• Title/Summary/Keyword: 금속 합금

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Effect of Ice-Quenching After Degassing on the Hardness Change During Simulated Porcelain Firing in a Metal-Ceramic Pd-Au-Ag Alloy (Pd-Au-Ag계 금속-도재용 합금의 탈가스 처리 후 급냉 처리가 모의소성과정에서 경도변화에 미치는 영향)

  • Kim, Sung-Min;Shin, Hye-Jung;Kwon, Yong-Hoon;Kim, Hyung-Il;Seol, Hyo-Joung
    • Korean Journal of Dental Materials
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    • v.43 no.4
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    • pp.317-322
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    • 2016
  • The effect of ice-quenching after degassing on the hardness change during simulated porcelain firing in a metal-ceramic Pd-Au-Ag alloy was investigated by means of hardness test, field emission scanning electron microscopic observations, and X-ray diffraction analysis. The hardness decreased by ice-quenching after degassing, which was induced by the homogenization of the ice-quenched specimen. The decreased hardness by ice-quenching after degassing was recovered from the 1st opaque stage which was the first stage of the remaining firing process for bonding porcelain. The microstructural change showed that the increase in hardness during the remaining firing process was caused by precipitation. The ice-quenching after degassing did not affect the hardness change during the subsequent porcelain firing process.

Research Trend on Conversion Reaction Anodes for Sodium-ion Batteries (나트륨이차전지용 전환반응 음극 소재 기술 동향)

  • Kim, Suji;Kim, You Jin;Ryu, Won-Hee
    • Journal of the Korean Electrochemical Society
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    • v.22 no.1
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    • pp.22-35
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    • 2019
  • Development of low cost rechargeable batteries has been considered as a significant task for future large-scale energy storage units (i.e. electric vehicles, smart grids). Sodium-ion batteries (SIBs) have been recognized as a promising alternative to replace conventional lithium-ion batteries (LIBs) because of their abundancy and economic benign. Nevertheless, Na ions have larger ionic radius than that of Li ions, resulting in sluggish transport of Na ions in electrodes for cell operation. There have been efforts to seek suitable anode materials for the past years operated based on three different kinds of reaction mechanism (intercalation, alloy reaction, and conversion reaction). In this review, we introduce a class of conversion reaction anode materials for Na-ion batteries, which have been reported.

Investigation on Size Distribution of Tungsten-based Alloy Particles with Solvent Viscosity During Ultrasonic Ball Milling Process (초음파 볼밀링 공정에 의한 용매 점도 특성에 따른 텅스텐계 합금 분쇄 거동)

  • Ryu, KeunHyuk;So, HyeongSub;Yun, JiSeok;Kim, InHo;Lee, Kun-Jae
    • Journal of Powder Materials
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    • v.26 no.3
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    • pp.201-207
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    • 2019
  • Tungsten heavy alloys (W-Ni-Fe) play an important role in various industries because of their excellent mechanical properties, such as the excellent hardness of tungsten, low thermal expansion, corrosion resistance of nickel, and ductility of iron. In tungsten heavy alloys, tungsten nanoparticles allow the relatively low-temperature molding of high-melting-point tungsten and can improve densification. In this study, to improve the densification of tungsten heavy alloy, nanoparticles are manufactured by ultrasonic milling of metal oxide. The physical properties of the metal oxide and the solvent viscosity are selected as the main parameters. When the density is low and the Mohs hardness is high, the particle size distribution is relatively high. When the density is high and the Mohs hardness is low, the particle size distribution is relatively low. Additionally, the average particle size tends to decrease with increasing viscosity. Metal oxides prepared by ultrasonic milling in high-viscosity solvent show an average particle size of less than 300 nm based on the dynamic light scattering and scanning electron microscopy analysis. The effects of the physical properties of the metal oxide and the solvent viscosity on the pulverization are analyzed experimentally.

