• 열처리공학회지
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• 제10권4호
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• pp.237-245
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• 1997

A study was conducted to examine the effects of In addition on the precipitation behaviors of Al-2.1Li-2.9Cu alloy by differential scanning calorimetry, transmission electron microscopy and micro-hardness tester. DSC analysis was measured over the temperature range of $25{\sim}550^{\circ}C$ at a heating rate of $2{\sim}20^{\circ}C$/min. The heat evolution peaks due to the formation of GP zone and ${\delta}$'phase shift to higher temperature and the peaks to $T_1$ and ${\theta}$'phases shift to lower temperature by In addition. From this result, it was proved that the formation of GP zone and ${\delta}$'phase is suppresed whereas that of $T_1$ and ${\theta}$'phases are accelerated by the In addition of 0.15wt%. The age hardening curve aged at $190^{\circ}C$ showed that the In bearing alloy(alloy B) has more faster age hardening response and a higher peak hardness than In-free alloy(alloy A), attributed to the fine and homogeneous distribution of $T_1$ and ${\theta}$'phases. The activation energies for the formation of ${\delta}$'phase in In-free and In-bearing alloys are 22.3kcal/mol and 18.6kcal/mol, respectively. Those for $T_1(+{\theta}^{\prime})$ phase of In-free and In-bearing alloys are 24.3 and 37.5kcal/mol, respectively. Quenched-in excess vacancies play an important role to the formation of precipitates.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.231-232
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• 1998

The purpose of this study was to examine whether the precipitation of calcium phosphate on titanium surface was affected by surface modification. To improve the bone conductivity, of titanium, samples were devided into 4 groups. Group 1 was immersed in 5M-NaOH solution at $60^{\circ}C$ for 24 hours. Group 2 was immersed in 5M-NaOH solution at $60^{\circ}C $ for 24 hours and heat-treated at $600^{\circ}C$ for 1 hour. Group 3 was anodized in Hanks' solution at 1V, $25^{\circ}C$ for 1 hour. Group 4 was anodized in Hanks' solution at 5V, $80^{\circ}C$ for 5 minutes. And then, all specimens were immersed in the MEM Eagle's medium whose composition was similar to that of extracellular fluid for 30 days. The precipitation of the calcium phosphate on implant surface was increased by the immersion in the NaOH solution, and more highly accelerated by heat treatment at $600^{\circ}C$. The precipitation of the calcium phosphate on titanium implant was increased with the treatment of the anodic oxidation in Hanks' solution at 5V, $80^{\circ}C$.

• 한국압력기기공학회 논문집
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• 제12권1호
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• pp.41-48
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• 2016

To investigate the effect of long-term thermal aging on the microstructural and mechanical characteristics of weldment made of nickel base alloy and its weld metal, an accelerated heat treatment was applied to simulate the process of long-term thermal aging in the operating condition of nuclear power plant. A representative nickel-based weldment with Alloy 600 and Alloy 182 was fabricated and heat-treated at $400^{\circ}C$ for 1,713 h and 3,427 h to simulate the thermal aging for the period equivalent to 15 and 30 years in operating pressurized water reactors, respectively. The microstructural and mechanical characteristics were analyzed by using optical microscopy, scanning electron microscopy and Vickers microhardness measurement. Changes were observed in precipitation behavior and microhardness of each specimen, and these changes were mainly attributed to the change in precipitated morphology and residual stress across the weld during the thermal aging process.

• 한국식품과학회지
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• 제52권6호
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• pp.616-621
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• 2020

본 연구에서는 다양한 pH 환경에서 식품의 가공 및 조리과정 중에 빈번히 적용되는 가열처리 과정을 적용하여 시나핀산의 화학 안정성, 산화방지활성 및 세포독성 등의 생리활성 변화를 조사하였다. 95℃에서 각 시간별로 가열처리한 시나핀산은 가열시간이 증가할수록 더 많이 분해되었으며 pH가 상승할수록 더 신속하게 분해되었다. 가열처리에 의해 시나핀산의 ABTS 라디칼소거능 및 FRAP 환원능이 모두 감소하였으며, 특히 pH 7과 8에서는 가열처리 시간에 유의적으로 현저하게 감소하였다. HCT116 인간 대장암세포에 대한 시나핀산의 세포독성 평가에서 가열처리 전의 시나핀산은 500 μM 농도까지 세포독성을 나타내지 않은 반면, pH 8에서 가열처리한 후에는 해당 농도에서 유의적인 세포독성을 발현하였으며 세포 내 glutathione 수치 또한 감소되었다. 본 연구결과는 시나핀산의 화학 안정성 및 생리활성이 가열처리와 pH 환경에 의해 많은 영향을 받으며, 시나핀산이 함유된 식품을 알칼리 조건에서 가열처리 시 성분의 손실 및 활성의 변화를 초래할 수 있음을 시사한다.

