Availableonlineatwww.sciencedirect.com Aerospace BCIENCE RECTO Science Technolo ELSEVIER Aerospace Science and Technology 7(2003)135-146 Microstructures of ceramic composites ith glass-ceramic matrices reinforced by sic-based fibres Jean Vicens *, Gaelle Farizy, Jean-Louis Chermant LERMAT CNRS FRE 2149. 6 Boulevard Marechal Juin 14050 Caen Cedex france Received 14 February 2002; accepted 1 July 2002 Abstract A lot of studies have been carried out on the fibre/matrix interfaces in glass-ceramic matrix composites reinforced by SiC based fibres Chemical and structural analyses at the nanometer scale have shown that the fibre/matrix interface has a very complex structure consisting of several sublayers. The most important point is the existence of a thin carbon layer which is often found textured close to the fibre carbon layer acts as a mechanical fuse with a low or extremely low interfacial debonding energy. The mechanism responsible of the carbon formation and of the complex interfacial microstructure is still mater of controversy. This review will be focused on the microstructure of the interfacial region and on the different techniques which have been used to obtain chemical and microstructural parameters of the fibre/matrix interfaces in a large variety of glass-ceramic composites. The approaches concerning the sic/Bn dual-coated Nicalon SiC fibre-reinforced BMAS matrix composites will be described as well as the thermomechanical properties of this class of glass-ceramic composites and future esearch e 2002 Editions scientifiques et medicales Elsevier SAs. All rights reserved Keywords: Glass-ceramic matrix composite; Carbon interphase, SiC Nicalon fibre/HRTEM 1. Introduction where low density materials with high temperature capa- ility are needed: in st The new class of materials-ceramic matrix composites els with stifiners, high dimensional stability structures for (CMCs)-is concerned with a ceramic matrix reinforced by mirror or antenna) or in turbines(rear frame liners, mixer ceramic fibres, whiskers or particles. The matrix is made flow, petals, exhaust cones, . )[11, 19, 29, 32, 33]. Unfortu of either a monolithic ceramic(SiC, Al2O3, Si3N4,. ) or nately many CMCs with a glass-ceramic matrix have shown a glass-ceramic. The first ones are prepared from ceramic during high temperature and long term tests that some mor- routes(melting or chemical vapor infiltration-CVI-, poly- phological and chemical changes arise in the matrix mi- mer infiltration-PIP-processes)and the second ones result crostructure, leading also to the development of some vis- from the glass route which is easier to produce and needs a cous phases( from a mechanical point of view)at tempera lower temperature. Among the large variety of CMCs, com- tures higher than 1273 K. That is the reason why today only posites with long ceramic fibres have been extensively in- CMCs with a monolithic matrix are considered for applica- vestigated over the last decade because of their interesting tions at high temperatures and high stresses [10).Neverthe- behavior at high temperatures. Many research activities in less, mainly due to their low density, high corrosion resis- the field of the aeronautical and space domains concern the tance and cheaper process cost, CMCs with a glass-ceramic development of new equipment able to be used in severe matrix have a potential field of applications in a domain of conditions, such as high temperature, high stress level, ag- low low stresses and low temperatures(873-1073 K)[2].The gressive environment: this was the challenge of the ceramic present paper will focus on CMCs with a glass-ceramic ma- matrix composites reinforced by ceramic fibres CMCs have trix reinforced by Sic Nicalon fibres. It is well known that potential applications in relation to the aerospace sector CMCs are tough when the fibre-matrix bonding is controlled during processing, via the use of an interphase [31] Corresponding author. In CMCs fabricated by CVl, the design of the fibre/matrix interfacial zone is based on precoated fibres where a weak 1270-9638/02/S-see front matter o 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved i:10.1016/1270-9638(02)01178-1Aerospace Science and Technology 7 (2003) 135–146 www.elsevier.com/locate/aescte Microstructures of ceramic composites with glass–ceramic matrices reinforced by SiC-based fibres Jean Vicens ∗, Gaëlle Farizy, Jean-Louis Chermant LERMAT, CNRS FRE 2149, 6 Boulevard Maréchal Juin, 14050 Caen Cedex, France Received 14 February 2002; accepted 1 July 2002 Abstract A lot of studies have been carried out on the fibre/matrix interfaces in glass–ceramic matrix composites reinforced by SiC based fibres. Chemical and structural analyses at the nanometer scale have shown that the fibre/matrix interface has a very complex structure consisting of several sublayers. The most important point is the existence of a thin carbon layer which is often found textured close to the fibre. This carbon layer acts as a mechanical fuse with a low or extremely low interfacial debonding energy. The mechanism responsible of the carbon formation and of the complex interfacial microstructure is still mater of controversy. This review will be focused on the microstructure of the interfacial region and on the different techniques which have been used to obtain chemical and microstructural parameters of the fibre/matrix interfaces in a large variety of glass–ceramic composites. The approaches concerning the SiC/BN dual-coated Nicalon SiC fibre-reinforced BMAS matrix composites will be described as well as the thermomechanical properties of this class of glass–ceramic composites and future research.  2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved. Keywords: Glass–ceramic matrix composite; Carbon interphase; SiC Nicalon fibre/HRTEM 1. Introduction The new class of materials – ceramic matrix composites (CMCs) – is concerned with a ceramic matrix reinforced by ceramic fibres, whiskers or particles. The matrix is made of either a monolithic ceramic (SiC, Al2O3, Si3N4,...) or a glass–ceramic. The first ones are prepared from ceramic routes (melting or chemical vapor infiltration -CVI-, poly￾mer infiltration -PIP- processes) and the second ones result from the glass route which is easier to produce and needs a lower temperature. Among the large variety of CMCs, com￾posites with long ceramic fibres have been extensively in￾vestigated over the last decade because of their interesting behavior at high temperatures. Many research activities in the field of the aeronautical and space domains concern the development of new equipment able to be used in severe conditions, such as high temperature, high stress level, ag￾gressive environment: this was the challenge of the ceramic matrix composites reinforced by ceramic fibres. CMCs have potential applications in relation to the aerospace sector * Corresponding author. E-mail address: jean.vicens@ismra.fr (J. Vicens). where low density materials with high temperature capa￾bility are needed: in structures (air intakes, structural pan￾els with stiffners, high dimensional stability structures for mirror or antenna) or in turbines (rear frame liners, mixer flow, petals, exhaust cones,...) [11,19,29,32,33]. Unfortu￾nately many CMCs with a glass–ceramic matrix have shown during high temperature and long term tests that some mor￾phological and chemical changes arise in the matrix mi￾crostructure, leading also to the development of some vis￾cous phases (from a mechanical point of view) at tempera￾tures higher than 1273 K. That is the reason why today only CMCs with a monolithic matrix are considered for applica￾tions at high temperatures and high stresses [10]. Neverthe￾less, mainly due to their low density, high corrosion resis￾tance and cheaper process cost, CMCs with a glass–ceramic matrix have a potential field of applications in a domain of low stresses and low temperatures (873–1073 K) [2]. The present paper will focus on CMCs with a glass–ceramic ma￾trix reinforced by SiC Nicalon fibres. It is well known that CMCs are tough when the fibre-matrix bonding is controlled during processing, via the use of an interphase [31]. In CMCs fabricated by CVI, the design of the fibre/matrix interfacial zone is based on precoated fibres where a weak 1270-9638/02/$ – see front matter  2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved. doi:10.1016/S1270-9638(02)01178-1