Silica replication of the hierarchical structure of wood with nanometer precision
- PDF / 339,652 Bytes
- 10 Pages / 584.957 x 782.986 pts Page_size
- 44 Downloads / 152 Views
Gerhard Fritz-Popovski and Oskar Paris Institute of Physics, Montanuniversitaet Leoben, A-8700 Leoben, Austria
Cordt Zollfranka) Department for Materials Science and Engineering—Glass and Ceramics, University of Erlangen-Nuremberg, D-91058 Erlangen, Germany (Received 3 January 2011; accepted 21 March 2011)
The structural features of wood were replicated in silica on all levels of hierarchy from the macroscopic to the nanoscopic level of the cellulose elementary fibrils. This was achieved by a series of processing steps on spruce wood templates. Sodium chlorite was used to partially remove the lignin matrix from the wood cell walls, exposing the cellulose fibrils. These were optionally functionalized with maleic acid anhydride to stabilize the fibrillar structure and reduce the shrinkage of the template. Repeated infiltration with tetraethyl orthosilicate in ethanol deposited silica on the fibrils. Calcination at 500 °C removed the rest of the organic template by oxidation and resulted in the fusion of the deposited material into a positive silica replica. Small-angle x-ray scattering evidenced fibrillar structures parallel to the original cellulose fibrils at length scales in the order of 10 nm, suggesting the successful nanoscopic replication of the cellulose fibrils and their orientation.
I. INTRODUCTION
Biomimetic mineralization is the replication of a biological template into an inorganic structural or functional material and provides a powerful tool to create complex material structures.1–3 These can include detailed structural features, such as undercuts, gradients, or continuous networks, which can only be elaborately produced with conventional top–down fabrication methods.4,5 Natural functional materials are interesting templates for converting them into inorganic materials for a wide range of materials for various applications.3,5–10 Wood is such a natural structural and functional material comprising several levels of hierarchy.11 Tracheids with diameters of 10–20 lm (latewood) or 30–40 lm (earlywood) are the dominating structural features of the xylems of softwoods such as spruce (Picea abies) or pine (Pinus silvestris).12 The wood xylem cell walls are composed of helically oriented cellulose fibril arrays embedded in a biopolymer matrix of lignin and hemicelluloses, which function as a connective intermediate.13,14 Several models have been proposed for the spatial arrangement of the biopolymer components in the wood cell wall.14–17 In native spruce wood, the fibril a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.98 J. Mater. Res., Vol. 26, No. 10, May 28, 2011
http://journals.cambridge.org
Downloaded: 20 Mar 2015
arrays have diameters of roughly 10–20 nm14 and are composed of elementary cellulose fibrils of about 2.5 nm in diameter,18 embedded in a hemicellulose and lignin matrix. In the dominatingly thick S2 cell wall layer of normal spruce early-sapwood, the cellulose fibrils are arranged parallel and their angle with respect to the cell axis is
Data Loading...
