Comparative analysis of the coating thickness on single particles using X-ray micro-computed tomography and confocal laser-scanning microscopy

•Coating layer thicknesses of single particles were measured using μ-CT and CLSM.•A geometrical method was derived for the comparison of μ-CT and CLSM data.•μ-CT yields precise thickness information of measured particles.•It was found out CLSM only yields surface information.•An alternative method was introduced to obtain depth information of CLSM data.

The quality of coated products depends strongly on the structure of the coating layer. Confocal laser-scanning microscopy (CLSM) and X-ray micro-computed tomography (μ-CT) are used as non-destructive techniques for the quantification of coating microstructures, especially coating layer thicknesses. Combined with image processing, it is possible to evaluate and correlate chord lengths and coating thicknesses. In this study two different kinds of core particles were coated with crystalline and film-forming coating materials by fluidized bed spray granulation. The thicknesses of the coating layers were investigated using both measuring methods. Motivated by observed differences in the obtained CLSM results for the layer thickness, a new evaluation procedure is developed and discussed.

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