathway to go the other way – techniques for measuring in manufacturing to be passed over into museum-type applications. But actually it was the other way around. There are all sorts of interesting synergies and interactions across very different subjects, leading to a very lively and diverse academic community. This also means that we can add valuevery quickly to different communities – and that’s fantastic. By using these unique techniques, we can often shed new light onto old challenges and questions.
This year you were named a Fellow of the Royal Society. What does this mean for your work?
Of course, I’m very excited about becoming a fellow of the Royal Society. Many of my childhood heroes were fellows. Hook springs to mind, who was working back when the microscope was in its infancy. Much of his development was connected with working with the Royal Society. He was a very strong character. Of course the history of electron microscopy within the UK, the development of X-ray imaging – all these things have a very strong lineage in the Royal Society. I hope that my role within the Royal Society will help me promote engineering applications and the input of science into engineering problems, because I think sometimes industrial and applied problems come across as somewhat low-level science. But what I’ve found by working with companies on applied problems is that there’s all sorts of really exciting science underlying an indus-trial problem – whether it’s understanding why the beer doesn’t foam or why a thermal barrier coating doesn’t adhere as well as one would hope. So I hope that my involvement in the Royal Society will maintain that thread between world-class science and industrial application, and I see the microscopy work that we do with ZEISS as very much part of that.
To conclude, let’s have another look into the future. How do you see the uptake of X-Ray microscopy into the manufacturing world? To date it’s really been the remit of research and universities, although there has been uptake from various organizations in industry. Do you see this field growing at a pace in the future or do you think X-ray microscopy will maintain its place mainly in research?
I think there’s two elements to industrial work where X-ray microscopy will play an increasing role. Obviously, as we develop new products and try to understand the problems with existing products, industrial research labs will often need to make use of the optical microscopes. I think the time is coming where many of those labs will have their own X-ray imaging system. An X-ray microscope can be an important tool for process development. There are also some opportunities in product evaluation. We’ve been working with methods which would enable you to scan products, for example in additive manufacturing. You would be able to ensure not just the shape of that object, but also its integrity and quality. So I think it’s conceivable that we will be able to develop systems using some of the manufacturing technologies we already know – X-ray imaging would do real-time evaluation of components and structures. I see that as particularly important in areas where additive manufacturing might be used more often, such as in aerospace and medical engineering. You can imagine the relationship between X-ray imaging and bespoke manufacturing for medical technology. I expect these things to occur, but I think there are two important things that need to happen in the meantime for that to become the case. First, the price is important, of course, but the costs and capabilities of machines are moving in the right direction. Second, we need to grow an educated community of qualified users, i.e. people who are familiar with analyzing 3D data. The number of X-ray imaging machines has risen exponentially each year, and I don’t see that changing in the short term. Sooner or later these systems will be used more often in industry. Frankly, I think the future is bright. I don’t think this change will happen overnight, but I think in ten to twenty years’ time we’ll be living in a 3D world.
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