POROSITY DEVELOPMENT OF DIATOMITE LAYERS PROCESSED BY TAPE CASTING

The processing from colloidal suspensions is a good method to obtain b odies with low microstructural heterogeneities, by careful control of the interfacial stresses. In previous papers we described the use of s lip and tape casting techniques to obtain diatomite porous layers, hav ing controlled morphology such as the amount and size of pores. The pr esent work reports the use of tape casting bodies for filtration purpo ses. As the maximum thickness of the layers produced by tape casting i s about 0.3 mm, their mechanical resistance is very low. It was necess ary to produce thicker compacts made by several single layers (up to 2 0), obtained by thermocompression at different temperatures between 20 and 90 degrees C followed by sintering at 1200 degrees C. By selectin g a careful heating programme, final bodies with 0.6-1.3 mm thickness were obtained, having porosity levels of about 44% and pore sizes betw een 0.1 and 1 mu m. High bending strength values (57 MPa) were obtaine d, enough to support mechanical stresses in use as a membrane. Permeab ility to an air flux was evaluated as a function of relevant morpholog ical parameters (porosity, thickness, etc.). (C) 1998 Elsevier Science Limited and Techna S.r.l. All rights reserved.