Case Study: Towards artefact-free X-ray diffraction tomography images

Companies involved:

Finden Ltd, University College London, ESRF

Challenge:

In X-ray diffraction computed tomography (XRD-CT), large crystallites can produce spots on top of the powder diffraction rings, which after data integration and tomographic reconstruction, lead to line/streak artefacts in the tomograms. This is a major issue as the chemical information present in the XRD-CT can be lost.

Figure 1 for case study 1

 

Sample:

Mn-Na-W/SiO2 catalyst (powder form) in combination with a BCFZ perovskite hollow-fibre ceramic membrane.

Solution:

We developed a new data processing strategy to remove the line or “streak” artefacts generated in reconstructed XRD-CT images due to the presence of large crystallites in the sample. In our simple approach, we take the polar transform of collected 2D diffraction patterns followed by directional median/mean filtering prior to integration, yielding artefact-free images. For example, in this specific materials system, after the filtering process, we were able to observe that the Mn-Na-W/SiO2 catalyst chemically interacts with the BCFZ membrane forming a new stable phase, identified as BaWO4. Such information is crucial for the design of improved catalytic membrane reactors that exhibit long-term stability.

Benefits:

The line or “streak” artefacts are very common in XRD-CT data. Finden scientists have the necessary technical tools to remove such artefacts and generate artefact-free images where the chemical information is preserved.

Figure 2 Case Study 1

Further reading:

Removing multiple outliers and single-crystal artefacts from X-ray diffraction computed tomography data A. Vamvakeros, S.D M. Jacques, M. Di Michiel, V. Middelkoop, C. K. Egan, R. J. Cernik and A.M. Beale. Journal of Applied Crystallography (2015) 48, 1943

 


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The research project receives funding from the European Community‘s Framework Programme for Research and Innovation Horizon 2020 (2014-2020) under grant agreement no. 679933.