• 한국수소및신에너지학회논문집
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• 제23권4호
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• pp.390-396
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• 2012

In order to understand the nature of dendritic zinc growth, electrochemical zinc redox reaction on nickel plate was investigated in aqueous solutions containing different concentrations, 0.2, 0.1 and 0.02 $mol{\cdot}dm^{-3}$ (M), of zinc sulfate ($ZnSO_4$) or zinc chloride ($ZnCl_2$). Zinc ion was efficiently reduced and oxidized on nickel in the high-concentration (0.2 M) solution, whereas relatively poor efficiency was obtained from the other low-concentration solutions (0,1 and 0.02 M). Cyclic voltammetry (CV) analysis revealed that the 0.2 M electrolyte solution decomposes at more positive potentials than the 0.1 and the 0.02 M solutions. These results suggested that the concentration of electrolyte solution and anion would be an important factor that suppresses the reaction of the zinc dendrite formation. Scanning Electron Microscopy (SEM) data revealed that the shape of dendritic zinc and its growing behavior were also influenced by electrolyte concentration.

• 한국기계가공학회지
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• 제1권1호
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• pp.71-78
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• 2002

Since the early 1980's the use of zinc-aluminum alloy-coated steel sheet(Galvalume) for vehicular corrosion protection has increased drastically. It is consisting of 55%Al-43.4% Zn-1.6%Si. Galvalume has a good corrosion resistance, heat reflectivity and shiny appearance, which has a dendritic structure of alloy layer. It has a good corrosion resistance due to dendritic structure. But, this also has a weak point against moisture during long period of transportation as sheeted and or coiled without any relation of chromating on the surface of steel sheet or not because of high humidity and temperature. Here, We studied the corrosion mechanism by the moisture.

• 한국표면공학회지
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• 제18권2호
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• pp.53-60
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• 1985

The microstructure of zine electrodeposits was investigated by using zinc sulfate solution in still bath. The cathode current efficiency decreased with increasing current density, and decreasing temperature. The preferred orientation of the zinc electrodeposits changed from (10.3) texture to(10.${\ell}$)-(00.1)(${\ell}$=1, 2, 3) texture through (10.2)-(10.3) preferred orientation with increasing cathode over potential. The surface morphology of zinc electrodeposits changed from the dendritic growth with granular crystallites to the blocks of hexagonal crystallites packed together with increasing current density. The microstructure of cross section of the above deposits are the rough granular structure and columnar structure respectively.

• Bulletin of the Korean Chemical Society
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• 제29권7호
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• pp.1353-1358
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• 2008

Benzyl arylether dendrimers with zinc porphyrin core and terminal vinyl groups have been synthesized and their photophysical properties and the influence of dendritic environments were investigated. Free base porphyrin-cored benzyl arylether dendrimers 1a-1c and 3a-3c, and their zinc derivatives 2a-2c and 4a-4c have been prepared. Absorption spectra are similar for all porphyrin-cored benzyl arylether dendrimers, except that absorption intensity at 280 nm increases in the higher generation of dendrimer. Fluorescence spectra are similar with two bands for all free base porphyrin dendrimers 1a-1c and 3a-3c, although fluorescence intensity ratio of shorter wavelength emission band to longer wavelength band varies with the generation of dendrimer. Emission efficiencies of 1a-1c and 3a-3c are lower than that of TTP. Emission efficiencies of 2a-2c and 4a-4c are higher than that of ZnTTP. Absorption and emission properties of 1a-1c, 2a-2c, 3a-3c, and 4a-4c were affected negligibly with dendritic environments.

• Corrosion Science and Technology
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• 제23권2호
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• pp.93-103
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• 2024

In the present work, a phase-field model for dendritic solidification is applied to hot-dip ZnAlMg coatings to elucidate the morphology of zinc dendrites and the solute segregation leading to the formation of eutectics. These aspects define the microstructure that conditions the corrosion resistance and the mechanical behaviour of the coating. Along with modelling phase transformation and solute diffusion, the implemented model is partially coupled with the tracking of crystal orientation in solid grains, thus allowing the effects of surface tension anisotropy to be considered in multi-dendrite simulations. For this purpose, the composition of a hot-dip ZnAlMg coating is assimilated to a dilute pseudo-binary system. 1D and 2D simulations of isothermal solidification are performed in a finite element solver by introducing nuclei as initial conditions. The results are qualitatively consistent with existing analytical solutions for growth velocity and concentration profiles, but the spatial domain of the simulations is limited by the required mesh refinement.

• Applied Microscopy
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• 제36권4호
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• pp.299-305
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• 2006

Onuf 핵이란 척수 앞회색질뿔에 위치하는 운동핵으로 음부신경을 통해 방광과 항문괄약근을 조절하는 운동핵의 하나이다. Onuf핵은 앞회색질뿔내 다른 운동신경핵과는 달리 회색질척수염과 같은 병적인 상황에서도 상당기간 손상되지 않고 기능을 유지하며, 퇴행성변화의 정도가 미약한데 정확한 원인에 관해서는 논란의 여지가 많다. 본 연구는 흰쥐 척수회색질내 바깥요도조임근을 신경지배하는 Onuf핵의 위치를 HRP 추적법으로 확인하였으며, 이들 신경핵내 운동신경세포와 연접해 있는 zinc함유(ZEN)신경종말의 미세구조를 zinc selenium조직화학법(AMG)으로 염색하여 관찰하였다. HRP 추적법의 결과로는, Onuf핵은 랫드 척수회색질앞뿔의 내측에서 가지돌기의 무리와 거의 맞닿고 있었으며, 모양은 대개 구형 또는 난원형을 띠었다. 이들 신경핵내 운동신경세포의 세포체의 크기는 다른 운동핵의 신경세포보다 다소 작았다. 한편 AMG로 염색한 표본에서는 Onuf핵에 분포하는 ZEN신경종말은 다른 운동핵의 ZEN 신경종말과 비교하여 매우 높은 밀집도를 보였으나, 크기 면에서도 상대적으로 작았다. 미세구조 관찰로는 Onuf 핵내 ZEN신경종말은 운동핵의 세포체 및 가지돌기와 신경연접은 이루고 있었다. 이들 ZEN 신경종말은 주로 납작한 연접소포를 함유하였으며, 대칭적인 신경연접구조를 이루고 있었다.