Morphology and Characteristics of Corrosion of Archaeological Bronzes (출토 청동유물 부식의 형태학적 고찰 및 부식생성물의 특성 연구)

  • Lee, Eun-woo;Kim, So-jin;Han, Woo-rim;Hwang, Jin-ju;Han, Min-Su
    • Korean Journal of Heritage: History & Science
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    • v.46 no.3
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    • pp.4-15
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    • 2013
  • The study of corrosion products generated by archaeological bronzes that have been buried for a long time can provide certain evidence that enables us to understand the natural corrosion process of bronze and helps us develop conservation and preservation methods. In the present study, the specimens taken from two bronze mirrors and three bronze swords were used to study the corrosion morphology and the related phenomena such as selective corrosion of ${\alpha}$ or ${\alpha}+{\delta}$ phases, decuprification, destannification, and secondary copper. Furthermore, corrosion development was discussed based on the ions distributed throughout the corrosion layers.

Study on Tensile Properties of AlSi10Mg produced by Selective Laser Melting (SLM 공정 기법으로 제작한 AlSi10Mg 인장특성에 관한 연구)

  • Kim, Moosun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.12
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    • pp.25-31
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    • 2018
  • Selective Laser Melting is one of the representative 3D printing techniques for handling metal materials. The main factors influencing the characteristics of structures fabricated by the SLM method include the build-up angle of structures, laser power, laser scan speed, and scan spacing. In this study, the tensile properties of AlSi10Mg alloys were investigated by considering the build-up angle of tensile test specimens, laser scanning speed and scan spacing as variables. The yield stress, tensile strength, and elongation were considered as tensile properties. From the test results, it was confirmed that the yield stress values were lowered in the order of 0, 45, and 90 based on the manufacturing direction of the tensile specimen. The maximum yield stress value was obtained at 1870 mm / min based on the laser scan speed. The yield stress size decreased with decreasing scan speed. Based on the laser scan spacing, as the value increases, the yield stress increases, but the variation is smaller than the other test criteria. The tendency of the tensile strength and elongation variation depending on the test conditions was difficult to understand.

Interfacial Properties of Friction-Welded TiAl and SCM440 Alloys with Cu as Insert Metal (삽입금속 Cu를 이용한 TiAl 합금과 SCM440의 마찰용접 계면 특성)

  • Park, Sung-Hyun;Kim, Ki-Young;Park, Jong-Moon;Choi, In-Chul;Ito, Kazuhiro;Oh, Myung-Hoon
    • Korean Journal of Materials Research
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    • v.29 no.4
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    • pp.258-263
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    • 2019
  • Since the directly bonded interface between TiAl alloy and SCM440 includes lots of cracks and generated intermetallic compounds(IMCs) such as TiC, FeTi, and $Fe_2Ti$, the interfacial strength can be significantly reduced. Therefore, in this study, Cu is selected as an insert metal to improve the lower tensile strength of the joint between TiAl alloy and SCM440 during friction welding. As a result, newly formed IMCs, such as $Cu_2TiAl$, CuTiAl, and $TiCu_2$, are found at the interface between TiAl alloy and Cu layer and the thickness of IMCs layers is found to vary with friction time. In addition, to determine the relationship between the thickness of the IMCs and the strength of the welded interfaces, a tensile test was performed using sub-size specimens obtained from the center to the peripheral region of the friction-welded interface. The results are discussed in terms of changes in the IMCs and the underlying deformation mechanism. Finally, it is found that the friction welding process needs to be idealized because IMCs generated between TiAl alloy and Cu act to not only increase the bonding strength but also form an easy path of fracture propagation.

Formation of Anodic Al Oxide Nanofibers on Al3104 Alloy Substrate in Pyrophosphoric Acid (피로인산 전해질에서 양극산화를 통한 알루미늄 3104 합금 나노섬유 산화물 형성)

  • Kim, Taewan;Lee, Kiyoung
    • Journal of the Korean Electrochemical Society
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    • v.24 no.1
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    • pp.7-12
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    • 2021
  • In this study, we investigated the formation of the metal oxide nanostructure by anodization of aluminum 3104H18 alloy. The anodization was performed in pyrophosphoric acid (H4P2O7) electrolyte. By the control of anodization condition such as concentration of electrolyte, anodization temperature and applied voltage, nanoporous or nanofiber structures were obtained. The optimal anodization condition to form nanofiber structures are 75 wt% of H4P2O7 at 30 V and 20℃. When anodization was performed at over 40 V, nanoporous structures were formed due to accelerated dissolution reaction rate of nanofiber structures or increasing thickness of channel wall.

