• Title/Summary/Keyword: microsphere

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Synthesis of Microspheric Silicone Polymer Beads by UV Irradiation and Alkoxy Hydrolysis (UV 조사와 Alkoxy 가수분해 법을 이용한 구형 실리콘 마이크로 고분자 비드의 합성)

  • Park, Seung-Wook;Kim, Jung-Joo;Hwang, Eui-Hwan;Hwang, Taek-Sung
    • Polymer(Korea)
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    • v.32 no.4
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    • pp.377-384
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    • 2008
  • In this study, the microsphere silicone polymer beads were synthesized by UV irradiation and alkoxy hydrolysis. The coefficient of variation (CV) of microsphere silicone polymer beads were decreased with increasing UV intensity, reaction time. The mean particle diameter, refractive index, and pH value were $4.1{\mu}m$, 1.43 and 7.5, respectively. Also, the true and bulk specific gravity, moisture content were 1.30, and 0.40, below 2%. The mean particle diameter and CV were the lowest at 0.1 wt% hexamethyldisilazane (HMDS) and their roundnesses were $0.95{\sim}0.98{\mu}m$ values. The particle dispersion index of microsphere silicone polymer beads was 4.92 at 450 W, 90 min and the yield was increased to 11.3% at 20 wt% methyltrimethoxysilane (MTMS). The mean particle diameter was decreased with increasing the stirring rate and reaction temperature.

Graphene Attached on Microsphere Surface for Thermally Conductive Composite Material (그래핀이 표면에 분포된 미립자를 이용한 열전도 복합재료의 개발)

  • Choi, Jae-Yong;Lee, Joo Hyuk;Kim, Mi Ri;Lee, Ki Seok;Cho, Kuk Young
    • Clean Technology
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    • v.19 no.3
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    • pp.243-248
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    • 2013
  • Thermally conductive materials are widely used in various applications where effective heat dissipation is required. Graphene shows high potential for various uses owing to high electrical conductivity, good mechanical strength, and high thermal conductivity. Generally previous works used organic solvents are generally used for the dispersion of graphene in fabrication procedure. In order to achieve clean fabrication it is required to use water media. In this study, we fabricated graphene attached poly(methyl methacrylate) (PMMA) microsphere via microfluidic method. With the aid of surfactant, graphene was well dispersed in water which was used as continuous flow. Thermal conductivity was improved with the small amount of graphene addition and this indicate potential use of this system for thermally conductive composite material.

Effect of Emulsified Refine Cooking Oil and Expandable Microsphere on Durability of High-Volume Blast Furnace Slag Concrete (정제유지류 및 팽창성 인공 기포 조합이 고로슬래그 다량치환 콘크리트의 내구성 및 미시적 특성에 미치는 영향)

  • Han, Min-Cheol;Han, Dongyeop;Lee, Myung-Ho
    • Journal of the Korea Institute of Building Construction
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    • v.15 no.2
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    • pp.201-207
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    • 2015
  • In this paper, a series of experiments was conducted to evaluate the resistibility of carbonation and freeze-thawing damage of the high-volume blast furnace slag concrete using expancel, the expandable microsphere, and ERCO, emulsified refine cooking oil. The concrete mixture of 0.45 water-to-binder ratio with 60% of blast furnace slag was evaluated for carbonation, freeze-thawing resistibility, SEM, and porosity. According to the previous research, replacing ERCO contributes on improving carbonation resistibility with capillary pore filling effect by soap foaming reaction of ERCO while significantly decreased freeze-thawing resistibility. To improve this decreased freeze-thawing resistibility, expancel was used, and thus freeze-thawing resistibility was improved as the replacement ratio of expancel was increased. It is considered that the selective volume shrunken effect of expancel due to the external pressure and decreased air void spacing factor due to expancel.

Confined Pt and CoFe2O4 Nanoparticles in a Mesoporous Core/Shell Silica Microsphere and Their Catalytic Activity

  • Kang, Dong-Hyeon;Eum, Min-Sik;Lee, Byeong-No;Bae, Tae-Sung;Lee, Kyu-Reon;Lim, Heung-Bin;Hur, Nam-Hwi
    • Bulletin of the Korean Chemical Society
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    • v.32 no.10
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    • pp.3712-3719
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    • 2011
  • Confined Pt and $CoFe_2O_4$ nanoparticles (NPs) in a mesoporous core/shell silica microsphere, Pt-$CoFe_2O_4$@meso-$SiO_2$, were prepared using a bi-functional linker molecule. A large number of Pt NPs in Pt-$CoFe_2O_4$@meso-$SiO_2$, ranging from 5 to 8 nm, are embedded into the shell and some of them are in close contact with $CoFe_2O_4$ NPs. The hydrogenation of cyclohexene over the Pt-$CoFe_2O_4$@meso-$SiO_2$ microsphere at $25^{\circ}C$ and 1 atm of $H_2$ yields cyclohexane as a major product. In addition, it gives oxygenated products. Control experiments with $^{18}O$-labelled water and acetone suggest that surface-bound oxygen atoms in $CoFe_2O_4$ are associated with the formation of the oxygenated products. This oxidation reaction is operative only if $CoFe_2O_4$ and Pt NPs are in close contact. The Pt-$CoFe_2O_4$@meso-$SiO_2$ catalyst is separated simply by a magnet, which can be re-used without affecting the catalytic efficiency.

