Mixing sub-micron particles in a ProCell type spouted bed

Mixing sub-micron particles of two different materials produce hetero-aggregates, which can exhibit innovative and superior properties over homo-aggregates of a single material. The present study investigates the hetero-aggregate formation from sub-micron particles in ProCell type spouted bed equipment. Sub-micron particles can exist in the form of homo-aggregates, clusters of particles of the same material that are held together by cohesive forces such as van der Waals forces. In the special spouted bed used, the inlet air velocities are significantly higher than in conventional fluidized beds and can be expected to exert an influence that promotes aggregate breakage and rearrangement. Indeed, by use of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), it is shown that mixing is achieved at sub-agglomerate level. Region of interest with a size of 2.5 μm (which is more than double the size of the bigger primary particle) is found to be a reasonable scale to investigate the mixing of sub-micron sized particles in compressed wafers and also in single agglomerates (by a new method of quantification).