• Journal of Electrochemical Science and Technology
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• 제5권2호
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• pp.53-57
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• 2014

With the use of diffusion-limited aggregation modeling, we have investigated the effect of particle drift for dendritic growth. It is found that the morphology of dendritic growth is sensitive to the particle drift, i.e., the larger drift effect results in the denser growth of dendrite. From the analysis using the correlation function, we found the fractional dimension of each dendrite increases as the particles drift increases. Furthermore, we showed the height of dendrite significantly decrease for the slight change of particles drift. Finally, we discussed the strategy to reduce dendritic growth by modifying the transport properties of electrolytes.

• 한국수소및신에너지학회논문집
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• 제24권2호
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• pp.172-178
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• 2013

This study examined the electrochemical deposition and dissolution of lithium on nickel electrodes in 1 mol $dm^{-3}$ (M) $LiPF_6$ dissolved in propylene carbonate (PC) containing different 1,2-dimethoxyethane (DME) concentrations as a co-solvent. The DME concentration was found to have a significant effect on the reactions occurring at the electrode. The poor cycleability of the electrodes in the pure PC solution was improved considerably by adding small amounts of DME. This results suggested that the dendritic lithium growth could be suppressed by using co-solvents. After hundredth cycling in the 1 M $LiPF_6$/PC:DME (67:33) solution, almost no dead lithium has been found from the disassembled cell, resulting from suppression of dendritic lithium growth. Scanning electron microscopy revealed that dendritic lithium formation was greatly affected by the ratio of DME. Raman spectroscopy results suggested that the structure of solvated lithium ions is a crucial important factor in suppressing dendritic lithium formation.

• 한국주조공학회지
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• 제14권6호
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• pp.508-513
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• 1994

For Pb-20wt%Cu alloys, severe macrosegregation due to density difference of the resulting phases in normal directional solidification has been minimized and a uniformly aligned dendritic structure has been produced by axially rotating the sample of 5mm diameter in conjunction with horizontal directional solidification. Under the constant growth velocity of $20{\mu}m/sec$, increasing the rotation rate from 0.18 to 12rpm results in a transition from an aligned columnar to an equiaxed Cu-dendritic structure. With a constant rotation rate of 0.18rpm, increasing the growth velocity from 10 to $50{\mu}m/sec$ also has promoted a transition from columnar to equiaxed structure.

• 한국주조공학회지
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• 제37권4호
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• pp.108-114
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• 2017

In this study, we investigated the effect of the Si content on the secondary dendrite arm spacing (SDAS) of hypoeutectic Al-Si binary alloys in the range of 4~10 wt% Si. Cooling curves were measured during the solidification of the alloy cast in a step-wise mold. We compared two kinds of solidification time: the first is the total solidification time for both dendritic and eutectic growth, and the second is the solidification time for only dendritic growth. The proportional constant in the relationship between SDAS and cooling rate was estimated, as this constant represents the stability of the cast microstructure. The proportional constant decreased with the Si contents from 4 wt% to 8 wt%, and it remains relatively uniform with up to 10 wt% of Si.

• Bulletin of the Korean Chemical Society
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• 제32권11호
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• pp.3933-3940
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• 2011

General, fast, and efficient stitching methods for the synthesis of dendrimers with linear PEG units at a core, as dendritic-linear-dendritic materials, were developed. The synthetic strategy involved the click reaction between an alkyne and an azide. The linear core building blocks, three dialkyne-PEG units, were chosen to serve as the alkyne functionalities for dendrimer growth via click reactions with the azide-dendrons. These three building blocks were employed together with the azide-functionalized Fr$\acute{e}$chet-type dendrons in a convergent strategy to synthesize the Fr$\acute{e}$chet-type dendrimers with different linear core units. Their structure of dendrimers was confirmed by $^1H$ and $^{13}C$ NMR spectroscopy, IR spectroscopy, mass spectrometry, and GPC analysis.

• 한국결정성장학회지
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• 제4권3호
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• pp.276-283
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• 1994

Dendritic-web 방법으로 성장된 규소의 결정속에 존재하는 여러 결합을 화학적 etching 방법으로 규명하였다. Twin plan상에 존재하는 전위의loop이 관찰되었고 이들은 규소의 self - interstital이 condensation되어서 형성된 것으로 판단된다. 이들 규소의 self-interstitial은 응고 온도로 부터의 급냉에 의하여 혹은 oxide precipitation에 의하여 생성되 것으로 여겨진다.

