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Simple synthesis of Black TiO2 Nanofibers Via Calcination in Inert Atmosphere

Ji Myeongjun, Kim Eung Ryong, Park Mi-Jeong, Jeon Hee Yeon, Moon Jaeyun, Byun Jongmin, Lee Young-In

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1481--1486

EN

Black TiO2 nanofibers have recently emerged as a promising material that has both advantages of black metal oxide and one-dimensional nanostructure. However, current reduction-based synthesis approaches are not compatible with practical applications because these processes require high process costs, complicated processes, and sophisticated control. Therefore, it is still necessary to develop a simple and facile method that can easily introduce atomic defects during the synthesis process. This work suggests an electrospinning process with an antioxidant and subsequent calcination process for the facile synthesis of black TiO2 nanofibers. The synthesized black TiO2 nanofiber has an average diameter of 50.3 nm and a rutile structure. Moreover, this nanofiber represented a noticeable black color and a bandgap of 2.67 eV, clearly demonstrating the bandgap narrowing by the introduced atomic defects.

2

Homogeneous Dispersion of Yttrium Oxide Particles in Nickel-Based Superalloy by High Pressure Homogenizing and Ball Milling Method

Byun Jongmin, Lee Young-In, Oh Sung-Tag

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 4

1055--1058

EN

An optimum route to fabricate the Ni-based superalloy with homogeneous dispersion of Y2O3 particles is investigated. Ni-based ODS powder was prepared by high-energy ball milling of gas-atomized alloy powders and Y2O3 particles treated with a high-pressure homogenizer. Decrease in particle size and improvement of dispersion stability were observed by high-pressure homogenization of as-received Y2O3 particles, presumably by the powerful cavitation forces and by collisions of the particles. Microstructural analysis for the ball-milled powder mixtures reveal that Ni-based ODS powders prepared from high-pressure homogenization of Y2O3 particles exhibited more fine and uniform distribution of Ni and Y elements compared to the as-received powder. These results suggested that high-pressure homogenization process is useful for producing Ni-based superalloy with homogeneously dispersed oxide particles.

3

Direct Energy Deposition of Mo Powder Prepared by Electrode Induction Melting Gas Atomization

Roh Goo-Won, Park Eun-Soo, Moon Jaeyun, Lee Hojun, Byun Jongmin

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 3

795--798

EN

Molybdenum (Mo) is used to form a barrier layer for metal wiring in displays or semiconductor devices. Recently, researches have been continuously attempted to fabricate Mo sputtering targets through additive manufacturing. In this study, spherical Mo powders with an average particle size of about 37 um were manufactured by electrode induction melting gas atomization. Subsequently, Mo layer with a thickness of 0.25 mm was formed by direct energy deposition in which the scan speed was set as a variable. According to the change of the scan speed, pores or cracks were found in the Mo deposition layer. Mo layer deposited with scan speed of 600 mm/min has the hardness value of 324 Hv with a porosity of approximately 2%. We demonstrated that Mo layers with higher relative density and hardness can be formed with less effort through direct energy deposition compared to the conventional powder metallurgy.