Abstract
The removal of binder from ceramic or metal moldings by thermolysis involves the transport of degradation products through the parent organic phase and the vacated porous body. A numerical model has been developed to combine an equation which takes into account different gas-flow regimes with an equation for the transport of organic molecules in molten polymers. Computer modeling reveals the critical heating rate above which defects occur due to boiling of the polymer-monomer solution at the center of the molding. The situation in which a porous outer layer of the molding develops, offering resistance to flow of the evolved monomer gas, is then treated. This gives rise to a moving boundary with a variable concentration of diffusant which is dependent on the surface flux, gas transport coefficient, and thickness of the porous layer. The contributions of diffusion and viscous flow to gas transport are considered.
Similar content being viewed by others
References
M. J. Edirisinghe and J. R. G. Evans, Int. J. High Tech. Ceram. 2, 1, 249 (1986).
K. M. Haunton, J. K. Wright, and J. R. G. Evans, Br. Ceram. Trans. J. 89, 33 (1990).
P. Hammond and J. R. G. Evans, J. Mater. Sci. Lett. 10, 294 (1991).
J. Greener and J. R. G. Evans, J. Mater. Sci. 28, 6190 (1993).
R. M. German, K. F. Hens, and S. T. P. Lin, Bull. Am. Ceram. Soc. 70, 1294 (1991).
R. M. German, Powder Injection Moulding (Metal Powder Industries Fed., NJ, 1990).
P. Calvert and M. Cima, J. Am. Ceram. Soc. 73, 575 (1990).
J. R. G. Evans, M. J. Edirisinghe, J. K. Wright, and J. Crank, Proc. R. Soc. London A 432, 321 (1991).
S. A. Matar, M. J. Edirisinghe, J. R. G. Evans, and E. H. Twizell, J. Mater. Res. 8, 617 (1993).
H. M. Shaw and M. J. Edirisinghe, Philos. Mag. A72, 267 (1995).
S. A. Matar, M. J. Edirisinghe, J. R. G. Evans, E. H. Twizell, and J. H. Song, J. Mater. Sci. 30, 2805 (1995).
M. Barone and J. C. Ulicny, J. Am. Ceram. Soc. 72, 3323 (1990).
M. J. Cima, J. A. Lewis, and A. Devoe, J. Am. Ceram. Soc. 72, 1192 (1989).
R. German, Int. J. Powder Met. 23, 237 (1987).
G. C. Stangle and I. A. Aksay, Chem. Eng. Sci. 45, 1719 (1990).
D-S. Tsai, A.I.Ch.E.J. 37, 547 (1991).
H. H. Angermann, F. K. Yang, and O. Van der Biest, J. Mater. Sci. 27, 2534 (1992).
H. H. Angermann and O. Van der Biest, Int. J. Powder Met. 29, 239 (1993).
N. Wakao, S. Otani, and J. M. Smith, A.I.Ch.E.J. 11, 435 (1965).
J. A. Lewis and M. J. Cima, J. Am. Ceram. Soc. 73, 2702 (1990).
D. W. Sproson and G. L. Messing, in Better Ceramics Through Chemistry III, edited by C. J. Brinker, D. E. Clark, and D. R. Ulrich (Mater. Res. Soc. Symp. Proc. 121, Pittsburgh, PA, 1988), pp. 528–537.
J. L. Duda, J. S. Vrentas, S. T. Ju, and H. T. Lui, A.I.Ch.E.J. 28, 279 (1982).
J. H. Song, J. R. G. Evans, M. J. Edirisinghe, and E. H. Twizell, in Advanced Ceramics for Structural and Tribiological Applications, edited by H. M. Hawthorne and T. Troczynski (The Met. Soc. of the Canadian Inst. of Mining, Metallurgy and Petroleum, Montreal, Canada, 1995), pp. 49–60.
A. Wheeler, Catalysis 2, 105 (1955).
S. Reyes and K. F. Jensen, Chem. Eng. Sci. 40, 723 (1985).
C. N. Scatterfield and P. J. Cadle, Ind. Eng. Chem. Fundam. 7, 202 (1968).
J. R. Partington, An Advanced Treatise on Physical Chemistry (Longmans, London, 1967), Vol. 1, p. 874.
A. Bondi and D. J. Simkin, A.I.Ch.E.J. 6, 191 (1960).
F. A. L. Dullien, Porous Media, Fluid Transport and Pore Structure (Academic Press, New York, 1979), p. 222
R. N. Maddox and A. L. Hines, Mass Transfer Fundamentals and Applications (Prentice-Hall, Englewood Cliffs, NJ, 1985), p. 151.
E. H. Twizell, Computational Methods for Partial Differential Equations (Ellis Horwood, Chichester, and John Wiley, New York, 1984), p. 212.
G. D. Smith, Numerical Solutions of Partial Differential Equations: Finite Difference Methods, 3rd ed. (Oxford University Press, Oxford, 1985), Chap. 3.
G. E. Forsythe and C. B. Moler, Computer Solution of Liner Algebraic Systems (Prentice-Hall, Englewood Cliffs, NJ, 1967), p. 114.
G. R. Youngquist, D. Ind. Engrg. Chem. 62, 53 (1970).
Y. Bao and J. R. G. Evans, J. Euro. Ceram. Soc. 8, 81 (1991).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Song, J.H., Edirisinghe, M.J., Evans, J.R.G. et al. Modeling the effect of gas transport on the formation of defects during thermolysis of powder moldings. Journal of Materials Research 11, 830–840 (1996). https://doi.org/10.1557/JMR.1996.0101
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1557/JMR.1996.0101