Proposed Submission Title

Power Characterization: Measuring Adhesion Forces

Keywords

Powder Characterization, Adhesion, van der Waals force

Select the category the research project fits.

Physical Sciences

Is this submission part of ICaP/PW (Introductory Composition at Purdue/Professional Writing)?

No

Abstract

Powder behavior is a complex topic that influences many industrial processes, especially those involved with food and pharmaceutical processing, and has an important role in homeland security and military applications involving explosives and explosive residues. The goal of the research is to be able to predict bulk flow behavior from milligram-level quantities of powder. This is important for designing better industrial processes, and also for measuring forces between explosive particles and binders for controlling detonations. In order to characterize a powder, a centrifuge is used to determine the rotational speed, in RPM, needed to remove particles of different size from a surface of interest. Based on the size of the particles removed at each speed, their adhesion force can be determined. Using a modified van der Waals force model, it is possible to fit a distribution of ‘effective’ Hamaker constants to the adhesion force data. These constants are matched to the powder’s particle size distribution. Using the van der Waals force model with the ‘effective’ Hamaker constant distribution, the adhesion behavior of the entire powder can now be described based only on the size distribution of the powder. Experiments are performed on flat surfaces with spherical particles to model the ideal case. More complex systems of ideal particles on rough surfaces are being studied to determine how surface roughness will affect the adhesion forces. These experiments will validate the theory that the adhesion force distribution of a powder, which is critically linked to its flow characteristics, can be described using simple experiments, an effective Hamaker constant distribution, and the size distribution of the powder.

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Power Characterization: Measuring Adhesion Forces

Powder behavior is a complex topic that influences many industrial processes, especially those involved with food and pharmaceutical processing, and has an important role in homeland security and military applications involving explosives and explosive residues. The goal of the research is to be able to predict bulk flow behavior from milligram-level quantities of powder. This is important for designing better industrial processes, and also for measuring forces between explosive particles and binders for controlling detonations. In order to characterize a powder, a centrifuge is used to determine the rotational speed, in RPM, needed to remove particles of different size from a surface of interest. Based on the size of the particles removed at each speed, their adhesion force can be determined. Using a modified van der Waals force model, it is possible to fit a distribution of ‘effective’ Hamaker constants to the adhesion force data. These constants are matched to the powder’s particle size distribution. Using the van der Waals force model with the ‘effective’ Hamaker constant distribution, the adhesion behavior of the entire powder can now be described based only on the size distribution of the powder. Experiments are performed on flat surfaces with spherical particles to model the ideal case. More complex systems of ideal particles on rough surfaces are being studied to determine how surface roughness will affect the adhesion forces. These experiments will validate the theory that the adhesion force distribution of a powder, which is critically linked to its flow characteristics, can be described using simple experiments, an effective Hamaker constant distribution, and the size distribution of the powder.