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Formation of mixed oxide powders in flames: Part I. TiO2−SiO2

Published online by Cambridge University Press:  31 January 2011

Cheng-Hung Hung
Affiliation:
Department of Chemical Engineering, The Johns Hopkins University, Baltimore, Maryland 21218
Joseph L. Katz
Affiliation:
Department of Chemical Engineering, The Johns Hopkins University, Baltimore, Maryland 21218
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Abstract

Mixed oxide powders, e.g., Al2O3−TiO2, SiO2−GeO2, and TiO2−SiO2, are used in industry to produce ceramics, optical fibers, catalysts, and paint opacifiers. The properties of these products depend upon the morphology of the powders. Ceramics and optical fibers are produced using either a uniform mixture of multicomponent particles or a uniform solution. The desired morphology for catalysts is a high surface area and many active sites. TiO2 coated with a layer of SiO2 is the desired structure for use as a paint opacifier. In this paper, TiO2−SiO2 mixed oxide powders were synthesized using a counterflow diffusion flame burner. TiCl4 and SiCl4 were used as source materials for the formation of oxide particles in hydrogen-oxygen flames. In situ particle sizes were determined using dynamic light scattering. A thermophoretic sampling method also was used to collect particles directly onto carbon coated grids, and their size, morphology, and crystalline form examined using a transmission electron microscope. A photomultiplier at 90° to the argon ion laser beam was used to measure the light-scattering intensity. The effect of temperature and of Si to Ti concentration ratio on particle morphology was investigated. Strong temperature dependence was observed. At high temperatures, TiO2 particles were covered with discrete SiO2 particles. At low temperatures, the structure changes to TiO2 particles encapsulated by SiO2. TEM diffraction pattern measurements showed that the TiO2 is rutile and the SiO2 is amorphous silica. At high Si to Ti ratios, SiO2-encapsulated TiO2 particles form. At low Si to Ti ratios, one obtains TiO2 particles covered with discrete SiO2 particles.

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Articles
Copyright
Copyright © Materials Research Society 1992

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References

1.Ulrich, G. D., C&EN 62, 22 (1984).Google Scholar
2.Suyama, Y., Ito, K., and Kato, A., J. Inorg. Nucl. Chem. 37, 1883 (1975).CrossRefGoogle Scholar
3.Asuncion, F., Leyrer, J., Gonzalez-Elipe, A. R., Munuera, G., and Knozinger, H., J. Catal. 112, 489 (1988).Google Scholar
4.Wiseman, T. J., in Characterization of Powder Surfaces, edited by Parfitt, G. D. and Sing, K. S. W. (Academic Press, New York, 1976), Chap. 4, pp. 159208.Google Scholar
5.Chung, S. L. and Katz, J. L., Combustion and Flame 61, 271 (1985).CrossRefGoogle Scholar
6.Katz, J. L. and Hung, C. H., “Ultrafine Refractory Particle Formation in Counterflow Diffusion Flames,” Combustion Sci. Technol. (1992, in press).CrossRefGoogle Scholar
7.Kostkowski, H. J. and Broida, H. P., J. Opt. Soc. Am. 46, 246 (1956).CrossRefGoogle Scholar
8.Dieke, G. H. and Crosswhite, H. M., J. Quant. Spectros. Radiat. Transfer 2, 97 (1962).CrossRefGoogle Scholar
9.Chung, S. L., Ph.D. Thesis, The Johns Hopkins University, Baltimore, MD, 1985.Google Scholar
10.Tokuhashi, K., Horiguchi, S., Urano, Y., Iwasaka, M., Ohtani, H., and Kondo, S., Combustion and Flame 82, 40 (1990).CrossRefGoogle Scholar
11.Dobbins, R. A. and Megaridis, C. M., Langmuir 3, 254 (1987).CrossRefGoogle Scholar
12.Kerker, M., The Scattering of Light and Other Electromagnetic Radiation (Academic Press, New York, 1969).Google Scholar
13.Felske, J. D., Hsu, P. F., and Ku, J. C., J. Quant. Spectros. Radiat. Transfer 35, 447 (1986).CrossRefGoogle Scholar
14.Hung, C. H., Ph.D. Thesis, The Johns Hopkins University, Baltimore, MD, 1991.Google Scholar
15.Pecora, R., Dynamic Light Scattering (Plenum Press, New York, 1985).CrossRefGoogle Scholar
16.Flower, W. L. and Hurd, A. J., Appl. Opt. 26, 2236 (1987).CrossRefGoogle Scholar
17.Zachariah, M. R., Chin, D., Semerjian, H. G., and Katz, J. L., Appl. Opt. 28, 530 (1989).CrossRefGoogle Scholar
18.Cummins, H. Z. and Swinney, H. L., Prog. Opt. 8, 135 (1970).Google Scholar
19.Ohsawa, T., Kobayashi, E., and Ozaki, T., Combustion and Flame 53, 135 (1983).CrossRefGoogle Scholar
20.Chang, P. H. P. and Penner, S. S., J. Quant. Spectros. Radiat. Transfer 25, 97 (1981).CrossRefGoogle Scholar
21.Bernard, J. M., J. Quant. Spectros. Radiat. Transfer 40, 321 (1988).CrossRefGoogle Scholar
22.Levin, E. M., Robbins, C. R., and McMuride, H. F., in Phase Diagrams for Ceramics, edited by Roser, M. K. (American Chemical Society, Columbus, OH, 1964).Google Scholar
23.Chung, S. L., Tsai, M. S., and Lin, H. D., Combustion and Flame 85, 134 (1991).CrossRefGoogle Scholar
24.Megaridis, C. M. and Dobbins, R. A., Combustion Sci. Technol. 71, 95 (1990).CrossRefGoogle Scholar