388 Zan Qingfeng et al. /Ceramics International 33(2007)385-388 Acknowledgement This work was supported by the National Science Foundation of China(NSFC)(( References [1] P.F. Becher, C. Hsueh. P. Angelini, T N. Tiegs. Toughening behavior in J. Am. Ceram. Soc. 71 (1988)1050-1061 [2] P.F. Becher, G.C. Wei, Development of Sic-whisker-reinforced ceramics, Am. Ceram. Soc. Bull. 64(1985)298-304 3]R V K. Sann. Fracture of whisker-reinforced ceramics. in Friedrich(Ed ) Application of Fracture Mechanics to Composite Materi- als, Elsevier Science Publisher B V, 1989. pp. 571-614 Fig. 4. Pull-out behavior of SiC whisker in AlO layers [4]B. wilshier, F Carreno, Deformation and failure processes during tensile reep of fiber and whisker reinforced SiC/Al2O3 composites, Mater. Sci. to propagating along the interface instead of through Al2O3 [5] PF Becher, in: K.S. Mazdiyasni(Ed. ) Fiber Reinforced Ceramic Com- layer, in other words, the resistance of longitudinal crack is posites. Noyes Publication, Park Ridge, NJ, USA, 1990. improved and the crack path is prolonged. On the other hand 间6]A. Goldstein,A.Si di, Al2O/TiC based metal cutting tools by some whiskers insert adjacent Ti3 SiC2 layers ineluctably. Some microwave sintering followed by hot isostatic pressing, J. Am. Ceram. Soc.83(20001530-1532. of the whiskers possibly act as a bridge bet ween layer and they 7l ,G: cvas AH. He. Transform atis toughening in ceramics proving the propagating resistance of transverse crack. The (1980)241-248. changes of the toughening mechanisms described above are [8] T H.J. Hannink, P.M. Kelly, B.C. Muddle, Transformation toughening in rconia-containing ceramics, J. Am. Ceram Soc. 83(2000)461-487 different from the individual toughening mechanisms by [9] W.J. Clegg, K Kendall, N.M. Alford, T.W. Button, J.D. Birchall,A simple multilayered structure or whisker toughening. Hence, there way to make tough ceramics, Nature 347(1990)455-457. effect between the lst-level and 2nd-level [10] D Kovar, M D. Thouless, J w. Halloran, Crack deflection and propagation toughening mechanisms in layered silicon nitride/boron nitride ceramics, J. Am. Ceram. Soc. 81 According to the toughness data of the multilayer ceramics (1998)1004-1012. [11 C.A. Wang. Y Huang, Q F. Zan, L H. Zou, S.Y. Cai, Control of composi- shown in Table l, the greatly improvement of work of fracture on and structure in laminated silicon nitride/boron nitride composites, J Am. Ceran.Soc.8502002)2457-246 multilayer structural toughening mechanisms and their synergy [121 L Zhang, V.D. Krstic, High toughness silicon carbide/graphite laminar effect [13] B. Hatton, P.S. Nicholson, Design and fracture of layered Al2O/TZ3Y mposites produced b 4. Conclusions [14] Q.F. Zan, C.A. Wang, Y. Huang, C.W. Li, S.Q. Li, Preparation of Al2O3/ By adding Sic whiskers into Al2O3 layers, the mechanical Ti3 SiC2 multilayer materials by in-situ synthesis, Key Eng. Mater. 224- properties of multilayered ceramics is obviously improved, the 226(2002)409-412 ptimal mechanical properties being obtained for 20 vol% [15] W.H. Tuan, J.K. Guo, Toughening ceramics by adding two toughening SiCw addition. Hence, the 2nd-level toughening by whiskers is [16)QF. Zan, C.A. Wang Y. Huang. S K Zhao, C.w. Li, The interface and an effective method to multilayer ceramics.The synergy effect interface layer in the AlO,/Ti3 SiC2 multilayer composites by in-situ between whisker toughening and multilayer structural tough synthesis, Mater. Lett. 57(2003)3826-3832. ening was induced in the multilayer ceramics with Sic [17] M W Barsoum, T El-Raghy, Synthesis and characterization of a remark able ceramic: Ti,,, J. Am. Ceram Soc. 79(1996)1953-1956 whiskers,and the improvement of toughness was attributed to [18)T El-Raghy, MWBarsoum,A.Zavaliangos,SRKalidindi,Processing the interaction between whisker toughening, multilayer and mechanical properties of Ti,SiC2. IL. Effect of grain size and structural toughening and synergy effect deformation temperature, J. Am. Ceram Soc. 82(1999)2855-2860to propagating along the interface instead of through Al2O3 layer, in other words, the resistance of longitudinal crack is improved and the crack path is prolonged. On the other hand, some whiskers insert adjacent Ti3SiC2 layers ineluctably. Some of the whiskers possibly act as a bridge between layers, and they can bridge the transverse crack propagating in the interface, improving the propagating resistance of transverse crack. The changes of the toughening mechanisms described above are different from the individual toughening mechanisms by multilayered structure or whisker toughening. Hence, there is a synergy effect between the 1st-level and 2nd-level toughening mechanisms. According to the toughness data of the multilayer ceramics shown in Table 1, the greatly improvement of work of fracture reflects the interaction of the whisker toughening mechanisms, multilayer structural toughening mechanisms and their synergy effect. 