Influence of sintering process on microstructure and fracture behavior of C_F/Si₃N₄ laminated ceramic composites

Abstract

Carbon fibre reinforced Si₃N₄ (C_F/Si₃N₄) biomimetic laminated ceramic composites were prepared through rolling, alternate stacking of two-dimensional carbon fibre cloth and Si₃N₄ green layers, burning out of organic components and hot-press sintering. The effects of the sintering process and sintering additives on the microstructure, fracture behavior and toughening mechanism of the composite were analysed. When sintered at 1850°C for 1.5 h with Al₂O₃, Y₂O₃ and MgO as sintering additives, a fully densified composite was obtained with homogeneous and moderate bonding interfaces between C_F and the Si₃N₄ matrix, presenting improved flexural strength of 374.93 MPa and fracture toughness of 10.71 MPa m^1/2, which were increased by 13.20% and 71.36% respectively, as compared with the monolithic Si₃N₄ ceramic. The primary toughening mechanism of the composite can be concluded as multiple crack deflection at the carbon fibre layers, fracture and pull-out of C_F bundles and single C_F within the carbon fibre layers.

Keywords:

• Biomimetic design
• C_F/Si₃N₄ laminated ceramic composite
• Hot-press sintering
• Fracture behavior
• Toughening mechanism

Acknowledgements

This research was financially supported by Shaanxi Industrial Science and Technology Research (2014K08-09), the National Natural Science Foundation of China (50172023) and the Scientific Research Program funded by Yulin City (2012).