• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.5
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• pp.196-201
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• 2023

In order to improve the efficiency of the water splitting system for hydrogen energy production, the high overvoltage in the electrochemical reaction caused by the catalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be reduced. Among them, transition metal-based compounds (hydroxide, sulfide, etc.) are attracting attention as catalyst materials to replace currently used precious metals such as platinum. In this study, Ni foam, an inexpensive metal porous material, was used as a support and β-Ni(OH)₂ microcrystals were synthesized through a hydrothermal synthesis process. In addition, changes in the crystal morphology, crystal structure, and water splitting characteristics of β-Ni(OH)₂ microcrystals synthesized by doping Fe to improve electrochemical properties were observed, and applicability as a catalyst in a commercial water electrolysis system was examined.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.1
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• pp.30-35
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• 2024

In order to improve the efficiency of the water splitting system for hydrogen production, the high overvoltage in the electrochemical reaction caused by the catalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be reduced. Among them, transition metal-based compounds are attracting attention as catalyst materials that can replace precious metals such as platinum that are currently used. In this study, nickel foam, an inexpensive metal porous material, was used as a support, and Fe-doped β-Ni(OH)₂ microcrystals were synthesized through a hydrothermal synthesis process. In addition, in order to improve OER properties, changes in the shape, crystal structure, and water splitting characteristics of Fe-Mo co-doped β-Ni(OH)₂ microcrystals synthesized by co-doping with Mo were observed. The changes in the shape, crystal structure, and applicability as a catalyst for water splitting were examined.

• Bangmulgwan gwa yeongu (The National Museum of Korea Journal)
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• v.1
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• pp.174-197
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• 2024

Personal ornaments made from precious metals that have been excavated from tombs dating to the Maripgan period (4th-6th century) of the Silla Kingdom are a major subject of analysis in the study of gender and hierarchy among the tomb occupants. Nonetheless, bracelets had been neglected until Ha Daeryong's recent research on determining gender through bracelets attracted attention. Accordingly, an examination and organization of the fundamental elements of Silla bracelets was needed. In response, this paper examines their physical characteristics, appearance, changes over time, and related wearing practices. The data for this study is derived from 176 bracelets, mostly made from silver or gold. Copper and glass bracelets are also included. Many of them were cast in a single-use earthen mold. Even the notched and protruding designs were created by casting rather than carving. Glass bracelets and bracelets with dragon designs were made using molds with round cavities. Excluding those produced using metal sheets, the rest of the bracelets are thought to have been cast in a mold with a long-string-shaped cavity and then bent round. After being bent, the two ends were either soldered together (closed type) or left open (open type). As demonstrated in the study by Lee Hansang, Silla bracelets evolved from plain rounded rod-shaped bracelets, such as the one excavated from the Northern Mound of Hwangnamdaechong Tomb, to versions with notched designs, and eventually to those with protruding designs, which gained popularity by the sixth century. The precedents of plain rounded rod-shaped bracelets are presumed to have been thin rod-shaped bracelets from the Proto-Three Kingdoms period. Bracelets need to be fit to the wrists so that they do not slip off easily when worn. The open type design was the preferable way to achieve this. Moreover, given the ductility of gold, silver, and copper, it seems that it would have been possible to stretch or deform them. In the end, I concluded that even if a bracelet is too small to pass man's hand, the open type could have been worn. Furthermore, if a closed-type bracelet were pressed into an oval shape, it would not be impossible for a man to put it on. When bracelets are divided according to their degree of deformability into type A (the open type) through type D, which is almost impossible to deform, type A is commonly found with wearers of thin hollow earrings, and types C and D (which are difficult to deform) are not found with wearers of thin hollow earrings, but only with wearers of thick hollow earrings. Therefore, it can be seen that men were allowed to wear bracelets, and the existing studies that differentiate between men and women based on the wearing of thin hollow earrings, thick hollow earrings, and swords remain valid.