• Title/Summary/Keyword: Pickering

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Cosmetic Emulsions: Stabilization by Particles (화장품 에멀젼: 입자에 의한 안정화)

  • Cho, Wan-Goo
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.36 no.1
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    • pp.1-16
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    • 2010
  • The preparation and properties of emulsions stabilized by the adsorption of solid particles at the oil-water interface are reviewed. Comparison is made with the behaviour of surfactant-stabilized emulsions. Many of the properties of Pickering emulsions are attributed to the large free energy of adsorption for particles. The main differences is due to the irreversible adsorption of particles to the interface. Phase inversion from w/o (water-in-oil) to o/w (oil-in-water) can be brought by increasing the volume fraction of water. Hydrophilic particles tend to form o/w emulsion whereas hydrophobic particles form w/o emulsion. The contact angle at the oil-water interface is main parameter to decide the emulsion type. The aspects of stability of Pickering emulsions are in contrast to general emulsions in some points. The possibility using Pickering emulsions for cosmetics is also proposed.

Preparation of $SiO_2-TiO_2$ Porous Composite Pigments Using a Pickering Emulsion Method as Template (피커링 에멀젼을 형판으로 하는 $SiO_2-TiO_2$ 다공성 분체의 제조)

  • Lee, Sang-Gil;Kim, Young-Ho;Hong, Jun-Ki;Pyo, Hyeong-Bae;Lee, Dong-Kyu
    • Journal of the Korean Applied Science and Technology
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    • v.29 no.3
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    • pp.377-392
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    • 2012
  • It has been known that small solid particles act as a stabilizer in pickering emulsion system. In this study, we successfully prepared stable pickering emulsion in n-hexylalcohol and water system with $TiO_2$ whose surface was treated by alkylsilane. The optimum condition to prepare pickering emulsion stabilized by $TiO_2$ particles was determined by amount of $TiO_2$ particles and ratio of water and oil phase. The type of pickering emulsion was dependent on wettability of particles for water and n-hexylalcohol. When the amount of $TiO_2$ particles increased up to 5.00 wt%, the stability of pickering emulsion was showed to be improved. The most stable pickering emulsion was prepared in the case of W/O type which has the ratio of oil and water phase (3 : 7). We tried to prepare porous $SiO_2-TiO_2$ composite pigments using a pickering emulsion as template at the optimal condition. Porous pigments were synthesized with Ludox HS-30 as an inorganic material by sol-gel process. The characteristics and shape of porous pigments were measured by optical microscope, SEM, BET, XRD and EDS.

A Recent Research Trends for Food Emulsions using Pickering Stabilization of Nano-particles (나노 입자의 피커링 안정화를 이용한 식품 에멀젼의 최근 연구동향)

  • Cho, Wan-Goo
    • Journal of the Korean Applied Science and Technology
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    • v.29 no.2
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    • pp.238-247
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    • 2012
  • Nanotechnology in the food industry is an emerging area with considerable research and potential products. Solid particles of nanoscale and microscale dimensions are becoming recognized for their potential application in the formulation of novel dispersed systems containing emulsified oil or water droplets. This review describes developments in the formation and properties of food-grade emulsion systems based on edible fat crystals, silica nanoparticles, and novel particles of biological origin nanocrystals. The special features characterizing the properties of Pickering stabilized droplets are focused in comparison with those of protein-stabilized emulsions. We also review describes application examples of these in the food industry.

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.

Preparation of Silica Hollow Composite Particles

  • Lee, Dong Hoon;Lee, Chang Hyun
    • Bulletin of the Korean Chemical Society
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    • v.35 no.11
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    • pp.3303-3306
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    • 2014
  • A facile and effective approach has been developed to prepare hybrid hollow microspheres, via consecutive processes of pickering mini-emulsion polymerization for core-shell formation, and calcination of the sacrificial core. The resulting hollow composite particles have mono-layered shells. The morphology and size characteristics of synthesized composite particles were investigated, using dynamic light scattering (DLS) and scanning electron microscopy (SEM) measurements.

A Review of Pressure Tube Failure Accident in the CANDU Reactor and Methods for Improving Reactor Performance

  • Yoo, Ho-Sik;Chung, Jin-Gon
    • Nuclear Engineering and Technology
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    • v.30 no.3
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    • pp.262-272
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    • 1998
  • The experiences and causes of pressure tube cracking accidents in the CANDU reactors and the development of the fuel channel at AECL(Atomic Energy Canada Limited) have been described. Most of the accidents were caused by Delayed Hydride Cracking(DHC). In the cases of the Pickering units 3&4 and the Bruce unit 2, excessive residual stresses induced by an improper rolled joint process played a role in DHC. In the Pickering unit 2, cracks formed by contact between the pressure and calandria tubes due to the movement of the garter spring were the direct cause of the failure. To extend the life of a fuel channel, several R&D programs examining each component of the fuel channel have been carried out in Canada. For a pressure tube, the main concern is focused on changing the fabrication processes, e.g., increasing cold working rate, conducting intermediate annealing and adding a third element like Fe, V, and Cr to the tube material. In addition to them, chromium plating on the end fitting and increasing wall thickness at both ends of the calandria tube are considered. There has also been much interest in the improvement of fuel channel performance in our country and several development programs are currently under way.

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양식어류의 선별과정중 수심감소와 어류의 수조이동에 따른 스트레스 반응

  • 허준욱;장영진;임한규;이복규
    • Proceedings of the Korean Society of Fisheries Technology Conference
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    • 2001.05a
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    • pp.285-286
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    • 2001
  • 양식장에서 빈번하게 발생할 수 있는 스트레스 요인은 인위적 및 환경적 요인으로 나뉘어지며, 어류의 성장과 항상성 유지에 상당한 영향을 미치는 것으로 알려져 있다(Pickering, 1992). 인위적 스트레스 요인중 성장차이가 나는 어류를 같은 크기의 그룹으로 조절하는 선별작업은 양식장에서 피할 수 없는 관리사항의 하나이며, 빈번하고도 난잡한 선별작업은 어류에게 상당한 스트레스 요인으로 작용할 것이다. (중략)

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A Study on Community Counter-terrorism (지역사회 대테러활동에 관한 연구)

  • Jung, Woo-Il
    • Korean Security Journal
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    • no.19
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    • pp.187-205
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    • 2009
  • In this study, Horgan(2005)'s argument highlights the centrality to any successful counter-terrorism strategy of understanding the social context in which terrorist ideologies take root. Counter-terrorism refers to the practices, tactics, techniques, and strategies that governments, militaries, police departments and corporations adopt in response to terrorist threats and/or acts, both real and imputed. Pickering et al.(2008) historically explained four counter-terrorism strategies as traditional counter-terrorism model, community intelligence model, belonging model, social cohesion model. It is thus proposed that counter-terrorism strategies are based in established networks within the community and proactively seeks to continually renew these relationships between the community and police. This approach must embrace an explicit recognition of multiculturalism and its political imperative and drive in a policing organization explicitly committed to social cohesion and human rights in both discourse and practice. We, therefore, suggests community tree counter-terrorism approaches, or community intelligence model, belonging model and social cohesion model to apply to counter-terrorism agencies in Korea. These models are on the basis of Pickering et al.'s counter-terrorism models, which by using community policing to boot socially cohesion police are better able to position themselves as mediators to negotiate settlements between the competing demands of different social groups.

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