S. Wannaparhun et al /Applied Surface Science 185(2002)183-196 from the surface. Therefore, only the calculated spec- acknowledge the project manager Mr C. Campbell for tra can be graphically manipulated supplying the samples and the funding support from 14 The calculated Al(2p), Si(2p), and o(ls)spectra of corridor and Siemens Westinghouse to carryout the the composite are shown in part(a) of Figs. 10-12, research. We are also thankful to UCF-CIRENT MCF respectively. In Fig. 15, the as-received and the cal- for utilizing the TEM facility culated spectra with the same BE range scale were ompared using a graphical superimposition method ach calculated spectrum was superimposed on the as-received spectrum and graphically adjusted the References intensity in order to fit the as-received spectra The calculated and the as-received Al(2p) are mostly [1] K.K. Chawla, Ceramic Matrix Composites, Chapman Hall, identical(Fig. 15a). In the case of Si(2p)and o(1s) [2] w Schafer, B Plege, W.D. Vogel, Key Eng Mater. 132-136 (Fig. 15b and c), there are small discrepancies between 1997)1966 the calculated and the as-received spectra. A small [3 T.P. Herbell, AJ. Eckel, Trans. ASME 115(1993) discrepancy between the two sets of spectra can be due [4]A K. Noor.S. to varying signal/noise ratio of the XPS instrument and Dynamics-Assessment and Future Directions, Vol. 3 Ceramics and Ceramic-Matrix Composites, ASME, New itself. From these observations. it can be concluded York,1992. that the surface/interface chemical alteration of the [5 A. Szweda, T.E. Easler, D.R. Petrak, V.A. Black, ASME Nextel-720 fiber and the alumina matrix in sol-gel manufacturing of the CMC is negligible, except the [6] G.P. Gaudenzi. C. Taut, K. Ifflander, S. Corcoruto, Key Eng presence of the silicon contaminant in the matrix Mater.132-136(1997)1637 [71 A.G. Razzell, L. Molliex, M. Holmquist, O. Sudre, ASME 98-GT [8] N.K. Rizk, ASMEGT87, P. 11. 4. Conclusions [9 K.O. Smith, A. Fahme, ASME 96-GT-318, June 1996 [10] J.H. Yu, Proceedings of the International Conference XPS was successfully used to analyze the surface Energy and Environment, ICEE 1996, Begell House, Inc pp.657-666. chemistry of mullite, alumina, Nextel-720 and the [11] R. Lundberg, L. Eckerborn, Design and processing of all- CMC. Presence of silicon in aluminosilicate form is xide composites, in: High-temperature Ceramic Matrix evident from the pure alumina matrix. This may be due Composites, Vol. Il. pp 95-105 to the manufacturing of alumina using sol-gel process. [12 H.C. Cao, et al. J. Am. Ceram. Soc. 73(1990). 1691 Both as-received and calculated XPS spectra of the [13] L.R. Dharani, S.B. Haug, Collection of technical papers- AlAA/ASME/ASCE/AHS/ASC structures, Struct. Dyn CMC indicate a very small discrepancy in the compo- Mater. Conf. 2(1999)1159. site chemistry. This indicates a negligible chemical [14] K.K. Chawla, Proceedings of the Engineering Foundation interaction between the Nextel-720 fiber and the alu Conference 1997, TMS. Warrendale, PA, pp. 235-245 nina matrix. As a matter of suggestion, this discrepancy [151 JJ. Haslam, K.E. Berroth, E.F. Lange, J.Eur.Ceram Soc.20 can be interpreted into a number using a statistical 2000)607. [16]CG.Levi,etal.,Z. Metal.9(12)(1999)1037 [17 w.C. Tu, F F. Lange, A.G. Evans, J. Am. Ceram. Soc. 79 degree of discrepancy between the as-received and (1996)417 calculated spectra) and mechanical properties can be [18 V.A. Kramb, R. John, L P. Zawada, J. Am. Ceram. Soc. 82 established based on a large number of sampling, which is required to establish a precise quality control standard [19 F.F. Lange, W.C. Tu, A.G. Evans, Mater. Sci. Eng. A 195 (1995)145 for future fabrication of the Nextel-720/alumina CMC [20] F. Zok, F. Lange, F. Porter, R. John, J. Am. Ceram Soc. 74(8) [21] K.T. Faber, Annu. Rev. Mater. Sci. 27(1997)499. Acknowledgement [22]M. Schmuecker, J. Eur. Ceram Soc. 20(14-15)(2000)2491 (231 J.P. Rigueiro, P. Herrero, J Llorca, Proceedings of the 14th The authors would like to thank Mr. P. Varghese and International Congress on Electron Microscopy, Vol. 2, 1998, Dr S Jha for participating in the project. We gratefully [24]RN. Singh, J. Am. Ceram Soc. 72(9)(1989)1764from the surface. Therefore, only the calculated spec￾tra can be graphically manipulated. The calculated Al(2p), Si(2p3 ), and O(1s) spectra of