Correlative X-ray micro-nanotomography with scanning electron microscopy at the Advanced Light Source

Area of Science:

• Geosciences
• Materials Science
• Analytical Chemistry

Background:

• Geological samples exhibit properties across multiple scales, necessitating nano-scale characterization for a complete understanding.
• X-ray tomography provides 3D microstructural information but lacks chemical details.
• Scanning Electron Microscopy with Energy-Dispersive Spectroscopy (SEM-EDS) offers chemical analysis but typically at lower resolution or in 2D.

Purpose of the Study:

• To develop and validate a correlative methodology for measuring multi-scale 3D microstructure and chemistry in geological samples.
• To integrate X-ray micro- and nanotomography with SEM-EDS for comprehensive sample characterization.
• To demonstrate the application of this protocol on serpentine and basalt rock samples.

Main Methods:

• Performed micro X-ray tomography on rock cores.
• Utilized laser milling for sub-sample preparation for nanotomography.
• Conducted nanotomography, followed by SEM-EDS imaging and compositional mapping on prepared samples.

Main Results:

• Revealed multiscale 3D structures, including mineral phases and pore networks, in serpentine and basalt.
• Observed significant variations in pore and mineral phase volume fractions based on imaging resolution.
• Leveraged SEM-EDS chemical mapping to aid in segmenting phases with low contrast in X-ray imaging.

Conclusions:

• A correlative multiscale approach is essential for accurately characterizing complex geological aggregates like rocks.
• The integrated methodology provides complementary microstructural and chemical information.
• This protocol is broadly applicable to 3D imaging studies at user facilities.