PORE STRUCTURE AND DIFFUSION TORTUOSITY OF POROUS ZRO2 SYNTHESIZED BY2 DIFFERENT COLLOID-AGGREGATION PROCESSES

The pore structure of column-packing materials plays a significant rol e in high-performance liquid chromatography (HPLC) and will be particu larly important for the separation of macromolecules. In this study, s pherical, porous zirconia particles 5-10 mu m in diameter were synthes ized by the controlled aggregation of 700-Angstrom colloids, Two diffe rent aggregation methods were used: oil emulsion processing and polyme rization-induced colloid aggregation (PICA), The pore structures of th e resulting materials were characterized by electron microscopy, nitro gen adsorption/desorption, mercury (Hg) intrusion/extrusion, pulsed fi eld gradient spin-echo NMR self-diffusion measurements, and NMR spin-l attice relaxation measurements. The tortuosity and hydraulic diameter resulting from the two aggregation methods are compared, The PICA-gene rated sample is less porous but shows a more well-connected pore struc ture, These results show the need to restore high porosity while retai ning the beneficial pore structure and the high degree of control of a ggregate size that are characteristics of the PICA process. (C) 1995 A cademic Press, Inc.