• Title/Summary/Keyword: Fe-Cr alloy

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Development of Amorphous Iron Based Coating Layer using High-velocity Oxygen Fuel (HVOF) Spraying (철계 비정질 분말을 활용한 초고속 용사 코팅층 개발)

  • Kim, Jungjoon;Kim, Song-Yi;Lee, Jong-Jae;Lee, Seok-Jae;Lim, Hyunkyu;Lee, Min-Ha;Kim, Hwi-Jun;Choi, Hyunjoo
    • Journal of Powder Materials
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    • v.28 no.6
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    • pp.483-490
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    • 2021
  • A new Fe-Cr-Mo-B-C amorphous alloy is designed, which offers high mechanical strength, corrosion resistance as well as high glass-forming ability and its gas-atomized amorphous powder is deposited on an ASTM A213-T91 steel substrate using the high-velocity oxygen fuel (HVOF) process. The hybrid coating layer, consisting of nanocrystalline and amorphous phases, exhibits strong bonding features with the substrate, without revealing significant pore formation. By the coating process, it is possible to obtain a dense structure in which pores are hardly observed not only inside the coating layer but also at the interface between the coating layer and the substrate. The coating layer exhibits good adhesive strength as well as good wear resistance, making it suitable for coating layers for biomass applications.

Phase analysis of simulated nuclear fuel debris synthesized using UO2, Zr, and stainless steel and leaching behavior of the fission products and matrix elements

  • Ryutaro Tonna;Takayuki Sasaki;Yuji Kodama;Taishi Kobayashi;Daisuke Akiyama;Akira Kirishima;Nobuaki Sato;Yuta Kumagai;Ryoji Kusaka;Masayuki Watanabe
    • Nuclear Engineering and Technology
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    • v.55 no.4
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    • pp.1300-1309
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    • 2023
  • Simulated debris was synthesized using UO2, Zr, and stainless steel and a heat treatment method under inert or oxidizing conditions. The primary U solid phase of the debris synthesized at 1473 K under inert conditions was UO2, whereas a (U, Zr)O2 solid solution formed at 1873 K. Under oxidizing conditions, a mixture of U3O8 and (Fe, Cr)UO4 phases formed at 1473 K, whereas a (U, Zr)O2+x solid solution formed at 1873 K. The leaching behavior of the fission products from the simulated debris was evaluated using two methods: the irradiation method, for which fission products were produced via neutron irradiation, and the doping method, for which trace amounts of non-radioactive elements were doped into the debris. The dissolution behavior of U depended on the properties of the debris and aqueous solution for immersion. Cs, Sr, and Ba leached out regardless of the primary solid phases. The leaching of high-valence Eu and Ru ions was suppressed, possibly owing to their solid-solution reaction with or incorporation into the uranium compounds of the simulated debris.

Effect of Solution Annealing Heat Treatment on the Localized Corrosion Resistance of Inconel 718 (Inconel 718의 국부 부식 저항성에 미치는 용체화 열처리의 영향)

  • Yoonhwa Lee;Jun-Seob Lee;Soon Il Kwon;Jungho Shin;Je-hyun Lee
    • Corrosion Science and Technology
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    • v.22 no.5
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    • pp.359-367
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    • 2023
  • The localized corrosion resistance of the Ni-based Inconel 718 alloy after solution heat treatment was evaluated using electrochemical techniques in a solution of 25 wt% NaCl and 0.5 wt% acetic acid. Solution heat treatment at 1050 ℃ for 2.5 hours resulted in an increased average grain diameter. Both Ti carbides (10 ㎛ diameter) and Nb-Mo carbides (1 - 9 ㎛ diameter) were distributed throughout the material. Despite heat treatment, the shape and composition of these carbides remained consistent. An increase in solution temperature led to a decrease in pitting potential value. However, the pitting potential value of solution heat-treated Inconel 718 was consistently higher than that of as-received Inconel 718 at all tested temperatures. Localized corrosion initiation occurred at 0.4 VSSE in a temperature environment of 80 ℃ for both as-received and solution heat-treated Inconel 718 alloys. X-ray photoelectron spectroscopic analysis indicated that the composition of the passive film formed on specimen surfaces remained largely unchanged after solution heat treatment, with O1s, Cr2p3/2, Fe2p3/2, and Ni2p3/2 present. The difference in localized corrosion resistance between as-received and solution heat-treated Inconel 718 alloys was attributable to microstructural changes induced by the heat treatment process.

