• Korean Journal of Metals and Materials
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• v.46 no.2
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• pp.65-68
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• 2008

Generally CCM (cold crucible melting) is not suitable for melting glass. However, in this study we described the quantitative relationship between the basic property of glass and power balance, the power absorption in the melt, the losses in the coil and the cold crucible, for melting glass in CCM. The dependence of power balance on the applied frequency and the electric conductivity has been found. Above 300 kHz, the glass (B) contained alkali ion which has the low resistance $3.0{\Omega}{\cdot}cm$ at $900^{\circ}C$ and $1.36{\Omega}{\cdot}cm$ at $1,100^{\circ}C$ was melted easily and 60% of the overall power was absorbed in the melt and 30% and 10% of the overall power was lost in the cold crucible and coil respectively. Under the same condition, the glass (A) contained non-alkali ion was not melted easily and 50% of the overall power was absorbed in the melt and 40% and 10% of the overall power was lost in the cold crucible and coil respectively. In conclusion, the small absorbed power of the overall power in melt prevented a successful melting as for glass A, and the successful melting depends on the relative size of the absorbed power in melt irrespective of the melting volume. Hence, as typical for direct induction heating method(CCM), the successful melting strongly depended on the chosen working frequency based on electric conductivity of glass, power balance and the control of the critical power which was absorbed in melt.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.402-405
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• 2005

부양용해 기술은 티타늄등 용해 및 주조에 어려움이 있는 기능성 금속의 용해 시 소재의 오염이나 고가의 도가니 없이 용해할 수 있는 기술로써 기계 부품 경량화 및 고강도를 위한 기술 및 신수요 창출을 위한 기반을 제공할 수 있다. 본 논문은 실기용 부양용해 cold crucible의 설계 및 제작에 앞서 실기 제작할 cold crucible에 대한 기초 자료를 바탕으로 컴퓨터 시뮬레이션을 위한 부양체를 포함한 3차원 전자기장 해석 model을 구축하여, 실제 cold crucible 설계 제작 시 다양한 형태로 활용될 수 있는 기본자료를 확보하는데 그 목적이 있다.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.885-887
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• 2003

부양용해 기술은 티타늄등 용해 및 주조에 어려움이 있는 기능성 금속의 용해 시 소재의 오염이나 고가의 도가니 없이 용해할 수 있는 기술로써 기계 부품 경량화 및 고강도를 위한 기술 및 신수요 창출을 위한 기반을 제공할 수 있다. 본 논문은 실기용 부양용해 cold crucible의 설계 및 제작에 앞서 모사 cold crucible에 대한 기초 자료를 바탕으로 컴퓨터 시뮬레이션을 위한 3차원 전자기장 해석 model을 구축하여, 모사 모델과의 측정값과 전자장 해석결과를 비교하여, 실제 cold crucible 설계 제작시 다양한 형태로 활용될 수 있는 기본자료를 확보하는데 그 목적이 있다.

• Journal of Korea Foundry Society
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• v.25 no.3
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• pp.115-122
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• 2005

In the present study, an EMC (Electromagnetic Casting) process, using a segmented Cu cold crucible under a high frequency alternating magnetic field of 20 kHz, was practiced for the fabrication of poly-crystalline Si ingot of 50 mm diameter. The effects of Joule heating and electromagnetic pressure in molten Si were systematically investigated with various processing parameters such as electric current and crucible configuration. A preliminary experimental work was initiated with the pure Al system for the establishment of a stabilized non-contact working condition, and further adapted to the semiconductor-off-grade Si system. A commercialized software such as Opera-3D was utilized in order to simulate electromagnetic pressure and Joule heating. In order to evaluate the meniscus shape of the molten melts, shape parameter was used throughout the research. A segmented graphite crucible, which was attached at the upper part of the cold crucible, was introduced to enhance significantly the heating efficiency of Si melt keeping non-contact condition during continuous melting and casting processes.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1206-1212
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• 2022

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.1
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• pp.24-31
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• 2019

The current study demonstrates an efficient procedure to create ingots from $Al_2O_3$ powder using the skull melting method to use these ingots as a starting material in conventional methods for growing synthetic single-crystal sapphire. Dimension of the cold crucible was 24 cm in inner diameter and 30 cm in inner height, 15 kg of $Al_2O_3$ powder was completely melted within 1 h at an oscillation frequency of 2.75 MHz, maintained in the molten state for 3 h, and finally air-cooled. The areal density and components of the cooled ingot by parts were analyzed through scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The areal density and $Al_2O_3$ content of the ingot were related to the temperature distribution inside the cold crucible during high-frequency induction heating, and the area with high temperature was high tends to be high in areal density and purity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.4
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• pp.141-148
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• 2006

Skull melting method can be a good candidate for growing oxide single crystals with high quality and for mass production because of its low production costs and high yield through recycling of crust. In this study, rutile single crystals were frown by the skull melting method and ingot characteristics with the variation of different growth conditions has been investigated. Conditions for high quality rutile ingot growth were used for producing cold-crucible size of ${\Phi}12cm{\times}H14cm$, capacity of 3000 pF tank condenser, work frequency of 2.84 MHz, melt-dwelling time of 9hrs and growing speed of 2 mm/h.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.226.2-226
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• 2001

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.4
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• pp.190-195
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• 2009

Na-tetrasilicic fluorine mica powders were synthesized by skull melting method. The staring materials having chemical composition of $Mg_3(OH)_2Si_4O_{10}:Na_2SiF_6:SiO_2=8.3:24.8:66.9$ mol% were charged into a cold crucible of 13 cm in diameter and 14cm in height and heated by R.F. generator at working frequency of 2.84 MHz. The materials were maintained for 1hr as a molten state and cooled down in the container. In this study, the specific electric resistance of mica was estimated and the columnar and plate shaped mica were synthesized.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.5
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• pp.175-181
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• 2005

Ingots of rutile single crystals were grown by the skull melting method, and their characteristics were compared in terms of melt-dwelling time for each melt. The method is based on direct inductive heating of an electrically conducted melt by an alternating RF field, and the heating is performed by absorption of RF energy. $TiO_2$ is an insulator at room temperature but its electric conductivity increases elevated temperature. Therefore, titanium metal ring(outside diameter : 6cm, inside diameter : 4cm, thickness 0.2cm) was embedded into $TiO_2$, powder (anatase phase, CERAC, 3N) for initial RF induction heating. Important factors of the skull melting method are electric resistivity of materials at their melting point, working frequency of RF generator and cold crucible size. In this study, electric resitivity of $TiO_2$, $(10^{-2}\~10^{-1}\;{\Omega}{\cdot}m)$ at its melting point was estimated by compairing the electric resitivities of alumina and zirconia. Inner diameter and height of the cold crucible was 11 and 14cm, respectively, which were determined by considering of the Penetration depth $(0.36\~1.13cm)$ and the frequency of RF generator.