In recent years, X-ray microscopy (XRM) has grown out of origins at synchrotron facilities and set new benchmarks in high resolution, nondestructive 3D characterization. With 3rd and now 4th generation synchrotrons, and accompanied by exponential improvements in data transfer speeds and processing power, recent progress at these tomography beamlines has been largely focused around increasing throughput by pushing 3D frame rates well into the sub-second regime and opening the door to a wide range of dynamic materials evolution studies. Furthermore, an expansion in the variety of imaging/spectroscopy modalities has created increasingly rich and descriptive data sets.
Many of these techniques have also translated to a broader community via analogous lab-based machines. Through incorporating synchrotron-style optics, lab-based XRM systems can now achieve comparable levels of resolution and contrast, moving CT beyond an inspection/NDT technique and well into the scientific realm. Also similarly to the synchrotron, in situ imaging in the lab has become more prevalent as well, albeit at a different time scale. In particular, although rapid dynamic studies remain out of reach, interrupted or prolonged ‘time-lapse’ studies are very feasible, and in fact sometimes preferable in the lab where consistent instrument access is possible. Lastly, the classical absorption tomography of CT or microCT is being supplemented with an increasing range of modalities available on lab XRM systems, most notably and recently that of diffraction contrast tomography (DCT). While rigorous 3D characterization of grain structures has long faced practical challenges, the development of DCT now complements X-ray absorption imaging with the collection of diffraction patterns as well, unlocking information behind the grain structure within bulk, polycrystalline materials.
This paper will explore these emerging laboratory-based methods, namely in situ and diffraction contrast tomography, and provide examples of their application in materials science along with comparison against their synchrotron-based counterparts.