化学气相渗透制备SiCw/SiC层状结构陶瓷

Tape casting (TC) combined with chemical vapor infiltration (CVI) was used to fabricate laminated SiCw/SiC structural ceramics. The effect of the TC-CVI fabrication process on the mechanical properties and microstructure of the ceramics was studied and the strengthening/toughening mechanisms of the ceramics were investigated. Toughened bulk SiC ceramics are widely used in the fabrication of small components that work under higher stress because of their limited toughness. Continuous fiber-reinforced SiC ceramic matrix composites (CMC-SiC) can overcome the brittleness of SiC ceramics; however, they are generally restricted to use in large components that work under lower stress because of their stress-strain nonlinearity. Laminated ceramics have shown favorable toughness and stress-strain linearity but they need to be further improved in terms of strength and toughness to be important structural materials. The development tendency of structural materials is that strengthening and toughening are mainly contributed by different constituents, and the key is cooperative design and control of the constituents. In laminated ceramics, whiskers with large volume fraction are necessary for strengthening, and interfacial and interlaminar crack deflection and bridging are necessary for toughening. Until now, laminated ceramics have been synthesized by laminating materials slice and sintering by hot pressing at high temperatures. In contrast to sintering, CVI can increase the whisker volume fraction, decrease whisker damage, and fabricate large-scale and complex-shaped components. This method can not only increase the strength of ceramics by increasing the volume fraction and reducing the damage of the SiC whiskers, but can also increase the toughness by controlling the interfacial bonding strength between the whiskers and the matrix, and the interlaminar bonding strength between layers. The volume fraction of whiskers in the laminated SiCw/SiC structural ceramics reached 40 vol%. Compared with bulk ceramics and 2D C/SiC, the laminated SiCw/SiC structural ceramics showed good toughness and linear mechanical behavior, respectively. The flexural strength, tensile strength, and fracture toughness of the ceramics were 315 MPa, 158 MPa, and 8.02 MPa m1/2, respectively. The thickness of the individual layers in the ceramics had a significant influence on the densification and interlaminar bonding strength between layers. The surface properties of the whiskers had a significant effect on the interfacial bonding strength between the whiskers and the matrix. The laminated SiCw/SiC structural ceramics benefitted from a synergistic effect of the laminated structure and the whiskers, and the main toughening mechanisms were interlaminar and interfacial crack deflection and bridging, and whisker pull-out.