Pair distribution function computed tomography

Abstract

An emerging theme of modern composites and devices is the coupling of nanostructural properties of materials with their targeted arrangement at the microscale. Of the imaging techniques developed that provide insight into such designer materials and devices, those based on diffraction are particularly useful. However, to date, these have been heavily restrictive, providing information only on materials that exhibit high crystallographic ordering. Here we describe a method that uses a combination of X-ray atomic pair distribution function analysis and computed tomography to overcome this limitation. It allows the structure of nanocrystalline and amorphous materials to be identified, quantified and mapped. We demonstrate the method with a phantom object and subsequently apply it to resolving, in situ, the physicochemical states of a heterogeneous catalyst system. The method may have potential impact across a range of disciplines from materials science, biomaterials, geology, environmental science, palaeontology and cultural heritage to health.

Radial distribution function imaging by STEM diffraction: Phase mapping and analysis of heterogeneous nanostructured glasses

“…However, depending on the cluster size, these peaks in the RDF will diminish with increasing radius as the distance approaches the correlation length in the cluster as demonstrated in [10]. Furthermore, because of the limited probe size (~ 1 nm) of the electron beam, which is necessarily small for providing sufficient resolution e.g.…”

“…The RDF can be determined from X-ray and neutron diffraction data [1][2] and has been widely applied to investigate amorphous materials such as organic solids [3], liquids [4] [5], metallic glasses [6], phase-change memory materials [7] and nanoscaled energy storage materials [8] [9]. Jacques et al combined RDF analysis with X-ray diffraction computed tomography (XRD-CT) [10] for spatially resolved RDF analysis of heterogeneous structures, where structural features around tens of micrometers could be resolved [11].…”

X‐ray Excited Optical Fluorescence and Diffraction Imaging of Reactivity and Crystallinity in a Zeolite Crystal: Crystallography and Molecular Spectroscopy in One

“…We exploit the full potential of X‐rays22, 23, 24, 25, 26, 27, 28, 29 by using one X‐ray beam to acquire both diffraction and spectral information. The local zeolite crystallinity, as measured by μ‐XRD, is correlated with the local presence of Brønsted acidity, as measured by μ‐XEOF.…”

Recent developments in the structural science of materials

“…The article of Ringe (2014) reviews the challenges posed by controlling and characterizing the external shape and crystal structure of such small nanocrystals and highlights the key role of nucleation and growth processes in determining nano-crystal structures and properties. Kuzmin & Chaboy (2014) review the role of X-ray spectroscopy (both XANES and EXAFS) in analysing nano-particle structures; their work again emphasizes the role of modelling and simulation in assisting structural analysis. The role of XAFS in elucidating complex nano-particulate structures of importance in catalytic applications is also shown in recent work on alloy nanoparticles of Gibson et al (2015).…”