A VISUALIZATION AND CHARACTERIZATION OF MICROSTRUCTURES OF COHESIVE POWDERS

In this work, a framework for the determination of the particle positions in a fluorescent powder structure was created. The feasibility of imaging and quantifying sedimented particulate samples in air was demonstrated by using micron-sized poly-dispersed electrophotographic printing particles. Particle positions were determined by a Confocal Laser Scanning Microscope (CLSM) to capture a stack of cross-sectional images of fluorescent particle clusters. The resulting images were analyzed using Matlab image processing tools. The XYZ coordinates and radii for these particles (assumed spherical) were calculated in several selected sampling volumes, and the packing fractions were calculated. A three-dimensional visualization of the particle structure was then created. The CLSM particle results obtained from this study were compared with Scanning Electron Microscopy (SEM) particle imaging results. A difference in the average particle radii of the CLSM results from the SEM results was observed. The three-dimensional reconstruction of these particles showed a highly porous structure. The average packing fraction of 14.07% ± 0.84% was comparable to the literature packing fraction values for cohesive particles [1]. The cohesive nature of toner was noted from this comparison. Based on this finding, the self-similar nature of the particle clusters was investigated in the samples. This methodology of three-dimensional particle mapping and visualization has the potential to lead to much needed materials and structural analyses for fine particles. The frame-by-frame particle-tracking method developed in this study can be adapted into other digital imaging methods like X-ray micro-computed tomography (μCT) where the scanned object is also digitized through layer-by-layer scanning