• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.597-598
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• 2011

• Progress in Superconductivity
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• 제3권1호
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• pp.5-12
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• 2001

Our experimental research focuses on manipulating pinning deflects to alter the phase diagram of vortex matter, creating new vortex phases. Vortex matter offers a unique opportunity for creating and studying these novel phase transitions through precise control of thermal, pinning and elastic energies. The vortex melting transition in untwinned YB $a_2$C $u_3$ $O_{7-}$ $\delta$/ crystals is investigated in the presence of disorder induced by particle irradiation. We focus on the low disorder regime, where a glassy state and a lattice state can be realized in the same phase diagram. We follow the evolution of the first order vortex melting transition line into a continuous transition line as disorder is increased by irradiation. The transformation is marked by an upward shift in the lower critical point on the melting line. With columnar deflects induced by heavy ion irradiation, we find a second order Bose glass transition line separating the vortex liquid from a Bose glass below the lower critical point. Furthermore, we find an upper threshold of columnar defect concentration beyond which the lower critical point and the first order melting line disappear together. With point deflect clusters induced by proton irradiation, we find evidence for a continuous thermodynamic transition below the lower critical point..

• 한국분말재료학회지
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• 제30권4호
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• pp.339-345
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• 2023

This study investigates the melting point and brazing properties of the aluminum (Al)-copper (Cu)-silicon (Si)-tin (Sn) alloy fabricated for low-temperature brazing based on the alloy design. Specifically, the Al-20Cu-10Si-Sn alloy is examined and confirmed to possess a melting point of approximately 520℃. Analysis of the melting point of the alloy based on composition reveals that the melting temperature tends to decrease with increasing Cu and Si content, along with a corresponding decrease as the Sn content rises. This study verifies that the Al-20Cu-10Si-5Sn alloy exhibits high liquidity and favorable mechanical properties for brazing through the joint gap filling test and Vickers hardness measurements. Additionally, a powder fabricated using the Al-20Cu-10Si-5Sn alloy demonstrates a melting point of around 515℃ following melting point analysis. Consequently, it is deemed highly suitable for use as a low-temperature Al brazing material.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.593-596
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• 2003

A proposed way to prepare $YBa_2Cu_3O_y$ wires or tapes is that Ag is used as substrate and melting point of $YBa_2Cu_3O_y$ is decreased to lower than the melting point of silver ($961\;^{\circ}C$). Therefore after the deposition of $YBa_2Cu_3O_y$ film on Ag substrate, the heat treatment can be carried out below the Ag melting point. Silver (Ag) and Lead oxide(PbO) were selected to be additives for $YBa_2Cu_3O_y$. Different Ag and PbO contents were added in $YBa_2Cu_3O_y$, the melting points of which were measured by DTA. In order to guarantee that the superconductivity of $YBa_2Cu_3O_y$ was not reduced after Ag and PbO added into $YBa_2Cu_3O_y$, their superconductivities were measured. It is proved that as additives, both Ag and PbO can reduce the melting point of $YBa_2Cu_3O_y$. For Ag doped $YBa_2Cu_3O_y$, $T_c$ is about 93K and ${\Delta}Tc$ is $2{\sim}3K$. For PbO doped $YBa_2Cu_3O_y$, $T_c$ is $88K{\sim}92K$ and ${\Delta}T_c$ is $11{\sim}12K$. When 10 wt% of Ag and 10 wt% PbO were added in $YBa_2Cu_3O_y$, the melting point of the mixture of $YBa_2Cu_3O_y$ (80 wt%), Ag (10 wt%) and PbO (l0 wt%) is $943^{\circ}C$. The transition temperatures ($T_c$) of the sample is 91.8 K.

• 한국세라믹학회지
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• 제15권2호
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• pp.72-78
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• 1978

The vapor pressure of the high melting point oxides, MgO, $Cr_2O_3$, and $MgCr_2O_4$ were measured over the temperature range 1300 to 175$0^{\circ}C$ under vacuum <$10^{-5}$ torr by the Langmuir and the Knudsen method. The Langmuir vapor pressure was increased with elevating temperature and with increasing porosity of the specimen. The difference between the vapor preseures measured by the Langmuir and the Knudsen method was decreased with elevating temperature and the Langmuir vapor pressure finally reached the Knudsen vapor pressure at the melting point when extrapolated. The vapor pressure of other important oxides with high melting points, i.e., $Al_2O_3$, $ThO_2$, $Yb_2O_3$ and $Y_2O_3$ were cited from the references. The Langmuir and the Knudsen vapor pressure of these oxides also showed the same results, i.e., they showed the same value at their melting points.

