Conditions of Powder Flow and Fill

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Understanding the conditions that contribute to powder flow are essential to anticipate the segregation of particles in flow situations. Although various methods are used to quantify powder flow and powder fill in industry, these methods fail to properly capture observed behavior, particularly as the particle size decreases, thereby failing to accurately predict powder flow, fill, and packing outside of a specific process. It is unclear if there is a specific boundary below which particle flow will not occur. The hypothesis of this study is that there is a correlation between particle size, density and flow behavior, and there is a critical particle mass necessary for free flow. This study analyzes the flow behavior of a broad range materials, including glass sphere standards 1018a, 1017a, and NBS 1003. The flow of these powders was analyzed by inclining a roughened copper plate until particles began to tumble. The copper plate dissipated electrostatic charge. The angles of both the onset of flow, when the first observation of movement occurred, and critical flow, where all the powder flowed, were recorded. Although two flow angles were identified for some of the powders, this does not necessarily mean there are two different flow behaviors. Rather this study purposes that the first flow is agglomerate or large particle flow and critical flow is either true powder flow or the gravitational forces overcoming the interparticle forces. The samples were imaged by SEM to estimate particle size for initial and critical flow. It can be concluded that the powder flow data is not affected by density and is mass independent.
Thesis completed in partial fulfillment of the requirements for the Alfred University Honors Program.
Honors thesis, Powder flow, Ceramics, Materials science