Fabrication and Mechanical Properties of SiCw(p)/SiC-Si Composites by Liquid Si Infiltration using Pyrolysed Rice Husks and SiC Powders as Precursors

Abstract

Dense silicon carbide (SiC) matrix composites with SiC whiskers and particles as reinforcement were prepared by infiltrating molten Si at 1550 °C into porous preforms composed of pyrolysed rice husks (RHs) and extra added SiC powder in different ratios. The Vickers hardness of the composites showed an increase from 18.6 to 21.3 GPa when the amount of SiC added in the preforms was 20% (w/w), and then decreased to 17.3 GPa with the increase of SiC added in the preforms up to 80% (w/w). The values of flexural strength of the composites initially decreased when 20% (w/w) SiC was added in the preform and then increased to 587 MPa when the SiC concentration reached 80% (w/w). The refinement of SiC particle sizes and the improvement of the microstructure in particle distribution of the composites due to the addition of external SiC played an effective role in improving the mechanical properties of the composites. Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China; b: Zhejiang Light-Tough Composite Materials Co., Ltd. Hangzhou, 310027, P. R. China; * Corresponding author: gaomx@zju.edu.cn (M. Gao); Tel. /Fax: +86-571-87952615 Keywords: SiC ceramics matrix composites; Rice husks; Liquid Si infiltration; Mechanical properties Contact information: a: State Key Laboratory of Silicon Materials & Department of Materials INTRODUCTIONSilicon carbide (SiC) ceramic matrix composites are widely used in structural, nuclear, and semiconductor applications due to their outstanding mechanical, thermal, and electrical properties (Amirthan et al. 2009;Chakrabarti et al. 2005;Wang et al. 2004). Liquid silicon infiltration (LSI), in which liquid Si infiltrates into porous preforms composed of carbon or mixtures of carbon and SiC powders, is a promising method to fabricate SiC ceramics. The process of infiltration results in formation of newly formed SiC grains by the reaction of Si with carbon. LSI is a simple fabrication technology that can fabricate dense SiC ceramics in a short time at a comparatively low temperature (Margiotta et al. 2010;Wang et al. 2004). The dimensional variation of the final product prepared by LSI is small. Such a near-net shape feature makes LSI an effective method in producing SiC ceramic parts with none or less expensive post-machining (Chen et al. 2002).In recent years, biological carbon-based precursors obtained via carbonisation of woods, bamboo coir, and cotton fabric have been investigated to fabricate SiC ceramics by LSI (Amirthan et al. 2009;Maity et al. 2010;Varela-Feria et al. 2008). Different from these biological plant materials, rice husks (RHs) are commonly used in low-value applications in agriculture such as fuel, or otherwise simply disposed as wastes. Pollution PEER-REVIEWED ARTICLE bioresources.com Zhu et al. (2014). "Si-C composites from rice husk," BioResources 9(2), 2572-2583. 2573is usually a result of the disposal process (Ramasamy et al. 2013;Sun and Gong 2001). These applications ignore the potential of RHs as a SiC source, for they have high content of ...