Dry particle coating processes are of key importance for creating functionalized materials. By a change in surface structure, initiated during coating, a surface property change and thus functionalization can be achieved. This study introduces an innovative approach employing 3D X-ray micro-computed tomography (micro-CT) to characterize coated particles, consisting of spherical alumina particles (d50 = 45.64 μm), called hosts, surrounded by spherical polystyrene particles (d50 = 3.5 μm), called guests. The formed structures, hetero-aggregates, are generated by dry particle coating using mechano-fusion (MF). A deeper understanding of the influence of MF process parameters on the coating structures is a crucial step toward tailoring of coating structure, resulting surface property and functionalization. Therefore, the influence of rotational speed, process time, and total mechanical energy input during MF is explored. Leveraging micro-CT data, acquired of coated particles, enables non-stereologically biased and quantitative coating structure analysis. The guest's coating thickness is analyzed using the maximum inscribed sphere and ray method, two different local thickness measurement approaches. Particle-discrete information of the coating structure are available after a proper image processing workflow is implemented. Coating efficiency and guest's neighboring relations (nearest neighbor distance and number of neighbors inside search radius) are evaluated.

During the mechano-fusion process for dry particle coating, (hetero)-aggregates are formed consisting of host particles coated by smaller guest particles. During this process, the latter are exposed to intense particle–particle interactions and particle–wall impacts, which lead to deformation of their original shape. These deformations on the nano- and microscale can heavily influence the effective macroscopic properties of the resulting coated particles. We present a method for quantification of shape deformation based on measurements acquired by atomic force microscopy and apply it to guest particles during mechano-fusion. The 3D shape of guest particles is reconstructed by means of an ellipsoidal fit. Using these reconstructed shapes, we quantify the degree of deformation by comparing the aspect ratios of the ellipsoidal fits before and after mechano-fusion. Such a quantification enhances the understanding of how process-related parameters influence geometric descriptors of involved particles, which in turn impacts overall macroscopic properties of the material.

This study presents a new approach in the quantification of the deposited amount of impurity inside a filter cake made up of filter aid material. For this purpose, three-dimensional imaging by X-ray tomography is applied. Based on the X-ray attenuation properties, a model system consisting of kieselguhr as filter aid and barium sulphate as impurity is chosen. Due to the impurity particle size being smaller than the spatial resolution of the measuring setup, a calibration approach is necessary to gain insight into subvoxel information. A so-called phantom of similar material composition is prepared. The grey values are linearly correlated with the impurity volume fraction resulting in a calibration function, which facilitates the calculation of impurity volume fraction based on grey values measured inside the filter cake. First results are presented, showing that the approach delivers valid results for the chosen material system and reveals unexpected characteristics of the filter cake structure. Challenges in the context of the phantom approach and their influence on the obtained results are discussed.