Scanning WAXS and microtomography for bulk structure characterization

THE RESULTS AND EXPECTED IMPACT

The left  figure displays a WAXS image that shows bright yellow, revealing that graphene is stacked in a graphite-like air barrier layer. The graphite flake plane is parallel to the thin NFCP film in a 150 x 210 µm measurement area from X-ray orientation analysis. This result will be used as the air barrier layer standardization baseline. No graphite scattering from the graphene functionalized WFC was observed, indicating that graphite stacking has been avoided in conductive composite during compounding.

For the first time in the world, the right figure shows a 3D rendering of a 3.4 mm³ µCT data volume from a part of a 3D-printed WFC kayak. The pore distribution, average fiber size, and density will be used to further standardize the process of 3D-printed biobased fiber composites for kayak and boat manufacturers.

THE INDUSTRIAL CHALLENGE

Biobased composite companies aim to use graphene for new functionalities. Wood fiber composite manufacturer Biofiber Tech AB needs to avoid graphene layer stacking into graphite to ensure optimal conductivity in wood fiber composite (WFC) for electromagnetic shielding and 3D printing materials. On the other hand, pulp manufacturer Holmen AB needs to optimize the graphene stacking thickness as air barrier layer in the nanocellulose/polymer (NFCP) composite. However, distinguishing between crystalline scattering from biobased fiber, polymer, and graphene crystallinity and dispersion to standardize production has been challenging.

WHY USING A LARGE SCALE FACILITY

Lab-based X-ray scattering methods and electron microscopy techniques have been inefficient and inflexible for industrial applications, often taking days to characterize few samples and failing to effectively characterize biobased fiber crystallinity or graphene in polymer blends as composites. Synchrotron radiation facilities offer highly coherent X-rays that enable efficient industrial characterization, capable of distinguishing crystalline scattering from biobased fiber, polymer, and graphene at the atomic scale in milliseconds. X-ray tomography can achieve 3-dimensional characterization in micrometer scale of bulk microstructures without requiring additional sample preparation. This enables versatile sample characterization, including films, injection-molded pieces, and 3D-printed objects, enhancing sample flexibility for industrial use.

HOW THE WORK WAS DONE

The experiments were conducted at the European Synchrotron Radiation Facility (ESRF) in France. Scanning wide-angle X-ray scattering (WAXS) was performed at the ID13 beamline to identify the stacking of graphene layers in NFCP films and WFC injection-molded dumbbell samples. Micro-computed tomography (µCT) at the BM05 beamline was used to obtain high-contrast bulk information on WFC samples, including a section from a 3D-printed kayak. Dimitrios Georgouvelas from Biofiber Tech AB conducted the measurements with the assistance of ESRF scientists Dr. Michael Sztucki (ID13) and Dr. Phil Cook (BM05).

“The first time we see the 3D visualized bulk structures of biobased fiber composites. Beneficial to product development and demonstration to our customers.” / Luis   Valencia, Biofiber Tech AB