the composite are shown in part (a) of Figs. 10–12, respectively. In Fig. 15, the as-received and the cal￾culated spectra with the same BE range scale were compared using a graphical superimposition method. Each calculated spectrum was superimposed on the as-received spectrum and graphically adjusted the intensity in order to fit the as-received spectra. The calculated and the as-received Al(2p) are mostly identical (Fig. 15a). In the case of Si(2p3 ) and O(1s) (Fig. 15b and c), there are small discrepancies between the calculated and the as-received spectra. A small discrepancy between the two sets of spectra can be due to varying signal/noise ratio of the XPS instrument itself. From these observations, it can be concluded that the surface/interface chemical alteration of the Nextel-720 fiber and the alumina matrix in sol–gel manufacturing of the CMC is negligible, except the presence of the silicon contaminant in the matrix. 4. Conclusions XPS was successfully used to analyze the surface chemistry of mullite, alumina, Nextel-720 and the CMC. Presence of silicon in aluminosilicate form is evident from the pure alumina matrix. This may be due to the manufacturing of alumina using sol–gel process. Both as-received and calculated XPS spectra of the CMC indicate a very small discrepancy in the compo￾site chemistry. This indicates a negligible chemical interaction between the Nextel-720 fiber and the alu￾mina matrix. As a matter of suggestion, this discrepancy can be interpreted into a number using a statistical approach. The correlation between the number (the degree of discrepancy between the as-received and calculated spectra) and mechanical properties can be established based on a large number of sampling, which is required to establish a precise quality control standard for future fabrication of the Nextel-720/alumina CMC. Acknowledgements The authors would like to thank Mr. P. Varghese and Dr. S. Jha for participating in the project. We gratefully acknowledge the project manager Mr. C. Campbell for supplying the samples and the funding support from I4 corridor and Siemens Westinghouse to carryout the research. We are also thankful to UCF-CIRENT MCF for utilizing the TEM facility. References [1] K.K. Chawla, Ceramic Matrix Composites, Chapman & Hall, London, 1993. [2] W. Schafer, B. Plege, W.D. Vogel, Key Eng. Mater. 132–136 (1997) 1966. [3] T.P. Herbell, A.J. Eckel, Trans. ASME 115 (1993) 64. [4] A.K. Noor, S.L. Venneri, Flight-vehicle Materials, Structures, and Dynamics—Assessment and Future Directions, Vol. 3: Ceramics and Ceramic–Matrix Composites, ASME, New York, 1992. [5] A. Szweda, T.E. Easler, D.R. Petrak, V.A. Black, ASME 99-GT-189, 1999. [6] G.P. Gaudenzi, C. Taut, K. Ifflander, S. Corcoruto, Key Eng. Mater. 132–136 (1997) 1637. [7] A.G. Razzell, L. Molliex, M. Holmquist, O. Sudre, ASME 98-GT-30, 1998. [8] N.K. Rizk, ASMEGT87, p. 11. [9] K.O. Smith, A. Fahme, ASME 96-GT-318, June 1996. [10] J.H. Yu, Proceedings of the International Conference on Energy and Environment, ICEE 1996, Begell House, Inc., pp. 657–666. [11] R. Lundberg, L. Eckerborn, Design and processing of all￾oxide composites, in: High-temperature Ceramic Matrix Composites, Vol. II, pp. 95–105. [12] H.C. Cao, et al., J. Am. Ceram. Soc. 73 (1990) 1691. [13] L.R. Dharani, S.B. Haug, Collection of technical papers— AIAA/ASME/ASCE/AHS/ASC structures, Struct. Dyn. Mater. Conf. 2 (1999) 1159. [14] K.K. Chawla, Proceedings of the Engineering Foundation Conference 1997, TMS, Warrendale, PA, pp. 235–245. [15] J.J. Haslam, K.E. Berroth, F.F. Lange, J. Eur. Ceram. Soc. 20 (2000) 607. [16] C.G. Levi, et al., Z. Metall. 90 (12) (1999) 1037. [17] W.C. Tu, F.F. Lange, A.G. Evans, J. Am. Ceram. Soc. 79 (1996) 417. [18] V.A. Kramb, R. John, L.P. Zawada, J. Am. Ceram. Soc. 82 (11) (1996) 3087. [19] F.F. Lange, W.C. Tu, A.G. Evans, Mater. Sci. Eng. A 195 (1995) 145. [20] F. Zok, F. Lange, F. Porter, R. John, J. Am. Ceram. Soc. 74 (8) (1991) 1880. [21] K.T. Faber, Annu. Rev. Mater. Sci. 27 (1997) 499. [22] M. Schmuecker, J. Eur. Ceram. Soc. 20 (14–15) (2000) 2491. [23] J.P. Rigueiro, P. Herrero, J. Llorca, Proceedings of the 14th International Congress on Electron Microscopy, Vol. 2, 1998, p. 799. [24] R.N. Singh, J. Am. Ceram. Soc. 72 (9) (1989) 1764. S. Wannaparhun et al. / Applied Surface Science 185 (2002) 183–196 195