• 한국세라믹학회지
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• 제49권5호
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• pp.454-460
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• 2012

The nano-sized zirconia powders were synthesized in an impregnation method using pulp and $ZrOCl_2{\cdot}8H_2O$ as an initial material. The synthesized powders were characterized by XRD and FE-SEM. The particle size of the powder was controlled by preparation conditions, such as drying temperature and time. As a result of the various drying and calcination conditions, 30~50 nm sized homogeneous zirconia particles were obtained at $800^{\circ}C$ for 1 h. Crystallization and the rapid growth of particles were accelerated with increasing calcination temperature and time. Tetragonal phase generated below $800^{\circ}C$ were transferred to monoclinic phase with increasing calcination temperature and time. Moreover, above $800^{\circ}C$, heat treatment time had very large influence on the particle growth, and the change of drying condition also had large influence on the growth of a crystal.

• Journal of Welding and Joining
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• 제14권6호
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• pp.101-108
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• 1996

In this study, WC-l7wt% Co composite powder for thermal spray was fabricated by spray drying method. The agglomerated composite powder had spheroidal morphology and the particle size distribution was 20~60${\mu}{\textrm}{m}$. WC and Co were distributed homogeneously. However, the strength of the spray-dried agglomerate was low due to the pores within the agglomerate. Therefore, the spray-dried agglomerate was broken down during HVOF thermal spray and the microstructure was inhomogeneous with many pores within the coating layer. And the decomposition of WC to W and $W_{6}$ $C_{2.54}$ was accelerated. The strength and flowability of the agglomerate were greatly improved by sintering heat treatment(110$0^{\circ}C$, 1 hour, hi atmosphere), and then the coating layer showed dense and homogeneous microstructure with well-developed splats. The hardness of the coating layer was H $v_{300}$ = 1072.2.2.

• 한국안전학회지
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• 제15권4호
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• pp.8-14
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• 2000

The remaining life estimation for the aged components in power plants as well as chemical plants are very important because mechanical properties of the components are degraded with time of service exposure in the high temperature. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, accelerated aging technique are needed to estimate and analyse the material degradation. In the this study, test materials with 4 different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C$. And tensile test, $k_{IC}$ test, hardness test and Scanning Electron Microscope analysis were performed in order to evaluate the degradation of 1Cr-1Mo-0.25V steels.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.548-551
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• 2002

The crystallization of amorphous silicon (a-Si) was achieved using a field aided lateral crystallization (FALC) process at 350 $^{\circ}C$. Under the influence of an electric field, Cu is found to drastically enhance the lateral crystallization velocity of a-Si. When an electric field was applied to the selectively Cu-deposited a-Si film during the heat treatment at temperature as low as 350 $^{\circ}C$, dendrite-shaped crystallization of a-Si progressed toward Cu-free region and the crystallization from negative electrode side toward positive electrode side was accelerated. We identified that 1000${\AA}$ thick a-Si film was completely crystallized by Cu-FALC process at 350 $^{\circ}C$ by TEM analysis.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 고액공존금속의 성형기술 심포지엄
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• pp.183-195
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• 1997

The micorstructural characteristics, particularly $\alpha$-halo formation, in semi-solid state processed hypereutectic Al-Si alloy was investigated. The microstructural changes during reheating of wedge type mold cast ingot, hot-rolled sheet, and Si particulate reinforced Al composite was compared with those occurred during stirring of semi-solid state hypereutectic alloy. In the case of semi-solid state reheating of wedge type ingot and hot-rolled sheet, fine particles of Si as well as $\alpha$-halo formed after heat treatment. Although there seemed to be no coarsening with variations of holding time, the region of $\alpha$-halo decreased due to homogenization. Nucleation and recrystallization was accelerated with the addition of alloying elements during hot rolling resulting in primary Si particle size decrease and $\alpha$-halo formation. In the case of extruded specimens, very little morphological change of reinforcing Si particles was observed. Almost no $\alpha$-halo formed during reheating because of the oxide film formed on the reinforcing Si particles which acted as a diffusion barrier between the matrix and the primary Si particles.

• 한국재료학회지
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• 제9권7호
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• pp.740-747
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• 1999

결정립 미세화는 강도와 인성을 동시에 향상시킬 수 있는 유일한 방법이다. 제어압연과 가속냉각은 공정 중에 재결정과 결정립 조대화 거동을 조절함으로써 기계적 성질을 향상시키는 효과적인 방법으로 알려져 있으며, 반복열처리에 의한 반복상변태는 결정립 미세화 방법 중의 하나이다. 본 연구에서는 제어압연과 반복열처리를 복합 적용하여 그 효과를 관찰하였다. Mo 첨가효과와 공정변수의 효과를 관찰하기 위해 Mo이 첨가된 저탄소강 시편을 준비하여 Gleeble로 가공열처리 모의실험을 하였다. Mo첨가는 결정립 조대화 온도를 상승시키고, 오스테나이트 재결정을 억제하는 효과를 나타내었다. 오스테나이트 결정립 미세화에 가장 효과적인 공정조건은 반복 열처리 제어압연을 두번 실시하는 것이고, 첫번째보다 두번째 압연율을 더 크게 하는 것이었다