Page 35 - Book Hosokawa Nanoparticle Technology Handbook

FUNDAMENTALS CH. 1 BASIC PROPERTIES AND MEASURING METHODS OF NANOPARTICLES
3. Establishing traceability of measurement, transmission electron microscope (TEM), and the par-
4. Determination of the uncertainty of the obtained ticle shape indices can be calculated from the captured
images by image analysis software. For the shape
results.
analysis of fine particle over micrometer order, auto-
For representing the particle size distribution in math- matic particle shape analyzers using two-dimensional
ematical equation, log-normal distribution and image of particles in a sheath flow are available. This
Rosin–Rammler distribution can be well applied and analyzer captures particle images automatically by an
special graph papers are available for them. optical microscope with CCD camera under strobo-
scope flush lighting.
References
1.3.2 Three-dimensional particle image
[1] K. Okuyama, H. Masuda and S. Morooka: Biryuushi
Kougaku – Fine particle technology, Ohmsha, Tokyo, In the particle shape measurement of flaky particle or
porous particle including hole or space inside the par-
p. 3 (1992).
ticle, the shape analysis of a two-dimensional particle
[2] Society of Powder Technology, Japan (ed.):
projection picture is inadequate, and three-dimensional
Terminology Dictionary of Powder Technology, 2nd
shape analysis is necessary [1].
ed., Nikkan Kogyo Co., p. 223 (2000).
Although it is difficult to measure the thickness of
[3] Standard Powders Committee, APPIE: Powder Sci. a particle by the ordinary electron microscope, the
Eng., 35 (6), 75–79 (2003). thickness or surface roughness can be measured by
[4] H. Yoshida, H. Masuda, K. Fukui and Y. Tokunaga: three-dimensional scanning electron microscope
Adv. Powder Technol., 12, 79–94 (2001). (3D-SEM). 3D-SEM takes two microscopic pictures
[5] H. Masuda: Powder Sci. Eng., 34 (5), 65–72 (2002). from slightly different angles and obtains the three-
[6] A. Itoh: Powder Sci. Eng., 37 (7), 72–77 (2005). dimensional information including thickness and
surface roughness geometrically. However, if one of
[7] Y. Mori, H. Yoshida and H. Masuda: Particulate
the pictures has the hidden area in the shadow of a
Systems Analysis 2005, Stratford-upon-Avon, UK
particle, the three-dimensional information of the
(2005).
area is hidden. When well dispersed nanoparticles
[8] H. Masuda, K. Iinoya: J. Chem. Eng., Jpn., 4, 60–66
adhere on a flat substrate, the height difference
(1971). between the particle surface and the flat substrate
[9] H. Masuda, K. Gotoh: Adv. Powder Technol., 10, can be measured accurately, and the thickness of
159–173 (1999). nanoparticle is obtained.
[10] ISO Guide35, Certification of reference materials – Using the TEM, 120 transmission images are taken
General and statistical principles, p. 25 (1989). when a sample is rotated 1 degree interval from 60
to 60 degrees. This three-dimensional imaging tech-
nique called TEM-CT [2], which is similar to the
1.3 Particle shape
computer aided tomography [1], is expected to be
applied for detailed three-dimensional shape meas-
The fundamental particle properties such as particle urement of nanoparticles.
diameter, particle shape of nano-size or fine particles Using the scanning probe microscope (SPM)
influence the character of the particle-packed bed. In including atomic force microscope (AFM), the
these particle properties, the particle diameter meas- surface roughness can be measured by tiny probe
urement equipment based on various principles can with the high resolution under nano-meter order.
be marketed, and it is easy to measure particle diame- SPM are very effective for thickness measurement of
ter distribution. But a particle shape analyzer for nanoparticles. The vertical direction length such as
nanoparticle cannot be easily found and the shape particle thickness can be measured accurately by
index of nanoparticles can be calculated from particle SPM, but the measured horizontal length becomes
images observed using various types of microscopes. bigger about the diameter of the probe. It means that
the particle diameter in horizontal direction measured
1.3.1 Two-dimensional particle projection image by SPM is bigger than real particle size. Moreover, for
a soft particle or an adhesive particle, a particle posi-
In order to measure the particle shape, the outline of tion changes by contact of probe or a particle adheres
particle shape of two-dimensional projection images to probe, and an accurate image is not obtained.
captured from microscopic photograph is analyzed.
Since the diameter of a nanoparticle is smaller than the 1.3.3 Particle shape index using particle diameter ratio
wavelength of visible light, a nano-size particle cannot
be observed by an optical microscope. Usually, the Once the microscopic particle image is captured,
two-dimensional projection image of nanoparticles is quantification of particle shape can be performed by
captured by scanning electron microscope (SEM) or the same method as a coarse particle even if it is a

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