Recovery of Nickel from Waste Iron-Nickel Alloy Etchant and Fabrication of Nickel Powder (에칭 폐액으로부터 용매추출과 가수분해를 이용한 니켈분말제조에 관한 연구)

  • Lee, Seokhwan;Chae, Byungman;Lee, Sangwoo;Lee, Seunghwan
    • Clean Technology
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    • v.25 no.1
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    • pp.14-18
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    • 2019
  • In general after the etching process, waste etching solution contains metals. (ex. Nickel (Ni), Chromium (Cr), Zinc (Zn), etc.) In this work, we proposed a recycling process for waste etching solution and refining from waste liquid contained nickel to make nickel metal nano powder. At first, the neutralization agent was experimentally selected through the hydrolysis of impurities such as iron by adjusting the pH. We selected sodium hydroxide solution as a neutralizing agent, and removed impurities such as iron by pH = 4. And then, metal ions (ex. Manganese (Mn) and Zinc (Zn), etc.) remain as impurities were refined by D2EHPA (Di-(2-ethylhexyl) phosphoric acid). The nickel powders were synthesized by liquid phase reduction method with hydrazine ($N_2H_4$) and sodium hydroxide (NaOH). The resulting nickel chloride solution and nickel metal powder has high purity ( > 99%). The purity of nickel chloride solution and nickel nano powders were measured by EDTA (ethylenediaminetetraacetic) titration method with ICP-OES (inductively coupled plasma optical emission spectrometer). FE-SEM (field emission scanning electron microscopy) was used to investigate the morphology, particle size and crystal structure of the nickel metal nano powder. The structural properties of the nickel nano powder were characterized by XRD (X-ray diffraction) and TEM (transmission electron microscopy).

A COMPARATIVE STUDY ON THE PHYSICAL PROPERTIES OF ORTHODONTIC PLIERS ACCORDING TO TYPES OF STERILIZATION (멸균 방법에 따른 교정용 플라이어의 물성 변화에 대한 비교 연구)

  • Cho, Il-Je;Son, Woo-Sung
    • The korean journal of orthodontics
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    • v.28 no.2 s.67
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    • pp.329-341
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    • 1998
  • Sterilization has received much attention in orthodontic practices over the past several years. The present study was undertaken to investigate the effects of sterilization on the physical properties of orthodontic pliers-AEZ, Unitek, and Dentronix ligature cutters. This study was designed to examine the tips of ligature cutters before and after 200 and 400 sterilization cycles using the Bowmar RHT-1000, the Dentronix DDS-5000, and the Eschmann SES-2000. The tip surface and the fracture surface were observed with a scanning electron microscope. The microstructure was observed with an optical microscope. The hardness test was carried out with the mic개-Vickers hardness tester and the Rockwell C Scale hardness tester. The chemical composition was analyzed by energy dispersive X-ray spectrometer. The results of this study were as follows : 1. The number and the size of corrosion products on the tip surface and the proportion of cleavage planes in fractured specimen increased, but the hardness of the tip decreased in proportion to sterilization cycles. From these observations, it was considered that mechanical properities decreased in proportion to sterilization cycles. 2. The number and the size of chromium carbides increased in proportion to sterilization cycles. Coarse microstructure decreased mechanical properities. 3. The AEZ and Unitek ligature cutters were Fe-Cr stainless steels, but the Dentronix ligature cutter was Co-Cr alloy. There were many differences among manufactures, but the chemical composition was .not changed after sterilization cycles. 4. The tip edge of ligature cutter used in a clinic revealed microcracks with the SEM observation. Clinical experience confirmed that ligature cutters were gradually degraded by sterilization.

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Microstructure of Co-base superalloy prepared by a investment casting (정밀주조법으로 제조된 Co계 초내열 합금의 미세구조)

  • Lee, Jung-Il;Lee, Ho Jun;Cho, Hyun Su;Paeng, Jong Min;Park, Jong Bum;Ryu, Jeong Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.27 no.6
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    • pp.313-318
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    • 2017
  • The microstructure of a cobalt-base superalloy (ECY768) obtained by an investment casting process was studied. This work focuses on the resulting microstructures arising from different melt and mold temperatures in normal industrial environmental conditions. The characterization of the samples was carried out using optical microscopy, field emission scanning electron microscopy and energy-dispersive spectroscopy. In this study, the as-cast microstructure is an ${\alpha}-Co$ (face-centered cubic) dendritic matrix with the presence of a secondary phase, such as $M_{23}C_6-type$ carbides precipitated at grain boundaries. These precipitates are the main strengthening mechanism in this type of alloy. Other minority phases, such as the MC-type phase, was also detected and their presence could be linked to the manufacturing process and environment.

Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.302-303
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    • 2010
  • Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

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