Preparation and Evaluation of Polymer Microspheres Containing Broussonetia Kazinoki Root Extract (닥나무 뿌리 추출물을 함유하는 고분자 마이크로입자 제조 및 평가)

  • Lim, Hyung Jun;Lee, Jin Young;Kim, Han Byul;Kim, Do-Hoon;Shin, Song Seok
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.39 no.2
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    • pp.89-96
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    • 2013
  • This study demonstrate that polymeric microspheres composed of poly (ethylene adipate) (PEA) and poly (methyl methacrylate) (PMMA) can encapsulate and remarkably stabilize Broussonetia kazinoki root extract. We compared the long-term stability and the activity of Broussonetia kazinoki root extract in polymeric microspheres fabricated with different polymer ratio of PEA and PMMA. PMMA was incorporated to the PEA microsphere in order to reinforce the physical strength of microsphere, and there was no noticeable negative effect on the activity of Broussonetia kazinoki root extract. Optical microscope (OM), polarized microscope (PM), and scanning electron microscope (SEM) results showed that PMMA incorporated microspheres were very spherical and had smoothsurface. On the other hand, PEA microspheres showed relatively irregular morphology due to the low physical strength of microspheres. Moreover, the mushroom tyrosinase activities were measured for testing the inhibitory activity of Broussonetia kazinoki root extract encapsulated in polymeric microspheres, and these microspheres showed the effective suppression of mushroom tyrosinase activity. Consequently, polymeric microspheres produced in this study may be beneficial for the research of improving stability and protecting labile substances incorporated into the polymeric microspheres.

Preparation and In Vitro Release of DNA-Loaded Poly(D,L-lactic-co-glycolic acid) Microspheres (DNA가 봉입된 Poly(D,L-lactic-co-glycolic acid) 미립구의 제조 및 시험관내 방출)

  • Son, Hye-Jung;Kim, Jin-Seok
    • Polymer(Korea)
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    • v.29 no.1
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    • pp.69-73
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    • 2005
  • To overcome the main disadvantages of non-viral gene delivery systems such as repeated administration due to the low transfection efficiency, poly(D,L-lactide-co-glycolide) was applied to encapsulate pDNA in its microsphere formulation. Free pDNA or various ratios (w/w) of chitosan/pDNA complexes was used for encapsulation, with the resulting encapsulation efficiency of 44%, 5%, and 8% for free pDNA, 0.7:1 and 1:1 ratios, respectively. Scanning electron micrographs of poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres encapsulating pDNA or chitosan-condensed pDNA revealed a smooth spherical shape immediately after microsphere preparation and a collapsed porous shape in 41 days due to the degradation of PLGA. In vitro release profile showed that the 0.7:1 (w/w) ratio formulation exerted 47% release in 26 days, whereas free pDNA or 1:1 (w/w) ratio formulation did only 15% or 32%, respectively.

Bioavailability of Microspheres Containing Felodipine (필로디핀이 함유된 미립구의 생체이용률)

  • 양재헌;나성범;김영일;김남순
    • YAKHAK HOEJI
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    • v.44 no.5
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    • pp.440-447
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    • 2000
  • Microspheres of felodipine, which is one of the calcium channel blocker using a mixture of Eudragi $t^{R}$ RL, L, E, and cellulose on the base of Eudragi $t^{R}$ RS were investigated. Cremopho $r^{R}$ was added to each preparation of polymers in order to increase the release of felodipine from microspheres. Felodipine-loaded microspheres were prepared by a solvent evaporation method, which is based on dispersion of methylene chloride containing felodipine and polymers in 0.5 w/v % polyvinyl alcohol solution. The average diameter based on the size distribution of the felodipine-loaded microspheres was observed to be ca. 40-55 ${\mu}{\textrm}{m}$. A good and smooth surface were showed in all types of the microspheres. The amount of felodipine loaded was over 90 w/w % in all types of microspheres. The dissolution profiles of felodipine from microspheres were similar with each type of polymer, and about a 60 w/w % of the total amount of felodipine loaded to microsphere was released within 7 hours. Dissolution rate of felodipine from the microsphere was increased by addition of Cremophor. After oral administration of the felodipine-loaded microspheres in PVA solution and felodipine alone in PEG solution to rats, respectively, the pharmacokinetic study revealed that the Tmax values of the microspheres were observed in the range of 0.67~l.0 hr while that of the felodipine solution was obtained 0.33 hr. In addition, the AUC of the microspheres at 0 to 7 hr was remarkably increased in comparison to that of felodipine solution. These results revealed that the microspheres based on Eudragit RS could be a good candidate for the controlled release drug delivery system for felodipine.e.e.e.

