• 한국결정성장학회지
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• 제16권5호
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• pp.210-215
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• 2006

본 연구에서는 순 Cu 및 Nb 혼합분말에 대하여 Ar 분위기 중 고에너지 볼밀처리를 실시하여 기계적 합금화(MA) 효과를 조사하였다. $Cu_xNb_{100-x}$(x=5-50) 조성의 혼합분말을 각각 120시간까지 MA 처리 한 결과, Cu의 bcc-Nb 과포화 고용체가 30 at% Cu까지 넓어짐을 X선 회절분석, DSC 열분석 및 저온비열 측정을 통한 초전도 천이온도 변화로부터 알수 있었다. 120시간 MA 처리한 $Cu_{30}Nb_{70}$ 조성합금의 열분석 결과 broad한 발열반응만이 관찰되었으며, 볼밀처리에 의하여 계에 축적되는 에너지는 볼밀시간에 따라 증가하여 7.5kJ/mol 에 포화됨을 알 수 있었다. Miedema et al.의 계산에 의하면 $Cu_{30}Nb_{70}$ 혼합분말과 과포화 고용체의 자유에너지 차가 7kJ/mol이며, 본 연구에서 MA에 의하여 계에 축적된 에너지 값과 거의 같은 사실로부터 이 계에서 열역학적으로 과포화 고용체가 충분히 얻어질 수 있음을 나타내는 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제34권5호
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• pp.445-454
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• 2002

The sorption of U(Vl) on a domestic granite is studied as a function of experimental conditions such as contact time, solution-solid ratio, ionic strength, and pH using a batch procedure. The distribution coefficients, $K_{d}$＇s, of U(VI) are about 1-100mL/g depending on the experimental conditions. The sorption of U(VI) onto granite particles is greatly dependent upon the contact time, solution-solid ratio, and pH, but very little is dependent on the ionic strength. It is noticed that an U(VI)-carbonate ternary surface complex can be formed in the neutral range of pH. In the alkaline range of pH above 7, U(VI) sorption onto granite particles is greatly decreased due to the formation of anionic U(VI)-carbonate aqueous complexes.s.

• 한국분말재료학회지
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• 제10권3호
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• pp.164-167
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• 2003

The mechanical alloying effect has been studied on the three Cu-based alloy systems with a positive heat of mixing. The extended bcc solid solution has been formed in the Cu-V system and an amorphous phase in the Cu-Ta system. However, it is round that a mixture of nanocrystalline Cu and Mo Is formed in the Cu-Mo system. The neutron diffraction has been employed at a main tool to characterize the detailed amorphization process. The formation of an amorphous phase in Cu-Ta system can be understood by assuming that the smaller Cu atoms preferentially enter into the bcc Ta lattice during ball milling.

• 한국세라믹학회지
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• 제22권2호
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• pp.25-32
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• 1985

Effect of alkali $SO_3$ and $C_2S$ content and cooling condition of clinker on the formation of unstable alkali and cooling condition of clinker on the formation of unstable alkali was investigated. As a result alkali and $SO_3$ content of clinker were the main factors of unstable alkali formation and equation (7) in which the two factors were the variables showed a good agreement with the observed results. Water soluble alkali content of sulphate was decreased with increase of $C_2S$ content of clinker resulted by the increase of solid solution rate of alkali to clinker minerals. But change of unsatble alkali content accordint to the increase of $C_2S$ content was slight. A increasing tendency of ignition loss of clinker with increase of unstable alkali content was found.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1196-1200
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• 2003

The degree of supersaturation is an important measure for the operation of crystallization processes, because it is directly related to the control of crystal size distribution and shape. A conventional technique utilizing solution composition and temperature has a variety of problems caused from the measurement error and the handling of analyzing samples. A monitoring system of the supersaturation using a quartz crystal sensor is proposed here, and its performance is examined applying different manipulations of coolant temperature. The experimental outcome and photographic examination indicate that the measurements of resonant frequency and resistance of the sensor can be used for the prediction of the formation and growth of solid crystal from the crystallization process. The monitoring system eliminates the intrinsic error source of the conventional system to give the improved measurement and on-line application availability.

