Key message

X-ray diffraction allows indirect measurement of the microfibril angle (MFA) in green and dry wood, revealing that there are statistical differences between the MFAs of these woods.

Abstract

Wood drying is essential for most wood uses; however, the removal of water from wood can lead to defects. Although it is consolidated that water removal to below the fibers saturation point causes a decrease in the distance between cellulose microfibrils, little is known about how the microfibril angle (MFA) behaves in dry wood in terms of the cell wall ultrastructure. The hypothesis investigated in this study is that with the reduced distance between cellulose microfibrils after drying, there is a simultaneous decrease in MFA. Therefore, the objective of the work was to estimate the microfibril angle of dry and green wood using X-ray diffraction (XRD) and then to compare the MFA of the wood in both conditions mentioned. The basal discs from stems of Eucalyptus grandis with age of 22 years were used to produce the samples used in the measurement of MFA by polarized light microscopy and of the T value by XRD. The mean MFA measured by polarized light microscopy was 7.0°. MFA could be estimated by T value obtained from XRD using the cubic model. The mean MFA estimated by this model was 9.0° for green wood and 7.5° for dry wood, concluding that the MFA in dry wood is slightly lower than in green wood.

中文翻译：

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X射线衍射在评估绿色和干燥大桉木微纤维角度中的应用

关键信息

X 射线衍射允许间接测量绿色和干燥木材中的微纤维角 (MFA)，表明这些木材的微纤维角 (MFA) 之间存在统计差异。

摘要

对于大多数木材用途来说，木材干燥是必不可少的；然而，去除木材中的水分会导致缺陷。尽管水分去除到纤维饱和点以下会导致纤维素微纤丝之间的距离减小这一观点得到证实，但关于微纤丝角 (MFA) 在干燥木材中的细胞壁超微结构的表现知之甚少。本研究中调查的假设是，随着干燥后纤维素微纤维之间距离的减小，MFA 同时降低。因此，这项工作的目的是使用 X 射线衍射 (XRD) 估算干燥木材和生木材的微纤维角度，然后比较上述两种条件下木材的 MFA。巨桉茎的基盘使用年龄为 22 岁的样品制备用于通过偏光显微镜测量 MFA 和通过 XRD测量T值的样品。通过偏光显微镜测量的平均 MFA 为 7.0°。MFA 可以通过使用三次模型从 XRD 获得的T值来估计。该模型估计的平均 MFA 为绿木 9.0°，干木为 7.5°，结论是干木的 MFA 略低于绿木。