• Polymer(Korea)
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• v.30 no.6
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• pp.505-511
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• 2006

We tried to prepare polystyrene composite particles containing carbon black by suspension polymerization with water as a reaction medium. Hydrophobic silica was selected as a stabilizer and oil-soluble azobisisobutyronitrile (AIBN), as an initiator. All polymerization reactions were carried out at a fixed temperature of $75^{\circ}C$. Stabilizer concentration was varied from $0.17{\sim}3.33wt%$ compared to water, where particles with $7.96{\mu}m$ in average diameter were obtained at 1.57 wt% of stabilizer. Increase in divinylbenzene concentration, as a crosslinking agent, from $0.1{\sim}1.0 wt%$ compared to monomer exhibited a large increase in average particle diameter Incorporation of 1wt% of carbon black compared to monomer produced an increase in average diameter It is speculated that viscosity lower than that necessary to induce even dispersion of carbon black particles led to poor dispersion, and as a result, large particles. For a styrene mixture containing 3 wt% carton black compared to monomer, enhanced dispersion due to an increase in carbon black concentration reduced average particle diameters. For styrene mixtures containing 1 and 3 wt% carbon black compared to monomer, preparticles before polymerization and polymer composite particles after polymerization showed a similar tendency towards particle formation. When carbon black concentration compared to monomer was increased to 5 and 7 wt%, styrene mixtures exhibited a large increase in viscosity and thus better dispersion of carbon black particles, which led to a decrease in preparticle diameters. However, these particles experienced agglomeration in the polymerization process, and polystyrene composite particles increased in average diameter.

• Elastomers and Composites
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• v.57 no.4
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• pp.215-221
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• 2022

In this study, high-penetration asphalt with low greenhouse gas emissions was used in the asphalt mixing process to reduce the carbon emissions during the reaction due to its capacity to be produced even at low temperatures. In effect, cationic, anionic, and non-ionic dispersants were added and mixed in different feeding ratios, seeking an effective dispersion of the modifiers (SIS, PS, TPEE, and SEBS) into the high-penetration asphalt matrix and forming an asphalt binder with a melting point of 120 ℃. The compatibility of the modifiers and the high-penetration asphalt was examined using SEM and DSC techniques, and the role of NDP-1 as a dispersant was carefully investigated with respect to dissolution time. The analyses showed that: (1) the dispersibility of the asphalt binder is good when the non-ionic dispersant is used; (2) as the concentration of the non-ionic dispersant increases, the dissolution time decreases and the domain size contracts; (3) the ND70-PS has the shortest dissolution time, the lowest agglomeration rate, and a single Tg value.

• Journal of Powder Materials
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• v.16 no.2
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• pp.131-137
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• 2009

This paper deals with the effects of the surfactant and preplate process (sensitization and activation) on electroless copper plating on carbon nano-fiber (CNF). Ultrasonic irradiation was applied both during dispersion of CNF and during electroless plating containing preplate process. The dispersion of CNF and flatness of the plated copper film were discussed based on the changes in surfactant concentration and preplate process time. It was clearly shown that high concentration of surfactant and long time of preplate process could promote the agglomeration of CNF and uneven copper plating on CNF.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1378-1381
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• 2006

The CNTs are the most extensively studied material which are characterized by the complete property of matter, structure, and the large thermal conductivity (Thermal conductivity of $CNTs\;{\sim}>2000W/mK$ vs. Thermal conductivity of Aluminum ${\sim}\;>204W/mK$). Thus, they are successfully applied to the various fields. However, due to the strong agglomeration caused by the van der waal's force, their applications are limited. In the present study, a new method for CNTs dispersion was developed by using the mechanical dispersion, acid treatment, and then Cu was coated. This process produces CNTs/Cu nanocomposite powders, whereby the CNTs are homogeneously located within the Cu powders. The thermal properties of the CNTs/Cu nanocomposite were investigated.

• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.1-4
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• 1998

SiC whisker reinforced Al2O3-SiC composite was fabricated by reaction synthesis method whish is cost ef-fective and allows good dispersion of whiskers. Fracture strength at room temperature showed the highest value with 150$0^{\circ}C$ reaction temperature because a lot of SiC whiskers was formed. Fracture strength at 135$0^{\circ}C$ did not show big differences with reaction temperature due to agglomeration of whiskers and formation of sil-icon oxynitride during hot MO(modulus of rupture) test probably promoting grain boundary sliding.

• Analytical Science and Technology
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• v.32 no.3
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• pp.77-87
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• 2019

High viscosity carbon black dispersions are used in various industrial fields such as color cosmetics, rubber, tire, plastic and color filter ink. However, carbon black particles are unstable to heat due to inherent characteristics, and it is very difficult to keep the quality of the product constant due to agglomeration of particles. In general, particle size analysis is performed by dynamic light scattering (DLS) during the dispersion process in order to select the optimum dispersant in the carbon black dispersion process. However, the existing low viscosity analysis provides reproducible particle distribution analysis results, but it is difficult to select the optimum dispersant because it is difficult to analyze the reproducible particle distribution at high viscosity. In this study, dynamic light scattering (DLS) and asymmetrical flow field-flow fractionation (AsFlFFF) analysis methods were compared for reproducible particle size analysis of high viscosity carbon black. First, the stability of carbon black dispersion was investigated by particle size analysis by DLS and AsFlFFF according to milling time, and the validity of analytical method for the selection of the optimum dispersant useful for carbon black dispersion was confirmed. The correlation between color and particle size of particles in high viscosity carbon black dispersion was investigated by using colorimeter. The particle size distribution from AsFlFFF was consistent with the colorimetric results. As a result, the correlation between AsFlFFF and colorimetric results confirmed the possibility of a strong analytical method for determining the appropriate dispersant and milling time in high viscosity carbon black dispersions. In addition, for nanoparticles with relatively broad particle size distributions such as carbon black, AsFlFFF has been found to provide a more accurate particle size distribution than DLS. This is because AsFlFFF, unlike DLS, can analyze each fraction by separating particles by size.

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.439-443
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• 2010

Nano sized SiC particles (270 nm) are easily agglomerated in nickel sulfamate electrolytic bath during a composite electrodeposition process. The agglomeration of nano particles in composite coatings can significantly reduce the mechanical properties of the composite coatings. In this study, Ni-SiC nano composite coatings were fabricated using a conventional electrodeposition process with the aid of ultrasound. Nano particles were found to be distributed homogeneously with reduced agglomeration in the ultrasonicated samples. Substantial improvements in mechanical properties were observed in the composite coatings prepared in presence of ultrasound over those without ultrasound. Ni-SiC composite coatings were prepared with variable ultrasonic frequencies ranging from 24 kHz to 78 kHz and ultrasonic powers up to 300 watts. The ultrasonic frequency of 38 kHz with ultrasonic power of 200 watt was revealed to be the best ultrasonic conditions for homogeneous dispersion of nano SiC particles with improved mechanical properties in the composite coatings. The microstructures, phase compositions, and mechanical properties of the composite coatings were observed and evaluated using SEM, XRD, Vickers microhardness, and wear test. The Vickers microhardness of composite coatings under ultrasonic condition was significantly improved as compared to the coatings without ultrasound. The friction coefficient of the composite coating prepared with an ultrasonic condition was also smaller than the pure nickel coatings. A synergistic combination of superior wear resistance and improved microhardness was found in the Ni-SiC composite coatings prepared with ultrasonic conditions.

