• 대한기계학회논문집B
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• 제38권8호
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• pp.695-700
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• 2014

본 논문에서는 수정된 증발법을 이용하여 제작된 주석(Sn) 나노입자의 녹는점 강하 특성에 대한 연구를 진행하였다. 이를 위해 대량생산이 가능한 수정된 증발법을 이용하여 10nm 급 주석 나노입자를 제조하였다. 주석 나노입자 표면의 산화 방지를 위하여 Benzyl Alcohol 을 기본유체로 사용하였으며, 제작된 주석 나노입자의 형상과 입자크기를 알아보기 위하여 투과전자현미경(TEM)을 사용하였다. 제작된 나노입자의 녹는점은 시차주사열량계(DSC)를 통해 측정하였으며, 광전자분광분석기(XPS)를 사용하여 제작된 주석 나노입자의 성분 분석을 진행 하였다. 주석 나노입자의 녹는점은 주석의 녹는점인 $232^{\circ}C$보다 44% 감소한 $129^{\circ}C$로 측정되었다. 녹는점 측정 결과는 Gibbs-Thomson 식 및 Lai 의 식과 비교하였으며, 그 결과 Lai의 식이 실험결과를 잘 예측함을 확인할 수 있었다.

• 한국생활과학회지
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• 제12권4호
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• pp.529-537
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• 2003

This study was conducted to manufacture the soluble micro-fiber and to synthesize low melting polymer for the interior fabric not to use the polyurethane resin causing some problems. Low melting polyester for weft yarn was introduced by adding 30-40 mol% ratio of isophthalic acid to a main chain of polyethylene terephthalate to decrease the melting temperature up to heat setting temperature. Micro-fiber for warp yarn consisted of both soluble and insoluble components with multi-layered structure. When the soluble micro-fiber was treated by alkaline hydrolysis with 3-5% concentration of NaOH, it showed the turning point at 28% weight loss since soluble polyester was hydrolyzed approximate five times faster than regular polyester.

• 설비공학논문집
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• 제2권3호
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• pp.208-217
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• 1990

A rectangular test section is devised by assuming two dimensional melting of a solid phase change material heated from two sides which are maintained at constant temperature and allowing a free expansion due to density difference between solid and liquid. The timewise melting shape is recorded photographically by the shadow graph method for several experimental conditions. The analysis shows that the melting process consists of four regimes. At first, the pure conduction heat transfer is dominant, and as time goes by natural convection grows and plays a role greatly. Experiments are carried out varying not only the wall temperature but height of the wall. Each effect of them on the melting process is obtained in the form of combination of dimensionless parameters, $Ste^{0.8}\;FoRa^{0.2}$. An algebraic correlation is suggested, which predicts the melted fraction well.

• 대한설비공학회지:설비저널
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• 제15권2호
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• pp.196-203
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• 1986

The melting phenomena of horizontal cylindrical ice-bar immersed in water and air concentrically in the cylinder are experimentally investigated for the temperature range from $3.5^{\circ}C\;to\;2.5^{\circ}C$. The shapes of the melting ice-bar are recorded photographically by the shadowgraph method. The shadowgraphs of the melting ice-bar show that water adjacent to the bar flows upward for the temperature range from $3.5^{\circ}C\;to\;5.8^{\circ}C$ while above $5.8^|\circ}C$ the flow is downward direction. The local and average Nusselt numbers are obtoined with the recorded shadowgraphs and comparator. Melting shapes of the ice-bar in the air show the vortex motion in the bottom portion of the bar, whereas no vortex motion appears in the bottom portion when the bar is melted in the water.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.448-456
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• 2016

Severe accident scenarios in nuclear reactors, such as nuclear meltdown, reveal that an extremely hot molten core may fall into the nuclear reactor cavity and seriously affect the safety of the nuclear containment vessel due to the chain reaction caused by the reaction between the molten core and concrete. This paper reports on research focused on the type and amount of vapor produced during the reaction between a high-temperature molten core and concrete, as well as on the erosion rate of concrete and the heat transfer characteristics at its vicinity. This study identifies themass fraction and melting temperature as the most influential properties of concrete necessary for a safety analysis conducted in relation to the thermal interaction between the molten core and the basemat concrete. The types of concrete that are actually used in nuclear reactor cavities were investigated. The $H_2O$ content in concrete required for the computation of the relative amount of gases generated by the chemical reaction of the vapor, the quantity of $CO_2$ necessary for computing the cooling speed of the molten core, and the melting temperature of concrete are evaluated experimentally for the molten core-concrete interaction analysis.

