COMPOSITES SCIENCE AND TECHNOLOGY ELSEVIER Composites Science and Technology 61(2001)355-362 www.elsevier.com/locate/compscitech Physico-chemistry of interfaces in inorganic-matrix composites J. Bouix *, M.P. Berthet, F. Bosselet, R. Favre, M. Peronnet, O. Rapaud, J.C. Viala C. Vincent.H.Ⅴ Incent Laboratoire des Multimateriaux et Interfaces, UMR CNRS 5615, Universite Claude Bernard Lyon 1, 43 bvd 11 Novembre 1918, F69622 villeurbanne Cedex. france Received 26 May 1999: received in revised form 20 October 1999; accepted 2 May 2000 Abstract The performances of metal matrix composites(MMCs)or ceramic matrix composites(CMCs)are mited by the char acteristics of the fibre/matrix interface or more generally those of the interfacial zone. Concerning M optimization of this zone involves control of the chemical reactivity between the reinforcement and the matrix, which te usually an out-o quilibrium system. In the case of CMCs, it is possible to obtain a non-brittle material by associating two brittle components and to exhibit a good resistance to oxidation. The physical chemist is able to offer a significant contribution for solving these problems by ting on the reinforcement surface, the matrix composition or the manufacturing conditions of the composite.@ 2001Elsevier Science Ltd. All rights reserved 如mm小oMmu 1. Introduction a dissolution-growth process and does not ave an protecting effect on the fibre which is attacked in deptl All of the recent studies show that the mechanical and Consequently, the mechanical properties fall away and thermomechanical behaviour of ceramic and metallic- the composite is highly sensitive to corrosion by humid matrix composites depends widely on the nature of the air with emission of methane. It is therefore necessary to interfacial bonding which forms between the reinforce- limit this reactivity as far as possible. Conversely ment, consisting for instance of fibres, and the matrix between the same fibres and molten magnesium, neither chemical reactivity nor wettability are noticed(Fig. 1b) Generally speaking, this bonding must be strong In this last case, it will be necessary to create a strictly nough to provide good load transfer from the matrix controlled reactivity at the fibre/matrix interface [4] to the fibres, but weak enough to deflect cracks along In ceramic-matrix composites (CMCs), chemical the interface and to avoid their propagation through the reactivity between the fibre and the matrix can also be fibre with a brittle failure of the composite an important topic. For example, when carbon or silicon In ceramic-fibre-reinforced metallic-matrix compo- carbide fibres(Nicalon)are associated with an oxide sites(MMCs), the strength of the interfacial bond base matrix, interfacial oxidation-reduction reactions depends generally on the chemical interactions occurring may proceed at high temperature. In C/C, Sic/Sic or composite. For instance, low-graphitized carbon fibres no longer take place. However, the tion reactions can between fibre and matrix during the fabrication of the C/SiC CMCs, such oxidation-reduction reactions can x-PAN T 300 or ex-Pitch P 55) have a high tensile area remains a preferential path for oxygen diffusion and strength but they are highly reactive with oxygen and therefore constitutes a weak point concerning the resis- with metals like aluminium giving the carbide Al4C3 As tance to oxidation In the case of composites working in shown in Fig. la, this carbide forms as large crystals by air and at high temperature, it is therefore important to make use of oxidation-resistant or self-repairable inter phases. Nevertheless, the main function of the interface consists in conferring a non-brittle behaviour on materials 0266-3538/01/S. see front matter C 2001 Elsevier Science Ltd. All rights reserved PII:S0266-3538(00)00107-XPhysico-chemistry of interfaces in inorganic-matrix composites J. Bouix *, M.P. Berthet, F. Bosselet, R. Favre, M. Peronnet, O. Rapaud, J.C. Viala, C. Vincent, H. Vincent Laboratoire des MultimateÂriaux et Interfaces, UMR CNRS 5615, Universite Claude Bernard Lyon 1, 43 bvd 11 Novembre 1918, F69622 Villeurbanne Cedex, France Received 26 May 1999; received in revised form 20 October 1999; accepted 2 May 2000 Abstract The performances of metal matrix composites (MMCs) or ceramic matrix composites (CMCs) are usually limited by the char￾acteristics of the ®bre/matrix interface or more generally those of the interfacial zone. Concerning MMCs, the optimization of this zone involves control of the chemical reactivity between the reinforcement and the matrix, which constitute usually an out-of￾equilibrium system. In the case of CMCs, it is possible to obtain a non-brittle material by associating two brittle components and to exhibit a good resistance to oxidation. The physical chemist is able to o€er a signi®cant contribution for solving these problems by acting on the reinforcement surface, the matrix composition or the manufacturing conditions of the composite. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: A. Carbon ®bres; A. Ceramic-matrix composites (CMCs); A. Metal-matrix composites (MMCs); B. Interfaces; E. Chemical vapour deposition (CVD) 1. Introduction All of the recent studies show that the mechanical and thermomechanical behaviour of ceramic and metallic￾matrix composites depends widely on the nature of the interfacial bonding which forms between the reinforce￾ment, consisting for instance of ®bres, and the matrix [1±3]. Generally speaking, this bonding must be strong enough to provide good load transfer from the matrix to the ®bres, but weak enough to de¯ect cracks along the interface and to avoid their propagation through the ®bre with a brittle failure of the composite. In ceramic-®bre-reinforced metallic-matrix compo￾sites (MMCs), the strength of the interfacial bond depends generally on the chemical interactions occurring between ®bre and matrix during the fabrication of the composite. For instance, low-graphitized carbon ®bres (ex-PAN T 300 or ex-Pitch P 55) have a high tensile strength but they are highly reactive with oxygen and with metals like aluminium giving the carbide Al4C3. As shown in Fig. 1a, this carbide forms as large crystals by a dissolution-growth process and does not have any protecting e€ect on the ®bre which is attacked in depth. Consequently, the mechanical properties fall away and the composite is highly sensitive to corrosion by humid air with emission of methane. It is therefore necessary to limit this reactivity as far as possible. Conversely, between the same ®bres and molten magnesium, neither chemical reactivity nor wettability are noticed (Fig. 1b). In this last case, it will be necessary to create a strictly controlled reactivity at the ®bre/matrix interface [4]. In ceramic-matrix composites (CMCs), chemical reactivity between the ®bre and the matrix can also be an important topic. For example, when carbon or silicon carbide ®bres (Nicalon) are associated with an oxide base matrix, interfacial oxidation-reduction reactions may proceed at high temperature. In C/C, SiC/SiC or C/SiC CMCs, such oxidation-reduction reactions can no longer take place. However, the ®bre/matrix interfacial area remains a preferential path for oxygen di€usion and therefore constitutes a weak point concerning the resis￾tance to oxidation. In the case of composites working in air and at high temperature, it is therefore important to make use of oxidation-resistant or self-repairable inter￾phases. Nevertheless, the main function of the interface consists in conferring a non-brittle behaviour on materials 0266-3538/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0266-3538(00)00107-X Composites Science and Technology 61 (2001) 355±362 www.elsevier.com/locate/compscitech * Corresponding author