Dry Coating Characterization of Coverage by Image Analysis: Methodology

Dry coating is an interesting process for creating added value binary powders composites. The principle is to mix ‘host’ particles with ‘guest’ particles with 10 to 100 times smaller size. But, behind the apparent simplicity of the process, the implied mechanisms are very complex. As a result, it is not possible so far to predict the resulting end-use properties of the produced composite powder, even if we know the properties of the host and guest powders. This papers aims at illustrating a first step to characterize more precisely the process itself and the result of the coating, i.e. coverage, homogeneity or thickness… In this work we describe the methodology to characterize the dry coating coverage through image analysis by using Environmental Scanning Electron Microscopy. A first part of this paper gives the technical and statistical aspects of the image acquisition in the electron microscope (Philips XL 30). A second part develops the image processing methodology with Matlab Image Processing Toolbox. A third part describes a validation step of the methodology by comparing the automated procedure to a ‘manual’ derivation of the coverage. The presented results imply the coverage of ‘model’ powders: host particles of ca. 100 μm and guest particles of ca. 10 μm. This work illustrates the assets of the image analysis to quantitatively characterize the average coverage and its homogeneity in dry coating application, for example when partial breakage or attrition occurs. Further results with the application of this methodology will be published in a further paper.