The metal dendrite structure becomes an aggregate of extremely fine structures due to the fractal structure. In particular, Cu dendrites have industrial value. Cu dendrite crystals can be formed by a simple electroplating method and can be mass-produced. When viewed as a sheet, this Cu dendrite is expected to be used as a metal filter that can adsorb electrolytes and radioactive isotopes. In addition, mass production of Cu microparticles is expected by crushing Cu dendrite crystals. Cu particles are used as a base for electrically conductive inks used in printing electronics. It is also expected to be put into practical use as a bonding base for electrical parts through low-temperature sintering. In this study, we investigated a method for controlling the growth of Cu dendrites created by electrolytic plating. We focused on the growth substrate surface potential, that is, the anode substrate surface structure during electrolytic plating, as the main factor in growth control. The anode substrate surface was polished with abrasive paper to systematically modify the surface structure. It was confirmed that the number of convex portions on the anode substrate surface increased as the particle size of the abrasive paper changed. The anode substrate surface was polished with various particle sizes, the surface was observed with SEM, and the average length of the unevenness width was calculated. From this, we clarified the relationship between the number of convex portions on the anode substrate surface and the abrasive paper particle size. It was confirmed that the number of protrusions increased as the grain size of the abrasive paper increased. It is thought that the increase in the number of protrusions increased the total amount of electrons and copper ions ionized by the anode reaction, leading to an increase in the size of the dendrite structure formed on the surface of the Cu plating film.

In recent years, the demand for fine Au particles in advanced science and technology has increased. Chemical and physical methods are typically employed to produce fine metal particles. To prepare Au particles, chemical methods are primarily adopted because Au is malleable. The direct physical energy from the crusher transforms Au into a thin film instead of fine particles. In this study, we investigate a thin-film rupture method that uses indirect energy provided by cavitation to create Au particles. We hypothesized that the microbubbles generated in the solution owing to cavitation would apply shock waves to the surface of the Au thin film, break the film, and facilitate the formation of fine particles. The Au thin film to be fractured was fabricated via electrolytic plating on a Zn–Al alloy plate. Au plating on a Zn–Al alloy plate can be peeled off after a thin Au-plating film is formed. A thin Au-plating film with a three-dimensional structure was fabricated by adjusting the plating bath temperature and agitation speed of the plating solution during plating. We successfully obtained Au particles by applying shock waves from microbubbles to a thin Au-plating film. Furthermore, the surfaces of the fine Au particles were protected by adding a dispersant. As a result, collisions between Au particles were suppressed, and Au particle sizes of approximately 5‒10 μm were obtained.