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The trial-and-error method used in ceramics research has certain limitations such as the high blindness of material component design. Moreover, calculations of the toughness of ceramics using the extended finite element method, which is the most broadly applied technique, are complicated. To overcome these issues, in this study, multilayer graphene (MLG)/Si 3 N 4 whisker (Si 3 N 4w)-reinforced Si 3 N 4 ceramics (MWSCs) were used as the model material, and the modeling of MWSCs was conducted using Voronoi tessellation. Additionally, a more concise novel approach was applied for the prediction of the fracture toughness of MWSCs. Furthermore, the optimal MLG and Si 3 N 4w contents were predicted, and then they were verified by fabricating MWSCs using spark plasma sintering (SPS). Simulation results indicated that the optimum MLG and Si 3 N 4w contents to enable the toughness and hardness to reach the maximum values (9.87 MPa·m1/2 and 23.19 GPa) were 1 wt% and 3 wt%, which were consistent with the experimental results. Consequently, the effectiveness of the proposed method was verified. Moreover, the experimental values of the maximum fracture toughness and hardness were 11.04 MPa·m1/2 and 20.29 GPa, which were 47.20% and 12.10% higher than those of Si 3 N 4 ceramics reinforced with 1 wt% MLG, respectively. The synergistic toughening effects of MLG and Si 3 N 4w were significantly reflected. The load-bearing effect, bridging, and crack deflection induced by MLG and Si 3 N 4w were the key reasons for the improvement in the mechanical properties of MWSCs. [ABSTRACT FROM AUTHOR]

This work aimed at investigating the superiorities of multilayer graphene (MLG) and β-Si 3 N 4 whisker (β-Si 3 N 4w) in synergistically enhancing the toughness of Si 3 N 4 ceramic composites. First, Si 3 N 4 ceramic composites with hybrid 1 wt% MLG and 0 – 5 wt% β-Si 3 N 4w were sintered by spark plasma sintering. Phase constitutions and microstructures of Si 3 N 4 -based ceramic composites were characterized by X-rays diffraction, Raman spectra, and scanning electron microscope. Then, the optimal β-Si 3 N 4w content and sintering process of MLG/β-Si 3 N 4w -toughened Si 3 N 4 ceramic composites were comprehensively optimized by orthogonal experiments. Results indicated that in the case of maintaining the hardness of 15.87 – 18.84 GPa, the fracture toughness of Si 3 N 4 ceramic composites incorporated with 1 wt% MLG and 3 wt% β-Si 3 N 4w was advanced to 11.04 MPa·m1/2, which was 11.29% and 87.12% higher than that of 1 wt% MLG- and 3 wt% β-Si 3 N 4w -reinforced Si 3 N 4 ceramic composites, respectively. Orthogonal experiments demonstrated that 1 wt% MLG/3 wt% β-Si 3 N 4w -toughened Si 3 N 4 ceramic composites sintered at 1600 ℃, 40 MPa, and holding time for 6 min had optimum comprehensive mechanical properties. MLG wrapping and the synergistic effects of pull out, crack deflection, crack branching, and bridging resulted by MLG and β-Si 3 N 4w were the main responsible for the enhancement of toughness. [Display omitted] • MLG/β-Si 3 N 4w synergistic toughened Si 3 N 4 ceramics were sintered by SPS. • Fracture toughness of Si 3 N 4 -based ceramics was enhanced to 11.04 MPa·m1/2. • Optimal contents of MLG and β-Si 3 N 4w were 1 wt% and 3 wt%. • Optimum sintering process were 1600 ℃, 40 MPa, and holding time for 6 min. [ABSTRACT FROM AUTHOR]