Conversion of wooden structures into porous SiC with shape memory synthesis

Abstract

Synthesis of structured silicon carbide materials can be accomplished using wooden materials as the carbon source, with various silicon impregnation techniques. We have explored the low cost synthesis of SiC by impregnation of carbon from wood with SiO gas at high temperatures, which largely retains the structure of the starting wood (shape memory synthesis). Suitably structured, porous SiC could prove to be an important type of catalyst support material. Shape memory synthesis (SMS) has earlier been tried on high surface area carbon materials. Here we have made an extensive study of SMS on carbon structures obtained from different types of wood. #

Synthesis, characterization, and wear and friction properties of variably structured SiC/Si elements made from wood by molten Si impregnation

“…This stage involves the decomposition of the polyaromatic hydrocarbon polymers like cellulose, hemicellulose and lignin, to form a pure carbon structure. 13,20,36 The third stage is a crystallization process where samples are heated to 1200 • C at a higher heating rate of 5 • C/min for 6 h. This heating leads to crystallization and purification of the carbon structures. Chances of oxidation and burning of the wood were minimized by carrying out all the process steps in an argon flow.…”

“…Since length contraction during pyrolysis of wood is orientation dependent, the contractions along radial-, axial-, and tangential directions are different. 13,20,[34][35][36] Pyrolysis of wood is done in three stages. During the first stage, samples were heated to 70 • C for 2 h to remove the moisture.…”

“…The XRD patterns suggest that the samples made by silicon impregnation are more crystalline than for shape memory synthesis. 20 …”

“…Thus SiC components have been successfully synthesized from wood using methods such as molten silicon impregnation, [10][11][12][13][14][15][16] silicon vapour impregnation, 17 carbothermal reduction after tetraethyl orthosilicate (TEOS) impregnation, 6,18 and shape memory synthesis using SiO vapour impregnation. 19,20 In the molten silicon impregnation method, molten silicon is forced to penetrate into the pore channel system of previously carburized wood by capillary forces and spontaneous wetting, undergoing a local solid-liquid reaction to form ␤-SiC. This method nearly retains the shape of the starting wood as a crystallized structure, in addition to the filling or capping of pores and voids with silicon.…”

“…4 During the last two decades, biological materials [5][6][7][8] have been favoured as raw materials for synthesizing engineering ceramics and composites. Natural materials like rice hulls, 9 cotton fibers 10 and woods from different kind of trees [11][12][13][14][15][16][17][18][19][20] have thus * Corresponding author. Tel.…”