Cellulose crystallinity assessment is important for optimizing the yield of cellulose products, such as bioethanol. X-ray diffraction is often used for this purpose for its perceived robustness and availability. In this work, the five most common analysis methods (the Segal peak height method and those based on peak fitting and/or amorphous standards) are critically reviewed and compared to two-dimensional Rietveld refinement. A larger (n ¼ 16) and more varied collection of samples than previous studies have presented is used. In particular, samples (n ¼ 6) with low crystallinity and small crystallite sizes are included. A good linear correlation (r 2 ! 0:90) between the five most common methods suggests that they agree on large-scale crystallinity differences between samples. For small crystallinity differences, however, correlation was not seen for samples that were from distinct sample sets. The least-squares fitting using an amorphous standard shows the smallest crystallite size dependence and this method combined with perpendicular transmission geometry also yielded values closest to independently obtained cellulose crystallinity values. On the other hand, these values are too low according to the Rietveld refinement. All analysis methods have weaknesses that should be considered when assessing differences in sample crystallinity.

Composite fibres that contain cellulose and lignin were produced from ionic liquid solutions by dry-jet wet spinning. Eucalyptus dissolving pulp and organosolv/kraft lignin blends in different ratios were dissolved in the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate to prepare a spinning dope from which composite fibres were spun successfully. The composite fibres had a high strength with slightly decreasing values for fibres with an increasing share of lignin, which is because of the reduction in crystallinity. The total orientation of composite fibres and SEM images show morphological changes caused by the presence of lignin. The hydrophobic contribution of lignin reduced the vapour adsorption in the fibre. Thermogravimetric analysis curves of the composite fibres reveal the positive effect of the lignin on the carbonisation yield. Finally, the composite fibre was found to be a potential raw material for textile manufacturing and as a precursor for carbon fibre production.

Balsa, with its low density and relatively high mechanical properties, is frequently used as the core in structural sandwich panels, in applications ranging from wind turbine blades to racing yachts. Here, we describe both the cellular and cell wall structure of balsa, to enable multi-scale modelling and an improved understanding of its mechanical properties. The cellular structure consists of fibers (66-76%), rays (20-25%) and vessels (3-9%). The density of balsa ranges from roughly 60 to 380 kg/m 3 ; the large density variation derives largely from the fibers, which decrease in edge length and increase in wall thickness as the density increases. The increase in cell wall thickness is predominantly due to a thicker secondary S2 layer. Cellulose microfibrils in the S2 layer are highly aligned with the fiber axis, with a mean microfibril angle (MFA) of about 1.4°.The cellulose crystallites are about 3 nm in width and 20-30 nm in length. The degree of cellulose crystallinity appears to be between 80-90%, considerably higher than previously reported for other woods. The outstanding mechanical properties of balsa wood in relation to its weight are likely explained by the low MFA and the high cellulose crystallinity.