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Abstract

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.
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Bibliography

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Authors and Affiliations

Jongmin Byun
1
ORCID: ORCID
Young-In Lee
1
ORCID: ORCID
Sung-Tag Oh
1
ORCID: ORCID

  1. Seoul National University of Science and Technology, Department of Materials Science and Engineering & The Institute of Powder Technology, Seoul 01811, Republic of Korea
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Abstract

In this study, the effects of adding niobium and vanadium to Fe-based oxide dispersion strengthened alloys are confirmed. The composition of alloys are Fe-20Cr-1Al-0.5Ti-0.5Y2O3 and Fe-20Cr-1Al-0.5Ti-0.3V-0.2Nb-0.5Y2O3. The alloy powders are manufactured by using a planetary mill, and these powders are molded by using a magnetic pulsed compaction. Thereafter, the powders are sintered in a tube furnace to obtain sintered specimens.

The added elements exist in the form of a solid solution in the Fe matrix and suppress the grain growth. These results are confirmed via X-ray diffraction and scanning electron microscopy analyses of the phase and microstructure of alloys. In addition, it was confirmed that the addition of elements, improved the hardness property of Fe-based oxide dispersion strengthened alloys.

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Authors and Affiliations

Chun Woong Park
Jongmin Byun
ORCID: ORCID
Won June Choi
Young Do Kim
ORCID: ORCID
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Abstract

In this study, a molybdenum alloy with dispersed high-entropy particles was fabricated using the powder metallurgy method. The high-entropy powder, composed of Nb, Ta, V, W, and Zr elements with a same atomic fraction, was prepared via high-energy ball milling. Using this powder, an ideal core-shell powder, composed of high-entropy powder as core and Mo powder as shell, was synthesized via the milling and reduction processes. These processes enabled the realization of an ideal microstructure with the high-entropy phase uniformly dispersed in the Mo matrix. The sintered body was successfully fabricated via uniaxial compaction followed by pressureless sintering. The sintered body was analyzed by X-ray diffraction and scanning electron microscope, and the high-entropy phase is uniformly dispersed in the Mo matrix.

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Authors and Affiliations

Won June Choi
CheonWoong Park
Jongmin Byun
ORCID: ORCID
Young Do Kim
ORCID: ORCID
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Abstract

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.
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Bibliography

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[2] G.H. Oh, S. Kim, T. Kim, J. Alloys Compd., (2020). DOI: https://doi.org/10.1016/j.jallcom.2020.157901 (in press).
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[4] K . Mukai, T. Magaya, L. Brandt, Z. Liu, H. Fu, S. Hunegnaw, Adhesive enabling technology for directly plating copper onto glass, 9th International Microsystems, Packaging, Assembly and Circuits Technology Conference, Taipei, Taiwan, IEEE (2014).
[5] B. He, J. Petzing, P. Webb, R. Leach, Opt. Lasers Eng. 75, 39-47 (2015).
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[7] L. Guo, W.Y. Zhang, Z.N. Xin, C.S. Yao, Int. J. Refract. Met. Hard Mater. 78, 45-50 (2019).
[8] X. Gao, L. Li, J. Liu, X. Wang, H. Yu, Int. J. Refract. Met. Hard Mater. 88, 105186 (2020).
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[12] C. Wongwanitwatta1, M. Horprathum, C. Chananonnawathorn, AIP Conf. Proc. 2279, 120007 (2020).
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[15] D.R. Feenstra, A. Molotnikov, N. Birbilis, Mater. Des. 198, 109342 (2021).
[16] R. Ohser-Wiedemann, U. Martin, H. J. Seifert, A, Müller, Int. J. Refract. Met. Hard Mater. 28 (4), 550-557 (2010)
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Authors and Affiliations

Goo-Won Roh
1 2
ORCID: ORCID
Eun-Soo Park
2
ORCID: ORCID
Jaeyun Moon
3
ORCID: ORCID
Hojun Lee
4
ORCID: ORCID
Jongmin Byun
4
ORCID: ORCID

  1. University, Department of Materials Science and Engineering, Seoul 04763, Republic of Korea
  2. Research and Development Center, Eloi Materials Lab (EML) Co. Ltd., Suwon 16229, Republic of Korea
  3. University of Nevada, Department of Mechanical Engineering, Las Vegas, 4505 S. Maryland PKWY Las Vegas, NV 89154, United States
  4. Seoul National University of Science and Technology, Department of Materials Science and Engineering Seoul 01811, Republic of Korea
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Abstract

The sintering behavior of p-type bismuth telluride powder is investigated by means of dilatometric analysis. The alloy powders, prepared by ball milling of melt-spun ribbons, exhibit refined and flake shape. Differential thermal analysis reveals that the endothermic peak at about 280oC corresponds to the melting of bismuth, and peaks existing between 410oC and 510oC are presumably due to the oxidation and crystallization of the powder. The shrinkage behavior of ball-milled powders was strongly dependent of heating rate by the thermal effect exerted on specimens. In the case of 2oC/min, the peak temperature for the densification is measured at 406oC, while the peak temperature at a heating rate of 20oC/min is approximately 443oC. The relative density of specimen pressureless-sintered at 500oC exhibited relatively low value, and thus further study is required in order to increase the density of sintered body.

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Authors and Affiliations

Ju-Yeon Han
Jongmin Byun
ORCID: ORCID
Young-In Lee
ORCID: ORCID
Byung Joon Choi
ORCID: ORCID
Hogyoung Kim
Sung-Tag Oh
ORCID: ORCID
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Abstract

Black TiO 2nanofibers 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 TiO 2 nanofibers. The synthesized black TiO 2 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.
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Authors and Affiliations

Myeongjun Ji
1
ORCID: ORCID
Eung Ryong Kim
1
ORCID: ORCID
Mi-Jeong Park
1
ORCID: ORCID
Hee Yeon Jeon
1
ORCID: ORCID
Jaeyun Moon
2
ORCID: ORCID
Jongmin Byun
1
ORCID: ORCID
Young-In Lee
1
ORCID: ORCID

  1. Seoul National University of Science and Technology, Department of Materials Science and Engineering, Seoul, 01811, Republic of Korea
  2. University of Nevada, Department of Mechanical Engineering, Las Vegas, 4505 S. Maryland PKWY Las Vegas, NV 89154, United States

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