Int./. Appl Ceram. Technol., 2/2/75-84(2005) pplied Ceramic Tech ceramic Product Development and Commercialization SiC-Matrix Composites: Nonbrittle Ceramics for Thermo- Structural application oger asain Laboratory for Thermostructural Composites, UMR-5801(CNRS-SNECMA-CEA-UBI), University Bordeaux 1, 33600 Pessac, france C/SiC and SiC/SiC composites are tough ceramics when the fiber-matrix bonding is properly optimized, usually through a thin layer of an interfacial material referred to as the interphase. These composites can be fabricated by a variety of techniques that are briefly described and compared. The design of the interphase, matrix, and coating at the nanometer scale, in order to promote microcrack deflection and to enhance the oxidation resistance is discussed. Selected properties of the composites are presented and discussed. Examples of application in engines, heat shields, braking systems, and high-temperature nuclear factors are shown to illustrate the potential of these materials and the key points that still require research and development Introduction ceramic material, potentially allows their use as struc tural materials for HT application in corrosiv e atmos- The ceramic matrix composites(CMCs)considered pheres and explains the tremendous effort of research here consist of ceramic fibers(mainly carbon-or SiC- and development in this field based fibers, generally arranged in multidirectional pre- Although SiC-matrix composite forms)embedded in a SiC-matrix. They have been first materials for application in severe environments, their imagined to replace the carbon/carbon(C/C)compos- development raises a number of issues that will be dis- ites in long-term application at high temperature(Ht) cussed in terms of processing, material design,main hen the atmosphere is oxidizing. It was further d properties, and actual or potential applications in var- covered in a fortuitous manner, and then confirmed by ious fields. a more detailed analysis has been recently theoretical considerations, that CMCs could display a presented elsewhere nonbrittle behavior if the fiber-matrix(FM) bonding was lowered enough, e.g., through the in situ formation of a suitable interfacial reaction zone or the use of a so- Processing called interphase deposited on the fber before the infil tration of the matrix. 4.The damage-tolerant character CMCs are fabricated according to gas phase routes of these CMCs, which is an outstanding property for a CVI: chemical vapor infiltration), liquid phase routes either from polymers(PIP: polymer impregnatic pyrolysis), or molten elements reacting with the the atmosphere (RMi: reactive meltSiC-Matrix Composites: Nonbrittle Ceramics for Thermo￾Structural Application Roger R. Naslain* Laboratory for Thermostructural Composites, UMR-5801 (CNRS-SNECMA-CEA-UB1), University Bordeaux 1, 33600 Pessac, France C/SiC and SiC/SiC composites are tough ceramics when the fiber–matrix bonding is properly optimized, usually through a thin layer of an interfacial material referred to as the interphase. These composites can be fabricated by a variety of techniques that are briefly described and compared. The design of the interphase, matrix, and coating at the nanometer scale, in order to promote microcrack deflection and to enhance the oxidation resistance is discussed. Selected properties of the composites are presented and discussed. Examples of application in engines, heat shields, braking systems, and high-temperature nuclear reactors are shown to illustrate the potential of these materials and the key points that still require research and development. Introduction The ceramic matrix composites (CMCs) considered here consist of ceramic fibers (mainly carbon- or SiC￾based fibers, generally arranged in multidirectional pre￾forms) embedded in a SiC-matrix. They have been first imagined to replace the carbon/carbon (C/C) compos￾ites in long-term application at high temperature (HT) when the atmosphere is oxidizing.1,2 It was further dis￾covered in a fortuitous manner, and then confirmed by theoretical considerations, that CMCs could display a nonbrittle behavior if the fiber–matrix (FM) bonding was lowered enough, e.g., through the in situ formation of a suitable interfacial reaction zone3 or the use of a so￾called interphase deposited on the fiber before the infil￾tration of the matrix.4,5 The damage-tolerant character of these CMCs, which is an outstanding property for a ceramic material, potentially allows their use as struc￾tural materials for HT application in corrosive atmos￾pheres and explains the tremendous effort of research and development in this field. Although SiC-matrix composites are promising materials for application in severe environments, their development raises a number of issues that will be dis￾cussed in terms of processing, material design, main properties, and actual or potential applications in var￾ious fields. A more detailed analysis has been recently presented elsewhere.6 Processing CMCs are fabricated according to gas phase routes (CVI: chemical vapor infiltration), liquid phase routes either from polymers (PIP: polymer impregnation and pyrolysis), or molten elements reacting with the preforms or the atmosphere (RMI: reactive melt Int. J. Appl. Ceram. Technol., 2 [2] 75–84 (2005) Ceramic Product Development and Commercialization *naslain@lcts.u-bordeaux1.fr