E D. Rodeghiero et al/ Materials Science and Engineering 4244(1998)11-21 EHT=25, 00 KV 6 m Photo no, =3 Detector= SE Fig. 8. Secondary electron SEM micrograph demonstrating interface debonding and whisker pullout in a 10/90 vol. SiC(whisker)/-AlO ceramIc-ceramic composite nature of the sol-gel synthesis employed in preparing Acknowledgements these highly uniform composites has no doubt had a positive impact on the final mechanical properties as This work was supported by onr (grant no well. In particular, many researchers presently feel that N001492J 1526)and AFOSR (grant no. F49620 homogeneity and good dispersion are the most impor- 93 10235). EDR and okT acknowledge the support of tant factors in synthesizing ceramic matrix composites, DoD fellowships. BCM, BSw, and Mw participated as if good overall fracture behavior(i.e. both high fracture part of an undergraduate research program. This study ughness and high fracture strength) is to be obtained benefited from the use of MrL Central Facilities [40]. In this light, fracture strength experiments(along funded by the National Science Foundation(grant no ith creep measurements) constitute the next crucial DMR-9121654) effor, gation to be undertaken in connection with this References 4. Conclusions Brinker. D. R. Ulrich(Eds ) Better Ceramics Through Chemistry, North-Holland, New York, 1984 ol-gel techniques have been used to synthesize C.J. Brinker. G. W. Scherer. Sol-Gel Science. Academic Press. San Diego, CA, 1990, Pp. 11-12. ge variety of ceramic matrix composites. The fund 3 B.E. Yoldas, A transparent porous alumina, Am. Ceram. Soc. mental advantage of using such a synthesis approach Bul.54(3)(1975)286-288. has been the production of extremely uniform and 4 B.E. Yoldas, Alumina sol preparation from alkoxides, Am. disperse microstructures not achievable using conven Ceram.Soc.Bull54(3)(1975)289-290. 5 B.E. Yoldas, Alumina gels that form porous transparent Al,O tional processing techniques. The composites produced J. Mater.Sci.10(1975)1856-1860 have included both metal-ceramic and ceramic-ce- 6C. Brinker, G.w. Scherer, Sol-Gel Science, Academic Press, ramic materials, some carefully doped with additional San Diego, CA, 1990, pp. 839-880 phases (a task made easy with sol-gel techniques) [7R. Roy, s Komarneni, D M. Roy, in C.J. Brinker, D E. Clark, Finally, the materials have displayed favorable physical nd D.R. Ulrich(Eds ) Better Ceramics Through Chemistry and mechanical properties, some of which can be at North-Holland, New York, 1984, pp. 347-359 [8R w. Rice, Ceramic composites-processing challenges, Ceram. tributed to the nature in which they were synthesized Eng.Sci.Proc.2(7-8)(1981)493-50820 E.D. Rodeghiero et al. / Materials Science and Engineering A244 (1998) 11–21 Fig. 8. Secondary electron SEM micrograph demonstrating interface debonding and whisker pullout in a 10/90 vol.% SiC(whisker)/a-Al2O3 ceramic–ceramic composite. nature of the sol–gel synthesis employed in preparing these highly uniform composites has no doubt had a positive impact on the final mechanical properties as well. In particular, many researchers presently feel that homogeneity and good dispersion are the most impor￾tant factors in synthesizing ceramic matrix composites, if good overall fracture behavior (i.e. both high fracture toughness and high fracture strength) is to be obtained [40]. In this light, fracture strength experiments (along with creep measurements) constitute the next crucial investigation to be undertaken in connection with this effort. 4. Conclusions Sol–gel techniques have been used to synthesize a large variety of ceramic matrix composites. The funda￾mental advantage of using such a synthesis approach has been the production of extremely uniform and disperse microstructures not achievable using conven￾tional processing techniques. The composites produced have included both metal–ceramic and ceramic–ce￾ramic materials, some carefully doped with additional phases (a task made easy with sol–gel techniques). Finally, the materials have displayed favorable physical and mechanical properties, some of which can be at￾tributed to the nature in which they were synthesized. Acknowledgements This work was supported by ONR (grant no. N0014 92 J 1526) and AFOSR (grant no. F49620 93 1 0235). EDR and OKT acknowledge the support of DoD fellowships. BCM, BSW, and MW participated as part of an undergraduate research program. This study benefited from the use of MRL Central Facilities funded by the National Science Foundation (grant no. DMR-9121654) References [1] C.J. Brinker, D.E. Clark, D.R. Ulrich (Eds.), Better Ceramics Through Chemistry, North-Holland, New York, 1984. [2] C.J. Brinker, G.W. Scherer, Sol–Gel Science, Academic Press, San Diego, CA, 1990, pp. 11–12. [3] B.E. Yoldas, A transparent porous alumina, Am. Ceram. Soc. Bull. 54 (3) (1975) 286–288. [4] B.E. Yoldas, Alumina sol preparation from alkoxides, Am. Ceram. Soc. Bull. 54 (3) (1975) 289–290. [5] B.E. Yoldas, Alumina gels that form porous transparent Al2O3, J. Mater. Sci. 10 (1975) 1856–1860. [6] C.J. Brinker, G.W. Scherer, Sol–Gel Science, Academic Press, San Diego, CA, 1990, pp. 839–880. [7] R. Roy, S. Komarneni, D.M. Roy, in C.J. Brinker, D.E. Clark, and D.R. Ulrich (Eds.), Better Ceramics Through Chemistry, North-Holland, New York, 1984, pp. 347–359. [8] R.W. Rice, Ceramic composites-processing challenges, Ceram. Eng. Sci. Proc. 2 (7–8) (1981) 493–508