The enamel powders used traditionally in Korea are produced by a ball-milling process. Because of their irregular shapes, enamel powders exhibit poor flowability. Therefore, polygonal enamel powders are only used for handmade cloisonné crafts. In order to industrialize or automate the process of cloisonné crafts, it is essential to control the size and shape of the powder. In this study, the flowability of the enamel powders was improved using the spheroidization process, which employs the RF plasma treatment. In addition, a simple grid structure and logo were successfully produced using the additive manufacturing process (powder bed fusion), which utilizes spherical enamel powders. The additive manufacturing technology of spherical enamel powders is expected to be widely used in the field of cloisonné crafting in the future.

In the present work, spheroidization of angular vanadium powders using a radio frequency (RF) thermal plasma process is investigated. Initially, angular vanadium powders are spheroidized successfully at an average particle size of 100 μm using the RF-plasma process. It is difficult to avoid oxide layer formation on the surface of vanadium powder during the RF-plasma process. Titanium/vanadium/stainless steel functionally graded materials are manufactured with vanadium as the interlayer. Vanadium intermediate layers are deposited using both angular and spheroidized vanadium powders. Then, 17-4PH stainless steel is successfully deposited on the vanadium interlayer made from the angular powder. However, on the surface of the vanadium interlayer made from the spheroidized powder, delamination of 17-4PH occurs during deposition. The main cause of this phenomenon is presumed to be the high thickness of the vanadium interlayer and the relatively high level of surface oxidation of the interlayer.

Various inorganic fillers improve the thermal conductivity and physical properties of organic products. Alumina has been used a representative filler in the heat radiation sheet for the heat radiation of electric device. The high filling rate of alumina increases the thermal conductivity and properties of products. We successfully developed the spherical alumina by flame fusion process using the oxygen burner with LPG fuel. In the high temperature flame (25003000) of oxygen burner, sprayed powders were melting and then rotated by carrier gas. This surface melting and rotation process made spherical alumina. Especially effects of chemical composition and particle size of stating materials on the melting behavior of starting materials in the flame and spheroidization ratio were investigated. As a result, spheroidization ratio of boehmite and aluminum hydroxide with endothermic reaction of dehydration process was lower than that of the sintered alumina without dehydration reaction.