Modelling the Removal of Organic ‎Vehicle from Ceramic or Metal ‎Mouldings: The Effect Of Gas Permeation ‎On The Incidence Of Defects

Dr Sameer A Matar's picture
Journal Title, Volume, Page: 
Journal of Materials Science, Volume 30, Issue 15, pp 3805-3810
Year of Publication: 
1995
Authors: 
S. A. Matar
Department of Mathematics and Statistics, Brunel University, UB8 3PH, Uxbridge, Middlesex, UK
Current Affiliation: 
Department of Mathematics, Faculty of Science, An-Najah National University, Nablus, Palestine
M. J. Edirisinghe
Department of Materials Technology, Brunel University, UB8 3PH, Uxbridge, Middlesex, UK
J. R. G. Evans
Department of Materials Technology, Brunel University, UB8 3PH, Uxbridge, Middlesex, UK
E. H. Twizell
Department of Materials Technology, Brunel University, UB8 3PH, Uxbridge, Middlesex, UK
J. H. Song
Department of Materials Technology, Brunel University, UB8 3PH, Uxbridge, Middlesex, UK
Preferred Abstract (Original): 

A shrinking undegraded core and a porous outer layer result, if the organic vehicle used for shaping ceramic or metal powder mouldings recedes in the interparticle space of the moulded body during pyrolysis. In the present work, a numerical model has been used which simulates the undegraded shrinking core situation and quantifies degradation of the organic vehicle and the diffusion of the resulting products in solution in the organic phase during pyrolysis of a ceramic moulding. This model is extended to include gaseous mass transport in the porous outer layer for a moulding in the shape of an infinite cylinder. The effect of resistance to gaseous mass transport in the porous outer region on defects originating in inner regions was estimated. It is shown that the greatest obstruction to mass transport is diffusion of degradation products in solution in the organic phase. However, the permeability coefficient for gas transport in the outer region begins to affect the critical heating rate required for avoidance of defects only when it is less than 10−15m2.