Preparation of Monosized Copper Micro Particles by Pulsated Orifice Ejection Method

Abstract

A pulsated orifice ejection method (POEM) has attained mass-production of monosized spherical micro particles of solder. In this method, the micro droplet melts are emitted from a small orifice by applying both mechanical pulses and constant gas pressure to the melt. This paper reports further development of this method for alternative monosized copper spherical particles with a size in the order of 100 mm. The possibility of the droplet formation was strongly determined by the wettability of orifice material to the melt. Droplets of molten copper could be stably formed at a particularly high contact angle. Using an orifice with the low wettability, monosized copper particles are obtained in a wide range of process parameters such as the rod displacement and gas pressure. Their particle size was also clarified to vary with changes in the two parameters. Especially, the gas pressure may linearly control the particle size from 75 to 120 mm, which is equivalent to 75 to 120% of the orifice diameter. All monosized particles produced by the POEM have an excellent mono-dispersivity less than 2.0 in standard deviation.

Preparation of Fe-based monodisperse spherical particles with fully glassy phase

“…These particles had particularly smooth surfaces compared to the crystalline metal particles that had ever been obtained by atomization including the POEM. The crystalline particles have more or less a rough surface texture due to grain boundaries and preferred growth orientation [12,13], but the present particles showed no crystalline vestige. In the case of the indicated particles, the average diameter, the size distribution, and the sphericity were determined to be 311 m, 1.24 m, and 1.57%, respectively.…”

“…The repetition of this sequence at a quick rate enables the mass-production of monodisperse particles. The details of the POEM have been described in previous studies [12,13].…”

“…Selecting material for the parts that are directly exposed to the molten alloy was the most important factor to achieve stable ejection and purity of droplets. Our previous studies have shown that the ejection of droplets is mainly governed by the wettability of the molten raw material to the orifice surface [12]. Hence, the contact angles of the alloy to boron nitride and alumina, which were chosen as the ceramic candidates for the orifice, were measured by a sessile drop method in an argon atmosphere.…”

“…Hitherto, we have successfully developed a unique atomization process which is capable of producing monodisperse particles of various materials, by a method called the pulsated orifice ejection method (POEM) [12,13]. The POEM is able to mass-produce monodisperse particles of the desired diameter in the range of several tens to hundreds of micrometers.…”

Formation of uniformly sized metal droplets from a capillary jet by electromagnetic force

“…Many techniques have been developed for metals to produce uniformly sized particles and small spheres [6][7][8]. Minemoto et al proposed the jet-splitting method for fabricating uniformly sized spherical silicon particles with a diameter of 1 mm for spherical silicon solar cells [7].…”