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Effect of the Surfactant Concentration on the Formation of Water Glass-based Porous Hollow Silica Microsphere (Porous한 물유리 기반 실리카 중공 미세구 형성에 대한 계면활성제 농도의 영향)

  • Lee, Jihun;Kim, Younghun;Kim, Taehee;Park, Hyung-Ho
    • Journal of the Microelectronics and Packaging Society
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    • v.28 no.4
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    • pp.79-83
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    • 2021
  • In this study, hollow silica microspheres (HSM) of various sizes formed according to the concentration of surfactants using water glass as a precursor, which is advantageous for commercialization due to its lower unit cost compared to conventional silicon alkoxide (tetraethyl orthosilicate, TEOS) was synthesized. The physical properties of the silica hollow microspheres according to the concentration of surfactant were analyzed using Fourier transform infrared, contact angle measurement, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda analyzers and field emission scanning electron microscopy. When porous water glass-based hollow silica spheres were prepared by adding a surfactant at an appropriate concentration, it was confirmed that excellent hollow silica spheres were formed with a specific surface area of 169 m2/g, an average particle size of 25.3 ㎛, and a standard deviation of 6.25.

Properties of Light-weight Expanded Bonded Leather Using Thermal Expandable Microspheres (열 팽창성 Microsphere를 적용한 경량 발포 재생피혁 특성 분석)

  • Shin, Eun-Chul;Kim, Won-Ju;Kim, Yeong-Woo
    • Journal of Adhesion and Interface
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    • v.21 no.3
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    • pp.81-85
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    • 2020
  • Shaving dust is a collagen fiber that is the leather waste occurred for thickness adjustment during the natural leather manufacturing process, and causes problems such as an environmental contamination because of a chromium (Cr) contained when it comes to reclaiming process. Various studies applying the shaving dust are currently being conducted in many countries across the world with an initiative by the EU. Of those applications, the bonded leather is being highlighted as a substitute for natural leather. Since the bonded leather, however, uses latex as a binder, accordingly it entails a high weight and a poor ventilation, which are deemed as disadvantages due to its dense internal tissues compared to other synthetic leathers. To address such disadvantages, this study employed the thermally expandable micro sphere to improve its air permeability and light weight by alleviating the internal structure. This is a study on the manufacturing of light bonded leather using the shaving dusts. In the study, the shaving dusts were forced to foam under 100~120℃ considering the heat resistance of collagen fiber after applying the thermally expandable micro sphere, and then the tendency was analyzed. In the analysis results, the most excellent foaming rate was exhibited when the shaving dusts were treated under 120℃ for 8 minutes and the variation of internal structure according to a foaming was observed through SEM analysis for the cross-section of the bonded leather.

Synthesis of porous-structured (Ni,Co)Se2-CNT microsphere and its electrochemical properties as anode for sodium-ion batteries (다공성 구조를 갖는 (Ni,Co)Se2-CNT microsphere의 합성과 소듐 이차전지 음극활물질로서의 전기화학적 특성 연구)

  • Yeong Beom Kim;Gi Dae Park
    • Clean Technology
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    • v.29 no.3
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    • pp.178-184
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    • 2023
  • Transition metal chalcogenides have garnered significant attention as anode materials for sodium-ion batteries due to their high theoretical capacity. Nevertheless, their practical application is impeded by their limited lifespan resulting from substantial volume expansion during cycling and their low electrical conductivity. To tackle these issues, this study devised a solution by synthesizing a nanostructured anode material composed of porous CNT (carbon nanotube) spheres and (Ni,Co)Se2 nanocrystals. By employing spray pyrolysis and subsequent heat treatments, a porous-structured (Ni,Co)Se2-CNT composite microsphere was successfully synthesized, and its electrochemical properties as an anode for sodium-ion batteries were evaluated. The synthesized (Ni,Co)Se2-CNT microsphere possesses a porous structure due to the nanovoids that formed as a result of the decomposition of the polystyrene (PS) nanobeads during spray pyrolysis. This porous structure can effectively accommodate the volume expansion that occurs during repeated cycling, while the CNT scaffold enhances electronic conductivity. Consequently, the (Ni,Co)Se2-CNT anode exhibited an initial discharge capacity of 698 mA h g-1 and maintained a high discharge capacity of 400 mA h g-1 after 100 cycles at a current density of 0.2 A g-1.