Laser Diffraction

Particle size measurement using static light scattering (Particle size determination by laser diffraction)

The particle size distribution as a parameter to specify a powder or dispersion plays a central role in many applications. Examples are construction material (sands, cements), pharmaceuticals, lime stones, ceramics, colored pigments, fertilizers, emulsions and many more. The range of applications is increasing permanently and hence the requirements on the measurement methods regarding size range, measuring time and reproducibility are increasing. Particularly the precise and reproducible detection of particles with sizes close to the measuring range limits as well as the simultaneous determination of particle sizes of very small particles (nanometer range) as well as large particles (lower millimeter range) for the characterization of polymodally or very broadly distributed samples provides a challenge. State-of-the-art laser diffraction particle size analyzer such as the Bettersizer S3 Plus solves these tasks by an innovative design of the optical bench for the detection of backscattered light of very small particles and by detecting large particles by an integrated high-speed CCD camera or the combination of static light scattering and automated imaging.
  • 3D Printing and Powdered Metals 3D Printing and Powdered Metals

    Provide you particle size distribution and particle shape analysis data of metals.The manufacturing of metals includes various physical and chemical processes including smashing, atomization, reductio...

    Learn More
  • Abrasives Abrasives

    Bettersize instruments provide the particle size distribution and particle shape analysis of silicon carbide, diamond, corundum and other materials.Widely used, abrasive is the ‘teeth’ of the manufa...

    Learn More
  • Agrochemical Analysis Agrochemical Analysis

    Bettersize instruments are necessary tools for the particle size testing and particle shape analysis of all kinds of suspension agents.Such environmentally friendly water-based agrochemicals as suspen...

    Learn More
  • Cement Cement

    Bettersize instruments provide the particle size distribution and powder physical property data of cement products.Cement production is a typical high energy consumption industry, and the powder grind...

    Learn More
  • Ceramics Ceramics

    Bettersize instruments offer the particle size distribution testing and production control of ceramic products.In the production of ceramics, the appropriate particle size of the preform body, glaze, ...

    Learn More
  • Chemicals Chemicals

    Bettersize instruments are widely used in the study and production control of the particle size, particle shape and powder characteristics of chemicals.In order to develop and optimize the production ...

    Learn More
  • Coal Industry Coal Industry

    Bettersize instruments provide the particle size analysis data of coal industry products (coal, coal water slurry and coal ash).Thermal power plants generally smash raw coal into coal fines. The good ...

    Learn More
  • Electronics

    Bettersize instruments provide the particle size distribution testing and particle shape testing of the raw materials of electronic products.In the electronics industry, many materials and processes h...

    Learn More
  • Food and Beverage Food and Beverage

    The particle size distribution testing of the food and drink industry provides necessary data for improving quality and production efficiency.The performance of the food and drink industry is closely ...

    Learn More
  • Fuel Cells/Batteries Fuel Cells/Batteries

    Bettersize instruments provide particle size distribution, bulk density, tap density and other physical property data of cathode and anode materials so as to contribute to the technological developmen...

    Learn More
  • Mining and Minerals Mining and Minerals

    Bettersize particle size and shape analysis instruments are widely used in the research, manufacturing and application of all kinds of mining and minerals, bringing favorable profits.The Bett...

    Learn More
  • Oil and Petrochemicals Oil and Petrochemicals

    Particle size is a very important parameter in the petrochemical industry.Bettersize laser particle size analyzer wet dispersion system can help you to detect:● Catalysts: including the research and ...

    Learn More
  • Paints, Inks, Pigments and Coatings Paints, Inks, Pigments and Coatings

    Bettersize instruments provide such physical data as the particle size distribution and powder flowability of paints, inks and coating products.The differences between the particle size and particle s...

    Learn More
  • Pharmaceutical Development Pharmaceutical Development

    Bettersize instruments provide test data of particle size distribution and the physical performance of powder so as to contribute to the whole process of pharmaceutical research, development and produ...

    Learn More
  • Soil and Sediment Science Soil and Sediment Science

    Bettersize instruments provide the particle size analysis and sand content analysis data of soil and sediment samples.Particle size distribution is a widely accepted method of determining soil texture...

    Learn More

Measuring method

In static light scattering laser light (monochromatic, coherent light) interacts with the particles, which have to be characterized in terms of particle size. In dependence of the particles' size, the light waves are scattered by the particles in a characteristic manner: the larger the particles are, the greater is the scattering in forward direction. With particles smaller about 100 nm, the scattering intensity is nearly identical in all directions.


Laser diffraction at particles with different size

The scattering intensity is determined by stationary detectors depending on the angle (light scattering intensity distribution). State-of-the-art laser diffraction systems such as the Bettersizer S3 Plus laser scattering particle size analyzer guarantee the determination of scattering intensities in a continuous angular range of 0.02 – 165°, i. e. in forward, side and backward direction. This is achieved by means of a so-called double lens design and oblique incidence optical system (DLOIOS technology): Fourier lenses (collective lens) are positioned between the laser and particles as well as between particles and detectors. The particles will interact with the light within a parallel laser beam. This offers the advantage that the scattered light can also be detected at very large angles (in backward scattering direction) and thus even very small particles can be measured precisely. Thanks to DLOIOS technology, the problems of conventional measurement setups can also be avoided. Therefore, neither the suitable lenses for the corresponding particle size measurement range have to be selected prior to the measurement (in comparison to the Fourier optics), nor do measurement inaccuracies result from different particle to detector distances, if not all particles lie in one plane (in comparison to the inverse Fourier optics).


Schematic drawing of the innovative DLOIOS-technique of Bettersizer S3 PLUS and CCD-camera system (x0.5 and x10)

To calculate the particle size distribution from the measured scattering spectra, the theory of either FRAUNHOFER or MIE is applied. The FRAUNHOFER theory is based on the hypothesis of opaque and spherical particles: the scattered pattern corresponds to a thin opaque two-dimensional plate – diffraction only occurs at the edges. Therefore no additional optical input constants of the material are necessary for this calculation.

In contrast the MIE theory uses the hypothesis of virtually translucent and spherical particles, meaning that the light permeates the matter and is scattered elastically at the atoms of the particle. The knowledge of the complex refractive index of the particles and the liquid as well is necessary. This theory is applicable for particles of all sizes.

The following figure shows an example of a volume-related particle size distribution of a calcium carbonate powder – measured with a Bettersizer S3 Plus.


Laser diffraction measurement example

The cumulative throughput curve Q3 (blue) and the resulting histogram (q3, black bar) can be seen.

Literature and norms
ISO 13320 – Particle size analysis – Laser diffraction methods
  • No.9, Ganquan Road, Jinquan Industrial Park, Dandong, Liaoning, China.
    No.9, Ganquan Road, Jinquan Industrial Park, Dandong, Liaoning, China.
  • 86-415-6163800