Metal powder testing with the employment of electrical impedance spectroscopy

• Electrical impedance spectroscopy of powdered metals. • Measurement of coil resistance and reactance for powdered conductive materials. • Testing mixtures of sand, Fe 2 O 3 and Fe 3 O 4 iron oxides. • A 0.2 % change in the powder content brings about over 15 % change in the coil impedance. • The presented method may be used for ferromagnetic and paramagnetic metal powders. This paper presents a completely new approach for testing metal powders using electrical impedance spectroscopy. The developed method can be employed in powder metallurgy and in soil, sand, and sediment studies. Ampoules with powder mixtures are placed inside coils that have been designed and constructed specifically for this purpose. The measured values of the coil impedance made it possible to distinguish between mixtures with different metal powder contents. In this way, two- and three-component mixtures were tested based on paramagnetic Fe 2 O 3 powder, ferromagnetic Fe 3 O 4 powder, and sand. The measurements are performed with two coils within the frequency range from 100 kHz to 170 kHz, and the results are presented on impedance diagrams and in the form of numerical data. In all cases, very large changes in the coil resistance and reactance are obtained, which allows for an unambiguous distinction between the tested mixtures. The developed method enables the measurement of a single sample in the entire frequency range in just a few seconds. The cheap and easy-to-use measurement system consists merely of a coil and an impedance meter, which allows its widespread use in every laboratory.