• Title/Summary/Keyword: molten salt

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Formation Process of Barium Ferrite Crystallites in Molten Salts and its Magnetic properties (용융염내에서의 Ba-ferrite 결정의 생성과정 및 그 자기적 특성)

  • 정지형;김창곤;윤석영;신학기;김태옥
    • Journal of the Korean Ceramic Society
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    • v.38 no.11
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    • pp.1015-1022
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    • 2001
  • In this study, formation process of Ba-ferrite by using molten salt synthesis and its magnetic properties were investigated. Among starting materials, BaC $O_3$was only soluble in the molten salts, but other starting material such as $\delta$-FeOOH or F $e_2$ $O_3$was not soluble even at 105$0^{\circ}C$. It implies that the dissolved $Ba^{2+}$ diffused on surfaces of F $e_2$ $O_3$(or $\delta$-FeOOH), therefore, Ba-ferrtites were formed through surface reaction. However, the magnetic properties of Ba-ferrite prepared by two starting materials (F $e_2$ $O_3$and $\delta$-FeOOH) were not different. On the other hand, compared $\delta$-FeOOH with F $e_2$ $O_3$m, morphologies and dispersibility of Ba-ferrites prepared by using $\delta$-FeOOH were good and Ba-ferrites were obtaioned at lower temperature.

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A Study on the Corrosion Behavior of Fe-Ni-Cr Alloys in Molten Salts of LiCl and LiCl-${Li_2}O$ (LiCl 및 LiCl-${Li_2}O$ 용융염에서 Fe-Ni-Cr 합금의 부식거동 연구)

  • Jo, Su-Haeng;Jang, Jun-Seon;Hong, Sun-Seon;Sin, Yeong-Jun;Park, Hyeon-Su
    • Korean Journal of Materials Research
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    • v.10 no.7
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    • pp.471-477
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    • 2000
  • Corrosion behavior of Fe-Ni-Cr alloy in molten salts of LiCl and LiCl-$Li_2O was investigated in the tempera-ture range of $650~850^{\circ}C$. In the molten salt of LiCl, and internal oxidation of Fe occurred in the KSA(Kaeri Superalloy)-1 alloy without containing Cr, while a dense protective oxide scale of $LiCrO_2$ was formed in the KSA-4, Incoloy 800H and KSA-5 alloys. In the mixed molten salt of LiCl-$Li_2O$, internal oxidation of Fe and Cr took place in the KSA-1 and KSA-4 alloys, respectively. Non-protective porous oxide scales consisting of $LiCrO_2$ and Ni were formed in the Incoloy 800H and KSA-5. The corrosion rate of the alloys increased with the increase in Cr content and the corrosion rate followed the parabolic law for the alloy containing Cr content less than 8%, and the linear law for the alloy containing Cr content more than 8%. Such a corrosion behavior of the alloy in the mixed molten salt of LiCl-$Li_2O$ was interpreted in terms of the basic fluxing mechanism of protective oxide scale of $Cr_2O_3$.

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Thermal dehydration tests of FLiNaK salt for thermal-hydraulic experiments

  • Shuai Che;Sheng Zhang;Adam Burak;Xiaodong Sun
    • Nuclear Engineering and Technology
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    • v.56 no.3
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    • pp.1091-1099
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    • 2024
  • Fluoride-salt-cooled High-temperature Reactor (FHR) is a promising nuclear reactor technology. Among many challenges presented by the molten fluoride salts is the corrosion of salt-facing structural components. Higher moisture contents, in the FLiNaK (LiF-NaF-KF, 46.5-11.5-42 mol%) salt, aggravate intergranular corrosion and pitting for the given alloys. Therefore, several thermal dehydration tests of FLiNaK salt were performed with a batch size suitable for thermal-hydraulic experiments. Thermogravimetric Analysis (TGA) was performed for the three constituent fluoride salts individually. Preliminary thermal dehydration plans were then proposed for NaF and KF salts based on the TGA curves. However, the dehydration process may not be required for LiF since its low mass loss (<1.3 wt%). To evaluate the performance of these thermal dehydration plans, a batch-scale salt dehydration test facility was designed and constructed. The preliminary thermal dehydration plans were tested by varying the heating rates, target temperature, and holding time. The sample mass loss data showed that the high temperatures (>500 ℃) were necessary to remove a significant amount of moisture (>1 wt%) from NaF salt, while relatively low temperatures (around 300 ℃) with a long holding time (>10 h) were sufficient to remove most of the moisture from KF salt.

