查看更多>>摘要：Reference aerosols for the calibration of common aerosol instruments such as condensation particle counters (CPCs) and differential mobility analyzers (DMAs), must fulfill certain criteria. The aerosol must be stable and reproducible in particle size and number density, ideally be monodisperse and nonvolatile and comprise a uniform non-reactive material. To this end, a new Silver Particle Generator (SPG) from Catalytic Instruments (Catalytic Instruments, Rosenheim, Germany) was characterized extensively with regard to aerosol properties within an overall framework of operator convenience. The SPG produced number densities up to around 2 x 10(10) cm(-3) of thermally stable, solid, unimodal aerosol with geometric standard deviation smaller than 1.45. The aerosol production in the SPG resembles that of a classic tube furnace, however, the device is easier to set up and configure, and offers long-term stability using controlled standardized procedures and operation settings. The SPG has two operational modes (simply, Modes 1 & 2 for the smallest and largest aerosol, respectively). The aerosol exhibited an intraday stability and day-to-day reproducibility in geometric mean mobility diameter (GMDmob) within a standard deviation of 4%. Based on measurements by transmission electron microscopy (TEM), particles from Mode 1 were spherical when default settings (air as carrier/dilution gas) were applied, whereas larger particles from Mode 2 comprised both compact near-spherical particles, and larger aggregates. Switching to nitrogen as a carrier gas and sintering at 800 degrees C reshaped the aggregate fraction of the aerosol from Mode 2 into uniformly spherical particles. Suitable applications of the SPG include the calibration of CPCs, DMAs, particle measurement program (PMP)-compliant measurement including particle number counters (PNCs) and the characterization of complete particle number-portable emissions measurement systems (PN-PEMS) systems and other particle counters for air quality monitoring.
NSTL
Elsevier