• 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.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.442-454
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• 2021

The porous transport layer (PTL) is essential to effectively remove oxygen and hydrogen gas from the electrode surface at high current density operation conditions. In this study, the effect of PTL with different characteristics such as pore size, pore gradient, interfacial coating was investigated by multi-layered sintered mesh. A water electrolysis single cell of active area of the 34.56 cm² was constructed, and IV performance and impedance analysis were conducted in the range of 0 to 2.0 A/cm². It was confirmed that the multi-layered sintered mesh PTL, which have an average pore size of 25 to 57 ㎛ and a larger pore gradient, removed bubbles effectively and thus seemed to improve IV performance. Also, it was confirmed that the catalytic metals such as Ni, NiMo coating on the PTL reduced activation overpotential, but increased mass transport overpotential.

• 한국환경과학회지
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• 제20권10호
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• pp.1329-1336
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• 2011

The objectives of this study are to examine the processing of oils contamination soil by means of using a micronano-bubble soil washing system, to investigate the various factors such as washing periods, the amount of micro-nano bubbles generated depending on the quantity of acid injection and quantity of air injection, to examine the features involved in the elimination of total petroleum hydrocarbons (TPHs) contained in the soil, and thus to evaluate the possibility of practical application on the field for the economic feasibility. The oils contaminated soil used in this study was collected from the 0~15 cm surface layer of an automobile junkyard located in U City. The collected soil was air-dried for 24 hours, and then the large particles and other substances contained in the soil were eliminated and filtered through sieve No.10 (2 mm) to secure consistency in the samples. The TPH concentration of the contaminated soil was found to be 4,914~5,998 mg/kg. The micronano-bubble soil washing system consists of the reactor, the flow equalization tank, the micronano- bubble generator, the pump and the strainer, and was manufactured with stainless material for withstanding acidic phase. When the injected air flow rate was fixed at 2 L/min, for each hydrogen peroxide concentrations (5, 10, 15%) the removal percents for TPH within the contaminated soil with retention times of 30 minutes were respectively identified as 4,931 mg/kg (18.9%), 4,678 mg/kg (18.9%) and, 4,513 mg/kg (17.7%). And when the injected air flow rate was fixed at 2 L/min, for each hydrogen peroxide concentrations (5, 10, 15%) the removal percents for TPH within the contaminated soil with retention times of 120 minutes were respectively identified as4,256 mg/kg (22.3%), 4,621 mg/kg (19.7%) and 4,268 mg/kg (25.9%).

• 한국재료학회지
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• 제18권3호
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• pp.163-168
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• 2008

The morphology of three-dimensional (3D) cross-linked electrodeposits of copper and tin was investigated as a function of the content of metal sulfate and acetic acid in a deposition bath. The composition of copper sulfate had little effect on the overall copper network structure, whereas that of tin sulfate produced significant differences in the tin network structure. The effect of the metal sulfate content on the copper and tin network is discussed in terms of whether or not hydrogen evolution occurs on electrodeposits. In addition, the hydrophobic additive, i.e., acetic acid, which suppresses the coalescence of evolved hydrogen bubbles and thereby makes the pore size controllable, proved to be detrimental to the formation of a well-defined network structure. This led to a non-uniform or discontinuous copper network. This implies that acetic acid critically retards the electrodeposition of copper.

• 공업화학
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• 제26권4호
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• pp.421-426
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• 2015

미세조류 Arthrospira platensis는 단백질 함량이 높고, 불포화 지방산 등을 다량함유하고 있어 건강보조식품 및 다양한 분야에서 활용되고 있다. 또한 phycocyanin, myxoxanthophyll, zeaxanthin 등의 색소를 함유하고 있어서 항산화물질, 식품 첨가물로도 이용되고 있다. 나노기포 수소수는 수소 기체를 나노기포 상태로 물속에 주입하여 포화용해도 이상으로 용해시킨 것이다. 이런 나노기포 수소수는 항산화능이 높고, 항암효과가 있는 것으로 알려져 있다. Arthrospira platensis를 일반 증류수 배지와 수소수로 제조한 배지에서 배양한 후 특성을 확인하였다. 배양 결과, 세포 성장 및 광합성으로 인한 색소인 chlorophyll과 carotenoid의 함량은 수소수 배지에서 배양하였을 경우 대조군에 비해 15% 정도 증가한 것으로 나타난다. 그리고 phycocyanin 역시 7% 정도 증가하였다. 하지만, 지질함량은 수소수 배지 배양과 일반 배지 배양 간에 큰 차이가 없는 것을 확인하였다. 항산화물질의 함량을 확인하기 위해 flavonoid 및 polyphenol의 함량을 측정하였다. Flavonoid는 수소수 배지에서 배양하였을 경우 대조군에 비해 70% 이상 증가함을 보이고 있다. 하지만 polyphenol은 대조군과 유사한 함량을 보이고 있다.

