An approach for predicting the true density of powders based on in-die compression data

March 21, 2023, midnight - by Ramy N. Elsergany , Gerrit Vreeman , Changquan Calvin Sun

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Helium pycnometry, a widely employed technique for assessing the true density of powders, is susceptible to the impact of volatiles released during measurement. This susceptibility can result in an overestimation of the true density. Therefore, there is a pressing need for a precise method to determine the true density of powders that include volatile components. In this context, a method based on in-die compression data obtained through a compaction simulator underwent evaluation. Specifically, the stress transmission coefficient (STC), measured using an instrumented die, was utilized to forecast the in-die Heckel mean yield pressure (Py). A true density was derived by iteratively conducting Heckel analysis using estimated true density values until the predicted Py value aligned with the measured STC value from in-die density-pressure data. This innovative method underwent validation using a set of water-free powders. Furthermore, by employing crystalline hydrates, the study demonstrated that the calculated true densities closely approximated values derived from crystal structure compared to those obtained from helium pycnometry. Therefore, this method holds potential for determining the true density of powders based on their STC values.

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