Debinding behaviors of injection molded ceramic bodies with nano-sized pore channels during extraction using supercritical carbon dioxide and n-heptane solvent

Abstract

Debinding behaviors related on changes in capillary pore structure during extraction with supercritical carbon dioxide and n-heptane, respectively were investigated for injection molded ceramic bodies consisting of skeleton pores of 68 nm. For the debinding processes, both debinding curves showed a square root of time dependence but significantly deviated in the middle or end period of debinding because of structural changes with pores during extraction. The debinding bodies experienced capillary changes having a debinding front separating the undebinded region with fluid state into the debinding region with pendular state in the wax-based green bodies. The debinding rate of the supercritical fluid extraction was five times higher than that of the solvent extraction because of a higher interdiffusion diffusivity and a formation of relatively large pore channels. An abrupt change of pore structures between debinded and undebinded region in the green bodies caused severe defects during the solvent extraction even at a low rate of debinding at 313.15 K, while the severity of the capillary changes was overcome during the supercritical fluid extraction and the debinded ceramic bodies were free from defects even at a high rate of debinding at 328.15 K. It is attributed to a reduction of the capillary stress developed on debinding front during the supercritical fluid extraction. (C) 2009 Elsevier B.V. All rights reserved.