• Journal of Electrochemical Science and Technology
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• 제14권2호
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• pp.194-204
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• 2023

Models based on diffusion-limited aggregation (DLA) have been extensively used to explore the mechanisms of dendritic particle aggregation phenomena. The physical and chemical properties of systems in which DLA aggregates emerge are given in their fractal. In this paper, we present a comprehensive study of the growth of electrodeposited copper dendrites in flat plate electrochemical cells from a fractal perspective. The effects of growth time, applied voltage, copper ion concentration, and electrolyte acidity on the morphology and fractal dimension of deposited copper were examined. 'Phase diagram' set out the variety of electrodeposited copper fractal morphology analysed by metallographic microscopy. The box counting method confirms that the electrodeposited dendritic structures manifestly exhibit fractal character. It was found that with the increase of the voltage and copper ion concentration. The fractal copper size becomes larger and its morphology shifts towards a dendritic structure, with the fractal dimension fluctuating around 1.60-1.70. In addition, the morphology of the deposited copper is significantly affected by the acidity of the electrolyte. The increase in acidity from 0.01 to 1.00 mol/L intensifies the hydrogen precipitation side reactions and the overflow path of hydrogen bubbles affects the fractal growth of copper dendrites.

• Macromolecular Research
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• 제17권7호
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• pp.499-505
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• 2009

General, fast, and efficient stitching methods are presented for the synthesis of Fr$\acute{e}$chet-type dendrimers with linear units at a core, as a preliminary investigation for the synthesis of dendritic-linear-dendritic materials. The synthetic strategy involved an inexpensive, 1,3-dipolar, cycloaddition reaction between an alkyne and an azide in the presence of the Cu(I) species, which is known as the best example of click chemistry. The linear core building blocks, 1,7-octadiyne and 1,6-diazidohexane, were chosen to serve as the alkyne and azide functionalities for dendrimer growth via click reactions with the azide and alkyne-dendrons, respectively. These two building blocks were employed together with the azide- and alkyne-functionalized Fr$\acute{e}$chet-type dendrons in a convergent strategy to synthesize two kinds of Fr$\acute{e}$chet-type dendrimers with different linear core units. This comparative efficiency of the click methodology supports the fast and efficient synthesis of dendritic-linear-dendritic materials with the tailor made core unit.

• IMMUNE NETWORK
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• 제5권2호
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• pp.105-109
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• 2005

Background: Dendritic cells (DCs) are the most potent APCs (antigen-presenting cells) and playa critical role in immune responses. Galectin-3 is a biological lectin with a beta-galactoside binding affinity. Recently, proteomic analysis revealed the presence of galectin-3 in the exosome of mature DCs. However, the expression and function of galectin-3 in DCs remains unclear yet. Methods: We used bone marrow-derived DCs of mouse and showed the expression of galectin-3 in DCs by using flow cytometry analysis and Western blot analysis. Results: Galectin-3 was determined as single band of 35 kDa in Western blot analysis. Flow cytometry analysis showed the major growth factor for DCs, granulocyte-macrophage colony stimulating factor (GM-CSF) and maturing agents, anti-CD40 monoclonal antibody (mAb) and lipopolysaccharide (LPS) consistently increased the intracellular expression of galectin-3 in DCs compared to medium alone. In addition, DCs treated with maturing agents did marginally express galectin-3 on their surface. Conclusion: This study suggests that galectin-3 in DCs may be regulated by critical factors for DC function.

• 한국결정성장학회지
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• 제8권1호
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• pp.187-192
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• 1998

일반적으로 재료의 응고조직은 주상정과 등축정 수지상 영역으로 이루어지는데 이것은 제품의 기계적, 물리적 성질과 밀접한 관계를 가지기 때문에 주상정-등축정 천이에 관한 많은 이론적 연구가 행하여지고 있다. 본 연구에서는 J.D. Hunt에 의하여 일방향응고시 주상정앞에서의 핵생성과 결정성장조건을 이용하여 구하여진 해석학적 주상정-등축정 조건식을 바탕으로 응고속도에 따라 변하는 분배계수와 액상선기울기를 적용하여 수정된 조건식을 구하였다. 그리고 Al-Cu합금에 대하여 응고변수인 핵생성수, 핵생성온도, 합금의 조성, 응고속도 온도기울기에 따른 천이현상의 변화를 조사하였다.