Three types of instruments are available for particle size and morphological analysis, depending on the material, the size range and the sample structure. These methods include Horiba light scattering, size broadening by X-ray diffraction, and direct observation on a scanning electron microscope.
Laser light scattering is the most common method for particle size and distribution analysis for loose or lightly agglomerated particles. Particles in the range of 10 nm to 3,000 µm are examined by a Mie Scattering (Laser Diffraction) method to quickly yield the average, mean and median particle size along with the size distribution. Powders can be run either wet or dry and agglomerates can be broken up by either ultrasonication or air jet streams. Accuracies are better than 0.6% with a precision of 0.1%.
The SEM is also commonly used to examine grain size and morphology of loose powders or grains within a solid sample. Calibration standards can be used to insure accurate measurements of the particle size. More importantly, the SEM can reveal the particle morphology and habit planes, which the other methods cannot do.
X-ray diffraction utilizes a line broadening method to compute an average particle size and size distribution in the 1 – 100 nm size range for either loose particle or solid samples. This technique is especially useful for analyzing catalysts where the particles may be too small for either of the other two methods. In addition to the size measurements, XRD can also measure the accompanying stress within the particle ensemble.