Atomic-scale microstructures of Zr2Al3C4 and Zr3Al3C5 ceramics

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3850 Z.J. Lin et al. / Acta Materialia 54 (2006) 3843–3851 Fig. 8. (a) Z-contrast image of ZrC inclusions in an elongated Zr 3 Al 3 C 5 grain. (b, c) NBD patterns of cubic ZrC with the electron beam parallel to [110] and [111] directions. Fig. 9. (a) FFT image from a region containing ZrC twins. (b) Initial high-resolution Z-contrast STEM image of a twinned ZrC with three Al layers at the twin boundaries. (c) FFT filtered image of (b). The microstructural characteristics of TiC, another binary TMC with NaCl-type structure, have been extensively investigated [32,33]. Previous investigations showed that TiC has a high stacking fault energy. Interestingly, impurities such as Al and Si could stabilize the twinned TiC structure and induced the formation of ternary Ti–Si(Al)–C carbides [34,35]. Since ZrC and TiC have the same rocksalt structure, it is reasonable that Al can also efficiently reduce the twin boundary energy of ZrC and consequently lead to the formation of ternary Zr–Al–C carbides. It is also clear that ZrC serves as the intermediate phase during the synthesis of ternary Zr–Al–C carbides from Zr, Al, and graphite elemental powders. This result leads to the interpretation that ternary Zr–Al–C carbides can be synthesized using elemental Zr, Al, and graphite powders as in this work, or ZrC and Al as in previous works [11–13]. 4. Conclusions The microstructural characteristics were investigated for Zr 2 Al 3 C 4 and Zr 3 Al 3 C 5 ceramics. The point group and space group of both carbides were determined to be 6/mmm and P6 3 /mmc, respectively, form SAED and CBED analyses. The lattice parameters of asprepared Zr 2 Al 3 C 4 (a = 0.33 nm and c = 2.24 nm) and Zr 3 Al 3 C 5 (a = 0.33 nm and c = 2.76 nm) were obtained. The atomic-scale microstructures of these two carbides were determined through high-resolution imaging and Z-contrast STEM imaging. Zr 3 Al 3 C 5 was identified to form an intergrown structure with Zr 3 Al 3 C 5 . Stacking faults in Zr 3 Al 3 C 5 resulted from the insertion of an additional Zr–C layer.
Z.J. Lin et al. / Acta Materialia 54 (2006) 3843–3851 3851 Minor amounts of rounded ZrC inclusions were observed in the elongated Zr 3 Al 3 C 5 grains. Al was found to induce a twinned ZrC structure and lead to the formation of ternary Zr–Al–C carbides. Acknowledgements The authors thank Miss Y. Cui for revising this manuscript. This work was supported by the National Outstanding Young Scientist Foundation for Y.C.Z. under Grant No. 59925208, Natural Sciences Foundation of China under Grant Nos. 50232040, 50302011, and 90403027. References [1] Nowotny H, Windisch S. Annu Rev Mater Sci 1973;3:171. [2] Pietzka MA, Schuster JC. J Phase Equilib 1994;15:392. [3] Wang XH, Zhou YC. Acta Mater 2002;50:3141. [4] Wang XH, Zhou YC. Oxid Met 2003;59:303. [5] Salama I, El-Raghy T, Barsoum MW. J Alloy Compd 2002;347:271. [6] Barsoum MW. Prog Solid State Chem 2000;28:201. [7] Schuster JC, Nowotny H, Vaccaro C. J Solid State Chem 1980;32:213. [8] Schuster JC, Nowotny H. Z Metallkd 1980;71:341. [9] Mikhalenko SI, Kuz’ma YB, Popov VE, Gurin VN, Nechitailov AP. Izv Akad Nauk SSSR, Neorgan Mater 1979;15:1948. [10] Parthé E, Chabot B. Acta Crystallogr 1988;C44:774. [11] Hashimoto S, Yamaguchi A, Yasuda M. J Mater Sci 1998;33:4835. [12] Leela-adisorn U, Choi SM, Hashimoto S, Honda S, Awaji H. In: Proceedings of the 21st international Korea–Japan seminar on ceramics; 2004. p. 339. [13] Leela-adisorn U, Choi SM, Tera N, Takeuchi T, Hashimoto S, Honda S, Awaji H, Hayakawa K, Yamaguchi A. J Ceram Soc Jpn 2005;113:188. [14] He LF, Zhou YC, Bao YW, Wang JY, Li MS [unpublished work]. [15] Fukuda K, Mori S, Hashimoto S. J Am Ceram Soc 2005;88:3528. [16] Gesing TM, Jeitschko W. J Solid State Chem 1998;140:396. [17] Arunajatesan S, Carim AH. Mater Lett 1994;20:319. [18] Ma XL, Zhu YL, Wang XH, Zhou YC. Philos Mag 2004;84:2969. [19] Hahn T. International tables for crystallography, vol. A: space-group symmetry. Dordrecht: Kluwer; 1989. [20] Lin ZJ, Zhuo MJ, Zhou YC, Li MS, Wang JY. Acta Mater 2006;54:1009. [21] Sun EY, Becher PF, Hsueh CH, Painter GS, Waters SB, Hwang SL, Hoffmann MJ. Acta Mater 1999;47:2777. [22] Perera DS, Mitchell DRG, Leung S. J Eur Ceram Soc 2000;20:789. [23] Pennycook SJ, Boatner LA. Nature 1988;336:565. [24] Browning ND, Chisholm MF, Pennycook SJ. Nature 1993;366:143. [25] Pennycook SJ, Yan YF. In: Zhang Xiao-Feng, Zhang Ze, editors. Progress in transmission electron microscopy, vol. 1. Berlin: Springer; 2001. p. 86. [26] Palmquist JP, Li S, Persson POÅ, Emmerlich J, Wilhelmsson O, Högberg H, Katsnelson MI, Johansson B, Ahuja R, Eriksson O, Hultman L, Jansson U. Phys Rev B 2004;70:165401. [27] Yu R, Zhan Q, He LL, Zhou YC, Ye HQ. Philos Mag Lett 2003;83:325. [28] Wang JY, Zhou YC, Lin ZJ, Liao T, He LF. Phys Rev B 2006;73:134107. [29] Green DJ. An introduction to the mechanical properties of ceramics. Cambridge: Press Syndicate of the University of Cambridge; 1998. [30] Morgiel J, Lis J, Pampuch R. Mater Lett 1994;27:85. [31] Lanin AG, Marchev EV, Pritchin A. Ceram Int 1991;17:301. [32] Hollox GE, Smallman RE. J Appl Phys 1966;37:818. [33] Das G. J Less-Common Met 1982;83:17. [34] Yu R, Zhan Q, He LL, Zhou YC, Ye HQ. Acta Mater 2002;50:4127. [35] Yu R, He LL, Ye HQ. Acta Mater 2003;51:2477.
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Atomic-scale microstructures of Zr2Al3C4 and Zr3Al3C5 ceramics

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