Availableonlineatwww.sciencedirect.com SCIENCE DIRECT MATERIALS ELSEVIER Materials Letters 57(2003)1670-1674 www.elsevier.com/locate/matlet Thermal shock behavior of SiC whisker reinforced Si3N4/BN fibrous monolithic ceramics ShuQin Li", Yong Huang, Yong Ming Luo, ChangAn Wang, Cui we State key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Enginering. TSinghua Universiy. Received 25 June 2001; received in revised form 20 June 2002: accepted 30 June 2002 Abstract Sic whisker reinforced Si3 N,/BN fibrous monolithic ceramics were fabricated by in situ synthesizing. The specimens were heated up to the test temperature and then quenched in a water bath of 25C. The therma resistance parameters were calculated according to the elastic modulus, Poisson ratio, thermal expansion coefficient and work of fracture. The thermal shock resistance critical temperature, AT, was 700C, which was improved more than SiC whisker reinforced Si3N4 ceramic BN soft cell boundaries had an effect on the thermal shock behavior of the si3 N4/Bn fibrous monolithic ceramics. The microstructures of the composites were observed by SEM o 2002 Elsevier Science B.V. All rights reserved. Keywords: Fibrous monolithic ceramics: Thermal shock resistance: Microstructure 1. Introduction years, laminated and fibrous monolithic ceramics have been developed to improve the toughness of ceramics Silicon nitride-based ceramics possess excellent through design of the macro- and microstructure of high temperature strength, oxidation resistance, good composites [3-7]. Therefore, the fracture toughness thermal shock resistance, low density and low coef- was improved greatly due to the change of the ficient of thermal expansion [1, 2]. These properties structure make them ideal candidate materials for high-temper- An important property of the ceramics for high ature applications, such as aerospace structural parts temperature applications is the thermal shock resist and turbine engines. However, the nature of brittleness ance. Sic whisker reinforcement in Si3 N4 matrix is a and thereby the lack of damage tolerance is one of the well-established method of enhancing the thermal most crucial problems in their applications. In recent shock resistance and the addition of bn in silicon nitride ceramic increases a/Ea [8] which improves the thermal shock resistance. In this paper, the effects composition structure on thermal shock resistance of Si3N4/Bn fibrous monolithic ceramic were investi E-mailaddress:Isq97(@mails.tsinghua.edu.cn(S.Li). gated systematically 0167-577X/02/S- see front matter c 2002 Elsevier Science B v. All rights reserved P:s0167-577X(02)01049-2Thermal shock behavior of SiC whisker reinforced Si3N4/BN fibrous monolithic ceramics ShuQin Li *, Yong Huang, YongMing Luo, ChangAn Wang, CuiWei Li State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, People’s Republic of China Received 25 June 2001; received in revised form 20 June 2002; accepted 30 June 2002 Abstract SiC whisker reinforced Si3N4/BN fibrous monolithic ceramics were fabricated by in situ synthesizing. The specimens were heated up to the test temperature and then quenched in a water bath of 25 jC. The thermal shock resistance parameters were calculated according to the elastic modulus, Poisson ratio, thermal expansion coefficient, strength and work of fracture. The thermal shock resistance critical temperature, DT, was 700 jC, which was improved more than SiC whisker reinforced Si3N4 ceramic. BN soft cell boundaries had an effect on the thermal shock behavior of the Si3N4/BN fibrous monolithic ceramics. The microstructures of the composites were observed by SEM. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Fibrous monolithic ceramics; Thermal shock resistance; Microstructure 1. Introduction Silicon nitride-based ceramics possess excellent high temperature strength, oxidation resistance, good thermal shock resistance, low density and low coef￾ficient of thermal expansion [1,2]. These properties make them ideal candidate materials for high-temper￾ature applications, such as aerospace structural parts and turbine engines. However, the nature of brittleness and thereby the lack of damage tolerance is one of the most crucial problems in their applications. In recent years, laminated and fibrous monolithic ceramics have been developed to improve the toughness of ceramics through design of the macro- and microstructure of composites [3 –7]. Therefore, the fracture toughness was improved greatly due to the change of the structure. An important property of the ceramics for high￾temperature applications is the thermal shock resist￾ance. SiC whisker reinforcement in Si3N4 matrix is a well-established method of enhancing the thermal shock resistance and the addition of BN in silicon nitride ceramic increases r/Ea [8] which improves the thermal shock resistance. In this paper, the effects of composition structure on thermal shock resistance of Si3N4/BN fibrous monolithic ceramic were investi￾gated systematically. 0167-577X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII: S0167-577X(02)01049-2 * Corresponding author. E-mail address: lsq97@mails.tsinghua.edu.cn (S. Li). www.elsevier.com/locate/matlet Materials Letters 57 (2003) 1670 – 1674