• Macromolecular Research
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• 제17권7호
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• pp.469-475
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• 2009

We investigated the feasibility of dispersion polymerization without any stabilizer, which has been considered essential for ensuring colloidal stability. By employing small amounts of a lyophilic comonomer, 4-vinyl pyridine, styrene was successfully polymerized by dispersion polymerization in aqueous alcohol without stabilizer to afford stable poly(styrene-co-4-vinyl pyridine) copolymer microspheres. The stable microspheres were produced in the 4-vinyl pyridine range of 2-15 wt% to styrene. Without 4-vinyl pyridine, severely coagulated particles were obtained, implying that the poly(4-vinyl pyridine) moiety endowed colloidal stability. The polymerization kinetics, behavior, and properties of the ultimate particles showed general features of dispersion polymerization. The study results suggest that stabilizer- tree dispersion polymerization is possible, thereby facilitating the synthesis of impurity(stabilizer)-tree polymer particles.

• Journal of the Optical Society of Korea
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• 제3권1호
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• pp.20-22
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• 1999

We present numerically simulated results on stabilities of optical soliton transmission in highly-dispersion-perturbed optical fiber systems. We have found that the perturbation of dispersion along the transmission line does not significantly degrade stability of soliton transmission as long as the average soliton concept is obeyed.

• Transactions on Electrical and Electronic Materials
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• 제5권6호
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• pp.233-236
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• 2004

Copper metallization has been used in high-speed logic ULSI devices instead of the conventional aluminum alloy metallization. One of the key issues in copper CMP is the development of slurries that can provide high removal rates. In this study, the effects of slurry chemicals and pH for slurry dispersion stability on Cu CMP process characteristics have been performed. The experiments of copper slurries containing each different alumina and colloidal silica particles were evaluated for their selectivity of copper to TaN and $SiO_{2}$ films. Furthermore, the stability of copper slurries and pH are important parameters in many industries due to problems that can arise as a result of particle settling. So, it was also observed about several variables with various pH.

• 공업화학
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• 제24권6호
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• pp.656-662
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• 2013

원자력발전소의 2차 계통수 중에 존재하는 철산화물(magnetite)은 열전달 튜브의 표면에 침착(fouling)되어 열전달 성능을 떨어뜨리거나 부식을 유발한다. 이와 같은 문제를 방지하기 위해, 원전 2차 계통수 중에 고분자 분산제(polymeric dispersant) 주입을 통해 철산화물의 분산 안정성 향상을 도모하는 연구를 수행하였다. 카르복실기(-COOH, carboxyl group)를 함유한 3종의 음 이온성 고분자(PAA, PMA, PAAMA)를 선정하였으며, 이들에 농도변화(1~1000 ppm)에 의한 마그네타이트 분산 특성을 평가하기 위해 침강시험, 투과율 측정, 입도 측정, 제타전위 측정을 수행하였다. 고분자 분산제는 수용액 중 철산화물 분산안정성에 큰 영향을 미쳤다. 분산제가 주입되면 분산 안정성이 향상되는 경향을 보였으나, 분산제 농도 증가에 따라 마그네타이트의 분산 안정성이 선형적으로 비례하여 증가하지 않았다. 이는 임계 분산제 농도 이상에서는 철산화물 사이의 응집(agglomeration)이 발생하기 때문인 것으로 사료된다. 분산안전성 향상 효과는 분산제-철산화물의 농도비(ppm, 분산제/마그네타이트)가 0.01~0.1 범위에서 현저하였다. 분산제 주입을 통한 철산화물 제거 효과를 최대화하기 위해서는 적용 환경 특성, 철산화물 농도, 분산제 농도 및 철산화물-분산제 농도비의 최적화가 필요한 것으로 판단된다.

• 공업화학
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• 제22권2호
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• pp.133-137
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• 2011

본 연구에서는 다양한 용도로 사용되는 일라이트의 분산성 및 분산안정성을 향상시키고자, 습식 볼밀 분쇄법을 이용하여 일라이트의 입도를 저감하였다. 분쇄 시간에 따른 일라이트의 입도와 입도분포 및 분산특성의 변화를 고찰하였으며, 또한 여러 가지 pH조건에서 두 시간 동안 습식 볼밀 분쇄 처리하여 얻은 일라이트 분산용액의 분산성 및 분산안정성을 평가하였다. 일라이트의 입도분석 결과 분쇄시간의 증가에 따라 입자의 크기가 현저히 감소하였으며, 2 h의 분쇄시간을 기점으로 입도저감의 효과가 저하됨을 확인하였다. 또한, 입도분포분석 결과 분쇄시간의 증가에 따라 입자가 균일해지는 것을 확인하였다. X-선 회절분석 결과 분쇄에 의한 결정구조의 변화는 나타나지 않았으나 입도저감 또는 박리현상으로 인하여 특성 피크의 강도가 입도저감 시간의 증가에 따라 약해지는 것을 확인하였다. Zeta potential 분석 결과, 분쇄시간이 증가함에 따라서 분산성이 높아지는 것을 확인하였다. 분산 안정성 측정 결과 pH 2에서 분쇄처리한 일라이트의 분산안정성이 가장 낮았고 pH가 증가함에 따라서 표면 이온화도의 증가로 분산성 및 분산안정성이 향상되는 것을 확인하였다. 이러한 결과로부터 일라이트는 습식 볼밀 분쇄처리 시간을 증가시킬수록 입자 크기가 감소하고 표면 에너지 증가 및 입자간의 반발력 상승으로 분산성 및 분산안정성이 향상되는 것을 확인할 수 있었다.

