L Mariappan er al. /Materials Chemistry and Physics 75(2002) 284-290 inerals such as Kaolin, Sillimanite and Zircon. The reac- Mr. Krishna (lISc)for taking XRD patterns and Mr. M.A. tion starts at 1550C and is completed at 1650C Beyond Venkataswamy (NAL) for helping us in SEM studies 1650C the product phases start reacting among them- selves and form new phases [ll]. Carbon black gives a Ref better product both in terms of whisker formation as well as in generating a controlled reaction at the optimum tem- [1]SE Khalafalla, L.A. Haas, High Temp. Sci. 2(1970)95 perature of 1650C. The tetragonal form of zirconia could 22] Bechtold, Cutler, J. Am. Ceram Soc. 63(1980)271 be obtained without any addition of stabilisers by this pro [3]AC D. Chaklader, S Das Gupta, E.C.Y. Lin, J. Am. Ceram. Soc. cess if the starting precursor sizes were maintained around 75(1992)2283 I um. The other matrix materials, alumina and Sic having [4] P.K. Panda, L Mariappan, T.S. Kannan, Ceram. Int. 25(1999)467 5] P.K. Panda, L. Mariappan, V.A. Jaleel, T.S. Kannan, J. Dubois, G. a higher elastic modulus than zirconia, help in retaining the Fantozzi, J Mater. Chem. 6(1996)1395 tetragonal form of zirconia. [6] P.K. Panda, L. Mariappan, V.A. Jaleel, T.S. Kannan, J. Dubois, A mroune, G. Fantozzi, J. Mater. Sci. 31(1996)4277. [7 M. Bohmer, E.A. Almond, Mater Sci Eng. A 105-106(1988)105 [8E.L. Exner, C K. Jun, L L. Moravansky, Ceram. Eng Acknowledgements (1988)597 [9] F.F. Lange, J Mater. Sci. 17(1982)225 [10A.C D. Chaklader, S.M. B. Veiga, M.M. Veiga, J.C. Bressiani, Advan- The authors thank Miss K. Geetha (lISc)for the help ced Ceramic Structures for Tribological Applications, 1995, P. 107. rendered during the course of this work. We also thank [11]A K Mishra, J. Am. Ceram Soc. 74( 1991)345.290 L. Mariappan et al. / Materials Chemistry and Physics 75 (2002) 284–290 minerals such as Kaolin, Sillimanite and Zircon. The reac￾tion starts at 1550 ◦C and is completed at 1650 ◦C. Beyond 1650 ◦C the product phases start reacting among them￾selves and form new phases [11]. Carbon black gives a better product both in terms of whisker formation as well as in generating a controlled reaction at the optimum tem￾perature of 1650 ◦C. The tetragonal form of zirconia could be obtained without any addition of stabilisers by this pro￾cess if the starting precursor sizes were maintained around 1m. The other matrix materials, alumina and SiC having a higher elastic modulus than zirconia, help in retaining the tetragonal form of zirconia. Acknowledgements The authors thank Miss K. Geetha (IISc) for the help rendered during the course of this work. We also thank Mr. Krishna (IISc) for taking XRD patterns and Mr. M.A. Venkataswamy (NAL) for helping us in SEM studies. References [1] S.E. Khalafalla, L.A. Haas, High Temp. Sci. 2 (1970) 95. [2] Bechtold, Cutler, J. Am. Ceram. Soc. 63 (1980) 271. [3] A.C.D. Chaklader, S. Das Gupta, E.C.Y. Lin, J. Am. Ceram. Soc. 75 (1992) 2283. [4] P.K. Panda, L. Mariappan, T.S. Kannan, Ceram. Int. 25 (1999) 467. [5] P.K. Panda, L. Mariappan, V.A. Jaleel, T.S. Kannan, J. Dubois, G. Fantozzi, J. Mater. Chem. 6 (1996) 1395. [6] P.K. Panda, L. Mariappan, V.A. Jaleel, T.S. Kannan, J. Dubois, A. Amroune, G. Fantozzi, J. Mater. Sci. 31 (1996) 4277. [7] M. Bohmer, E.A. Almond, Mater. Sci. Eng. A 105–106 (1988) 105. [8] E.L. Exner, C.K. Jun, L.L. Moravansky, Ceram. Eng. Sci. Proc. 9 (1988) 597. [9] F.F. Lange, J. Mater. Sci. 17 (1982) 225. [10] A.C.D. Chaklader, S.M.B. Veiga, M.M. Veiga, J.C. Bressiani, Advan￾ced Ceramic Structures for Tribological Applications, 1995, p. 107. [11] A.K. Mishra, J. Am. Ceram. Soc. 74 (1991) 345.