• 한국재료학회지
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• 제19권9호
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• pp.468-472
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• 2009

The silver nanofluids were synthesized by the pulsed wire evaporation (PWE) method in a liquid-gas mixture. The size and microstructure of nanoparticles in the deionized water were investigated by a particle size analyzer (PSA), transmission electron microscope (TEM), and scanning electron microscope (SEM). Also, the synthesized nanofluids were investigated in order to assess the stability of dispersion of nanofluid by the zetapotential analyzer and dispersion stability analyzer. The results showed that the spherical silver nanoparticle formed in the deionized water and mean particle size was about 50 nm. Also, when explosion times were in the range of 20$\sim$200 times, the absolute value of zeta potential was less than -27 mV and the dispersion stability characteristic of low concentration silver nanofluid was better than the high concentration silver nanofluid by turbiscan.

• 한국염색가공학회지
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• 제28권4호
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• pp.280-289
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• 2016

Silica microgel was prepared by sol-gel process and then functional groups, epoxy group and ethoxy group, were introduced on the particle by coupling treatment with 3-glysidoxypropyltrimethoxysilane. The functional silica microgel(functional SiGel) formation was identified using FT-IR spectrometry. Phase stability for DMF solution of functional SiGel, PU resin and pigment was evaluated by Turbiscan Lab. And physical properties of artificial suede including hand values, morphology and dyeing fastness were investigated. The mean particle size and the specific surface area of the functional SiGel were $0.77{\mu}m$ and $380m^2/g$. Mixture containing the functional SiGel, PU resin and pigment was more stable than the functional SiGel-free mixed solution. Artificial suede prepared by the functional SiGel had appearance and feeling close to natural suede. The migration fastness, the solvent wicking fastness and rubbing fastness of the artificial suede were enhanced to 4~5 grades, 4~5 grades and 3~4 grades, respectively.

• 한국분말재료학회지
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• 제20권6호
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• pp.479-486
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• 2013

In the present work, physicochemical treatments were introduced for de-aggregation and stable dispersion of detonation nanodiamonds (DND) in polar solvents. The DNDs in water exhibited a particle size of 138 nm and high dispersion stability without particular treatment. However, the DNDs in ethanol were severely aggregated to several micrometers in size and showed poor dispersion stability with time. To break down aggregates of DNDs and enhance the dispersion stability of them in ethanol, mechanical force and chemical surfactant were introduced as functions of zirconia ball size, kind of surfactant and amount of surfactant added. From the analyses of average particle size and Turbiscan results, it was suggested that the size of DNDs in ethanol can be reduced by only mechanical force; however, the DNDs were re-aggregated due to high surface activity. The long-term dispersion stability can be achieved by applying mechanical force to break down the aggregates of DNDs and by preventing re-aggregation of them using proper surfactant.

• 폴리머
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• 제38권3호
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• pp.378-385
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• 2014

초음파를 이용한 수중 반응을 통하여 친수성 고분자인 poly(vinyl alcohol) (PVA)를 다중벽 탄소나노튜브 표면에 개질하였다. 초음파 인가 시 PVA는 라디칼을 지닌 상태로 절단되며 탄소나노튜브는 일반적으로 라디칼 스캐빈저 역할을 하므로 생성된 PVA 라디칼과 반응하여 PVA 사슬이 탄소나노튜브 표면에 그래프트 된다. PVA의 그래프트 반응을 조절하기 위하여 초음파 인가 조건을 300과 500 W로 선택하였으며, 인가 시간은 최대 50분으로 하였다. 탄소나노튜브 표면에 그래프트된 PVA는 FTIR, TGA, SEM, 및 TEM을 통하여 분석하였다. 또한 PVA로 개질된 탄소나노튜브의 분산안정성을 분석하였다. 그래프트된 PVA의 양은 초음파의 인가 출력과 인가 시간에 비례하여 증가하였으며, PVA로 개질된 탄소나노튜브는 물 속에서 매우 안정적인 분산성을 보였다. 이는 복잡한 화학반응 과정없이 초음파를 이용하면 탄소나노튜브를 고분자로 간단히 개질할 수 있음을 보여준다.

