Microstructure and phase morphology of wood derived biomorphous SiSiC-ceramics

• Published in: Journal of the European Ceramic Society Vol. 24; no. 2; pp. 495 - 506
• Main Authors: Zollfrank, Cordt, Sieber, Heino
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 2004; Elsevier
• Subjects: Applied sciences; Biomorphous ceramics; Biotemplating; Building materials. Ceramics. Glasses; Ceramic industries; Cermets, ceramic and refractory composites; Chemical industry and chemicals; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Other materials; Physics; SiC; Specific materials; Structural ceramics; Technical ceramics; Transmission electron microscopy; Biotemplating; Transmission electron microscopy; Biomorphous ceramics; SiC; Cell structure; Ceramic matrix composite; Scanning electron microscopy; Wood; Solid solid interface; Lignocellulosics; Experimental study; Porous material; Precursor; Composite material; Non oxide ceramics; Structural ceramic; Template; Biological compound; Optical microscopy; Silicon Carbides; Infiltration; Silicon; Manufacturing; Microstructure
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/S0955-2219(03)00200-0

Biomorphous SiSiC-ceramics were prepared by spontaneous Si-melt infiltration of beech and pine wood derived biocarbon templates (C B-templates) at 1550 °C for 1 h. The microstructure, phase distribution and interface morphology of the anisotropically structured, microcellular SiSiC-ceramic composite were investigated by X-ray diffraction (XRD) as well as by light, scanning and, in detail, by transmission electron microscopy (LM/SEM/TEM). The biomorphous SiSiC-ceramics consist of three different phases: solidified Si in the cell lumina, few residual carbon islands located in the middle of the former wood cell walls and two different, reaction-formed SiC-morphologies. While the majority of the SiC-phase exhibits a grain diameter of a few microns, a second nano-grained SiC-phase was identified at the interface between the coarse-grained SiC-phase and the residual biocarbon. The occurrence of the nano-grained SiC-phase is related to the density and pore size of the initial C B-template. While in large pores and narrow carbon struts (low density earlywood) of the C B-template an excess of Si-melt yields the formation of mainly the coarse-grained SiC-phase, in latewood sections (small pores and thick C-struts) of the biocarbon template the nano-grained SiC-phase forms layers of up to several μm in thickness. Due to the uni-directional pore structure of the wood derived C B-templates, the morphology of the biomorphous SiSiC-ceramics can be analysed in well-defined pore orientations. A microstructural model for the SiC-formation and phase growth will be proposed and discussed with respect to conventional processed SiSiC-materials.