(598h) Enhanced Centrifuge-Based Approach to Powder Characterization

Improvement in solids processing performance depends on a fundamental understanding of powder behavior, which is driven by the adhesion characteristics of the powder’s particulate ensemble.  Key physical properties of the particulate system, chiefly size, geometry, and surface roughness, affect particle adhesion.  These particulate properties can be extracted through particle adhesion measurements to effectively describe the powder.  Ultimately, adequate descriptions of the powder can in turn be used to exert control over powder behavior by optimizing process conditions.

A centrifuge-based technique is a practical method that measures particle adhesion.  The technique is simple to perform and describes the adhesion behavior of an ensemble of particles.  Further enhancement of the centrifuge-based technique can be developed to provide valuable insight at the particle scale by determining the aforementioned particulate properties.  This is accomplished through specially designed substrates that allow the extraction of particle characteristics. 

Substrates with hemispherical indentations provide a means by which particle size characteristics can be determined.  Adhesion forces were determined in silico, utilizing an in-house van der Waals force simulator, to describe the effects of the ratio of particle to indentation diameter for indentation diameters between 10 and 50 µm.  In this study, the ratio of the particle diameter to the indentation diameter was varied from 0.1 to 2 in 0.1 increments.  Idealized spherical geometries and smooth surfaces were used for the particle and indentation.  Simulations of a single particle and single indentation, symmetrically oriented along a centralized vertical axis, were the basis of the adhesion calculations.  By systematically varying the indentation size, particle size can be extracted due to large discrepancies in the particle-indentation adhesion forces.  Once a particle size distribution has been determined, systematic variation in roughness on the indentations affords a means for evaluating the size-specific roughness distribution on the particles.   This study establishes a viable strategy to enhance the centrifuge-based approach for powder characterization.