Characteristic of nanoparticles generated from different nano-powders by using different dispersion methods

Abstract

A standard rotating drum with a modified sampling train (RD), a vortex shaker (VS), and a SSPD (small-scale powder disperser) were used to investigate the emission characteristics of nano-powders, including nano-titanium dioxide (nano-TiO 2 , primary diameter: 21 nm), nano-zinc oxide (nano-ZnO, primary diameter: 30-50 nm), and nano-silicon dioxide (nano-SiO 2 , primary diameter: 10-30 nm). A TSI SMPS (scanning mobility particle sizer), a TSI APS (aerodynamic particle sizer), and a MSP MOUDI (micro-orifice uniform deposit impactor) were used to measure the number and mass distributions of generated particles. Significant differences in specific number and mass concentration or distributions were found among different methods and nano-powders with the most specific number and mass concentration and the smallest particles being generated by the most energetic SSPD, followed by VS and RD. Near unimodal number or mass distributions were observed for the SSPD while bi-modal number or mass distributions existed for nano-powders except nano-SiO 2 which also exhibited bimodal mass distributions. The 30-min average results showed that the mass median aerodynamic diameter (MMAD) and number median diameter (NMD) of the SSPD ranged 1.1-2.1 lm and 166-261 nm, respectively, for all three nano-powders, which were smaller than those of the VS (MMAD: 3.3-6.0 lm and NMD: 156-462 nm), and the RD (MMAD: 5.2-11.2 lm and NMD: 198-479 nm). For nano-particles (electric mobility diameter \ 100 nm), specific mass concentrations were nearly negligible for all three nano-powders and test methods. Specific number concentrations of nano-particles were low for the RD tester but were elevated when more energetic VS and SSPD testers were used. The quantitative size and concentration data obtained in this study is useful to elucidate the field emission and personal exposure data in the future provided that particle loss in the generation system is carefully assessed.

Fluidized Bed Generation of Stable Silica Nanoparticle Aerosols

“…This stabilization period might be related to the removal of large agglomerates on the surface of the beads, which are likely to be more affected by particle collisions. This effect has been also reported in the dustiness tests performed with nanoparticles (Jensen et al 2009;Tsai et al 2012). (3) The third stage corresponds to the generation of a stabilized nanoparticle aerosol.…”

A Cost-Effective Method of Aerosolizing Dry Powdered Nanoparticles

“…While the aerosols in this work are not spherical, as is assumed when d m is calculated, the particle morphology is noticeably more densely packed than are carbon nanotube aerosols. Work by Shin et al (2009) Tsai et al (2012) produces unimodal, but very broad, size distributions (with "peaks" that plateau over several hundred nanometers) for all three ENPs tested. The size distributions produced by the Palas RBG (rotating brush generator) and fluidized bed generator (FBG) utilized by Noel et al (2012) are also relatively broad, with interquartile (D 25 -D 75 ) ranges of 108-284 nm and 81-470 nm, respectively.…”

“…Direct comparison of aerosol number concentrations obtained in this study and by Tsai et al (2012) with the SSPD is challenging, as the SSPD results are normalized to aerosol mass. This direct method of aerosol mass measurement removes uncertainty about the density of ENP aerosols but can prohibit simple comparison of number concentration.…”

“…A recent intercomparison of three commercial dispersers supplied with metal oxide NP powders demonstrated that while all produced submicron aerosols, most size distributions had mode diameters ranging from 200 nm to 400 nm, and none were below 100 nm (Tsai et al 2012).…”

Aerodynamic and Chemical Characteristics of Six Engineered Nanomaterial Powders

“…Previous studies have assessed airborne release of ENM, by looking at multiple material types but with limited characterization methods (Tsai et al, 2012;Evans et al, 2013), or using more detailed characterization of a single material type, either in a controlled laboratory setting or associated with a manufacturing process (Maynard et al, 2004;Birch, 2011;Birch et al, 2011;Chen et al, 2011;Gottschalk and Nowack, 2011). Studies that have suspended ENM in controlled conditions have used multiple approaches to aerosolize the ENM powders.…”