An Aerosol Chemical Reactor for Coating Metal Oxide Particles with (NH4)SO4-H2SO4-H2O. 1. New Particle Formation

In situ atmospheric measurements (notably single-particle mass spectrometry) show that tropospheric aerosols are internally mixed, including both water-soluble and insoluble components. This fact notwithstanding, most process study laboratory work has concentrated on water-soluble electrolytes because the generation of particles composed of both soluble and insoluble components is difficult to achieve in the laboratory. Even so, such an aerosol is essential for accurate process studies of atmospheric aerosols and for the quantitative calibration of single-particle mass spectrometers. In the completed work, particles composed of a (NH₄)₂SO₄-H₂SO₄-H₂O coating on a TiO₂, Al₂O₃, or ZrO₂ core are prepared in a novel chemical reactor, which is a tube furnace with a linear-temperature gradient along its longitudinal axis. Reactor controls on the number size distribution are reported, including the linear flow velocity, the SO₃ vapor pressure, the NH₃ vapor pressure, the reactor temperature gradient, and the presence or the absence of insoluble seed nuclei (viz. TiO₂, Al₂O₃, and ZrO₂).