• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.393-395
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• 2005

The bonding for Aluminum and Copper in the air is investigated in this study. This bonding method does not include the special process of removing aluminum oxide films. In case of this bending, each metal Is heated at bonding temperature where is above eutectic temperature of Al-Cu system and below melting point of Aluminum. The liquefaction around the bonding surface occurs after the diffusion at solid state of each metal. This phenomenon is predicted by the temperature range above eutectic temperature of Al-Cu equilibrium phase diagram.

• 전기화학회지
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• 제8권2호
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• pp.106-114
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• 2005

This article covers the theoretical ac-impedance models for the analysis of oxygen reduction on the porous cathode electrode f3r solid oxide fuel cell (SOFC). Firstly, ac-impedance models were explained on the basis of the mechanism of oxygen reduction, which were classified into the rate-determining steps; (i) adsorption of oxygen atom on the electrode surface, (ii) diffusion of adsorbed oxygen atom along the electrode surface towards the three-phase (electrode/electrolyte/gas) boundaries, (iii) surface diffusion of adsorbed oxygen atom m ixed with the adsorption reaction of oxygen atom on the electrode surface and (iv) diffusion of oxygen vacancy through the electrode coupled with the charge transfer reaction at the electrode/gas interface. In each section for ac-impedance model, the representative impedance plots and the interpretation of important parameters attributed to the oxygen reduction reaction were explained. Finally, we discussed in detail the applications of the proposed theoretical ac-impedance models to the real electrode of SOFC system.

• 한국세라믹학회지
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• 제38권10호
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• pp.881-885
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• 2001

Kinetics and mechanisms of intermediate phases formation in $Ba(Mg_{1/3}Ta_{2/3})O_3$, obtained by a solid state reaction were studied. $Ba{Ta_2}{O_6}$ and ${Ba_4}{Ta_2}{O_9}$ as intermediate products were first formed at $700^{\circ}C$. $Ba(Mg_{1/3}Ta_{2/3})O_3$ was appeared at $800^{\circ}C$. Several reactions take place on heating process. $Ba{Ta_2}{O_6}$ is found at the first stage of the reaction, and then $Ba{Ta_2}{O_6}$ or ${Ba_4}{Ta_2}{O_9}$ react with MgO to form $Ba(Mg_{1/3}Ta_{2/3})O_3$. The reaction of $Ba(Mg_{1/3}Ta_{2/3})O_3$ formation does not complete until fired at $1350^{\circ}C$ for 60 min. The kinetics of solid-state reaction between powdered reactants was controlled by diffusion mechanism, and can be explained by the Jander's model for three-dimensional diffusion.

• Applied Science and Convergence Technology
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• 제23권6호
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• pp.371-375
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• 2014

Diffusion coefficient of Fe in polycrystalline host ZnSe as a mid-IR gain medium has been measured in the annealing temperature ranges of 850 to $950^{\circ}C$. The synthesis of the samples was carried out in quartz ampoule in which the Fe thin film deposited by physical vapor evaporation method on the ZnSe. One can realize that the diffusion coefficient strongly depends on the surface active surfactants through the cleaning process and the substrate temperature during the thin film deposition leading to $2.04{\times}10^{-9}cm^2/s$ for $Fe^{2+}:ZnSe$. The Annealing temperature dependence of the Fe ions diffusion in ZnSe was used to evaluate the activation energy, $E_a$=1.39 eV for diffusion and the pre-exponential factor $D_0$ of $13.5cm^2/s$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.480.1-480.1
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• 2014

In this study, we suggest the new emitter formation applied solid phase epitaxy (SPE) growth process using rapid thermal process (RTP). Preferentially, we describe the SPE growth of intrinsic a-Si thin film through RTP heat treatment by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD). Phase transition of intrinsic a-Si thin films were taken place under $600^{\circ}C$ for 5 min annealing condition measured by spectroscopic ellipsometer (SE) applied to effective medium approximation (EMA). We confirmed the SPE growth using high resolution transmission electron microscope (HR-TEM) analysis. Similarly, phase transition of P doped a-Si thin films were arisen $700^{\circ}C$ for 1 min, however, crystallinity is lower than intrinsic a-Si thin films. It is referable to the interference of the dopant. Based on this, we fabricated 16.7% solar cell to apply emitter layer formed SPE growth of P doped a-Si thin films using RTP. We considered that is a relative short process time compare to make the phosphorus emitter such as diffusion using furnace. Also, it is causing process simplification that can be omitted phosphorus silicate glass (PSG) removal and edge isolation process.

