Enhancing properties of oriented short carbon fiber-reinforced refractory castables through direct ink writing and in-situ synthesis of whiskers

Abstract

Additive manufacturing of high-density, high-strength mullite castables reinforced with oriented short carbon fibers was successfully achieved using direct ink writing. The carbon fibers were coated with a silica sol layer and co-printed with the mullite castable. To enhance the printability, the rheological properties of the slurries and printing parameters were adjusted. Moreover, the extrusion process facilitated the alignment of the carbon fibers within the printed filaments, which greatly enhanced the flexural strength and fracture toughness of the castables. During sintering, silicon carbide whiskers and mullite whiskers formed at the interface between the carbon fibers and the castable matrix, not only protecting the carbon fibers but also significantly improving the density and strength of the composites. Increasing the silica sol concentration from 10 to 30 wt% led to improvements in density (2.0–2.1 g/cm³), flexural strength (5.3–6.8 MPa), and residual flexural strength ratio (18.4–27.9 %).