• 한국가구학회지
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• 제19권2호
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• pp.106-110
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• 2008

This paper investigated and validated the mechanisms and principles for constructing reticular structure of plant fiber through frothing solution approach. After process, plant fibers became low-density reticular-structured block with all properties meeting Chinese standards for cushion packing materials. The bonds between fibers acted as knots in a truss and were strong enough to keep space occupied by bubbles in the frothing solution from shrinking in the subsequent draining process. The formation of the reticular structure depends mainly on the pressure difference between inside and outside bubble, the effect of surface adsorbent force on bubble film, and hydrogen bond among fiber hydroxide.

• 한국표면공학회지
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• 제49권2호
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• pp.141-146
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• 2016

In this study, electrophoretic paint (E-paint) was deposited on the knife-abraded surface of AZ31 magnesium alloy (AZ31), and its adhesion and corrosion resistance were examined by tape peel-test and salt spray test, respectively. E-paint started to deposit on AZ31 Mg alloy after an inductance time and pores were found in the E-paint layer which is ascribed to hydrogen bubbles generated on the surface during the painting process. The pores disappeared after curing for 15 min at $160^{\circ}C$. The E-paint on AZ31 exhibited good adhesion after immersion in deionized water for 500 h at $40^{\circ}C$. The E-paint sample without scratch showed no corrosion after 1500 h of salt spray test. However, on the scratched sample, blisters were visible adjacent to the scratched sites after 500 h of salt spray test.

• 한국토양환경학회지
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• 제4권1호
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• pp.49-55
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• 1999

본 연구에서는 고농도의 디젤로 오염된 토양을 효율적으로 정화하기 위해, 알칼리제와 과산화수소를 이용하는 새로운 방식의 토양세척기법에 대하여 일련의 회분식 실험을 통하여 최적의 운전조건을 검토하고자 하였다. 알칼리제인 NaOH를 이용하여 세척수의 pH를 상승시켜, 강 알칼리 상태에서 과산화수소를 주입하면 미세기포가 발생되며, 이 미세기포에 의해 토양에 흡착되어 있는 유류 오염물질이 효과적으로 탈착·부상된다. #60(0.25mm) 이하의 자연토양을 6,500mg TPH/kg dry soil로 오염시켜 사용하였으며, 세척수의 pH, 진탕비(토양중량 : 세척용액의 부피), 과산화수소 주입량, 세척시간에 의한 영향을 살펴보았다. 세척수의 pH는 12, 진탕비는 1 : 5, 과산화수소의 주입량은 1%, 세척시간은 1시간으로 적용한 결과 최대효율(60%)을 얻을 수 있었다.

• 대한화학회지
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• 제53권3호
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• pp.368-376
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• 2009

이 연구는 고등학교 화학I에서 이루어지는 금속의 반응성 실험에서 발견되는 문제점을 살펴보 고 이에 대한 이해를 목적으로 한다. 금속의 반응성 실험에서 제기된 문제는 세 가지로, 첫째 Al(s)이 전혀 반응하지 않는 이유와 반응을 관찰할 수 있는 방안, 둘째 Zn(s)과 FeS$O_4$(aq)의 반응에서 기포가 관찰 되는 이유, 셋째 FeS$O_4$(aq)와 Zn(s)의 반응에서 나타나는 침전의 정체 확인이다. 연구 결과 다음과 같은 결론을 내릴 수 있었다. 첫째, Al(s)은 산화피막 생성속도가 매우 빨라 반응을 관찰할 수 없으며, 강한 염산을 이용한 경쟁 반응을 이용하여 산화막 생성이 억제된 상태에서 알루미늄과 다른 금속 이온과의 반응을 관찰할 수 있다. 둘째, 발생하는 기포는 수소이온의 환원에 의한 수소기체로, 금속과 금속이온의 반응과 함께 물속의 수소이온이 특정한 농도범위에서 경쟁적으로 금속과 반응하고 있음을 확인하였다. 셋째, FeS$O_4$(aq)와 Zn(s)의 반응에서 Fe(s)은 관찰되지 않으며 Zn(s) 표면에 생성되는 검은색의 자성을 띠는 물질은 Fe3$O_4$(s)이고 용액 속에서 침전되는 적갈색의 고체는 $Fe_2O_3$(s)임을 광전자분광(X-Ray Photoelectron Spectroscopy) 분석으로 확인하였다.

• 천문학회지
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• 제38권2호
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• pp.69-72
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• 2005

The FIMS (Far-ultraviolet IMaging Spectrograph; also known as SPEAR, Spectroscopy of Plasma Evolution from Astrophysical Radiation) is the primary payload of the STSAT-1, the first Korean science satellite, which was launched in September, 2003. The FIMS performs spectral imaging of diffuse far-ultraviolet emission with the unprecedented wide field of view and the relatively good spectral resolution. We present far-ultraviolet spectral observations of highly ionized interstellar medium including supernova remnants, superbubbles, soft X-ray shadows, and the molecular hydrogen fluorescent emission lines. The FIMS has detected He II, C III, 0 III, O IV, Si IV, O VI, and $H_2$ fluorescent emission lines. The emission lines arise in shocked or thermally heated and in photo-ionized gases. We present an overview of the FIMS instrument and its initial observational results.