Page 33 - Book Hosokawa Nanoparticle Technology Handbook

FUNDAMENTALS CH. 1 BASIC PROPERTIES AND MEASURING METHODS OF NANOPARTICLES
material having crystalline size less than several [13] K. Kobayashi: J. Soc. Powder Technol., Jpn, 41,
hundred nanometers, the unique super-plastic phe- 473–478 (2004).
nomenon is seen that it is extended several to several [14] S. Sato, N. Asai and M. Yonese: Colloid Polym. Sci.,
thousand times from the original size at the elevated 274, 889–893 (1996).
temperature over 50 % of the melting point [17], [15] K. Niihara: J. Ceram. Soc. Jpn, 99 (10), 974–982 (1991).
which may provide the possibility of forming and pro- [16] T. Sekino: Mater. Integr., 13 (11) 50–54 (2000).
cessing of ceramics like metallic materials.
[17] F. Wakai, Y. Kodama, S. Sakaguchi, N. Murayama,
K. Izaki and K. Niihara: Nature, 344, 6265, 421–423
1.1.5 Existing conditions of particles and their
(29 March 1990).
properties
[18] T. Yokoyama: Sokeizai, 3, 6–11 (2005).
The nanoparticles usually exhibit collective functions.
Therefore, the dispersing state and the surrounding 1.2 Particle size
conditions in addition to the physical properties of the
particles themselves are important. In many cases, the
nanoparticles exist as aggregates of the primary parti- Particle size is the most important information in
cles by the adhesion and bonding during the produc- practical applications of powder-particles. Usually,
tion process because of their high adhesiveness. powder is constituted by particles of various sizes and,
The existing state of the nanoparticles is greatly therefore, it is necessary to obtain not only the mean
influenced by the surrounding conditions if they are in particle size but also the size distribution for the char-
gas, liquid, solid or in a vacuum and what sort of inter- acterization. Recently, the methods for particle size
action they have with the surrounding materials. The analysis have been greatly developed. Especially, the
nanoparticles are rarely used by themselves but dis- analyzers with prominent characteristics such as rapid
persed in other materials or combined with them. The response, high repeatability and covering wide range
dispersing process of the nanoparticles is a key for the of particle size are developed as in the case of laser
nanoparticle technology as well as their preparation scattering and diffraction method.
methods, since the performance of the final products
are affected by their dispersing conditions [18]. 1.2.1 Definition of particle size
In this way, it is expected with great possibility to
develop various new materials and applications by the A particle is usually three-dimensional and it may take
nanoparticle technology producing and processing the various shapes. “Particle size” is a term to represent
nanoparticles, which have different properties from the three-dimensional particle in one-dimensional
the bulk material by the size effects as mentioned scalar value. The size of any spherical particle can be
above and in the following sections. represented by its diameter with no ambiguity. For a
particle with irregular shape, the size is represented by
a geometrically obtained one-dimensional scalar
References
value, geometric size, or an equivalent size in relation
[1] M. Arakawa: J. Soc. Powder Technol., Jpn., 42, to practical methods of particle size measurements.
582–585 (2005). The geometric size is obtained through three-
dimensional measurements of a particle to get its
[2] M. Arakawa: Funsai (The Micrometrics), No.27,
width, thickness and length, and then calculating
54–64 (1983).
one-dimensional value such as arithmetic mean. In
[3] H. Maeda: J. Control. Release, 19, 315–324 (1992).
practice, however, one-dimensional value obtained
[4] K. Uchino, E. Sadanaga and T. Hirose: J. Am. Ceram.
based on the two-dimensional-projected silhouette is
Soc., 72(8), 1555–1558 (1989). utilized such as a diameter of a circle having the
[5] H. Suzuki, T. Ohno: J. Soc. Powder Technol., Jpn, 39, same area as the projected area. Statistical diameter
877–884 (2002). based on one-dimensional measurement is also well
[6] N. Wada: Chem. Eng., 9, 17–21 (1984). applied in practice such as a Feret diameter, which is
[7] I. Matsui: J. Chem. Eng., Jpn, 38 (8), 535–546 (2005). determined as the distance between pairs of parallel
[8] M. Takashige, T. Nakamura: Jpn. J. Appl. Phys., 20, tangents to the particle silhouette in some fixed
direction.
43–46 (1981).
As for the equivalent size in relation to practical
[9] K. Ishikawa: J. Soc. Powder Technol., Jpn, 38, 731–740
methods of particle size measurements, there are
(2001).
many different definitions such as sieve diameter
[10] K. Ishikawa, K. Yoshikawa and N. Okada: Phys. Rev. B,
based on sieving, equivalent light-scattering diame-
37, 5852–5855 (1988). ter, Stokes diameter based on particle motion in fluid,
[11] M. Haruta: Catalysts, 36 (6) 310–318 (1994). and the equivalent diameter based on the Brownian
[12] Y. Kurokawa, Y. Hosoya: Surface, 34 (2) 100–106 motion. These equivalent diameters give, usually,
(1996). different values depending on the measurement
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