• Title/Summary/Keyword: Colloidal systems

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Fabrication of Colloidal Clusters of Polymer Microspheres and Nonspherical Hollow Micro-particles from Pickering Emulsions

  • Cho, Young-Sang;Kim, Tae-Yeol;Yi, Gi-Ra;Kim, Young-Kuk;Choi, Chul-Jin
    • Bulletin of the Korean Chemical Society
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    • v.33 no.1
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    • pp.159-166
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    • 2012
  • We have introduced the Pickering emulsion systems to generate novel confining geometries for the selforganization of monodisperse polymer microspheres using nanoparticle-stabilized emulsion droplets encapsulating the building block particles. Then, through the slow evaporation of emulsion phases by heating, these microspheres were packed into regular polyhedral colloidal clusters covered with nanoparticle-stabilizers made of silica. Furthermore, polymer composite colloidal clusters were burnt out leaving nonspherical hollow micro-particles, in which the configurations of the cluster structure were preserved during calcination. The selfassembled porous architectures in this study will be potentially useful in various applications such as novel building block particles or supporting materials for catalysis or gas adsorption.

In vitro release test models for water-insoluble drugs loaded in colloidal carriers

  • Lee, Jung-Min;Choi, Sung-Up;Lee, Byoung-Moo;Lee, Sung-Jae;Choi, Young-Wook
    • Proceedings of the PSK Conference
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    • 2003.04a
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    • pp.295.1-295.1
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    • 2003
  • A suitable model for the estimation of the drug release from nanoparticles has been varied and problematic, especially for the release from lipid nanoparticles containing water-insoluble drugs, due to the difficult particle collection from the release medium. Dialysis membrane has been widely used for the release test from colloidal carrier systems. The amount of drug from the carriers in normal dialysis diffusion technique was very low typically. (omitted)

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Fabrication of a Hybrid Superhydrophobic/superhydrophilic Surface for Water Collection: Gravure Offset Printing & Colloidal Lithography (수분수집을 위한 초발수/초친수 복합 표면 제작: 그라비아 옵셋 프린팅과 콜로이달 리소그래피 공정)

  • Ji, Seung-Muk;Kim, In-Young;Kim, Eun-Hee;Jung, Jie-Un;Kim, Wan-Doo;Lim, Hyun-Eui
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.1
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    • pp.19-24
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    • 2012
  • We demonstrate the desert beetle back mimicking hybrid superhydrophilic/superhydrophobic patterned surface by using the combination method of colloidal lithography and gravure offset printing for nano and micro patterning, respectively. The two methods are cost-effective and industrially available techniques compared to the other nano/micro patterning methods. To verify the water collecting function of the hybrid surface, the water condensation behavior is investigated on the chilled surface in ambient temperature and high humidity. Due to the synergetic effect of drop and film wise condensation, the hybrid superhydrophobic/superhydrophilic surface shows the higher efficiency than one of single wettability surfaces. The work is underway to get the good patterns of hybrid surfaces for water collecting from the dew or fog.

Flocculation kinetics and hydrodynamic interactions in natural and engineered flow systems: A review

  • Oyegbile, Benjamin;Ay, Peter;Narra, Satyanarayana
    • Environmental Engineering Research
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    • v.21 no.1
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    • pp.1-14
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    • 2016
  • Flocculation is a widely used phase separation technique in industrial unit processes and is typically observed in many natural flow systems. Advances in colloidal chemistry over the past decades has vastly improved our understanding of this phenomenon. However, in many practical applications, process engineering still lags developments in colloidal science thereby creating a gap in knowledge. While significant progress has been made in environmental process engineering research over the past decades, there is still a need to align these two inter-dependent fields of research more closely. This paper provides a comprehensive review of the flocculation mechanism from empirical and theoretical perspective, discuss its practical applications, and examines the need and direction of future research.

