Jiang et aL. Polymer derived nitride matrix composites b Holes 26k 3 Scanning electron microscopy images of fracture surface of 2. 5D SiO2Si3Na-BN composites fabric because of the low viscosity and good wettal the pip method. which is a fast route to fabricate dense Together with the high ceramic yield, all contribl composites due to the good wettability and high char the fast weight pick-ups of 2 5D SiO2 si3N yield of the precursor. composites. The density of the composites reached The precoating process plays an important role in 1-68 or 1. 70 g cm3 after only four PIP cycles. controlling the microstructures and mechanical proper Therefore, PBSZ is a good precursor for preparing ties of the composites. The composites without fibre silica fibre preform reinforced nitride matrix composites. coating showed strong fibre/matrix interfacial bonding Generally after the maximum value of the load is and low mechanical properties, whereas the precoated reached, the subsequent extension degree of a ceramic composites exhibited controlled interfacial adhesion and matrix composite is strongly dependent on the nature of higher mechanical properties composite is consistent with its mechanical properties. 3 It is also well known that the interfacial bonding Acknowledgements strength can be evaluated by the morphology of fracture surfaces. Extensive fibre pull-out indicates relatively The project was supported by State Key Laboratory of weak fibre/matrix interfacial bonding, whereas little fibre Advanced Ceramic Fibres and Composites Foundation pull-out and short pull-out length indicates strong fibre/ under Contact No. 2004js51488-0101kg01-3 and matrix interfacial bonding. In the present study, strong Innovation Foundation of National University of interfacial bonding was observed for specimen A, thus Defense Technology for Graduate Student (No 0603) decreasing the mechanical properties, whereas for speci- The authors are also grateful to Mr J. F. Tian and X. z men B, the relatively weak interfacial bonding and the Zhao for their help in SEM examination energy absorbing ability by fibre pull-out contributed to gh mechanical properties, including the longitude References flexural strength and modulus. Considering the same reinforcing fibre fabric, precursor and preparation 1. Y. Matsuda. N. Akikawa and T. Satoh: Ceran Eng. Soc. Pre temperature, the difference in the mechanical property 2. K Jian, Z. H. Chen, Q.S. Ma and w.w. Zheng: Mater. Sci. Eng between specimens A and B is due to the different fibre/ A,2005,A390,154-157 matrix interfacial bonding state resulting from the fibre 3. J. P Brazel and R. Fenton: Proc. 13th Symp. on'Electromagnetic coating process. The fibre coating probably prevented windows, Atlanta, GA, USA, September 1976. Georgia Institute the chemical reactions between the fibres and the matrix of Technology, 9. under high temperature, which is interesting and 4. H Chen, L M. Zhang, G.Y. Jia, W.H. Luo and S. Yu: Key eng Mater,2003,249,159-162 currently in progress 5. L M. Manocha C.N. Panchal and S Manocha: Ceram. Eng. Sci. According to the literature, silica fibres and PbSZ Proc.,2002,23.655-661 derived Si3 N4-BN still remain amorphous at 800C; 6. G J Qi, C.R. Zhang, H. F Hu and F Cao: Mater. Sci. Eng. 4, 2006,A416,317-320 should be amorphous. What is more, a longitude 7. G. 1. O', C R. Zhang and H F. Hu: J. Non-crystz Solids, 2006,352 flexural strength of 129.5 MPa for specimen B is much 8 Y.G. Jiang. C.R. Zhang F Cao, S.Q.Wang,HFHu and GJ higher than that for the conventional continuous silica Qh:Adh. Eng. Mater.,2007,(1-2),114116 nforced ceramic matrix composites, which 9. GBoitier, J. Vcens and J. L. Chermant: Mater. Sci. Eng. A, 2000 proves that the PIP method is a promising route to A279.7380. prepare continuous silica fibre reinforcement nitrid 10. K. Su. E. E. Remsen. G.A. Zank and L. G. Sneddon: chem Mater,1993,5,547-5 matrix composites with excellent mechanical properties. 11. 0. Funayama, Y. Tashiro,AKamo,MOkumura and TIsoda: J. Mater. Sci. 1994. 29. 