Determination of particle shape distribution of clay using an automated AFM image analysis method

We have developed a direct imaging method for measuring particle shape distributions. It consists of a series of advanced automated algorithms that analyze 3D Atomic Force Microscopy (AFM) images of diluted pigment suspensions deposited onto glass cover slips. The method was applied to determine particle shape distributions of 10 different clay pigments from Brazil and Georgia, US. We found that the aspect ratio varies significantly and monotonically with particle diameter. The method gives generally lower average aspect ratios than those mentioned in previously published data, but still ranks pigments similarly. It was determined that Georgia clays generally have higher aspect ratios and broader shape distributions than Brazilian clays. This new direct automated AFM image analysis approach will be useful in pigment shape characterization and will provide important data for predicting coated paper performance.

Graphical abstractA direct method for measuring particle shape distributions of clays has been developed. It uses a series of advanced automated algorithms that analyze 3D AFM images. Lower aspect ratios than previously published data based on indirect methods were measured, but similar pigment rankings were obtained. It was determined that Georgia clays have higher aspect ratios and broader shape distributions than Brazilian clays.Figure optionsDownload full-size imageDownload as PowerPoint slide