AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Number-size Distribution of Nano-TiO2 Agglomerates Measured by NanoScan SMPS: Dispersion of Agglomerates across the Orifice Inlet
MAROMU YAMADA, Mitsutoshi Takaya, Isamu Ogura, Japan National Institute of Occupational Safety and Health
Abstract Number: 649 Working Group: Instrumentation and Methods
Abstract Nanomaterial particles exhibit a wide range of sizes because of the formation of agglomerates/aggregates. While measuring the size distribution of agglomerated particles, real-time aerosol instruments may output unexpected results because these instruments are generally calibrated using polystyrene latex particles, which are ideal particles that are monodisperse and spherical. In this study, we evaluated the performance of a recently commercialized instrument, a portable SMPS (NanoScan SMPS, Model 3910, TSI Inc.), which has an inlet composed of a cyclone with a 50% cut-off diameter of 0.5 micrometer and an orifice, by using polydispersed, agglomerated aerosol particles. The aerosol particles were generated from nano-TiO$_2 powder (P25, Evonik Industries) using a vortex shaker method. 1 cm$^3 of the powder was placed in a glass test tube and agitated using a vortex shaker at a constant rotational speed (2750 rpm). Then, the suspended particles were delivered to the aerosol sizers using HEPA-filtered air. We compared the data obtained using the NanoScan SMPS to a research-grade SMPS (Model 3936L10, TSI Inc.) with a cyclone that had a 50% cut-off diameter of 3 micrometer. The results showed obvious differences in the size distributions of the generated nano-TiO$_2 aerosol particles as measured by these instruments. However, the size distributions that were obtained from these instruments for indoor aerosol particles were similar. A possible reason for the observed differences is that the orifice of the NanoScan inlet acted as a disperser for the weakly agglomerated particles due to the higher-pressure loss (about 5.0 kPa) across its inlet. Consequently, the number concentration increased due to the breakup of the agglomerates.