CERAMICS INTERNATIONAL ELSEVIER Ceramics International 29(2003)323-326 Microstructure and fracture characteristics of alumina-based prismatic ceramic composites G.H. Min,D,, L X. Yang, T.H. Inoue a Materials Science and Engineering Institute, Shandong University, Jinan 250061, PR China Energy Conversion Department, Osaka National Research Institute, Osaka 563-8577, Jape Received 24 April 2002: received in revised form 15 June 2002: accepted 21 July 2002 Abstract e Al2O3 SiC prismatic ceramic composites have been prepared by a structure-controlled process, in which the high-aspect-ratio umina-based cells with a distinct prismatic texture were separated in three dimensions by thin SiC cell boundaries. The work-of- fracture of the composites has been improved greatly due to the developed paths for crack propagation by the weak cell bounda corresponding to longer displacement under reasonable load-carrying condition. The route of crack propagation depended greatly on the interfacial shear strength and boundary thickness. Crack deflecting and delamination are considered as two main contribu- tions at the earlier stage, whereas frictional sliding of fibrous cells becomes more dominant after cracking occurs, especially at l loading condition. These mechanisms are different from those observed in multilayered monolithic ceramics due to the conti structures of present materials. C 2002 Elsevier Science Ltd and Techna S r l. All rights reservec Keywords: B. Microstructure; C. Mechanical properties; Alumina-based composites; Fracture characteristic 1. ntroduction The objective of the present paper is to evaluate the bending properties such toughness and fracture Fibrous monolithic ceramics would prove to be can- energy, and to observe the crack propagation. The main didates for structural applications due to fabricating effort is focused to describe the differences in fracture with commercial powders and showing non-cata- behavior of fibrous ceramics against laminated ceramics strophic fracture behavior. More recently, an extensive and fiber-reinforced ceramics, and fracture mechanism effort had been made on the aspects of fabrication and of the prismatic ceramics is to be concluded fracture behavior of those fibrous ceramics, and several preliminarily systems had been developed such as by JW Holloran [1-5] and T H. Inoue and co-workers [6-9]. Those cera- mics fail non-catastrophically in a similar manner to 2. Experimental procedure whisker fiber-reinforced ceramics [10] and multilayered ceramic composites [11, 12]. However, it seems to have A commercial a-type Al_O3 powder with an average not been characterized for fracture behavior in fibrous particle size of 0.22 um and specific surface area of 12.3 monolithic ceramics. The mechanisms that govern the m/g(TM-D, Taimei Chemicals Co Ltd, Japan) was energy absorption ability of fibrous ceramics are unique, used as a fibrous'cell'. A fine B-Sic powder (UF-0741 almost referred to that of laminated ceramics or fiber Ibiden Co Ltd) was selected as the interfacial cell reinforced ceramics, which caused the experimental boundary results not to follow those existing models [1, 13-15 The prismatic fibrous ceramic was prepared by mold extruding and hot-pressing techniques. The green fibers with a diameter of 0.5 mm were prepared by mold Corresponding author. Tel: +86-531-839-5639: fax: +86-531 extrusion, and Sic slurry was sprayed on the surface of the arranged green fiber sheets as the thin inter-fiber layers. Then, dozens of sheets were stacked and com 0272-8842/03/S22.00C 2002 Elsevier Science Ltd and Techna S.r. l. All rights reserved PII:S0272-8842(02)00141-4Microstructure and fracture characteristics of alumina-based prismatic ceramic composites G.H. Mina,b,*, L.X. Yanga , T.H. Inoueb a Materials Science and Engineering Institute, Shandong University, Jinan 250061, PR China bEnergy Conversion Department, Osaka National Research Institute, Osaka 563-8577, Japan Received 24 April 2002; received in revised form 15 June 2002; accepted 21 July 2002 Abstract Al2O3/SiC prismatic ceramic composites have been prepared by a structure-controlled process, in which the high-aspect-ratio alumina-based cells with a distinct prismatic texture were separated in three dimensions by thin SiC cell boundaries. The work-of￾fracture of the composites has been improved greatly due to the developed paths for crack propagation by the weak cell boundaries, corresponding to longer displacement under reasonable load-carrying condition. The route of crack propagation depended greatly on the interfacial shear strength and boundary thickness. Crack deflecting and delamination are considered as two main contribu￾tions at the earlier stage, whereas frictional sliding of fibrous cells becomes more dominant after cracking occurs, especially at lower loading condition. These mechanisms are different from those observed in multilayered monolithic ceramics due to the controlled structures of present materials. # 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved. Keywords: B. Microstructure; C. Mechanical properties; Alumina-based composites; Fracture characteristic 1. Introduction Fibrous monolithic ceramics would prove to be can￾didates for structural applications due to fabricating with commercial powders and showing non-cata￾strophic fracture behavior. More recently, an extensive effort had been made on the aspects of fabrication and fracture behavior of those fibrous ceramics, and several systems had been developed such as by J.W Holloran [1–5] and T.H. Inoue and co-workers [6–9]. Those cera￾mics fail non-catastrophically in a similar manner to whisker fiber-reinforced ceramics [10] and multilayered ceramic composites [11,12]. However, it seems to have not been characterized for fracture behavior in fibrous monolithic ceramics. The mechanisms that govern the energy absorption ability of fibrous ceramics are unique, almost referred to that of laminated ceramics or fiber reinforced ceramics, which caused the experimental results not to follow those existing models [1,13–15]. The objective of the present paper is to evaluate the bending properties such as toughness and fracture energy, and to observe the crack propagation. The main effort is focused to describe the differences in fracture behavior of fibrous ceramics against laminated ceramics and fiber-reinforced ceramics, and fracture mechanism of the prismatic ceramics is to be concluded preliminarily. 2. Experimental procedure A commercial a-type Al2O3 powder with an average particle size of 0.22 mm and specific surface area of 12.3 m2 /g (TM-D, Taimei Chemicals Co Ltd, Japan) was used as a fibrous ‘cell’. A fine b-SiC powder (UF-0741, Ibiden Co Ltd) was selected as the interfacial ‘cell boundary’. The prismatic fibrous ceramic was prepared by mold extruding and hot-pressing techniques. The green fibers with a diameter of 0.5 mm were prepared by mold extrusion, and SiC slurry was sprayed on the surface of the arranged green fiber sheets as the thin inter-fiber layers. Then, dozens of sheets were stacked and com- 0272-8842/03/$22.00 # 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved. PII: S0272-8842(02)00141-4 Ceramics International 29 (2003) 323–326 www.elsevier.com/locate/ceramint * Corresponding author. Tel.: +86-531-839-5639; fax: +86-531- 295-5999. E-mail address: minguanghui@hotmail.com (G.H. Min)