• Journal of Electrochemical Science and Technology
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• 제10권1호
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• pp.55-60
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• 2019

Herein, the effect of counter anions on the formation of a solid electrolyte interphase (SEI) in a propylene carbonate (PC)-based electrolyte solution was investigated. Although the reversible capacities were different, reversible intercalation and de-intercalation of lithium ions occurred in the graphite negative electrode in the PC-based electrolyte solutions containing 1 M $LiClO_4$, $LiPF_6$, $LiBF_4$, and $LiCF_3SO_3$ at low temperature ($-15^{\circ}C$). This indicated that the surface films acted as an effective SEI to suppress further co-intercalation and decomposition reactions at low temperature. However, the SEIs formed at the low temperature were unstable in 1 M $LiPF_6$ and $LiBF_4/PC$ at room temperature ($25^{\circ}C$). On the other hand, increasing reversible capacity was confirmed in the case of $LiCF_3SO_3/PC$ at room temperature, because the SEI formed at the low temperature was still maintained. These results suggest that counter anions are an important factor to consider for the formation of effective SEIs in PC-based electrolyte solutions.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 춘계학술발표회논문집(2)
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• pp.769-774
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• 1995

In this study, a transport model was developed in order to analyze and predict the transport behaviors of radionuclides mediated by pseudo-colloid in the fractured rock media. It was resulted that the transport of Pu-239 was faster than Ni-63 because pseudo-colloid formation constant of Pu-239 was greater than that of Ni-63. Also, the effect of pseudo-colloid formation on the transport of a radionuclide was shown to be very significant when the apparent pseudo colloid formation constant, $K_{ap}(m^{3}/kg)$, was greater than 100. Thus, it can be concluded that acceleration of radionuclide migration may be occurred because the pseudo-colloid formation of radionuclides increases the amount of mobile components in the solution and consequently decreases the amount of radionuclides adsorbed on the stationary solid medium.

• 한국결정성장학회지
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• 제2권1호
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• pp.51-59
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• 1992

일차입경이 동일한 $Nb_20_5$분체의 응집 상태가 $Pb(Mg_{1/3}Nb_{2/3})O_3$의 생성 반응 및 소결에 미치는 영향을 조사하였다. 합성 방법으로는 고체 반응법과 용융염법으로 나누어 각각 실험하였다. 고체 반응법의 경우에는 perovskite 상의 생성 반응이 $Nb_20_5$의 응집도가 낮을수록 크게 영향을 받았으나, 용융법시에는 거의 영향을 받지 않았다. 그 이유는 고상 반응법시에는 perovskite 상의 생성이 중간생성물인 perovskite 상의 분포의 균일성, 즉 $Nb_20_5$의 응집도에 지배를 받게되나, 용해, 석출 과정에 의해 진행되는 용융염법에서는 반응물의 비표면적에 의존하므로, 응집도에는 그다지 영향을 받지않는 것으로 사료된다.

• 한국재료학회지
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• 제4권6호
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• pp.611-619
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• 1994

본 연구는 Lithium Alumino Silicate 기본계에 핵형성제로 $TiO_{2}$와 $ZrO_{2}$를 사용하여 기본유리를 제조하고 열처리에 따른 $\beta$-quartz고용체의 미결정 형성과정을 분석하였다. 또한 $\beta$-quartz고용체의 형성에 따른 열적 특성과 광학적 특성을 비교하였다. 그 결과, 기본 유리의 열팽창 계수는 $45\sim 55 \times 10^{-7} \textrm{cm}/^{\circ}C$였으며, 결정화 시편의 열팽창 계수는$ -8\sim +8 \times 10^{-7}\textrm{cm}/^{\circ}C$ ($25^{\circ}C \sim 525^{\circ}C$)였다. $900^{\circ}C$이하에서 열처리된 Glass Cermics의 결정은 $\beta$-quartz 고용체가 형성되었고, 결정의 크기가 0.21$\mu \textrm{m}$를 초과하지 않았으며, 최고의 투광도는 80%이상을 나타냈다. RO성분을 MgO와 ZnO를 사용한 경우보다 MgO 단독으로 사용한 시편을 결정입자의 크기가 온도에 의존하지 않고 일정함을 나타냈으며, ZnO의경우는 입자의 크기가 최소값(0.18$\mu \textrm{m}$)을 보이며 온도의존성이 크게 나타냈다.

• 한국세라믹학회지
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• 제31권4호
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• pp.443-447
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• 1994

Compacts of mixed SiO2-Si powder were liquid phase sintered at 145$0^{\circ}C$ for up to 60 min in a hydrogen atmosphere. In contrast to the conventional microstructures of liquid phase sintered materials, the specimens showed that the solid phase of SiO2 formed a matrix while the liquid phase of Si was the dispersed in the solid matrix. The dispersion of liquid Si pockets was attributed to the high wetting angle of liquid Si on solid SiO2. Because of relatively high solubility of SiO2 in liquid Si at 145$0^{\circ}C$, SiO2 particles accommodated their shape via a solution-reprecipitation process. The liquid Si pockets grew by coalescing with their neighbour pockets. In the latter stage of the sintering, plate-shape grains appeared in the liquid Si pockets. The grains were SiO2 phase precipitated from the liquid Si which was oversaturated with oxygen during cooling to room temperature. By the formation and subsequent removal of the gaseous SiO phase due to the reaction between SiO2 and Si, the specimens became porous.