7)179-184 C 1997 Elsevier Sciene PII:s0272-8842(96)00021 0272884219751700+00 Preparation of High Strength Ceramic Fibre Reinforced silicon Nitride Composites by a Preceramic polymer Impregnation Method H Morozumi, K. sato, A. Tezuka, H. Kaya &T Isoda Corporate Research and Development Laboratory, TONEN Corporation, 1-3-1 Nishiturugaoka, Ohimachi, Saitama 356, Japan Received 11 September 1995; accepted 20 December 1995) Abstract: High strength ceramic composites, reinforced with Si-N and Si-B-0-N ceramic fibres, were prepared by the preceramic polymer impregnation inethod Low-viscosity polysilazanes with a 70-90 wt% ceramic yield, were used as a matrix precursor. To obtain dense composites, the impregnation, curing and firing processes were repeated. Three-point flexural strength of the UD and 2D (cross-ply) ceramic fibre reinforced ceramic composites were shown to be as high as 1000 and 600 MPa, respectively, This resulted from the dense silicon nitride matrix and controlled fibre/matrix interface. c 1997 Elsevier Science Limite 1 INTRODUCTION pressure.(2)There are no aids in firing, so high purity ceramics are readily obtained. (3)Can be Ceramic fibre reinforced ceramic matrix compo- applied to complex and near-net shaped parts. (4) sites(CMCs)are being developed as excellent Dense and homogeneous matrices are readily materials with high strength and oxidation resis- obtained. Accordingly, with high expectation of tance at high temperature. Several processes, PCPl, our development activity has continued. In ncluding preceramic polymer impregnation addition, TONEN's preceramic polymer technolo (PCPD), 3chemical vapour infiltration(CVI), 4, gies have provided stoichiometric, homogeneous reaction bonding and hot-pressing, have been and high purity silicon nitride fibre(SNF). -9The employed for the fabrication of continuous fibre Snf has excellent properties, including high reinforced composites. The strength of the compo- strength and oxidation resistance at high tempera site that is obtained by the cvi process is relatively low, because the density of the matrix is as low as boron nitride fibre(SNBF)that has good potential 80%0 of the theoretical value. The reaction at elevated temperatures was described by bonding method provides residual metal in the Funayama et al. o We have reported on unidirec product, so the strength decreases at elevated tcm- tional(UD) carbon fibre reinforced composites peratures The hot-pressing method will degrade and UD SNF reinforced composites, prepared by the fibre reinforcement through treatment at high PCPI 3.1 Schwab et al. have reported on 2D temperature and pressure, and is not amenable to (plain weave laminate) silicon carbide fibre rein the production of complex shapes forced composites by a similar process. 12An PCPI is the fabrication process of CMCs derived initial attempt is made in this paper to apply SNF trom organometallic or inorganic precursors. The and SNBF in the fabrication of 2D(cross-ply) advantages of PCPI are as follows: (1) There is no composites. Furthermore, this paper describes the damage to the reinforcement because the firing influence of polysilazanes on the properties of process is at low temperature and atmospheric resultant productsPII: SO272-8842(96)00021-l Ceramics International 23 (1997) 179-I 84 0 1997 Elsevier Science Limited and Techna S.r.1. Printed in Great Britain. All rights reserved 0272~8842/97 $17.00+ .OO Preparation of High Strength Ceramic Fibre Reinforced Silicon Nitride Composites by a Preceramic Polymer Impregnation Method H. Morozumi, K. Sato, A. Tezuka, H. Kaya &T. lsoda Corporate Research and Development Laboratory, TONEN Corporation, 1-3-1 Nishiturugaoka, Ohimachi, Saitama 356, Japan (Received 11 September 1995; accepted 20 December 1995) Abstract: High strength ceramic composites, reinforced with Si-N and Si-B-O-N ceramic fibres, were prepared by the preceramic polymer impregnation method. Low-viscosity polysilazanes with a 70-90 wt% ceramic yield, were used as a matrix precursor. To obtain dense composites, the impregnation, curing and firing processes were repeated. Three-point flexural strength of the UD and 2D (cross-ply) ceramic fibre reinforced ceramic composites were shown to be as high as 1000 and 600 MPa, respectively. This resulted from the dense silicon nitride matrix and controlled fibre/matrix interface. 0 1997 Elsevier Science Limited and Techna S.r.1. 1 INTRODUCTION Ceramic fibre reinforced ceramic matrix compo￾sites (CMCs) are being developed as excellent materials with high strength and oxidation resis￾tance at high temperature. Several processes, including preceramic polymer impregnation (PCPI),ip3 chemical vapour infiltration (CVI),4,5 reaction bonding and hot-pressing,6 have been employed for the fabrication of continuous fibre reinforced composites. The strength of the compo￾site that is obtained by the CVI process is relatively low, because the density of the matrix is as low as 70-80% of the theoretical value. The reaction bonding method provides residual metal in the product, so the strength decreases at elevated tem￾peratures. The hot-pressing method will degrade the fibre reinforcement through treatment at high temperature and pressure, and is not amenable to the production of complex shapes. PCPI is the fabrication process of CMCs derived from organometallic or inorganic precursors. The advantages of PCPI are as follows: (1) There is no damage to the reinforcement because the firing process is at low temperature and atmospheric pressure. (2) There are no aids in firing, so high purity ceramics are readily obtained. (3) Can be applied to complex and near-net shaped parts. (4) Dense and homogeneous matrices are readily obtained. Accordingly, with high expectation of PCPI, our development activity has continued. In addition, TONEN’s preceramic polymer technolo￾gies have provided stoichiometric, homogeneous and high purity silicon nitride fibre (SNF).7-9 The SNF has excellent properties, including high strength and oxidation resistance at high tempera￾ture. Recently, progress in continuous silicon boron nitride fibre (SNBF) that has good potential at elevated temperatures was described by Funayama et al. lo We have reported on unidirec￾tional (UD) carbon fibre reinforced composites and UD SNF reinforced composites, prepared by PCPI.3,‘t Schwab et al. have reported on 2D (plain weave laminate) silicon carbide fibre rein￾forced composites by a similar process.i2 An initial attempt is made in this paper to apply SNF and SNBF in the fabrication of 2D (cross-ply) composites. Furthermore, this paper describes the influence of polysilazanes on the properties of resultant products. 179