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KeywordsWood anatomy Steam explosion treatment Topochemistry of lignin redistribution Staining Drying SummaryThe changes in anatomy, Ultrastructure and topochemistry of aspen wood degraded by steam explosion treatment were investigated by light, scanning and transmission electron microscopy. Light microscopy provided an overview of the general changes in wood architecture and revealed the opposite roles of the vessels and ray cells. Scanning electron micrographs showed the fibrillar architecture of the fibre surface. Transmission electron micrographs showed that in addition to lignin redistribution on both the inner and outer surfaces of the cell wall, this also occurs inside the cell wall itself Lamellar deposition of lignin within the secondary cell wall and free fibrils in the extract were also observed. Special studies were undertaken to ensure that the best method was used to dry the wet samples for examination in the scanning electron microscope. Observation on all the three different microscopical levels is probably the best possible approach to this ultrastructural problem. * 4.42Holzforschung / Vol. 49 / 1995 / No. 2

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The production of novel materials and value-added chemicals from lignin has received considerable attention in recent years. Due to its abundant occurrence in nature, there is a growing interest in utilizing lignin as a feedstock for functional materials production, for example aerogels. Much like in the synthesis of phenol-based resins, the vacant ortho positions of the aromatic rings in lignin can crosslink with formaldehyde and form polymeric gels. After drying the hydrogels with supercritical CO2, highly porous aerogels are obtained. Current study focuses on the preparation and thorough parametrization of organosolv lignins from different types of lignocellulosic biomass (aspen, pine, and barley straw) as well as their utilization for the preparation of lignin-5-methylresorcinol-formaldehyde aerogels. The thorough structural characterization of the obtained aerogels was carried out by gas adsorption, IR spectroscopy, and scanning electron microscopy. The obtained lignin-based monolithic mesoporous aerogels had specific surface areas and total pore volumes in the upward ranges of 450 m2/g and 1.4 cm3/g, respectively.

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