4. Conclusions By adding SiC whiskers into Al2O3 layers, the mechanical properties of multilayered ceramics is obviously improved, the optimal mechanical properties being obtained for 20 vol% SiCW addition. Hence, the 2nd-level toughening by whiskers is an effective method to multilayer ceramics.The synergy effect between whisker toughening and multilayer structural tough￾ening was induced in the multilayer ceramics with SiC whiskers, and the improvement of toughness was attributed to the interaction between whisker toughening, multilayer structural toughening and synergy effect. Acknowledgement This work was supported by the National Science Foundation of China (NSFC) (Grant no. 59982004). References [1] P.F. Becher, C. Hsueh, P. Angelini, T.N. Tiegs, Toughening behavior in whisker-reinforced ceramic matrix composites, J. Am. Ceram. Soc. 71 (1988) 1050–1061. [2] P.F. Becher, G.C. Wei, Development of SiC-whisker-reinforced ceramics, Am. Ceram. Soc. Bull. 64 (1985) 298–304. [3] R. Warren, V.K. Sarin, Fracture of whisker-reinforced ceramics, in: K. Friedrich (Ed.), Application of Fracture Mechanics to Composite Materi￾als, Elsevier Science Publisher B.V., 1989, pp. 571–614. [4] B. Wilshier, F. Carreno, Deformation and failure processes during tensile creep of fiber and whisker reinforced SiC/Al2O3 composites, Mater. Sci. Eng. A272 (1999) 38–44. [5] P.F. Becher, in: K.S. Mazdiyasni (Ed.), Fiber Reinforced Ceramic Com￾posites, Noyes Publication, Park Ridge, NJ, USA, 1990. [6] A. Goldstein, A. Singurindi, Al2O3/TiC based metal cutting tools by microwave sintering followed by hot isostatic pressing, J. Am. Ceram. Soc. 83 (2000) 1530–1532. [7] A.G. Evans, A.H. Heuer, Transformation toughening in ceramics: mar￾tensitic transformations in crack-tip stress fields, J. Am. Ceram. Soc. 63 (1980) 241–248. [8] T.H.J. Hannink, P.M. Kelly, B.C. Muddle, Transformation toughening in zirconia-containing ceramics, J. Am. Ceram. Soc. 83 (2000) 461–487. [9] W.J. Clegg, K. Kendall, N.M. Alford, T.W. Button, J.D. Birchall, A simple way to make tough ceramics, Nature 347 (1990) 455–457. [10] D. Kovar, M.D. Thouless, J.W. Halloran, Crack deflection and propagation in layered silicon nitride/boron nitride ceramics, J. Am. Ceram. Soc. 81 (1998) 1004–1012. [11] C.A. Wang, Y. Huang, Q.F. Zan, L.H. Zou, S.Y. Cai, Control of composi￾tion and structure in laminated silicon nitride/boron nitride composites, J. Am. Ceram. Soc. 85 (2002) 2457–2461. [12] L. Zhang, V.D. Krstic, High toughness silicon carbide/graphite laminar composite by slip casting, Theo. Appl. Fract. Mech. 24 (1995) 13–19. [13] B. Hatton, P.S. Nicholson, Design and fracture of layered Al2O3/TZ3Y composites produced by electrophoretic deposition, J. Am. Ceram. Soc. 84 (2001) 571–576. [14] Q.F. Zan, C.A. Wang, Y. Huang, C.W. Li, S.Q. Li, Preparation of Al2O3/ Ti3SiC2 multilayer materials by in-situ synthesis, Key Eng. Mater. 224– 226 (2002) 409–412. [15] W.H. Tuan, J.K. Guo, Toughening ceramics by adding two toughening agents, Key Eng. Mater. 224–226 (2002) 317–320. [16] Q.F. Zan, C.A. Wang, Y. Huang, S.K. Zhao, C.W. Li, The interface and interface layer in the Al2O3/Ti3SiC2 multilayer composites by in-situ synthesis, Mater. Lett. 57 (2003) 3826–3832. [17] M.W. Barsoum, T. El-Raghy, Synthesis and characterization of a remark￾able ceramic: Ti3SiC2, J. Am. Ceram. Soc. 79 (1996) 1953–1956. [18] T. El-Raghy, M.W. Barsoum, A. Zavaliangos, S.R. Kalidindi, Processing and mechanical properties of Ti3SiC2. II. Effect of grain size and deformation temperature, J. Am. Ceram. Soc. 82 (1999) 2855–2860. 388 Zan Qingfeng et al. / Ceramics International 33 (2007) 385–388 Fig. 4. Pull-out behavior of SiC whisker in Al2O3 layers