• 한국재료학회지
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• 제13권11호
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• pp.725-731
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• 2003

The effect of organic processing parameters on the dispersion stability of the BaTiO$_3$-based dielectric particles and borosilicate glass particulate suspensions was investigated in a system where organic solvents, dispersant, binder and modifier were used as processing additives in a low temperature cofired ceramic fabrication processes. Two- and three-component organic solvents were used to disperse ceramic particles and it was found the better stability in the particulate suspension prepared in a bi-solvent, which was consists of toluene and ethanol in a non-azeotropic composition. The addition amount of organic additives had a great impact on dispersion in the present investigation. The flow curves of the suspensions prepared with binder and modifier were fitted according to the power-law equation, which indicates that the internal structure of the suspension could be disturbed under the applied shear stress. Finally, the LTCC green tapes were successfully tape-cast based upon the optimum formulation of LTCC suspension and its microstructure was compared with that of the hard-agglomerates.

• Journal of Pharmaceutical Investigation
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• 제40권spc호
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• pp.97-102
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• 2010

A novel surface-attached solid dispersion is designed to improve the solubility and oral bioavailability of poorly water-soluble drugs without crystalline change. Accordingly, it draws increasing interest because of excellent stability and no pollution for accomplishing enhanced solubility and bioavailability, which have recently been highlighted in connection with a number of higher value-added poorly water-soluble drugs. In addition, excellent stability can be attained when the poorly water-soluble drugs are not dissolved but dispersed in water and provide no crystallinity change. This solid dispersion is given by means of attaching the dissolved carriers such as hydrophilic polymer and surfactant to the surface of dispersed drug particles followed by changing the hydrophobic drug to hydrophilic form. The aim of the present review is to outline the preparation, physicochemical property and bioavailability of novel surface-attached solid dispersion with improved solubility and bioavailability of poorly water-soluble drugs without crystalline change.

• Journal of Pharmaceutical Investigation
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• 제41권2호
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• pp.75-82
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• 2011

LB71350 is an HIV protease inhibitor with poor aqueous solubility and extensive first pass effect. The purpose of the present study was to test the feasibility of solid dosage form of LB71350 with improved bioavailability utilizing solid dispersion. Three different compositions with varying ratio of (LB71350: Gelucire 44/14: Tween 20) were studied. Capsule filling of these solid dispersion compositions was tested using a semi-automatic capsule filling system. Oral bioavailability in dog was tested. Chemical and physical stability at 4, 25 and $40^{\circ}C$ was monitored by HPLC assay, dissolution test, powder XRD and microscopy. The capsule filling system yielded uniform products of drug loading up to 10%. Oral bioavailability in dog was improved compared to the aqueous suspension of crystalline LB71350. Capsules were chemically stable for up to 6 months at $40^{\circ}C$. However, there were temperature and composition dependent physical changes. Decrease in dissolution rates after storage at $40^{\circ}C$ was due to the polymorphic change. In conclusion, manufacturing process, bioavailability, and physico-chemical stability have been considered to propose a solid dispersion capsule formulation for the HIV protease inhibitor with poor physico-chemical properties. A new less soluble crystalline form identified during the physical stability test warrants further study.

• 한국세라믹학회지
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• 제49권5호
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• pp.417-422
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• 2012

Copper nano particles have been considered as the materials for conductive ink due to its good thermal, electrical conductivity and low cost. However, copper nanoparticles oxidize easily, decreasing dispersion stability and electrical conductivity. Therefore, it is important to develop a method to minimize oxidation of copper nano particles to improve its dispersion stability property in copper nano ink. In this study, copper nano particles were coated with 1-Octanethiol VSAM(Vaporized Self Assembled Multilayers) to prevent oxidation and coated copper powders were dispersed in conductive ink successfully by studying its relationship of different chain length of solvents to 1-Octanethiol coating layer to fabricate nano ink. Various alcohol solvents, such as 1-Hexanol, 1-Octanol, and 1-Decanol were used. The coating layer was observed using FESEM and TEM. Furthermore, dispersion of copper nano particles in nano inks, was characterized using Turbiscan analyzer, viscometer, and contact angle measurement tool.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.459-462
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• 2008

슬러리 연료 제조 시 카본의 분산안정성에 미치는 공정변수의 영향을 조사하였다. 슬러리연료 저장용기의 세군데(위, 중간, 아래) 위치별로 채취된 시료에서 평균입도와 탄소함량을 분석하여 Jet A-1에서 카본의 분산안정성을 측정하였다. 여러 종류의 첨가제를 적용한 결과, NB463S84 사용 시 분산성과 증가된 중력 가속도하에서 안정성이 가장 우수하였다. 동일 조건에서 카본층 높이 변화와 카본의 평균입도 측정을 통하여 혼합장비의 성능을 비교하였고, 실험실 규모에서 얻은 제조조건을 bench 규모 제조에 적용하여 본 연구의 실용 가능성을 확인하였다.