Wood-Derived Porous Ceramics via Infiltration of SiO2-Sol and Carbothermal Reduction

Abstract

The use of wood as a structure-giving material may be the key to producing temperature-resistant ceramics featuring high and directed porosity combined with necessary strength. The objective of this study was to develop a simple process to convert the evolutionarily optimized material wood into highly porous ceramics. Beech and pine, known to be relatively permeable, were pyrolyzed in a nitrogen atmosphere. The carbon-templates formed were infiltrated with various kinds of silica sol (SiO 2 ). The resulting SiO 2 /C composite was transformed into a SiC-ceramic (silicon carbide) via carbothermal reduction. Through the described process the macroscopic pore-structure of wood was transformed exactly into SiC. The SiC-ceramic produced proved to be thermo-resistant. It remained stable in oxygen atmosphere at 1200°C, after a SiO 2 coating around the SiC had been formed. This study focused on the alteration of the cell wall microstructure during the conversion of wood into SiC. Furthermore, the optimization of the individual process steps, pyrolysis, infiltration and ceramization along the most efficient route was pursued.

Aluminium Metal Matrix Composites Based on Biomorphic Silicon Carbide

“…gel casting, [2,3] soft molding, [4] direct coagulation casting (DCC), [5] tape casting, [6,7] screen printing, [8,9] electrophoretic deposition (EPD), [10][11][12] lithographic structuring of pre-ceramic polymers, [13][14][15] injection molding [16,17] etc.…”

“…[5] Due to the three-dimensional interconnected structure of the porosity in the wood, [6] an interpenetrating network of reinforcing ceramic and metal phases results if the original wood structure can be preserved during ceramisation and the pores can be filled completely with metal. The feasibility of the process has already been proven with the example of squeeze casting aluminium into biomorphic SiC preforms.…”

Carbonization of hot-pressed ARBOFORM ®-mixtures

“…After pyrolysis and subsequently ceramization a change in the property profiles is the consequence. According to Klingner et al (2003) irreversible pit closure also inhibited silicium infiltration of pine.…”

Replication of jute stem for porous cellular ceramics/composites in the SiO2–SiC–C System

“…The carbon cellular precursor from plants may be used for fabrication of dense or porous composite ceramics such as Si/SiC [2], porous SiC [3] and others [4]. The process routes involve simultaneous melt infiltration and reaction [2][3][4] or sol/ solution infiltrations followed by treatment for reaction [5,6] or complete oxidation of the carbonaceous precursor [7].…”

“…Plant derived C-preforms infiltrated with silica sols or their organo-alkoxide precursors can yield C/SiO 2 hybrid precursors with morphological and structural features of the parent plant and can constitute a special route of synthesizing/fabricating SiC based ceramics/composites [5,[8][9][10].…”