Effect of electrolyte composition on the morphological structures of dendritic copper powders prepared by a spontaneous galvanic displacement reaction

Kai Zhuo,안창용,PADMANATHANKARTHICKKANNAN,서나리,박유선,정찬화 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.5

Dendritic copper powders are highly desirable in many applications, including electromagnetic interference shielding and conductive pastes, because of low cost and high conductivity. We prepared dendritic copper powders using the galvanic displacement reaction between the Al and Cu-ions in aqueous solution. This method is very simple and spontaneous at room temperature. During the process, the morphology of the copper powders is strongly affected by several variables, such as the displacement reaction rate and the amount of hydrogen evolution due to the reduction of proton. The effect of the different composition of electrolytes to morphological changes of copper powders was investigated in this study. In addition, the effects of concentration of chlorine ion, pH, termination time, and additives were monitored, which resulted in different morphology. Considering different applications, such as sensors, catalysts, and conductive pastes, the controllability of the morphology of dendritic copper powders plays an important role in achieving high performance in desired applications.

Effect of Electrolysis Parameters on the Fractal Structure of Electrodeposited Copper

Na Wu,Chunxia Zhang,Shanyu Han,Juan An,Wentang Xia The Korean Electrochemical Society 2023 Journal of electrochemical science and technology Vol.14 No.2

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.

Non-blinking dendritic crystals from C-dot solution

Ashmi Mewada,Ritesh Vishwakarma,Bhushan Patil,Chinmay Phadke,Golap Kalita,Maheshwar Sharon,Madhuri Sharon 한국탄소학회 2015 Carbon Letters Vol.16 No.3

Bio-imaging and drug carriers for delivery have created a huge demand for crystals. Crystals are fascinating materials that have been grown for a long time but obtaining biocompatible fluorescent crystals is a challenging task. We report on the growth of fluorescent crystals using a carbon dot (C-dot) solution by a hydrothermal process. The crystallization pattern of these C-dots exhibited a unique dendritic structure having a feather-like morphology. The growth temperature and pressure were maintained at 60°C and 200 mmHg, respectively, for crystal growth. A green fluorescence (under UV light) that was observed in the C-dot solution was retained in the crystals formed from the solution. Cytotoxicity studies on Vero cells revealed the crystals to be extremely biocompatible. These fluorescent crystals are extremely well suited for biomedical and optoelectronic applications.

메탄-프로판 하이드레이트의 성장 특성에 관한 연구

이주동(Lee, Ju-Dong),이만식(Lee, Man-Sig),김영석(Kim, Young-Seok),송명호(Song, Myung-Ho) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.06

Growth characteristics of methane-propane clathrate hydrate, growing under different undercooling conditions, was investigated. After the water within pressurized vessel was fully saturated with guest gas molecules by agitation, medium was rapidly undercooled and maintained at the constant temperature. The growth of hydrate was always Initiated with film formations at the upper bounding surface of liquid pool. The visual observation using microscope revealed detailed features of subsequent crystal nucleation, migration, growth and interference occurring within liquid pool. A number of small crystals ascended and settled at the hydrate film. When undercooling was small ({Delta}T=3.2K), some of the settled crystals slowly grew into faceted columns. As the undercooling increased, the downward growth of crystals underneath the hydrate film became dendritic and occurred with greater rate and with finer arm spacing. The shapes of the floating crystals were diverse and included octahedron and triangular or hexagonal platelet When the undercooling was small, the octahedral crystals were found dominant. As the undercooling increased, the shape of the floating crystals also became dendritic. The detailed characteristics of floating crystals were reported in this study.

Toughening of Epoxy Resin System Using a Novel Dendritic Polysiloxane

Songqi Ma,Weiqu Liu,Chaohui Hu,Zhengfang Wang,Chunyi Tang 한국고분자학회 2010 Macromolecular Research Vol.18 No.4

Dendritic polymers have attracted increasing attention in the field of epoxy resin toughening. This paper is the first report of the use of a novel dendritic polysiloxane (DPSO) bearing high epoxide groups to modify the diglycidyl ether of bisphenol-A (DGEBA). The thermal properties, toughness and morphology of the cured epoxy resins were examined by DSC, TGA, impact testing and SEM. The chemical structure of DPSO was confirmed by FTIR, 29Si NMR and GPC. The Tg increased by approximately 7 oC after introducing the DPSO. The TGA results under N2 and air atmospheres showed that the initial degradation temperature for 5% weight loss (Td 5%), temperature for 50% weight loss (Td 50%) and residual weight percent at 800 oC (R800) all increased after introducing DPSO. Moreover, the addition of 3 phr DPSO100 resulted in a 70.4% increase in impact strength compared to that of the neat epoxy. The morphology of the fracture surfaces shows that the miscibility of polysiloxane with epoxy resin increased with increasing number of epoxy groups in DPSO, and the improved toughness was attributed to the rubber-bridged effect. The high number of epoxy groups in dendritic polysiloxane can react during the curing process,and participate chemically in the crosslinking network. DPSO is expected to improve significantly the toughness and thermal stability of epoxy resin.

