Page 40 - Book Hosokawa Nanoparticle Technology Handbook

1.4 PARTICLE DENSITY FUNDAMENTALS
(4) Combined measurement of mass and volume
5000
If the volume of a particle selected by an APM is
measured directly with transmission electron
microscopy (TEM), the density of the particle can be
4000
Particle count (-) 3000 Doubly charged particles determined. The material density of DEPs ranging
from 50 to 220nm in mobility equivalent diameter
was measured with this method [8]. It is reported that,
after removing volatile components by heating
2000
particles to 300ºC, the density was 1.77±0.07 g/cm
irrespective of their mobility equivalent diameter. 3
1000
(5) Combined measurement of mobility and aerodynamic
diameter
0
0.0 0.1 0.2 0.3 0.4 The effective density of an individual particle can also
Particle mass (fg) be determined if both the mobility and the aerody-
namic diameter are known. This can be achieved by
Figure 1.4.3 measuring the aerodynamic diameter of particles
Mass distribution spectrum for NaCl particles having selected with a DMA. Traditionally, impactors have
mobility equivalent diameter of 50nm. often been used to measure the aerodynamic diameter
with this method [9, 10]. Recently, a time-of-flight
type device has sometimes been employed instead of
an impactor [11, 12]. The accuracy of the effective
2 density obtained with this method is generally much
1.8 higher than the accuracy obtained with the combined
DMA and impactor method.
1.6
Effective density (g/cm 3 ) 1.2 1 10% load [1] R. Utsumi, in Funtai kougaku binran (Powder
1.4
References

engineering handbook), 2nd ed., Nikkan Kougyo
0.8
Shinbun, pp. 42–47 (1998) (in Japanese).
0.6
0.4 70% load [2] H. Yanagida, supervised: Engineering System for Fine
Lower density particles Particles, Vol. 1, Fujitec Co. (2001) (in Japanese).
0.2 in atmospheric aerosols [3] JIS Z 8901: Test Powders and Test Particles, Japanese
(McMurry et al., 2002)
0 Standards Association (2006).
10 100 1000 [4] K. Ehara, K.J. Coakley and R.C. Hagwood: J. Aerosol
Mobility equivalent diameter (nm)
Sci., 27, 217–234 (1996).
[5] K. Park, F. Cao, D.B. Kittelson and P.H. McMurry:
Figure 1.4.4 Environ. Sci. Technol., 37, 577–583 (2003).
Size dependence of the effective density of diesel exhaust [6] P.H. McMurry, X. Wang, K. Park and K. Ehara:
particles, reconstructed from Park, K. et al., Environ. Sci.
Technol., 37 577-583 (2003). Aerosol Sci. Technol., 36, 227–238 (2002).
[7] A.D. Maynard, B.K. Ku, M. Emery, M. Stolzenburg
and P.H. McMurry: J. Nanoparticle Res., 9, 85–92
is smaller than the density of NaCl bulk crystal (2007).
3
(2.2 g/cm ). The exact reason for this difference in [8] K. Park, D.B. Kittelson, M.R. Zachariah and P.H.
density is not yet known, but it might be due to the McMurry: J. Nanoparticle Res., 6, 267-272 (2004).
dynamic shape factor of non-spherical NaCl particles. [9] W.P. Kelly, P.H. McMurry: Aerosol Sci. Technol., 17,
By varying the mobility of particles classified by 199–212 (1992).
the DMA, d -dependence of can also be deter- [10] S.V. Hering, M.R. Stolzenburg: Aerosol Sci. Technol.,
e
b
mined. Fig. 1.4.4 shows the effective density of 23, 155–173 (1995).
diesel exhaust particles (DEPs) with mobility equiv-
alent diameter ranging from 50 to 300nm, measured [11] P. DeCarlo, J.G. Slowik, D.R. Worsnop, P. Davidovits
with this method [5]. The influence of the engine and J.L. Jimenez: J. Aerosol Sci., 38, 1185–1205
load on the effective density of DEPs is observed in (2004).
Fig. 1.4.4. The same method has also been applied to [12] A. Zelenyuk, Y. Cai, L. Chieffo and D. Imre: Aerosol
atmospheric aerosols [6] and carbon nanotubes [7]. Sci. Technol., 39, 972–986 (2005).

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