Evaluation of aggregate breakdown in nanoslzed titanium dioxide via mercury porosimetry

Six nanosized titanias were investigated for aggregate breakdown. The powders all commonly exhibited particle (aggregate) sizes of approximately 1 micron via light scattering and primary particle sizes of approximately 20 nm via BET ESD estimation yet the powders appeared to show strongly different rheological characteristics. Investigation of the aggregate strength via compaction curves indicated yield points on the order of 500 MPa as compared with 4-20 Pa for suspension yield strength. Three distinct aggregate size regimes of size orders of approximately 100 microns, 10-20 microns and 1 micron were found with the variation in strengths observed corresponding to an attack on a different aggregate size regime. Investigations via mercury porosimetry found peaks for tape cast samples at -250-400 nm corresponding to intact 1 micron aggregate units. Peaks in the nanosized regime were found corresponding to loose coordination of 20 nm primary particles. Investigation of pressed pellets from compaction curves found the absence of this peak and the shift of nanosized peaks to values from 5-10 nm suggesting the attack of the I micron aggregated unit and the rearrangement of the 20 nm units.