Fabrication of high-strength silicon-based ceramic cores via an agarose network structure

For gel casting, a forming method used to prepare ceramic cores for turbine blades, appropriate binder selection is critical for meeting the low-viscosity requirement of the slurry and improving the strength of green bodies. However, most conventional binder systems have difficulty imparting sufficient green body strength under low-viscosity slurry conditions. In this study, a novel agarose-based binder system for silicon-based ceramic cores was developed, aiming to enhance the green body strength under the prerequisite of maintaining low slurry viscosity. The influence of agarose content on the viscosity of the slurry, as well as the mechanical performance of both green and sintered bodies, was systematically investigated. The results showed that at an agarose content of 3 wt%, the slurry exhibits pronounced shear-thinning behavior, with the viscosity decreasing to below 1Pa·s, thereby well meeting the requirements for gel casting. Molecular dynamics simulations revealed stronger agarose–SiO₂ binding than agarose–water interactions and shortened hydrogen-bond lengths with increasing agarose concentration, confirming network formation at the molecular level. As a result, the green body's flexural strength increases to 7.42 MPa due to the development of this network structure. Moreover this network architecture facilitates the uniform distribution of SiC and ZrO₂ reinforcing phases, allowing them to exert their full potential during sintering. Consequently, the sintered body achieved a flexural strength of 28.82 MPa, which provides a new theoretical basis for the design of binders for high-strength ceramic cores.