Particle Size

Particle size is a geometric characteristic that is usually assigned to material objects with sizes on scale from nano-meters to millimeters. There are multiple definitions of the particle size depending on the method of its measurement. For instance, sedimentation yields equivalent hydrodynamic particle size. Microscopy provides information on the area projection particle size. In order to reflect innate basis for a particular particle size measurement three different basses are used: numerical, area and weight.

Our Acoustic spectroscopy belongs to the group of macroscopic fitting methods. This group includes also light scattering, x-rays scattering, neutron scattering. All these particle size measurement methods display particle size on the weight basis. However, this basis is innate only for Acoustic spectroscopy. Attenuation of ultrasound caused by a single particle is proportional to the weight or volume of the particle. In contrary, for instance, light scattering depends on the 6th power of the particle size. This would require special recalculation down to the weight basis. Consequently, light scattering tends to overestimate contribution of large particles.

Additional information: Non-Aqueous Conductivity

Particle Size Measurement

Particle size measurement is extremely important method for research and development and for quality control in many industries. This includes pharmaceuticals, cement, ceramics, paints, emulsions, etc.

Acoustic spectroscopy makes possible particle size measurement in concentrated dispersions and emulsions with no dilution and no sample preparation. This is critical in many cases when dilution affects particle size distribution. Also, this method can be applied for structured dispersions. Structure contributes to ultrasound attenuation by itself, but this contribution can be subtracted using appropriate existing theory. In addition, acoustic spectroscopy could resolve particle size distributions of different species of particles in mixed dispersions, assuming that they have different densities.

This method can be used for continuous monitoring of particle size during milling, crystallization, and other industrial processes. One of the most important applications is particle sizing of nano-dispersions and other nano-particulates. Acoustics can monitor presence of nano-particles with precision of 1%. Nano-particles can be masked by larger particles if other methods are involved.