1. Scope

This International Standard specifies a laser diffraction method for measuring particle size distributions, by means of the detection of angular distributions of the intensity of light scattered by fine-ceramic raw powders dispersed in a liquid phase irradiated by a laser beam. A typical size range is 0,1 µm to 50 µm.

2. Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 3082:2000, Iron ores — Sampling and sample preparation procedures

ISO 13320-1:1999, Particle size analysis — Laser diffraction methods — Part 1: General principles

ISO 14703:2000, Fine ceramics (advanced ceramics, advanced technical ceramics) — Sample preparation for the determination of particle size distribution of ceramic powders

ISO 14887:2000, Sample preparation — Dispersing procedures for powders in liquids.

3. Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 13320-1 apply, together with the following.

3.1 angular distribution of intensity of light scattered 

intensity of light scattered as a function of scattering angle

3.2 scattering angle

angle between the directions of the transmitted laser beam and the scattered light detected

3.3 relative refractive index

ratio of the absolute refractive index of the sample to the real part of the dispersion medium

4. Principle of measurement

A particle illuminated by a collimated light beam of a known wavelength from a laser presents a scattering signature that is a function of the size, shape and relative refractive index of the particle. When particles dispersed in a liquid are irradiated by a laser beam, the scattering signature is supposed to be the summation of the signatures of each particle. In the basic optical system shown in Figure 1, the light scattered by the particles in the laser beam is collected by a Fourier lens on the detector placed on the focal plane of the lens, to detect the angular distribution of the scattered intensity. The size distribution of the particles is mathematically reduced from the measured angular distribution of the scattered intensity, so that it can be best-fitted with that predicted, based on the Mie scattering theory, Fraunhofer diffraction theory or the like.

NOTE 1 A detailed description of the principle of laser diffraction method is found in ISO 13320-1:1999, Annex D.

NOTE 2 For particles of smaller diameters, light scattering at angles in the side and back lobes may also be utilized for the determination of the size distribution of particles.

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