논문 : Pivalic Acid-Ethanol 및 Succinonitrile-Salol 계에서의 수지상정 선단의 형상

석명진 ( Myung Jin Suk ),박영민 ( Young Min Park ),오승탁 ( Sung Tag Oh ),장시영 ( Si Young Chang ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.7

The shape of a dendrite tip has long been approximated by a paraboloid of revolution, but many attempts have been made as well to more accurately match the dendrite tip profile using other mathematical functions: power function, 4th order polynomial, and hyperbolic function. In the present work, dendrite tip shapes were matched by parabolic function. The differences between the dendrite tip shapes of pivalic acid(PVA)-ethanol(Eth) and succinonitrile(SCN)-salol systems, characterized by anisotropic and isotropic solid-liquid interfacial properties, respectively, were quantitatively treated using shape parameters. The PVA-Eth system showed a slightly higher Z/R value than the SCN-salol system, their Z/R values lying in the range 2-4. (Z is the distance from the tip beyond which the parabolic fit starts to deviate from the profile, and R the tip radius.) λP is the distance from the tip beyond which side branching starts to appear, and is larger in the PVA-Eth system than the SCNsalol system. λP is different for both sides of the 2-dimensional dendrite profile. The difference of λP between both sides of the dendrite is larger for PVA-Eth system than for SCN-salol, implying that the dendrite of PVA-Eth is less symmetric than that of SCN-salol.

5-Hydroxytryptamine 6 Receptor (5-HT6R)-Mediated Morphological Changes via RhoA-Dependent Path-ways

Md. Ataur Rahman,김한나,이강호,윤형문,홍정화,김영재,추현아,박미경,임혜원 한국분자세포생물학회 2017 Molecules and cells Vol.40 No.7

The 5-HT6R has been considered as an attractive therapeutic target in the brain due to its exclusive expression in the brain. However, the mechanistic linkage between 5-HT6Rs and brain functions remains poorly understood. Here, we examined the effects of 5-HT6R-mediated cell morphological changes using immunocytochemistry, Western blot, and live-cell imaging assays. Our results showed that the activation of 5-HT6Rs caused morphological changes and increased cell surface area in HEK293 cells expressing 5-HT6Rs. Treatment with 5-HT specifically increased RhoA-GTP activity without affecting other Rho family proteins, such as Rac1 and Cdc42. Furthermore, live-cell imaging in hippocampal neurons revealed that activation of 5-HT6Rs using a selective agonist, ST1936, increased the density and size of dendritic protrusions along with the activation of RhoA-GTP activity and that both effects were blocked by pretreatment with a selective 5-HT6R antagonist, SB258585. Taken together, our results show that 5-HT6R plays an important role in the regulation of cell morphology via a RhoA-dependent pathway in mammalian cell lines and primary neurons.

Effective photocatalytic activity of Reduce Dendritic Fibrous Nano Titania on Tetracycline degradation

김진희,유효종 한국공업화학회 2023 한국공업화학회 연구논문 초록집 Vol.2023 No.1

The growth of AlN dendritic crystals with uniform morphology by an aluminum microdroplet localization approach

Nersisyan, Hayk H.,Lee, Seong Hun,Yoo, Bung Uk,Lee, Jong Hyeon Elsevier 2018 Combustion and Flame Vol.196 No.-

<P><B>Abstract</B></P> <P>We developed an attractive combustion approach for synthesizing uniformly shaped AlN dendritic crystals by combustion of Al + 0.1AlF<SUB>3</SUB> <SUB> </SUB>+ <I>k</I>Al<SUB>2</SUB>O<SUB>3</SUB> powder mixtures in a nitrogen atmosphere. The combustion temperature measured for various <I>k</I> values was between 1650 and 1750 °C and the micro-droplets of Al formed in the beginning stages of the process were enveloped by the solid layers of Al<SUB>2</SUB>O<SUB>3</SUB>, and the subsequent multipoint nucleation and crystallization produced morphologically and size uniform dendritic crystals. We proposed a theoretical model for calculating the thickness and the number of Al<SUB>2</SUB>O<SUB>3</SUB> layers around of Al microdroplets at known concentration of Al<SUB>2</SUB>O<SUB>3</SUB>. Depending on the concentration of Al<SUB>2</SUB>O<SUB>3</SUB>, these structures were simple stars with six points and stellar dendrites with multiple petals.</P>

5-Hydroxytryptamine 6 Receptor (5-HT₆R)-Mediated Morphological Changes via RhoA-Dependent Pathways

Rahman, Md. Ataur,Kim, Hanna,Lee, Kang Ho,Yun, Hyung-Mun,Hong, Jung-Hwa,Kim, Youngjae,Choo, Hyunah,Park, Mikyoung,Rhim, Hyewhon Korean Society for Molecular and Cellular Biology 2017 Molecules and cells Vol.40 No.7

The $5-HT_6R$ has been considered as an attractive therapeutic target in the brain due to its exclusive expression in the brain. However, the mechanistic linkage between $5-HT_6Rs$ and brain functions remains poorly understood. Here, we examined the effects of $5-HT_6R$-mediated cell morphological changes using immunocytochemistry, Western blot, and live-cell imaging assays. Our results showed that the activation of $5-HT_6Rs$ caused morphological changes and increased cell surface area in HEK293 cells expressing $5-HT_6Rs$. Treatment with 5-HT specifically increased RhoA-GTP activity without affecting other Rho family proteins, such as Rac1 and Cdc42. Furthermore, live-cell imaging in hippocampal neurons revealed that activation of $5-HT_6Rs$ using a selective agonist, ST1936, increased the density and size of dendritic protrusions along with the activation of RhoA-GTP activity and that both effects were blocked by pretreatment with a selective $5-HT_6R$ antagonist, SB258585. Taken together, our results show that $5-HT_6R$ plays an important role in the regulation of cell morphology via a RhoA-dependent pathway in mammalian cell lines and primary neurons.