3D x-ray microscopy (XRM)

3D x-ray microscopy achieves non-destructive characterisation of 3D microstructures of porous rocks in controlled environments and over time (4D). The Xradia 620 Versa uses a two-stage magnification architecture combining geometrical magnification by conventional microCT and optical magnification by microscope optics before acquisition by a CCD detector. This two-stage magnification enables submicron resolution tomographies across a diverse set of sample sizes and working distances. The XRM has a true spatial resolution of 500 nm with a minimum achievable voxel size of 40 nm. The resolution is still 1.0 µm at a working distance of 50 mm. The XRM records a series of 2D projection radiographs from various angles as well as a reference image (averaged blank image without sample) to reconstruct this stacked 2D projections to a 3D data set.

The data is processed with special visualisation and analysation software. The image processing includes usually adjustments of brightness, contrast and grey scale distribution as well as the filtering of the 3D data set. Visualisation is used to display relevant features of the sample in 2D cross-sections or as 3D volumes. Modification on the grey scale image could be clipping and colouring of the area of interest as well as adjustments in lightning, surface appearances and transparency.

The analysis of the processed image data provides different parameters, which are used for a characterisation of the sample material: e.g. particle sizes, particle forms, pore sizes and their distribution, connected and non-connected porosity, pore fillings, specific surfaces as well as lengths, volume and structures of agglomerates and cracks.

Equipment

High resolution 3D x-ray beam imaging system Xradia Versa 620

• objective lenses 0,4X, 4X, 20X, 40X and flat panel extension (Imaging of larger samples)
• 12 standard filters
• Deben CT5000-TEC, In situ heating/cooling/tensile/compression module, maximum stress 5 kN
• analyse workstation with DragonflyPro

Sample preparation

Porous materials up to a maximum sample height of 30 cm and a maximum weight of 15 kg can be examined in the XRM. The absorption of the x-rays increases with increasing thickness and density of the sample, which is leading to a darker image. Cylindrical sample are ideal for artefact-free measurements as they are rotated centrically during the measurement. Due to the proportionality between sample size and and true spatial resolution it applies: the smaller pore geometry the higher the achievable resolution with same sample material composition. Samples must be delivered with a short description of the material.

Contact

Dr. Sarah Hupfer (Lab management)

Michael Ude