Moisture imbibition in wood studied by time-resolved X-ray scattering

Wood is a commonly used material that has most of its properties change based on its moisture content. This makes studying wood-water interactions important. X-ray measurements provide a practical way to measure changes in the wood structure while it interacts with water. While modern lab sources can be sufficient for several different X-ray measurements of wood-moisture interactions, synchrotrons are still required when the timescale is short. One example of this is how dry wood and the fibres within absorb liquid water and how the nanoscale structure changes while the moisture travels across the wood sample.
We have measured the moisture imbibition of several different wood samples using the ForMAX beamline at MAX IV Laboratory. The samples consisted of spruce heartwood, spruce sapwood and birch sapwood dried using different methods (oven-, room-, and freeze-drying). Additionally, the effect of the fibre direction on the water transport was investigated by exposing the sample to water in a way where the water can either travel along or across the main fibre direction. Both small-angle and wideangle X-ray scattering was measured simultaneously.
In order to measure the samples, we created a sample environment where the wood could be exposed to water through a small, exposed volume while simultaneously measuring X-ray scattering as soon as the wood begins to imbibe moisture. This allowed us to measure with good temporal (~1 s) and spatial resolutions (<1 mm), the changes in the wood structure as water is transported across the sample.