Properties of double-layered anodizing films on Al alloys formed by two consecutive anodizings (알루미늄 합금의 연속식 양극산화법으로 형성시킨 이중 산화막층의 특성)

  • Jeong, Nagyeom;Choi, Jinsub
    • Journal of the Korean institute of surface engineering
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    • v.54 no.1
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    • pp.30-36
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    • 2021
  • In this study, double-layered anodizing films were formed on Al 5052 and Al 6061 alloys consecutively first in sulfuric acid and then in oxalic acid, and hardness, withstand voltage, surface roughness and acid resistance of the anodizing films were compared with single-layered anodizing films in sulfuric acid and oxalic acid electrolytes. Hardness of the double-layered anodizing film decreased with increasing ratio of inner layer to outer layer for both Al 5052 and Al 6061 alloys, suggesting that outer anodizing film formed in sulfuric acid electrolyte is damaged during the second anodizing in oxalic acid electrolyte. Withstand voltage of the double-layered anodizing films increased with increasing the thickness ratio of inner layer to outer layer. Surface roughness of the double-layered anodizing films were comparable with that of single-layered anodizing film formed in sulfuric acid but higher than that of single layer anodizing film formed in oxalic acid electrolyte. In acid resistance test, all of the double-layered and single-layered anodizing films showed good acid resistance more than 3 h without any visible gas evolution, which is attributable to sealing of pores. Based on the experimental results obtained in this work, it is possible to design a double-layered anodizing film with cost-effectiveness and improved physical and electrical properties by combining two consecutive anodizing processes of sulfuric acid anodizing and oxalic acid anodizing methods.

Measurement Method of Prior Austenite Grain Size of Nb-added Fe-based Alloys (Nb 첨가 철계 합금의 Prior austenite 결정립크기 측정 방법)

  • Ko, Kwang Kyu;Bae, Hyo Ju;Jung, Sin Woo;Sung, Hyo Kyung;Kim, Jung Gi;Seol, Jae Bok
    • Journal of Powder Materials
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    • v.28 no.4
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    • pp.317-324
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    • 2021
  • High-strength low-alloy (HSLA) steels show excellent toughness when trace amounts of transition elements are added. In steels, prior austenite grain size (PAGS), which is often determined by the number of added elements, is a critical factor in determining the mechanical properties of the material. In this study, we used two etching methods to measure and compare the PAGS of specimens with bainitic HSLA steels having different Nb contents These two methods were nital etching and picric acid etching. Both methods confirmed that the sample with high Nb content exhibited smaller PAGS than its low Nb counterpart because of Nb's ability to hinder austenite recrystallization at high temperatures. Although both etching approaches are beneficial to PAGS estimation, the picric acid etching method has the advantage of enabling observation of the interface containing Nb precipitate. By contrast, the nital etching method has the advantage of a very short etching time (5 s) in determining the PAGS, with the picric acid etching method being considerably longer (5 h).

A Review of SiCf/SiC Composite to Improve Accident-Tolerance of Light Water Nuclear Reactors (원자력 사고 안전성 향상을 위한 SiCf/SiC 복합소재 개발 동향)

  • Kim, Daejong;Lee, Jisu;Chun, Young Bum;Lee, Hyeon-Geun;Park, Ji Yeon;Kim, Weon-Ju
    • Composites Research
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    • v.35 no.3
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    • pp.161-174
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    • 2022
  • SiC fiber-reinforced SiC matrix composite is a promising accident-tolerant fuel cladding material to improve the safety of light water nuclear reactors. Compared to the current zirconium alloy fuel cladding as well as metallic accident-tolerant fuel cladding, SiC composite fuel cladding has exceptional accident-tolerance such as excellent structural integrity and extremely low corrosion rate during severe accident of light water nuclear reactors, which reduces reactor core temperature and delays core degradation processes. In this paper, we introduce the concept, technical issues, and properties of SiC composite accident-tolerant fuel cladding during operation and accident scenarios of light water nuclear reactors.