Study on the configuration of SiC slurry for grouting molding and the performance of billet

Abstract

Silicon carbide (SiC) ceramics demonstrate outstanding characteristics, encompassing a remarkably high melting point, exceptional hardness, superior wear resistance, excellent thermal shock resistance, high thermal conductivity and robust chemical stability. These properties span mechanical durability, thermal performance and environmental resilience, making SiC ceramics ideal for many applications such as semiconductors, high-temperature environments, heating and heat exchange systems, military, nuclear industries and photovoltaics. However, the extreme hardness of SiC ceramics poses significant machining challenges in post-processing, which has consequently led to slip casting attracting substantial research interest, particularly due to its capacity for shaping intricate components without requiring mechanical processing. In this paper, the surface of SiC particles was modified by using aluminum nitrate nonahydrate (Al(NO₃)₃·9H₂O) and sodium humate (C₉H₈Na₂O₄) as modifiers, improving the dispersion and stability of SiC particles in the slurry. After surface modification with 0.4 wt% Al(NO₃)₃·9H₂O and 0.8 wt% C₉H₈Na₂O₄, the angle of repose of SiC powder achieved minimum angle of repose at 38.1°. The Zeta potential of the SiC powder decreased from −27.83 mV to −53.9 mV after modification. The viscosity of the modified SiC slurry with a solid content of 50 vol% was 0.9272 Pa∙s. After adding 1.5 ml of water-borne epoxy resin (WER), the flexural strength of the dried green body could be increased to 14.56 MPa. At the same time, the apparent density and water content are 2.14 g/cm³ and 0.02 %, which fully meet the application for the reaction-bonded SiC ceramics. Silicon carbide ceramics which were fabricated via reactive sintering at 1700 °C for 2.5h under vacuum atmosphere, demonstrated a mean three-point flexural strength of 360 MPa.