Study on Frictional Characteristics of Sub-micro Structured Silicon Surfaces (서브 마이크로 구조를 가진 실리콘 표면의 마찰 특성 연구)

  • Han, Ji-Hee;Han, Gue-Bum;Jang, Dong-Yong;Ahn, Hyo-Sok
    • Tribology and Lubricants
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    • v.33 no.3
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    • pp.92-97
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    • 2017
  • The understanding of the friction characteristics of micro-textured surface is of great importance to enhance the tribological properties of nano- and micro-devices. We fabricate rectangular patterns with submicron-scale structures on a Si wafer surface with various pitches and heights by using a focused ion beam (FIB). In addition, we fabricate tilted rectangular patterns to identify the influence of the tilt angle ($45^{\circ}$ and $135^{\circ}$) on friction behaviour. We perform the friction test using lateral force microscopy (LFM) employing a colloidal probe. We fabricate the colloidal probe by attaching a $10{\pm}1-{\mu}m$-diameter borosilicate glass sphere to a tipless silicon cantilever by using a ultraviolet cure adhesive. The applied normal loads range between 200 nN and 1100 nN and the sliding speed was set to $12{\mu}m/s$. The test results show that the friction behavior varied depending on the pitch, height, and tilt angle of the microstructure. The friction forces were relatively lower for narrower and deeper pitches. The comparison of friction force between the sub-micro-structured surfaces and the original Si surface indicate an improvement of the friction property at a low load range. The current study provides a better understanding of the influence of pitch, height, and tilt angle of the microstructure on their tribological properties, enabling the design of sub-micro- and micro-structured Si surfaces to improve their mechanical durability.

Effects of Carbon Fiber on Mechanical Behaviour of Al2O3 Porous Ceramics

  • Basnet, Bijay;Lim, Hyung Mi;Lee, Kee Sung;Kim, Ik Jin
    • Journal of the Korean Ceramic Society
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    • v.56 no.5
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    • pp.513-520
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    • 2019
  • This study reports the improvement of mechanical properties of Al2O3 porous ceramics from colloidal suspension with the addition of carbon fiber by direct foaming. The initial colloidal suspension of Al2O3 was partially hydrophobized by surfactant to stabilize wet foam with the addition of carbon fiber from 2 to 8 wt% as stabilizer. The influence of carbon fiber on the air content, bubble size, pore size and pore distribution in terms of wet foam stability and physical properties of porous ceramics were discussed. The viscosity of the colloidal suspension was increased giving solid like properties with the increased in carbon fiber content. The mechanical properties of the sintered porous samples were investigated by Hertzian indentation test. The results show the wet foam stability of more than 90% corresponds to compressive loading of 156.48 N and elastic modulus of 57.44 MPa of sintered sample with 8 wt% of carbon fiber content.

Spectroscopic Characterization of Aqueous and Colloidal Am(III)-CO3 Complexes for Monitoring Species Evolution

  • Hee-Kyung Kim
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.20 no.4
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    • pp.371-382
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    • 2022
  • Carbonates are inorganic ligands that are abundant in natural groundwater. They strongly influence radionuclide mobility by forming strong complexes, thereby increasing solubility and reducing soil absorption rates. We characterized the spectroscopic properties of Am(III)-carbonate species using UV-Vis absorption and time-resolved laser-induced fluorescence spectroscopy. The deconvoluted absorption spectra of aqueous Am(CO3)2- and Am(CO3)33- species were identified at red-shifted positions with lower molar absorption coefficients compared to the absorption spectrum of aqua Am3+. The luminescence spectrum of Am(CO3)33- was red-shifted from 688 nm for Am3+ to 695 nm with enhanced intensity and an extended lifetime. Colloidal Am(III)-carbonate compounds exhibited absorption at approximately 506 nm but had non-luminescent properties. Slow formation of colloidal particles was monitored based on the absorption spectral changes over the sample aging time. The experimental results showed that the solubility of Am(III) in carbonate solutions was higher than the predicted values from the thermodynamic constants in OECD-NEA reviews. These results emphasize the importance of kinetic parameters as well as thermodynamic constants to predict radionuclide migration. The identified spectroscopic properties of Am(III)-carbonate species enable monitoring time-dependent species evolution in addition to determining the thermodynamics of Am(III) in carbonate systems.