Below you find a list of previously held seminars.
Title: Exploring Materials with High-Energy X-rays
Abstract: High-energy X-rays from 3rd generation synchrotron sources, including the Advanced Photon Source (APS), possess a unique combination of high penetration power and spatial, reciprocal space, and temporal resolution. These characteristics, coupled with extensive worldwide efforts over the past decades, have produced a variety of 3D imaging techniques using both density and diffraction/scattering contrast. I will describe our instrument which combines several of these techniques to study material microstructure through (i) absorption-based tomography, (ii) high-energy diffraction microscopy (HEDM or 3DXRD) and (iii) scattering tomography. The latter two approaches are complementary, as HEDM provides diffraction information (strain, orientation, shape and size) of individual grains in polycrystalline aggregates while scattering tomography yields spatially resolved but grain-averaged information, particularly relevant for fine-grained materials below HEDM limits as well as non-crystalline and amorphous materials.
These techniques operate in air with large working distances between optics, samples and detectors. This has enabled development and use of a variety of in situ environments to emulate the service conditions of a given material. I will describe several of these environments, as well as highlight some illustrative science cases. These include studies of plastic deformation and fracture in engineering materials for aerospace and nuclear applications, and inhomogeneities driving failure in emerging solid state battery materials. Finally, planned developments of high-energy x-ray capabilities after the imminent APS upgrade to a diffraction-limited source will be discussed.
Niels Møller Israelsen, DTU Photonics (7 December 2022)
Title: Optical CT
Peter Hedström, Professor in Materials Science, KTH (24 May 2022)
Title: Neutrons and high-energy x-rays for metallic materials research
Abstract: Neutrons and high-energy x-rays are complementary characterization tools due to their different interactions with the sample material, and both tools are highly suited for in-situ characterization of phenomena in metallic materials during industry relevant processes. Furthermore, high-energy synchrotron x-rays provide excellent temporal resolution to resolve fast phenomena. In this talk I will present some examples from our work to investigate mainly steels and cemented carbides, and how this is combined with post mortem characterization and materials modelling to further understand mechanisms and kinetic evolution of phase transformations and bulk deformation mechanisms. Some specific examples that will be presented are: nanostructural evolution leading to embrittlement of stainless steels, controlling phase transformations in steels during heat treatment, deformation of metastable austenite in steels and phase transformations during processing of cemented carbides.
Beamline Scientist Ana Diaz, PSI (20 January, 2022)
Title: Applications of X-ray ptychography for high-resolution imaging
Abstract: Ptychography is a microscopy technique that provides images of a sample with both absorption and phase contrast. Its implementation requires the use of a coherent illumination, scanning of the specimen, recording diffraction patterns in the far field with an area detector, and image reconstruction by means of iterative phase retrieval algorithms. Despite all these complications, the advantages of ptychographic imaging are often sufficient to motivate its practical application. This is the case in X-ray microscopy, especially in the hard X-ray regime, i.e. at photon energies higher than about 2 keV, where it is difficult to fabricate high-resolution aberration-free lenses. In this seminar I will explain the basic principles of X-ray ptychography and its implementation in a 3rd generation synchrotron beamline, highlighting the advantages of the technique compared to other X-ray microscopy methods. I will discuss the interpretation of absorption and phase contrast in the X-ray regime, including the case of crystals that are in Bragg condition, and I will show a few recent examples, even beyond imaging applications. Throughout this journey, I will make sure to separate established applications from those currently under development, leaving some open questions for the latter. Finally, I will mention the opportunities for X-ray ptychography in the context of brighter 4th generation synchrotron sources.
