SPONTANEOUS INFILTRATION OF NONCYLINDRICAL POROSITY - CLOSE-PACKED SPHERES

Previous experiments indicated that the contact angles required for sp ontaneous infiltration of molten metal alloys into particulate ceramic preforms are significantly less than 90 degrees. Analysis of capillar ity In pores between packed particles shows the origin of this effect to be in the non-cylindrical curvature of these pore surfaces. A simpl e geometrical approach for predicting critical contact angles, theta(c ), for spontaneous infiltration of non-cylindrical pores is presented and applied to the pore structure between close-packed spheres. Althou gh the critical contact angle for entry of the first layer of pores va ries with the direction of infiltration, complete spontaneous infiltra tion of the structure is limited by penetration of the tetrahedral por es, for which theta(c) = 50.7 degrees. (C) 1998 Acta Metallurgica Inc.