Abstract
Niobium and tantalum surfaces easily absorb oxygen. With decreasing particle size the content of oxygen increases. The role of this surface oxygen and oxygen in the sintering atmospheres on the first-stage sintering is not well established. Therefore the sintering behavior of high-purity niobium powders was studied by annealing cylindrical powder compacts (particle size <63 μm) in the temperature range from 1000°C to 1600°C in ultra-high vacuum and under low oxygen partial pressures, as well as in inert gas atrnospheres with low oxygen contents. The specific surface of the samples was determined by metallographic methods, adsorption, and capacitance measurements. Low oxygen partial pressures (10-3 Pa) lead to a slight enhancement of the surface diffusion which is controlling first-stage sintering. High heating rates (0T > 3000 min-1) to temperatures above the melting point of Nb2O5 (Tm = 1495 °C) enhances the neck growth due to the formation of a liquid oxide phase on the surface of the powder particles.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
P. Borchers and G. J. Korinek: inExtractive Metallurgy of Refractory Metals, Proc. of the Symp. on Extr. Metall., 110th AIME Annual Meeting, H.Y. Sohn, O.N. Carlson, and J.T. Smith, eds., TMS-AIME, 1981, p. 95.
R. E. Einziger, J. N. Mundy, and H. A. Hoff:Phys. Rev. B, 1978, vol. 17, p. 440.
V. Irmer and M. Feller-Kniepmaier:Phil. Mag., 1972, vol. 25, p. 1345.
G. Hörz and K. Lindenmaier:Z. Metallkde., 1972, vol. 63, p. 240.
E. E. Underwood:Quantitative Stereology, Addison Wesley, Reading, MA, 1970, p. 31.
N. F. Jackson and J. Hendy:Electrocomp. Sci. and Tech., 1974, vol. 1, p. 27.
W. A. Kaysser, M. Hofmann-Amtenbrink, and G. Petzow: inSintering—Theory and Practice, Proc. of the Vth Int. Round Table Conf. on Sint., Portoroz/Youg., D. Kolar, S. Pejovnik, and M. M. Ristic, eds., Mat. Sci. Monographs, Elsevier Publ.Comp., Amsterdam, 1982, vol. 14, p. 275.
W. D. Kingery and M. Berg:J. Appl. Phys., 1966, vol. 26, p. 1205.
R.L. Coble:J. Amer. Ceram. Soc, 1958, vol. 41, p. 55.
D. L. Johnson and I. B. Cutler:ibid., 1963, vol. 46, p. 541.
R. M. German and Z. A. Munir:Powder Met., 1977, vol. 20, p. 145.
R. M. German and Z. A. Munir: inSintering and Catalysis, Mat. Science Research, G.Kuczynski, ed., Plenum Press, New York, NY, 1975, vol. 10, p. 249.
R.M. German and Z. A. Munir:ibid., p. 259.
R.M. German and Z. A. Munir:J. Amer. Ceram. Soc, 1976, vol. 59, p. 379.
S. Pejovnik, V. Smolej, D. Susnik, and D. Kolar:Powder Met. Int., 1979, vol. 11, p. 22.
H.E. Exner:Met. Sci., 1982, vol. 16, p. 451.
W. A. Kaysser, M. Hofmann-Amtenbrink, and G. Petzow:P/M 82 in Europe, Proc. Int. Powder Metall. Conf., Florence, Italy, Associazione Italiana di Metallurgie, 1982, p. 17.
G. Petzow and H.E. Exner:Z. Metallkde., 1976, vol. 67, p. 611.
W. Schatt, H.E. Exner, E. Friedrich, and G. Petzow:Acta Metall., 1982, vol. 30, p. 1367.
W. Schatt and E. Friedrich:Z. Metallkde., 1982, vol. 73, p. 56.
M. Grundner and J. Halbritter:J. Appl. Phys., 1980, vol. 51, p. 397.
R. P. Elliot:Trans. ASM, 1960, vol. 52, p. 990.
F. B. Swinkels and M. F. Ashby:Powder Met., 1980, vol. 23, p. 1.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Krehl, M., Schulze, K. & Petzow, G. The influence of gas atmospheres on the first-stage sintering of high-purity niobium powders. Metall Trans A 15, 1111–1116 (1984). https://doi.org/10.1007/BF02644705
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF02644705