ELECTRICAL BREAKDOWN INITIATION OF ANODIC FILMS DURING ANODIZING IN MOLTEN BISULPHATE MELT

  • Han, S.H.;Thompson, G.E.
    • Journal of the Korean institute of surface engineering
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    • v.32 no.3
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    • pp.341-343
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    • 1999
  • The morphology and composition of anodic films, formed on aluminium at various current densities, in the range $1-100{\;}Am^{-2}$, in the molten bisulphate melt at different temperatures (418-498K), have been studied using transmission electron microscopy of ultramicrotomed film sections, and ion beam thinned films. The first sign of incipient breakdown revealed by transmission electron microscopy of stripped films, is always the appearance of dark regions about 1,000 nm in diameter, representing local overgrowth of the film. The breakdown mechanism is closely related to thermal effects, because temperature rises at regions representing local overgrowth in the stripped films were observed at voltages close to the breakdown voltage, likely arising through impact ionization.

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A Study on the Glass Strengthened in Salt Solution by Chemical Ion Exchange (염 용액에서의 화학적 이온교환 강화유리에 관한 연구)

  • 이종근;김인섭
    • Journal of the Korean Ceramic Society
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    • v.24 no.4
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    • pp.335-342
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    • 1987
  • There were several numbers of studies on chemically strengthening glass. Most of them were strengthened in molten salt bath below transformation range of glass. Apart from them, this study used solution hydration technique by Autoclave. After determining proper concentration of AgNO3 salt solution, experimental condition varied from 4hrs to 16hrs at relatively low temperature (180, 200, 220$^{\circ}C$). The results showed that the Soda-Lime-Silica glass could be strengthened by diffusion mechanism without influence of water above 15% salt solution. Because of Ag+ ion penetration in glass surface, yellow color appeared and decreased transmittance at visible range. Modulus of rupture was increased with the amount of exchange and brittleness was decreased.

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Effects of Salt Flux and Alloying Elements on the Coalescence Behaviour of Aluminum Droplets (알루미늄 Droplets 합체거동에 미치는 Salt Flux 및 합금원소 첨가의 영향)

  • Kim, Ye-Sik;Yoon, Eui-Pak;Kim, Ki-Tae;Jung, Woon-Jae;Jo, Duk-Ho
    • Journal of Korea Foundry Society
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    • v.20 no.1
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    • pp.38-45
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    • 2000
  • The remelting for recycling or thin aluminum scrap, such as aluminum chip generally involves melting of these pieces submerged in molten salt flux. In this study, the effects of salt flux compositions and alloying elements on the aluminum dropletscoalescence and oxide film removal were studied in 99.8%Al, Al-1.01%Cu, Al-1.03%Si, and Al-1.38%Mg alloys as a function of holding time at $740^{\circ}C$ Salt fluxes based on NaCl-KCl(1:1) with addition of 5wt.% fluorides(NaF, $Na_3AlF_6$, $CaF_2$) or 5 wt.% chloride($MgCl_2$, $AlCl_3$) were used. The experimental results show that NaCl-KCl(1:1) with addition of 5 wt.% fluorides exhibits better coalescence ability than that with chlorides. The oxide film is not removed by NaCl-KCl(1:1) with addition of 5 wt.%chlorides, while it is removed by NaCl-KCl(1:1) with addition of 5 wt.% fluorides. The aluminum droplets coalescence and oxide film removal by salt fluxes are related to interfacial tension tension between metal and salt flux.

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