UNUSUAL SINTERING BEHAVIOR OF POROUS CHROMATOGRAPHIC ZIRCONIA PRODUCED BY POLYMERIZATION-INDUCED COLLOID AGGREGATION

The effects of sintering temperature and duration on the pore structur e of chromatographic zirconia particles produced by the controlled pol ymerization-induced aggregation of 1000 Angstrom colloids are studied with an eye toward optimally strengthening the aggregates and eliminat ing small pores while preserving large pores. Nitrogen adsorption and mercury porosimetry are used to estimate the surface area, pore volume , and pore size distribution. Pulsed field gradient NMR measurements o f solvent diffusion are used to estimate the diffusion tortuosity of t he pore space. Initially of course, the pore volume and surface area d ecrease significantly, the decrease being more pronounced at higher te mperatures. With prolonged sintering, the pore size, pore volume, and surface area change much more slowly, but the diffusion tortuosity see ms to be minimized at a sintering temperature and time at which pores are allowed to redistribute so as to optimize large pores. The aggrega tes synthesized by this aggregation method apparently produce metastab le large pores which are not easily collapsed.