FEATURES OF POWDER-MATERIAL GRAIN-SIZE ANALYSIS METHODS
A. E. Stolina,
A. A. Smetkin,
and N. V. Pimenova
Translated from Novye Ogneupory, No. 10, pp. 46 – 49, October 2009.
Original article submitted May 25, 2009.
The grain-size composition of silicon powder has been determined by optical microscopy, laser diffraction,
photosedimentation, and differential high-velocity sedimentation. The results from the various methods are
compared in regions of intersection of their ranges, and the advantages of each of the four methods are identi
Keywords: grain-size analysis, silicon powder, particle morphology, mechanoactivation.
The grain-size composition of a powder material is a ma
jor characteristic governing the finished product quality in
various branches of industry such as powder metallurgy, the
chemical industry, refractory production of ceramics, and the
production of building materials. Various methods have been
developed for grain-size analysis of powders, which are used
in determining certain fractions . Here we give results for
silicon powder determined by optical microscopy, laser dif-
fraction, photosedimentation, and differential high-speed
The optical microscopy method of determining particle
size is a metallographic one. It is based on transforming the
optical signal into a television image. We have used a
metallographic system consisting of a METAM LV-31 opti
cal microscope and a digital camera, which are interfaced to
a personal computer. We used the VideoTest 4.0 software for
digital processing and image analysis with the Granulometry
method, which served to demonstrate the image of the sam
ple, choose a sufficient number of fields for analysis, exclude
from analysis particle clumps, distinguish particles, deter
mine their dimensions, and count the number of particles of
each size . The optical method is intended for analyzing
particles with sizes from 0.5 up to 300 mm.
The software allows one to calculate the mean particle
diameter and to construct histograms.
The particle size is determined from the equivalent diam
where A is the particle area.
The laser diffraction method was operated with an ana
lyzer for particle sizes: the Analysette 22 NanoTec made by
Fritsch in Germany. To obtain the size distribution by laser
diffraction one uses the physical principle of electromag-
netic-wave scattering. The particles in a parallel laser beam
scatter light into a constant solid angle, whose magnitude is
dependent on the particle diameter. A lens collects the scat-
tered light in an annulus and passes it to a detector, which is
placed in the focal plane of the lens. The energy distribution
in the scattered laser beam is measured by radially placed
sensor elements in the detector. The intensity distribution of
the laser beam at the detector is handled by a complex math-
ematics (Fraunhofer theory or Mie’s theory) to calculate the
size distribution. Then laser diffraction provides the particle
diameter equivalent to the diameter of a sphere, while the
calculated size distribution is the volume distribution of the
particle sizes (in three-dimensional measurements) . In the
first step, the Analysette 22 NanoTec is used in making a
measurement in the range 100 nm – 1000 mm, and in the sec
ond step the lower limit of the measurement range is reduced
to 10 nm.
Photosedimentation analysis is performed with a scan
ning photosedimentograph type SF-2 (PF Promsnabkom
plekt Corporation, Russia). Two physical processes form the
basis of the analysis :
1) steady-state deposition in an immobile medium in ac
cordance with Stokes’ law; and
2) light flux attenuation on passage through a layer of
suspension in accordance with the Bouguer-Lambert-Beer
The particles sink at rates dependent on the size: larger
ones at higher rates and smaller ones at smaller rates. Conse
quently, the particle concentration varies over the height of
Refractories and Industrial Ceramics Vol. 50, No. 5, 2009
1083-4877/09/5005-0383 © 2009 Springer Science+Business Media, Inc.
Powder Material Science Center, GOUVPO, Perm State Techni
cal University, Perm, Russia.