• The Korean Journal of Ceramics
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• 제5권4호
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• pp.336-340
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• 1999

Glasses in the system $CaO-TiO_2-SiO_2-Al_2O_3-ZrO_2-B_2O_3$ were investigated to find the glass seal compositions suitable for use in the planar solid oxide fuel cell (SOFC). Glass-ceramics prepared from the glasses by one-stage heat treatment at $1,000^{\circ}C$ showed various thermal expansion coefficients (i,e., $8.6\times10^{-6^{\circ}}C^{-1}$ to $42.7\times10^{-6^{\circ}}C^{-1}$ in the range 25-$1,000^{\circ}C$) due to the viscoelastic response of glass phase. The average values of contact angles between the zirconia substrate and the glass particles heated at 1,000-$1,200^{\circ}C$ were in the range of $131^{\circ}\pm4^{\circ}$~$137^{\circ}\pm9^{\circ}$, indicating that the glass-ceramic was in partial non-wetting condition with the zirconia substrate. With increasing heat treatment time of glass samples from 0.5 to 24 h at $1,100^{\circ}C$, the DC electrical conductivity of the resultant glass-ceramics decreased from at $800^{\circ}C$. Isothermal hold of the glass sample at $1100^{\circ}C$ for 48h resulted in diffusion of Ca, Si, and Al ions from glass phase into the zirconia substrate through the glass/zirconia bonding interface. Glass phase and diffusion of the moving ion such as $Ca^{2+}$ in glass phase is responsible for the electrical conduction in the glass-ceramics.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.833-841
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• 2021

During the postulated severe accident of nuclear reactor, eutectic reaction leads to low-temperature melting of fuel cladding and early failure of core structure. In order to model eutectic melting with the moving particle semi-implicit (MPS) method, the eutectic reaction model is developed to simulate the eutectic reaction phenomenon. The coupling of mass diffusion and phase diagram is applied to calculate the eutectic reaction with the uniform temperature. A heat transfer formula is proposed based on the phase diagram to handle the heat release or absorption during the process of eutectic reaction, and it can combine with mass diffusion and phase diagram to describe the eutectic reaction with temperature variation. The heat transfer formula is verified by the one-dimensional melting simulations and the predicted interface position agrees well with the theoretical solution. In order to verify the eutectic reaction models, the eutectic reaction of uranium and iron in two semi-infinite domains is simulated, and the profile of solid thickness decrease over time follows the parabolic law. The modified MPS method is applied to calculate Transient Reactor Test Facility (TREAT) experiment, the penetration rate in the simulations are agreeable with the experiment results. In addition, a hypothetical case based on the TREAT experiment is also conducted to validate the eutectic reaction with temperature variation, the results present continuity with the simulations of TREAT experiment. Thus the improved method is proved to be capable of simulating the eutectic reaction in the severe accident.

• 한국자기공명학회논문지
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• 제5권1호
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• pp.19-28
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• 2001

Miscibility and morphology in blends of bisphenol-A type polycarbonate and poly (ester-ether) elastomer with different compositions are studied by solid-state NMR spectroscopy. $^{13}$ C Solid-state NMR of CP/MAS/TOSS/DD, CP/MAS/DD, inversion recovery CP/MAS/DD, and 2D rotor driven spin diffusion techniques are used to identify the miscibility, morphology, and transesterification in blends. The blends of PC /BT elastomer with 15% to 42% of soft segment seem to be single phase miscible mixing and those of PC/PBT and PC/PBT elastomer with 62% of soft segment are cocontinuous two phase immiscible mixing. No significant transesterification reactions are observed in blends with different compositions.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.269-274
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• 1997

Recently, premature reinforcement corrosion in concrete structures exposed to chloride containing environments has an important problem. This is due to an increasing use of marine aggregate of chloride containing admixture a the mixing stage and due to an increase of concrete construction in marine environments. In this study, the behavior of chloride ions introduced into concrete from concrete surface by a marine environment was modeled. The physicochemcial processes including the diffusion of chloride ion in aqueous phase of pores, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete, and the chemical reaction of chloride ion with solid phase were analyzed by using the finite element method. The results of this study may be used to predict the onset of reinforcement corrosion, and identify the maximum limit of chloride ions contained in admixtures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.149-154
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• 1997

In order to predict the onset of the corrosion of steel bars in the concrete, a mathematical model including the diffusion of chloride ion in aqueous phase of pores, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete, and the chemical reaction of chloride ions with solid phase was established. Finite element method was employed to carry out numerical analysis. The chlorides penetrating through the wall of concrete structure from the external environment and the chlorides contained in the concrete admixture were confirmed to be two important factors to determine the onset of corrosion of steel bars.