mixing criteria

The quality criteria for the mixture describe the uniformity of a system of heterogeneous materials. This includes a uniform particle size distribution. Uniform colouring can also serve as a quality characteristic. It is important that the primary particles do not form agglomerates and that the moisture distribution is homogeneous. The flowability of a large batch is another indicator. The same applies to flow behaviour and storage stability. In synthesis reactions, a stable and uniform temperature level can be crucial. Chemical properties should not exhibit local deviations. Absorption properties should also remain constant throughout the batch. Various optical analysis techniques are available for evaluation. Laser diffraction, high-resolution image analysis, dynamic light scattering, and Raman and IR microscopy are used. In addition, optical coherence tomography, light sheet microscopy, phase contrast, and fluorescence microscopy provide valuable information about particle size, shape, and distribution.

Other criteria depend on the specific application. Density distribution must be homogeneous, especially in the case of functional materials and powder sintering processes. Electrical and thermal conductivity can be a measure of uniformity. In food technology, aroma distribution, solubility, dispersibility, sinking behaviour and water activity play an important role. For ceramic and metal powders, green strength and pressing behaviour are key indicators. For polymer powders, additive distribution and melting behaviour are relevant. Uniform wettability and consistent surface energies can also indicate good mixing quality. In reactive systems, uniform reactivity is crucial.