Met. Mater. Int., Vol. 17, No. 4 (2011), pp. 599~605 doi: 10.1007/s12540-011-0811-y Published 31 August 2011 Effect of SiC Particle Size on Flexural Strength of Porous Self-Bonded SiC Ceramics Gary Paul Kennedy 1 , Kwang-Young Lim 2 , Young-Wook Kim 2, * , In-Hyuck Song 3 , and Hai-Doo Kim 3 1 Department of Electrical Engineering, Korea University, Seoul 136-701, Korea 2 Department of Materials Science and Engineering, The University of Seoul, Seoul 130-743, Korea 3 Engineering Ceramics Group, Korea Institute of Materials Science, Changwon-si, Gyeongnam 641-010, Korea (received date: 4 October 2010 / accepted date: 7 February 2011) Porous self-bonded silicon carbide (SBSC) ceramics were fabricated from SiC powders with various particle sizes (0.7 µm, 25 µm, 50 µm, 65 µm), plus Si, C and boron (as a sintering additive). The effects of submicron (0.7 µm) SiC particle incorporation into the SBSC and the SiC particle size (25 µm, 50 µm, 65 µm) on the flexural strength and porosity of the ceramics were investigated as a function of sintering temperature. Incor- porating 0.7 µm SiC particles into the ceramic material containing 25 µm SiC particles increased the flexural strength by 3 times, from 11.7 MPa up to 35.5 MPa after sintering at 1800 ° C. Simultaneously, the porosity was reduced by ~5 %. Furthermore, the flexural strength of ceramic with 25 µm SiC particles was superior to that with 65 µm SiC particles. Generally, the flexural strength of the SBSC increased as, both, a function of submicron SiC particle incorporation along with relatively small micron-sized particles (25 µm) in the microstructure of the ceramic plus increased sintering temperature. Keywords: cellular materials, sintering, mechanical properties, scanning electron microscopy (SEM), silicon carbide 1. INTRODUCTION Porous silicon carbide ceramics are regarded as excellent materials for catalytic supports, molten metal filters, diesel particulate filters, membrane supports for hydrogen separa- tion, refractory plates, gas burner media, and preforms for the fabrication of metal matrix composites [1-10]. This is due to properties such as good thermal shock resistance as well as good mechanical and chemical resistance. Porous SiC ceramics are largely fabricated by replica, direct foaming, sacrificial template, and reaction sintering processes [11]. Self-bonded SiC (SBSC) ceramic is a promising material for use in applications such as vacuum chucks and gas filters where high refractoriness, good heat resistance, and low cost are very important. When SiC, silicon, and carbon powders are combined together and then sintered, the reaction of mol- ten silicon with carbon produces secondary silicon carbide [12,13]. Therefore, the microstructure of the SBSC ceramic is largely composed of SiC grains bonded with synthesized SiC. In our recent paper, the effect of sintering additives on the porosity and flexural strength of porous SBSC ceramics was investigated [14]. From this investigation it was deter- mined that the SBSC ceramics with 2 wt.% boron (B) showed better flexural strength than the SBSC ceramics with Al or no additive. This is consistent with the study by Whalen and Anderson, who reported that adding B into a Si melt improves the wetting of SiC grains [15] and activates mate- rial transport at the SiC-SiC boundaries [16,17], resulting in enhanced necking. In this study, the effects of (i) submicron SiC particle con- tent, (ii) SiC particle size, and (iii) sintering temperature on the porosity and strength of porous SBSC ceramics were investigated. 2. EXPERIMENTAL PROCEDURE Five different SBSC ceramic samples were investigated in this study (SBSC1-SBSC5), and their composition is out- lined in Table 1. They were prepared from commercially available materials: three different sizes of refractory-grade α-SiC and a submicron SiC, SiC1: (∼25 µm, Zhengxing *Corresponding author: ywkim@uos.ac.kr ©KIM and Springer