• 대한화학회지
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• 제46권3호
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• pp.252-264
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• 2002

이 연구는 끊는점과 녹는점에 관련된 실험 장치를 교육과정의 변화와 교과서의 유형에 따라 분석하고, 중등 과학교사들을 대상으로 이에 관련된 실험값과 교과서에 제시된 값이 다른 경우에 대한 인식을 조사하였다. 그리고 분별 증류, 온도계 보정의 실험 장치와 실 험 결과에 대한 인식도 조사하였다. 연구 결과, 교유고가정과 교과서의 종류에따라 끓는점과 녹는점에 관련된 실험 장치의 유형은 다양하게 변화되어 왔으며, 교사들의 인식도 전공과 근무 학교에 따라 다양하게 나타났다. 또한, 많은 교사들이 분별 증류 실험에서 실험값이 교과서에 제시된 값과 다른 원인을 교과서 내용의 잘못이나 실험 자체의 문제로 인식하고 있었다. 그리고 중학교에서 온도계 보정의 필요성에 대한 교사들의 인식은 다양하게 나타났는데, 화학을 전공한 교사들이 비화학 전공교사들보다 온도계 보정 필요성에 대한 인식이 더욱 높았다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권1호
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• pp.1-5
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• 2001

P(VDF/TrFE) copolymer thin films with 70/30 and 80/20 mol% VDF (polyvinylidene fluoride) and TrFE (trifluoroethylene) rates were prepared by using a vapor deposition method, During thin films were prepared, the substrate temperatures were maintained at 30 $^{\circ}C$ and 120 $^{\circ}C$, and the heating source temperature was fixed at 350 $^{\circ}C$. Contary to PVDF homopolymer, P(VDF/TrFE) copolymers showed the Curie point(Tc) below the melting point. The Curie point (Tc) and the melting point of the P(VDF/TrFE) copolymers were changed as a function of substrate temperature and the VDF mol%. The Curie point and the melting point of P(VDF/TreFE) thin films decreased and increased with increasing substrate temperature, respectively. Also with increasing VDF mol%, the melting point decreased slightly, however the Curie point increased.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.232-234
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• 2007

This study conducts numerical simulations of Isotropic conductive adhesives using low melting point alloy fillers during the reflow process. The CIP method and predictor-corrector method are used to simulate more accurately on free surface flow of low melting point alloy fillers. For finding out optical conditions to obtain reliable conduction paths, the present study conducts extensive numerical simulations.

• International Journal of Korean Welding Society
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• 제2권2호
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• pp.14-18
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• 2002

Titanium and titanium alloy are excellent in corrosion resistance and specific intensity, and also in the biocompatibility. On the other hand, the brazing is bonding method of which productivity and reliability are high, when the complicated and precise structure of the thin plate is constructed. However, though conventional titanium-based brazing filler metal was excellent in bond strength and corrosion resistance, it was disadvantageous that metal structure and mechanical property of the base metal deteriorated, since the brazing temperature ( about $1000^{\circ}C$ ) is considerably high. Authors developed new brazing filler metal which added Zr to Ti-Cu (-Ni) alloy which can be brazed at $900^{\circ}C$ or less about 15 years ago. In this paper, the development of more low-melting-point brazing filler metal was tried by the addition of the fourth elements such as Ni, Co, Cr for the Ti-Zr-Cu alloy. As a method for finding the low-melting-point composition, eutectic composition exploration method was used in order to reduce the experiment point. As the result, several kinds of new brazing filler metal such as 37.5Ti-37.5-Zr-25Cu alloy (melting point: $825^{\circ}C$) and 30Ti-43Zr-25Cu-2Cr alloy (melting point: $825^{\circ}C$) was developed. Then, the brazing joint showed the characteristics which were almost equal to the base metal from the result of obtaining metallic structure and strength of joint of brazing joint. However, the brazing filler metal composition of the melting point of $820^{\circ}C$ or less could not be found. Consequentially, it was clarified that the brazing filler metal developed in this study could be practically sufficiently used from results such as metal structure of brazing joint and tensile test of the joint.

• 설비공학논문집
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• 제19권12호
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• pp.883-888
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• 2007

As a starting point of investigating what molecular dynamic simulations can reveal about the nature of atomic level of heating and cooling process, argon described by the LJ potential is considered. Stepwise heating and cooling of constant rates are simulated in the NPT (constant number, pressure and temperature) ensemble. Hysteresis is found due to the superheating and supercooling. Drastic change of volume and energy is involved with phase change, but the melting point can not be obtained by simply observing the changes of these quantities. Since liquid and solid phases can co-exist at the same temperature, Gibbs free energy should be calculated to find the temperature where the Gibbs free energy of liquid is equal to that of the solid since the equilibrium state is the state of minimum Gibbs free energy. The obtained melting temperature, $T^*=0.685$, is close to that of the experiment with only 2% error.