Prof. John C. Mauro, Professor and Associate Head, Materials Science and Engineering (7 September, 2021)
Title: Decoding the Glass Genome
Abstract: Glasses have played a critical role in the development of modern civilization and will continue to bring new solutions to global challenges from energy and the environment to healthcare and information/communication technology. To meet the accelerated pace of modern technology delivery, a more sophisticated approach to the design of advanced glass chemistries must be developed to enable faster, cheaper, and better research and development of new glass compositions for future applications. In the spirit of the U.S. Materials Genome Initiative, here I describe an approach for designing new glasses based on a mathematical optimization of composition-dependent glass property models. The models combine known physical insights into glass composition-property relationships, together with data-driven approaches including machine learning techniques. Using such a combination of physical and empirical modeling approaches, we seek to decode the “glass genome,” enabling the improved and accelerated design of new glassy materials, including chemically strengthened glasses. I also review a series of grand challenges in the field of glass science which require future research attention.
Chris Jacobsen (31 August, 2021)
Title: How macro can we do nano? The challenges in X-ray nanoimaging of increasingly large specimens
Abstract: X-ray nanoimaging has undergone remarkable development worldwide. With the advent of diffraction-limited synchrotron light sources, we consider the opportunity for exploiting the high penetration power of X-rays to image larger samples. How far can we go? Can we image centimeter-sized samples at nanoscale spatial resolution? We consider questions such as the optimum photon energy, and experimental strategies and computational approaches for imaging beyond the traditional depth of focus limit.
Dr. Anna Fedrigo, ISIS Neutron and Muon Source, UK (1 July, 2021)
Title: ToF Neutron imaging and imaging applications in archaeology
Abstract: In this talk, I will give an overview of the neutron imaging activities at ISIS, focusing on Time of Flight ToF applications and capabilities, and how the IMAT imaging beamline will be upgraded.
I will then present a few case studies showing how neutron imaging can be used to investigate how metals have been transformed through human activity, their technological evolution, and how they degrade over time, spanning, e.g., from Viking swords to Samurai helmets.
In some cases, the combined use of X-rays and neutrons provides additional element-dependent information which is fundamental in case of multi-phase objects.
Watch the recorded seminar on YouTube
Prof. David Paganin, Monash University, Australia (20 April, 2021)
Title: How to get more from your neutrons and photons
Abstract: This talk will give a broad overview of an imaging method that was published by myself and others in 2002*. The method utilizes both the refractive and absorptive information that is present in a sample. Its main advantage, when applicable, is that it can significantly reduce exposure time. Typical exposure-time reductions for X-ray imaging are by several orders of magnitude. Similar exposure-time reductions are possible for neutrons. While the method has been widely employed for X-ray imaging, opportunities remain for applications to neutron imaging. Some broad remarks will also be made regarding optimal ways of applying the method with the divergent beam that is typical of neutron research. This talk will be at a very general level that assumes no prior experience with phase contrast imaging.
* Paganin, D., Mayo, S.C., Gureyev, T.E., Miller, P.R. and Wilkins, S.W. Simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object, Journal of Microscopy 206 33-40 (2002).
Watch the recorded seminar on YouTube
Prof. Marco Francesco Mario Stampanoni, ETH Zürich (4 March, 2021)
Title: ”The fascinating evolution of coherent X-ray imaging: from complex applications at synchrotron sources to early detection of breast cancer in hospitals”
Download abstract here
Physicist Daniel S. Hussey, NIST (24 February, 2021)
Title: High resolution neutron imaging
Download abstract here.
See the recorded seminar on Youtube
Prof. Peter W. Voorhees, Northwestern University (28 January, 2021)
Title: The Materials Genome Initiative and Additively Manufactured Metals: New Computational Tools and the Central Role of Materials Data
Find the presentation here
Prof. François Renard, Université Grenoble Alpes (10 December, 2020)
Title: 4D X-ray imaging of laboratory earthquakes
Download abstract here
Watch the recorded seminar on Youtube
Prof. Peter D. Lee, University of Manchester (6 November, 2020)
Title: Seeing Materials Through a Synchrotron Looking Glass: Inside Additive Manufacturing to Intact Covid-19 Injured Organs with Micron Resolution
Download abstract here