Laminated Si3N4/SiCw ceramics were successfully prepared by tape casting and hot-pressing. Its mechanical properties were measured and the impact resistance was discussed. The toughness of the laminated Si3N4/SiCw ceramics was 13.5 MPa m(1/2), which was almost 1.6 times that of Si3N4/SiCw composite ceramics, namely 8.5 MPa m(1/2). Moreover, the indentation strength of laminated Si3N4/SiCw ceramics was not sensitive to increasing indentation loads and exhibited a rising R-curve behaviour, indicating that the laminated Si3N4/SiCw ceramics had excellent impact resistance. The improved toughness and impact resistance of laminated Si3N4/SiCw ceramics was attributed to the residual stress caused by a thermal expansion coefficient mismatch between the different layers, resulting in crack deflection and bridging of SiC whiskers in the interface layer, thus consuming a large amount of fracture work.

Bionic laminated SiC/graphite ceramics were fabricated by tape casting. The mechanical properties and R-curve behaviour of the laminated SiC/graphite ceramics were evaluated and compared with those of monolithic SiC ceramics. The toughness of the laminated SiC/graphite ceramics was 9.48 MPa m(1/2), which was 3 times that of the monolithic SiC ceramics (3.56 MPa m(1/2)). The improvement in the toughness was mainly due to the deflection of the crack at the graphite interface layer and the pull-out of the graphite sheet, which consumed a lot of fracture work. In addition, the laminated SiC/graphite ceramics exhibited rising R-curve behaviour. The excellent damage resistance of the laminated SiC/graphite ceramics was attributed to the indentation surface collapse caused by the porous structure of the graphite interface layer, which consumed quite a large amount energy and reduced the formation of microcracks. Meanwhile, the step-like fracture mode prolonged the crack propagation path and avoided catastrophic damage.

In this study, bionic laminated ZrB2-SiC ceramics (LZN(w)) were fabricated using Si3N4 whiskers as an interface layer. The room-temperature flexural strength and fracture toughness of LZN(w) were determined to be 528 MPa and 15.3 MPa m(1/2), respectively. With increasing testing temperature up to 1500 degrees C, the flexural strength of LZN(w) remained higher than that of monolithic ZrB2-SiC ceramics (ZS). Specifically, at the peak temperature of 1500 degrees C, the flexural strength of LZN(w) was as high as 380 MPa, while that of ZS dropped to 219 MPa. This outstanding high-temperature strength of LZN(w) can be ascribed to the porous structure of the Si3N4 whisker interface layer, which absorbs the glassy phase accumulated at the crack tip, and the stepped fracturing pattern, which hinders the flow of the glassy phase, thus avoiding the grain boundary sliding caused by the enrichment of the glassy phase.

This study reports the preparation of laminated HfB2-SiC/SiCw ceramic (LHSw) with interfacial SiC whiskers (SiCw) by tape-casting followed by hot-pressing. The microstructure and mechanical properties of LHSw were studied in detail. The results showed that the flexural strength and fracture toughness of LHSw materials were 408 +/- 24 MPa and 10.6 +/- 0.4 MPa m(1/2), respectively. The fracture toughness of the LHSw material was higher by 2.6 times than that of a monolithic HfB2-SiC ceramic (HS) (4.1 +/- 0.2 MPa m(1/2)). This improvement was ascribed to the SiC whiskers with high aspect ratio in the interfacial layer, which was beneficial for the deflection and bifurcation of cracks. In addition, LHSw showed excellent resistance to thermal shock. It is found that the critical thermal shock temperature difference was approximately 553 degrees C, which is 1.2 times higher than that of HS (457 degrees C) and can be attributed to the porous structures formed in the interfacial layer of LHSw. Thus, micro-cracks formed in LHSw, but it was not penetrating cracks that formed in the HS after thermal shock.

With SiC whisker and SiC particle as interface layers, ZrB2-SiC-SiCw (LZ-S-w) and ZrB2-SiC-SiCp (LZ-S-p) laminated ceramics were prepared by tape casting and hot pressing. Fracture behaviors and accompanying microstructural changes were studied in the range from 20 to 1500 degrees C. At 20 degrees C, both LZ-S-w and LZ-S-p exhibited excellent flexural strengths in parallel direction of 607 +/- 58 and 568 +/- 46 MPa, respectively. From 20 to 1500 degrees C, the flexural strength of LZ-S-w was always higher than that of LZ-S-p. From 1200 to 1500 degrees C, the flexural strength of LZ-S-w declined relatively slowly while that of LZ-S-p dropped sharply. At 1500 degrees C, the flexural strength of LZ-S-w reached 361 MPa in the parallel direction, 66.4% higher than that of LZ-S-p (217 MPa). The superior high-temperature performance of LZ-S-w was caused by porous interface layers composed of SiC whiskers and ZrB2 particles, which reduced the enrichment of the glassy phase and avoided grain-boundary sliding.