• Current Photovoltaic Research
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• 제2권4호
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• pp.173-176
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• 2014

We have investigated the seed layer formation of front side contact using the inkjet printing process. Conductive silver ink was printed on textured Si wafers with 80 nm thick $SiN_x$ anti reflection coating (ARC) layers and thickened by light induced plating (LIP). The inkjet printable sliver inks were specifically formulated for inkjet printing on these substrates. Also, a novel method to prepare nano-sized glass frits by the sol-gel process with particle sizes around 5 nm is presented. Furthermore, dispersion stability of the formulated ink was measured using a Turbiscan. By implementing these glass frits, it was found that a continuous and uniform seed layer with a line width of $40{\mu}m$ could be formed by a inkjet printing process. We also investigated the contact resistance between the front contact and emitter using the transfer length model (TLM). On an emitter with the sheet resistance of $60{\Omega}/sq$, a specific contact resistance (${\rho}_c$) below $10m{\Omega}{\cdot}cm^2$ could be achieved at a peak firing temperature around $700^{\circ}C$. In addition, the correlation between the contact resistance and interface microstructures were studied using scanning electron microscopy (SEM). We found that the added glass particles act as a very effective fire through agent, and Ag crystallites are formed along the interface glass layer.

• 농업과학연구
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• 제43권2호
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• pp.249-257
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• 2016

In this study, rapeseed extracts were obtained by supercritical carbon dioxide fluid extraction of defatted rapeseed to evaluate the stability and antioxidant activity of an oil-in-water (O/W) emulsion system. The oil-in-water emulsions were prepared from stripped soybean oil with different concentrations (0.3, 0.4, 0.5, and 0.6%) of rapeseed extract as an emulsifier. Their emulsion stability was compared to that of emulsions prepared with the commercial emulsifier, Tween 20 (Polysorbate 20, 0.2%). After stripping the soybean oil, the total tocopherol content was reduced from 51.4 g/100 g to 1.1 g/100 g. Emulsion stability and oxidative stability of emulsions prepared with Tween 20 and rapeseed extract as emulsifiers were evaluated. For 30 days droplet sizes of emulsions containing rapeseed extract (0.4, 0.5, and 0.6%) were not significantly different (p > 0.05). Similar results were obtained for emulsion stability (ES) and Turbiscan analysis, suggesting that the addition of rapeseed extract increased emulsion stability. The addition of rapeseed extract at more than 0.4% resulted in an emulsion stability comparable to the addition of 0.2% Tween 20. The antioxidative ability of rapeseed extract increased with the amount added in the emulsion. Moreover, the addition of 0.6% rapeseed extract resulted in the lowest emulsion peroxide values (10.3 mEq/L) among all treatments. Therefore, according to the stability of its antioxidative and physical stability properties, rapeseed extract from super critical extraction could be successfully applied to the food and cosmetic industries.

• Macromolecular Research
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• 제17권2호
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• pp.128-132
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• 2009

Fucoidan, a sulfated polysaccharide derived from brown seaweed, is an important material valued for its various biological functions, including anti-coagulation, anti-aging, and immune system support. In this study, we examined the potential of fucoidan as a novel emulsifying agent in BSA (bovine serum albumin)-stabilized emulsion at a neutral pH. We measured the dispersed oil-droplet size, surface zeta-potential and creaming formation of 0.5 wt% BSA emulsion (20 wt% oil traction) in the absence and presence of fucoidan. The average particle size and zeta-potential value were 625.4 nm and -30.91 mV in only BSA-stabilized emulsion and 745.2 nm and -44.2 mV in 1.0 wt% fucoidan-added BSA emulsion, respectively. This result suggested that some positive charges of the BSA molecules interacted with the negative charges of fucoidan to inhibit the flocculation among the oil droplets. The creaming rate calculated from the backscattering data measured by Turbiscan dramatically decreased in 1.0 wt% fucoidan-added BSA emulsion during storage. Accordingly, the repulsion forces induced among the oil particles coated with 1.0 wt% fucoidan in emulsion solution resulted in significantly increased emulsion stability. The turbidity of the BSA-stabilized emulsion at 500 nm decreased during five days of storage. However, the fucoidan-added BSA emulsion exhibited a higher value of turbidity than the BSA-stabilized emulsion did. In conclusion, an anionic sulfated fucoidan lowered the surface zeta-potential of BSA-coated oil droplets via the electrostatic interaction, and subsequently inhibited the flocculation among the oil droplets, thereby clearly minimizing the creaming and phase separation of the emulsion.

