Study of the effect of continuous loading and compaction on the electrical resistance of powder materials

Abstract

The electrical conductivity of powder media depends on the composition, impurities, oxide films, morphology and the nature of the contact surface. We present the results of studying the electrical resistance of powder materials and their compounds under continuous loading by the four-contact method. The electrical resistance is determined using a special experimental cell. Industrial powders Al (ASD-1), Ti (PTK), Hf (GFM-1), soot and their mixtures, as well as TaC and HfC powders obtained by self-propagating high-temperature synthesis were studied. It is shown that an increase in the mechanical pressure up to 80 MPa leads to a decrease in the electrical resistance of the materials under study. The morphology of the particles (spherical or fragmentary shape), their dispersion affects the quality of the contact surface and, accordingly, the magnitude of the electrical resistance. Moreover, the electrical resistance of the material depends on the degree of cleaning of the particle surface from oxide films. The proposed method in combination with other analytical methods used for studying powder media allows us to reveal the regularities of this relationship, characteristic of all morphological features, composition and electrophysical properties of powders of various compositions under loading conditions. The results obtained can be used to select the optimal characteristics of consolidation by electric current depending on the initial pressure, as well as in case of high-voltage electric pulse consolidation of powder materials by spark plasma sintering and electrothermal explosion methods.