• Toxicological Research
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• v.29 no.2
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• pp.121-127
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• 2013

Nanotoxicological research has shown toxicity of nanomaterials to be inversely related to particle size. However, the contribution of agglomeration to the toxicity of nanomaterials has not been sufficiently studied, although it is known that agglomeration is associated with increased nanomaterial size. In this study, we prepared aerosols of nano-sized carbon black by 2 different ways to verify the effects of agglomeration on the toxicity and deposition of nano-sized carbon black. The 2 methods of preparation included the carbon black dispersion method that facilitated clustering without sonication and the carbon black dispersion method involving sonication to achieve scattering and deagglomeration. Male Sprague-Dawley rats were exposed to carbon black aerosols 6 hr a day for 3 days or for 2 weeks. The median mass aerodynamic diameter of carbon black aerosols averaged $2.08{\mu}m$ (for aerosol prepared without sonication; group N) and $1.79{\mu}m$ (for aerosol prepared without sonication; group S). The average concentration of carbon black during the exposure period for group N and group S was $13.08{\pm}3.18mg/m^3$ and $13.67{\pm}3.54mg/m^3$, respectively, in the 3-day experiment. The average concentration during the 2-week experiment was $9.83{\pm}3.42mg/m^3$ and $9.08{\pm}4.49mg/m^3$ for group N and group S, respectively. The amount of carbon black deposition in the lungs was significantly higher in group S than in group N in both 3-day and 2-week experiments. The number of total cells, macrophages and polymorphonuclear leukocytes in the bronchoalveolar lavage (BAL) fluid, and the number of total white blood cells and neutrophils in the blood in the 2-week experiment were significantly higher in group S than in normal control. However, differences were not found in the inflammatory cytokine levels (IL-$1{\beta}$, TNF-${\alpha}$, IL-6, etc.) and protein indicators of cell damage (albumin and lactate dehydrogenase) in the BAL fluid of both group N and group S as compared to the normal control. In conclusion, carbon black aerosol generated by sonication possesses smaller nanoparticles that are deposited to a greater extent in the lungs than is aerosol formulated without sonication. Additionally, rats were narrowly more affected when exposed to carbon black aerosol generated by sonication as compared to that produced without sonication.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.83-88
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• 2010

The composite electroplating is accomplished by adding inert materials during the electroplating. Permalloy is the term for Ni-Fe alloy and it is used for industrial applications due to its high magnetic permeability. Microhardness for microdevices is enhanced after composite coating and it increases the life cycle. However, the hydroxyl group on the silica makes their surface susceptible to moisture and it causes the silica nanoparticles to be agglomerated in the aqueous solution. The agglomeration problem causes poor dispersion which eventually interrupts uniform deposition of silica nanoparticles. In this study, the dispersion of silica nanoparticles in the permalloy electroplated layer is reported with variation of additives and sonication time. Longer sonication period guaranteed better silica nanopowder dispersion and sonication period also influenced on composition of deposits. The amount of silica nanopowder codeposition and surface morphologies were influenced with variation of additives. In alkaline bath, smooth surface morphology and relatively high contents of silica nanopowder codeposition were obtained with addition of sodium lauryl sulfate.

• Polymer(Korea)
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• v.24 no.3
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• pp.374-381
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• 2000

Composites of polypropylene (PP) and organically modified montmorillonite (org-MMT) were prepared by melt mixing in an intensive mixer. Three grades of PP's having different melt viscosities were employed to investigate the dispersion characteristics of the composites with various org-MMT's. Depending on the matrix viscosity and nature of the interlayer in org-MMT significant variations of the phase structure were found. Under the constant mixing condition and matrix viscosity, intercalation of PP chains into the interlayer of org-MMT was possible when initial interlayer distance and packing density were maintained in the optimum range; by which the loss in entropy associated with the confinement of polymer chains was compensated. The state of org-MMT particle dispersion was improved by increasing the matrix viscosity only in the case that dispersed phase is suitable for intercalation process thermodynamically, otherwise little variation was occurred regardless of the matrix viscosity. Due to the lack of specific interaction between PP and erg-MMT considered here, although the intercalation was possible for an appropriate org-MMT, the composites revealed unstable phase structure upon increasing the mixing time, which was characterized by agglomeration of the org-MMT domains.