48 Conclusions 12. W. V. Hough, C. R. Guibert and G. T. Hefferan: United States Patent4150097,17 PBSZ was used to fabricate amorphous composites of 13. Z F Chen, L. T. Zhang L F Cheng and Y D. xur: Ceram. Int 2·5-dim nal silica fibre reinforced nitride matrix by 005.31573-580 882 Materials Science and Technology 2007 VOL 23 No 7fabric because of the low viscosity and good wettability. Together with the high ceramic yield, all contribute to the fast weight pick-ups of 2?5D SiO2f/Si3N4–BN composites. The density of the composites reached 1?68 or 1?70 g cm23 after only four PIP cycles. Therefore, PBSZ is a good precursor for preparing silica fibre preform reinforced nitride matrix composites. Generally after the maximum value of the load is reached, the subsequent extension degree of a ceramic matrix composite is strongly dependent on the nature of the fibre/matrix interface and the microstructure of the composite is consistent with its mechanical properties.13 It is also well known that the interfacial bonding strength can be evaluated by the morphology of fracture surfaces. Extensive fibre pull-out indicates relatively weak fibre/matrix interfacial bonding, whereas little fibre pull-out and short pull-out length indicates strong fibre/ matrix interfacial bonding.2 In the present study, strong interfacial bonding was observed for specimen A, thus decreasing the mechanical properties, whereas for speci￾men B, the relatively weak interfacial bonding and the energy absorbing ability by fibre pull-out contributed to high mechanical properties, including the longitude flexural strength and modulus. Considering the same reinforcing fibre fabric, precursor and preparation temperature, the difference in the mechanical property between specimens A and B is due to the different fibre/ matrix interfacial bonding state resulting from the fibre coating process. The fibre coating probably prevented the chemical reactions between the fibres and the matrix under high temperature, which is interesting and currently in progress. According to the literature,10 silica fibres and PBSZ derived Si3N4–BN still remain amorphous at 800uC; therefore, the present 2?5D SiO2f/Si3N4–BN composite should be amorphous. What is more, a longitude flexural strength of 129?5 MPa for specimen B is much higher than that for the conventional continuous silica fibre reinforced ceramic matrix composites,4 which proves that the PIP method is a promising route to prepare continuous silica fibre reinforcement nitride matrix composites with excellent mechanical properties. Conclusions PBSZ was used to fabricate amorphous composites of 2?5-dimensional silica fibre reinforced nitride matrix by the PIP method, which is a fast route to fabricate dense composites due to the good wettability and high char yield of the precursor. The precoating process plays an important role in controlling the microstructures and mechanical proper￾ties of the composites. The composites without fibre coating showed strong fibre/matrix interfacial bonding and low mechanical properties, whereas the precoated composites exhibited controlled interfacial adhesion and higher mechanical properties. Acknowledgements The project was supported by State Key Laboratory of Advanced Ceramic Fibres and Composites Foundation, under Contact No. 2004js51488?0101.kg01?3 and Innovation Foundation of National University of Defense Technology for Graduate Student (No. 0603). The authors are also grateful to Mr J. F. Tian and X. Z. Zhao for their help in SEM examination. References 1. Y. Matsuda, N. Akikawa and T. Satoh: Ceram. Eng. Soc. Proc., 2001, 22, 463–470. 2. K. Jian, Z. H. Chen, Q. S. Ma and W. W. Zheng: Mater. Sci. Eng. A, 2005, A390, 154–157. 3. J. P. Brazel and R. Fenton: Proc. 13th Symp. on ‘Electromagnetic windows’, Atlanta, GA, USA, September 1976, Georgia Institute of Technology, 9. 4. H. Chen, L. M. Zhang, G. Y. Jia, W. H. Luo and S. Yu: Key Eng. Mater., 2003, 249, 159–162. 5. L. M. Manocha, C. N. Panchal and S. Manocha: Ceram. Eng. Sci. Proc., 2002, 23, 655–661. 6. G. J. Qi, C. R. Zhang, H. F. Hu and F. Cao: Mater. Sci. Eng. A, 2006, A416, 317–320. 7. G. J. Qi, C. R. Zhang and H. F. Hu: J. Non-cryst. Solids, 2006, 352, 3794–3798. 8. Y. G. Jiang, C. R. Zhang, F. Cao, S. Q. Wang, H. F. Hu and G. J. Qi: Adv. Eng. Mater., 2007, (1–2), 114–116. 9. G. Boitier, J. Vcens and J. L. Chermant: Mater. Sci. Eng. A, 2000, A279, 73–80. 10. K. Su, E. E. Remsen, G. A. Zank and L. G. Sneddon: Chem. Mater., 1993, 5, 547–556. 11. O. Funayama, Y. Tashiro, A. Kamo, M. Okumura and T. Isoda: J. Mater. Sci., 1994, 29, 4883. 12. W. V. Hough, C. R. Guibert and G. T. Hefferan: United States Patent 4150097, 17 April 1979. 13. Z. F. Chen, L. T. Zhang, L. F. Cheng and Y. D. Xu: Ceram. Int., 2005, 31, 573–580. a specimen A; b specimen B 3 Scanning electron microscopy images of fracture surface of 2?5D SiO2f/Si3N4–BN composites Jiang et al. Polymer derived nitride matrix composites 882 Materials Science and Technology 2007 VOL 23 NO 7