Page 176 - Book Hosokawa Nanoparticle Technology Handbook

FUNDAMENTALS CH. 3 CHARACTERISTICS AND BEHAVIOR OF NANOPARTICLES AND ITS DISPERSION SYSTEMS
the interaction forces between gold surfaces in thiol [4] I. Larson, C.J. Drummond, D.Y.C. Chan and F. Grieser:
solution. In addition, it is also possible to conduct J. Phys. Chem., 99, 2114–2118 (1995).
measurements between a colloid probe and a metal [5] S. Veeramasuneni, M.R. Yalamanchili and J.D. Miller:
surface, whose potential is altered [9]. J. Colloid Interface Sci., 184, 594–600 (1996).
Not only solid–solid but also solid–fluid interaction [6] G. Toikka, R. Hayes and J. Ralston: J. Chem. Soc.
forces can be measured with the AFM, including the Faraday Trans., 93, 3523–3528 (1997).
interactions between an air bubble and a particle [10, [7] Y.Q. Li, N.J. Tao, J. Pan, A.A. Garcia and S.M.
11], and an oil droplet and a particle [12]. In addition
to the tangential force, the friction force can be meas- Lindsey: Langmuir, 9, 637–641 (1993).
ured by scanning the colloid probe laterally over sam- [8] K. Hu, A.J. Bard: Langmuir, 14, 4790–4794 (1998).
ple surfaces [13]. By approaching the particle to the [9] R. Ratieri, M. Grattarora and H.-J. Butt: J. Phys.
surface with high velocity, the effect of the hydrody- Chem., 100, 16700–16705 (1996).
namic force can also be estimated [14]. An interesting [10] M.L. Fielden, R.A. Hayes and J. Ralston: Langmuir,
example is that specifically reacting complimented 12, 3721–3727 (1996).
molecules are attached to the free end of the polymers [11] M. Preuss, H.J. Butt: Langmuir, 14, 3164 (1998).
on the probe and flat surface, and they are hooked in [12] P. Mulvaney, J.M. Perera, S. Biggs, F. Grieser and G.W.
a manner similar to “fly-fishing” to estimate the Stevens: J. Colloid Interface Sci., 183, 184–186 (1996).
bonding energy between the molecules [15]. This [13] S. Biggs, R. Cain, N.W. Page: J. Colloid Interface
method has particularly become an important and
useful method for the investigation of biological sys- Sci., 232, 133–140 (2000).
tems. These studies have suitably shown the versatil- [14] V.S.J. Craig, C. Neto and D.R.M. Williams: Phys. Rev.
ity of the AFM. Lett., 80, 054504 (2001).
On the other hand, one of the disadvantages of the [15] M. Rief, F. Oesterhelt, B. Heymann and H.E. Gaub:
colloid probe method might be that very small parti- Science, 275, 1295–1297 (1997).
cles such as nanoparticles that are not observed opti- [16] I.U. Vakarelski, K. Higashitani: Langmuir, 22,
cally with a microscope or CCD cannot be used. 2931–2934 (2006).
Typically, the size of the smallest particles used in this [17] J.-M. Cho, W.M. Sigmund: J. Colloid Interface Sci.,
method is around 1 m. As the behavior of the parti- 245, 405–407 (2002).
cles is affected by the size and/or the shape of the par- [18] S.G. Flicker, J.L. Tipa and S.G. Bike: J. Colloid
ticle, it is unclear whether the force data for spherical
particles with a diameter of several micrometers Interface Sci., 158, 317–325 (1993).
could directly be applied to analyze the behavior of 3.5.3.3 Flowability of powder bed
real nanoparticles. Therefore, some methods to use
small materials such as nanoparticles [16] and carbon It is difficult to handle nanoparticles individually, and
nanotubes [17] have been proposed so far, which have so usually an assemblage of particles such as a pow-
not been, however, popular yet. In order to overcome der bed is handled for nanoparticles. In this case, it is
this problem fundamentally, it would be also useful to necessary to know the adhesion and flowability of
use other approaches such as computer simulation nanoparticle bed. In addition, the average value of
together with experiments. adhesion and flowability can be easily obtained from
One of the other important methods to measure the the investigation of powder bed. The measuring
interaction force is total internal reflection microscopy method of adhesion and flowability, and several quan-
[18]. This method measures the separation distance titative evaluation method of the powder bed includ-
between a prism and free particles by the interaction ing the nanoparticles are outlined below.
with the evanescent wave formed upon the total inter- a) Packing method
nal reflection of light emitted in the prism. As this
method has an advantage in that the interaction energy Packing characteristics of the fine powder have the
of the free particle in a liquid can be obtained, while it strong influence on adhesion and flowability of powder
is not suitable to measure short-range forces, this in comparison with the coarse particle. In the packing
method is expected to be developed further. method, adhesion and flowability are presumed from
the packing characteristic that can be measured easily.
The dispersed fine particle packed in the suitable con-
References tainer through a screen, void fraction or porosity is
calculated from measured apparent density and the
b
[1] W.A. Ducker, T.J. Senden and R.M. Pashley: Nature, particle material density , or particle packing volume
p
353, 239–241 (1991). V and mass M by following equation [1].
[2] J.P. Cleveland, S. Manne, D. Bocek and P.K. Hansma:
Rev. Sci. Instrum., 64, 403–405 (1993). M
1
[3] W.A. Ducker, T.J. Senden and R.M. Pashley: 1 b (3.5.58)
p
Langmuir, 8, 1831–1836 (1992). p V
152