Affiliations: Division of X-ray Physics, Department of Physical
Sciences, University of Helsinki, P.O. Box 64, FIN-00014 University of
Helsinki, Finland | Measurement and Sensor laboratory, University of Oulu,
Teknologiapuisto 127, FIN-87400 Kajaani, Finland
Note: [] Corresponding authors: Professor Ritva Serimaa, Division of
X-ray Physics, Department of Physical Sciences, University of Helsinki, P.O.
Box 64, FI-00014 University of Helsinki, Finland. Tel.: +358 9 19150630; Fax:
+358 9 19150639; E-mail: ritva.serimaa@helsinki.fi
Abstract: Partially crystalline cellulose microfibrils are wound helically
around the longitudinal axis of the wood cell. Microfibril angle distributions
were determined using x-rays from single cells and slices of wood. Differences
in results are discussed using model calculations, which are based on
diffraction conditions. Microfibril angle distributions (MFA) in single wood
cells were measured through a bordered pit using microbeam produced by
capillary optics and synchrotron radiation. For all cells measured, the MFA
distribution was asymmetric and narrow with full-width at half-maximum around
18 degrees. The mean MFA distributions of slices of wood were determined using
a conventional sealed x-ray tube. MFA distributions of single cells differed
from those determined from slices of wood. On the basis of model calculations
the differences were attributed to the variation in MFA distributions of
different cells of the wood sample, in the orientation of the cells, and in the
cross-sectional shape of the cells. These factors are hard to take into account
in data analysis, thus microdiffraction experiments offer a unique means for
studies of the detailed structure of single wood cells.
