The Motion of a 2 mm Tantalum Block Induced by Underwater Explosion

Abstract

The recycling technology of rare metals from wasted electronic scraps called as urban mines has been studied recently [1--3]. Several studies of the application of electrical disintegration (ED) to the separation of the rare metal-containing component from the electric component were conducted [2, 3]. In the ED method, the electrical discharge is performed directly toward the sample located inside the water tank, and the underwater explosion is generated by the discharge [4--6]. The studies of the application of ED have been focused on the research of the particle size distribution of liberated products. The size distribution of a tantalum (Ta) capacitor containing the rare metal Ta by ED was investigated [3]. The Ta capacitor consists mainly of a block of Ta-sintered body and the case covering the body. The study showed that the Ta-sintered body was liberated from the capacitor by ED. The electric flux line induced by the electric discharge in the ED for the Ta capacitor was studied numerically [3]. The numerical study confirmed that the discharge path was generated not only in the water between the electrode and the upper surface of Ta capacitor but also in the boundary between the Ta sintered body and the case inside the capacitor. Although the application of ED and the electric flux line in ED for the Ta capacitor was studied, little study has been done to actually clarify the mechanism of liberation of a block of Ta sintered from the capacitor. In order to disintegrate more efficiently, it is important to investigate the mechanism of liberation caused by ED. We have analyzed numerically the pressure generated from the discharge path inside the Ta capacitor to investigate the mechanism of ED. Numerical calculations indicated that the pressure fluctuation was induced by the shock wave generated in the boundary between the Ta-sintered body and the case where the discharge path occurred, resulting in the separation of the sintered body from the case. However, it remains to be clarified how the motion and liberation of a block of the Ta-sintered body are induced by the underwater explosion in ED.