Role of consolidation state in the measurement of bulk density and cohesion

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• 作者：Alisa Vasilenko ; Sara Koynov ; Benjamin J. Glasser ; Fernando J. Muzzio ; ^{fjmuzzio@yahoo.com}
• 关键词：Powder characterization ; Bulk density ; Tapped density ; Powder cohesion
• 刊名：Powder Technology
• 出版年：2013
• 出版时间：May, 2013
• 年：2013
• 卷：239
• 期：Complete
• 页码：366-373
• 全文大小：852 K

文摘

Characterization of powder consolidation and flow is important to a large number of industries that process solids. A variety of powder testers exist today, however most are application specific and results they provide are mainly qualitative. Comparison studies have been attempted previously; their main focus was whether various methods correlate, while the reasons for disagreement in the results have seldom been investigated.

Among the different methods used to characterize powder flow behavior, density-based methods are some of the simplest and most popular. They are also some of the least sensitive and least reproducible. A method comparison study was performed to characterize the variability in bulk density as measured by various powder flow characterization methods. It was found that the density of the powders tested in most unconsolidated methods had a near-perfect linear correlation with one another, suggesting that there exists a critical ¡°dilated¡± density value that is independent of the measurement method and can be considered a material property. The densities of the powders in consolidated states correlated poorly, especially for the methods where consolidation mechanisms were not tightly controlled (i.e. tapping). In addition, the effect of the consolidation state of the powder bed during testing on cohesion measurements was studied. The cohesion measured by shear cells at differing consolidation states and by an avalanching method, during which the powder bed is dilated, were compared. It was found that the differences in cohesion results from the shear cells tested can be attributed to differences in the powder consolidation state. Cohesion results acquired from a dilated powder bed correlate more linearly with the shear cell cohesion results at low consolidation stresses than at high consolidation stresses; further supporting the impact of the powder bed packing state on the measurement of cohesion.