(76b) Combined On-Line Differential Mobility and Particle Mass Analysis for Determination of Size Resolved Particle Density and Microstructure Evolution

A new application of on-line tandem differential mobility-particle mass analysis (DMA-APM) is used to obtain the density distribution, detect the reaction evolution, and investigate the mechanism of porous particle formation. The expected uncertainty of the density measurement is within 5%. The method has several advantages over absorption methods such as BET in which pore model is required. The methodology also enables a size resolved measurement to understand how particle porosity varies over a given particle population. The DMA-APM method is materials independent, and can measure the density even in a particle with inaccessible pores. In this paper we demonstrate the method in the synthesis of mesoporous iron oxide and copper oxide. For example, in the formation of iron oxide we found that small particles (~50 nm) in the size distribution had a higher density (~2.6 g/cm³) relative to larger 130 nm particles with a measured density of 2.2 g/cm³. Syntheses at higher temperatures lead to high density particles which were also less size sensitive.