• 한국재료학회지
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• 제26권3호
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• pp.136-142
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• 2016

To study the dispersion factors of silica sol prepared from fumed silica powder, we prepared silica sol under an aqueous system using a batch type bead mill. The dispersion properties of silica sol have a close relationship to dispersion factors such as pH, milling time and speed, the size and amount of zirconia beads, the solid content of fumed silica, and the shape and diameter of the milling impellers. Especially, the silica particles in silica sol were found to show dispersion stability on a pH value above 7, due to the electrostatic repulsion between the particles having a high zeta potential value. The shape and diameter of the impellers installed in the bead mill for the dispersion of fumed silica was very important in reducing the particle size of the aggregated silica. The median particle size ($D_{50}$) of silica sol obtained after milling was also optimized according to the variation of the size and amount of the zirconia beads that were used as the grinding medium, and according to the solid content of fumed silica. The dispersion properties of silica sol were investigated using zeta potential, turbiscan, particle size analyzer, and transmission electron microscopy.

• Tribology and Lubricants
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• 제31권6호
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• pp.251-257
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• 2015

Heavy oil production is receiving significant attention because of increased demands for thermal power generation systems of the diesel engine and boilers. However, asphaltene, which is a heavy oil components (6-8 wt%), reduces the heat efficiency of the fuels owing to its agglomerated sludge of asphaltene during the burning process. Therefore, for hassle-free operation, we should develop asphaltene dispersants to suppress the formation of the sludge. We prepare variable salt-type polymeric dispersants using poly(isobutenyl succinic anhydride) and poly(amine) through both condensation esterification and acid-base neutralization reactions, which we subsequently evaluate for dispersing performance, using Turbiscan measurement. Total acid number (TAN) and total base number (TBN) of 75Lec-25SynDis.2 composed of lecithin and the prepared polymeric salt having the ratio of 3 : 1 are 18.9 and 33.7 mg KOH/g, respectively, which are comparable to those of the commercial dispersants (15.8 and 26.5 mg KOH/g). We determine the initial turbidity observed for 15 min of the polymeric dispersant was determined with transmittance (%), which can be calculated to separability number (SN). The SN value of 75Lec-25SynDis.2 is close to zero, which is superior to that of commercial dispersants and lecithin (0.015 and 0.017).

• 산업식품공학
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• 제14권1호
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• pp.41-48
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• 2010

생식 첨가량을 3.7-11.7%로 조절한 생식음료의 분산안정성을 터비스캔을 사용하여 광학적 방법으로 측정하였다. 생식음료는 제조 후 시간이 경과함에 따라 음료 하부에서는 침전이 생성되어 후방산란광플럭스(이후 후광플럭스로 약칭)가 강해진 반면, 중간부에서는 청징현상에 의해 약해졌으며, 최상층부에서는 거품이 생성되어 다시 강해졌다. 생식 첨가량이 증가할수록 침전이 서서히 진행되었으며 전체 침전층은 두텁게 형성되었다. 침전에 의한 후광플럭스의 퍼센트변화율의 시간에 따른 변화는 로그 모델이 적용 되었으며 결정계수는 0.979-0.988로 높은 값을 보였다. 생식 첨가량은 생식음료의 상층부에 형성되는 청징층과 하층부의 침전층의 경계면, 즉 청징층 선단의 이동속도 뿐 만 아니라 분리된 층의 수에도 영향을 미쳤다. 생식 첨가량 3.7%의 경우는 2층으로, 5.7-9.7%의 경우는 3개 층으로, 11.7%는 4개 층으로 분리되었다. 생식음료 제조 후 17-29분 사이에 1차 청징층 발생이 시작되었고 22-53분간 지속되었으며, 생식첨가량이 낮을수록 청징층 두께는 증가하였다. 청징층 발생은 생식 첨가량 7.7%인 음료에서 가장 늦게 나타나 최대 분산안정성을 보였다.