• Corrosion Science and Technology
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• 제23권1호
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• pp.54-63
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• 2024

This work investigated the influence of concentration and applied potential on the characteristics of zinc powder (purity, apparent density, morphology, particle size distribution, and particle zeta potential) produced by the electrochemical process from waste brass. High-purity zinc powder is obtained using selective leaching of industrial brass waste in acidic, neutral, and alkaline solutions. The free immersion method with and without voltage using linear polarization technique is used. In the electrochemical process, hydrochloric acid HCl in three different concentrations (0.1, 0.2, and 0.3) M is used. The time and the distance between the electrodes are set to be 30 min and 3 cm, respectively. It has been found that the percentage purity is 98%, 96%, and 94% for the acidic, neutral, and alkaline solutions, respectively. In addition, the morphology of zinc powder analyzed by SEM was dendritic and mossy. It has been recorded that the purity of zinc increases with the increase of the concentration and applied potential. The highest value of purity for zinc powder was %98.58 in 1000 mV and 0.3M concentration for graphite cathode.

• Bulletin of the Korean Chemical Society
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• 제32권12호
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• pp.4247-4252
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• 2011

The porphyrin-incorporated arylether dendrimers ZnP-D1 and ZnP-D4 were investigated to discover the influence of dendritic environments for the axial ligation of pyridine and photoinduced electron transfer by methyl viologen. Absorption and fluorescence spectra of ZnP, ZnP-D1, and ZnP-D4 were measured in dichloromethane with the addition of pyridine or methyl viologen dichloride. Axial ligation of pyridine was confirmed by red-shifted absorption spectrum. The complex formation constants $K_f$ (Table 1) for axial coordination of pyridine on ZnP, ZnP-D1, and ZnP-D4 were estimated to be $4.4{\times}10^3\;M^{-1}$, $3.3{\times}10^3\;M^{-1}$, and $1.7{\times}10^3\;M^{-1}$, respectively. The photoinduced electron transfer to methyl viologen dichloride was confirmed by fluorescence quenching. Stern-Volmer constants Ksv for ZnP, ZnP-D1, and ZnP-D4 were calculated to be $2.6{\times}10^3$, $2.5{\times}10^3$, and $2.1{\times}10^3$, respectively. ZnP-D4 surrounded by 4 aryl ether dendrons shows the smallest $K_f$ and Ksv values, with comparison to ZnP and ZnP-D1.

• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.664-672
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• 2011

A series of hydrophilic chromophores was synthesized through introduction of dendritic sulfonate anions using click chemistry. A dendron structure bearing several sulfonate groups enhances hydrophilicity of attached chromophores. A click triazole formation connects chromophores with hydrophilic groups. A neutral trichloroethyl sulfonate has versatile features such as easy introduction, chemical endurance for isolation or storage, and convenient transformation to a hydrophilic anion. Zinc and OH mediated cleavage of trichloroethyl group from the neutral sulfonate undergoes to generate a water-soluble sulfonate anion. The solubility was examined with different counter cations and in different pH media and thus increased with the number of attached sulfonate ion. Two hydrophilic chromophores of stilbene-derived and azobenzene-derived dipolar structures exhibit clear negative and positive solvatochromism in protic solvents, respectively.

• 방사성폐기물학회지
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• 제7권2호
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• pp.125-131
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• 2009

건식공정에서 우라늄 수지상의 성장을 억제하는데 사용할 교반기를 개발하기 위하여, 수용액계로 된 모의시험 장치(아연 양극 - 갈륨 음극)에서 자체 제작한 여러 가지 교반기의 성능을 평가하였다. 교반기를 사용하지 않았을 경우에는 전착 후 1 시간 내에 액체음극 표면에서 아연이 수지상으로 성장되기 시작하여 6 시간 정도면 수지상 중의 일부가 도가니 바깥으로 자라게 되었다. 사각형 또는 경사형 교반기로 액체음극을 40${\sim}$150 rpm으로 교반하면 8 시간까지 아연이 수지상으로 성장되는 것을 억제할 수 있었으나, 회전수가 150 rpm으로 증가하면 전착물 중의 일부가 음극 도가니 바깥으로 흘러넘치게 되었다. 해로우형 교반기는 40 rpm에서는 수지상 성장을 억제하지 못하였으나, 100 rpm 이상에서는 수지상으로 전착되는 것을 억제할 수 있었고, 또한 아연 전착물이 150 rpm에서도 도가니 바깥으로 흘러넘치지 않았다. 파운더 교반기는 수지상의 성장을 어느 정도 억제할 수 있었으나 전위가 불규칙하게 변화되고 운전 장치가 복잡한 것이 단점으로 나타났다.