GAS-DYNAMIC MODEL OF THE FORMATION OF OPEN POROUS STRUCTURE IN MATERIALS FORMED BY SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS

We examine a model for the formation of open porous structure in a com bustion wave for self-propagating high-temperature synthesis systems t hat fuse. It is assumed that the pores are opened in a front that exte nds from the surface of the liquid phase to its center. We determine t he velocity of this front. By comparing this velocity with the combust ion velocity, we conclude that pores are opened in the combustion wave so long as the liquid phase exists; on the other hand, the finer stru cture of the open porous structure is formed in the crystallizing mate rial behind the wave. Based on the limited lifetime of the liquid phas e, we estimate the maximum size of a self-propagating high-temperature synthesis sample in which all pores will be opened.