• 한국염색가공학회지
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• 제21권3호
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• pp.37-42
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• 2009

The low melting PET yarn has sheath/core structure: sheath portion consists of low melting point PET and core portion is regular PET. Dyeing properties of fabric made from low melting PET yarn were investigated at different dyeing temperatures. It was found that the exhaustion yield on the low melting PET fabric was higher than on regular PET fabric. The total K/S value of the dyed low melting PET fabric increased as heat setting temperature increased above $150^{\circ}C$ because the sheath portion of the low melting yarn melted. Although fastness to light of the low melting PET fabric was similar to regular PET fabric, fastness to washing was inferior to regular PET fabric by 1 grade.

• 대한기계학회논문집B
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• 제22권12호
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• pp.1726-1734
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• 1998

This paper focuses on the unsteady close-contact melting phenomenon occurring between a phase change material kept at its melting temperature and a flat surface on which constant heat flux is imposed. Based on the same simplifications and framework of analysis as the case of constant surface temperature, an approximate analytical solution which depends only on the liquid-to-solid density ratio is successfully derived. In order to keep consistency with the known solution procedure, both the dimensionless wall heat flux and the Stefan number are properly redefined. The obtained solution proves to agree quite well with the published numerical data and to be capable of resolving the fundamental features of unsteady close-contact melting, especially in the presence of the solid-liquid density difference. The density ratio directly affects the film growth rate and the initial value of solid descending velocity, thereby controlling the duration of unsteady process. The effects of other parameters can be evaluated readily from the steady solution which is implied in the normalized result. Since the dimensionless surface temperature for the present boundary condition increases from zero to unity along the evolution path of the liquid film thickness, the unsteady process lasts longer than that for the case of isothermal heating.

• 한국염색가공학회지
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• 제24권2호
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• pp.113-120
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• 2012

Jacquard floor covering could be prepared from low-melting/regular sheath-core hybrid polyester, where the fiber is dyed in yarn state. With regard that the expected high shrinkage of the hybrid polyester in water makes problems in yarn dyeing, low-temperature dyeing properties of the hybrid polyester were studied. The rate of shrinkage of low-melting hybrid polyester exceeds 9% in hot water above $90^{\circ}C$, at such condition, cheese yarn dyeing is very difficult. Although disperse dyes exhaust in a relatively high speed on low-melting hybrid polyester, diffusion of these dyes to the core regular polyester was extremely slow under $90^{\circ}C$. Foron Blue E-BL 150, an anthraquinone E-type disperse dye, showed appreciable diffusion after 48hrs dyeing at $90^{\circ}C$. The fastness to rubbing and drycleaning were improved by one grade after reduction cleaning.

• 열처리공학회지
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• 제35권1호
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• pp.1-7
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• 2022

In this study, dissolution and melting phenomenon of the Al₂Cu was studied for the high-strength Al-Si-Cu aluminum alloy in automobile component. The Solution heat treatment was performed at 480℃ and 510℃ for 4hours. Microstructure analysis of the specimen was performed using the optical micrograph and scanning electron microscope for qualitative and quantitative analysis of various phases, the chemical composition of secondary phases was achieved by energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA). As a result of the electron probe micro analysis, a plate like Al₂Cu phase was observed, and eutectic Si phase was observed of a coarsen plate shape. At a temperature of 510, necking phenomenon occurs in a specific part of plate like Al₂Cu, and it is segmented and dissolved in the Al matrix. When the temperature of the alloy exceeds the melting point of Al₂Cu, incipient melting occurs at the grain boundary of undissolved Cu particles

• 센서학회지
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• 제18권1호
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• pp.86-94
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• 2009

Temperature measurement capability was inter-compared using the transfer standard platinum resistance thermometers(SPRT) among four laboratories of KRISS. The transfer SPRTs were primarily calibrated at the triple point of water and Ga melting point, then used at inter-comparison experiment. Temperature difference of calibration value between temperature laboratory and length laboratory at $20^{\circ}C$ was -0.7 mK and +2.4 mK at density laboratory. Temperature measured near $20^{\circ}C$, $25^{\circ}C$ and $30^{\circ}C$ at fluid flow laboratory was deviated by $34.2{\sim}80.4\;mK$ from the calibration values of the transfer SPRT. Ga melting points was inter-compared among three laboratories, and the difference of Ga melting points against the standard Ga melting point of temperature laboratory were $0.03{\sim}0.54\;mK$ at length laboratory and 0.02 mK at density laboratory.