Room temperature enhancement of flexural strength in silicon carbide green body via the addition of cellulose nanofiber

Silicon carbide (SiC) green bodies fabricated using robocasting were strengthened by incorporating cellulose nanofiber (CNF) into a SiC slurry and just drying at room temperature. The measured flexural strength of a SiC green body modified via the CNF with a liquid phase weight ratio (water-to-CNF slurry) of 80:20 was 813 ± 37 kPa, 1.5 times larger than the strength of an unmodified green body. The strength was improved due to the increased number of hydrogen-bonding sites between the raw particles and CNF. After annealing at 250 °C, the lowering of the flexural strength indicated the occurrence of the bonding sites via water that was trapped on the CNF. The addition of CNF increased the viscosity and yield stress of the SiC slurry, which remained in the Bingham pseudoplastic behavior regardless of the CNF used. Moreover, this addition showed no effect on the relative densities, microstructures, and crystalline phases of the sintered SiC body. Therefore, the addition of CNF to the SiC slurry aided in handling the green body during processing and showed no detrimental effects on robocasting.