• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.34 no.4
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• pp.7-15
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• 2002

It is of critical importance to understand the characteristics of papermaking additives and their reaction mechanisms to fully utilize the benefits they provide. Among the papermaking additives, retention aids play critical roles in improving productivity, product quality and process economy. Diverse research efforts to understand the reaction mechanisms between cationic polymers and anionic microparticles have been made since microparticle retention systems were introduced into the market. And it is most commonly accepted that flocs formed by the addition of cationic polymers are dispersed by shear force and the broken flocs are reflocculated instantly with the addition of microparticles. There are still many unanswered questions, however, on the reaction phenomena between cationic polymers and anionic microparticles. In this study, several cationic polymers including waxy maize starch, com starch and guar gum were used to investigate their retention efficiency when they were used along with anionic colloidal silica.

• Journal of Magnetics
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• v.20 no.3
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• pp.221-228
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• 2015

Colloidal particles consisted of individual nanosized magnetite grains on the surface of the silica cores were obtained by two-stage sol-gel technique. Size distribution and microstructure of the particles were analyzed using atomic force microscopy, X-ray diffraction and Nitrogen thermal desorption. Magnetic properties of the particles were studied by the method of the longitudinal nonlinear response. It has been shown that nanoparticles of magnetite have a size corresponding to a superparamagnetic state but exhibit hysteresis properties. The phenomenon was explained using the magnetostatic interaction model based on the hypothesis of iron oxide particles cluster aggregation on the silica surface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05b
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• pp.33-36
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• 2005

Colloidal Silica(CS)/silane sol solutions were prepared in variation with synthesizing parameters such as ratio of CS to silane and reaction time. In the case of LHSA CS/tetramethoxysilane(TMOS)/methyltrimethoxysilane(MTMS) CS/silane sol, coating film had stable contact angle with increasing reaction time excepting for 48hours. Also, the LHSA CS/TMOS/MTMS coating film had more enhanced flat surface with increasing the amount of MTMS and increasing reaction time. In the case of thermal stability, thermal dissociation of LHSA CS/MTMS sol did not occur up to $550^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.214-215
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• 2006

Colloidal Silica(CS)와 유기수지를 혼합하여 서로의 단점을 보완하는 나노복합재료를 합성하기 위해 친수성인 CS를 유기실란으로 표면처리하여 소수성화하고 유기수지와 복합체를 제조하였다. CS표면의 -OH기와 실란의 -OH기가 축합반응하여 화학결합을 형성함으로서 CS의 표면은 실란의 $CH_3$에 의해 소수성화되어 CS sol이 제조된다. CS sol과 유기수지는 공동용매에 의해 균일한 분산이 가능하고 필름 및 코팅제로의 제조가 가능하다. 사용된 무기물은 40nm 의 크기를 가지므로 가시광선영역의 빛을 산란하지 않아 투명하고 사용된 수지 또한 투명하여 우수한 광학적 특성을 나타낸다. 만들어진 필름은 CS의 영향으로 유기수지의 내열성보다 향상된 열분해온도와 높은 접촉각, 높은 절연율을 보였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.230-231
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• 2006

We synthesized sol according to kinds(particle size/stabilized ion) of colloidal silica(CS), content ratio of alkoxysilane versus CS and reaction degree in sol solution and studied the surface property of coated gel materials. The contact angle of the thin films prepared from LHSA/N1030 CS/tetramethoxysilane(TMOS)/methyltrimethoxysilane(MTMS) sol-gel reaction system showed a little good relationship with content ratio of TMOS/MTMS silanes. The surface roughness of LHSA CS/TMOS/MTMS reaction system showed flatter than that of LHSA/N1030 CS. The thermal degradation of LHSA CS/TMOS/MTMS coating flim occurred at $550^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.981-987
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• 2002

Monodispersed colloidal silica was prepared by Stober process. We have synthesized monodispersed colloidal silica of carious sizes (100 nm, 200 nm, 300 nm) by controlling volume ratios of TEOS(Tetraethylorthosilicate), $NH_4OH$, Ethanol and D. I. water. Shape and monodispersity of the synthesized colloidal particles were observed by Scanning Electron Microscopy(SEM) and laser light scattering particle analyzer. Self-assembled monolayer of monodispersed colloids was achieved by dipping Si substrate into a well-dispersed silica suspension. It was determined that uniformity and spatial extent of the self-assemble monolayer of monodispersed colloids are significantly influenced by the experimental parameters such as concentration, pH and surface tension of the colloidal suspension. We have observed a hexagonally well-ordered packing colloidal monolayer in a relatively large area (1.5 mm ${\times}$ 1.5 mm) as confirmed by SEM.

• Membrane Journal
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• v.24 no.3
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• pp.177-184
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• 2014

Silica membranes with high permeability were prepared using colloidal and polymeric silica sols on a porous stainless steel-tube support by a DRFF and SRFF method. Silica sols were derived with tetraethylorthosilicate (TEOS) by sol-gel method and analyzed with DLS, FE-SEM, and $N_2$ adsorption. The coating of the intermediate layer with colloidal silica sol on the stainless steel-tube support led to a denser surface morphology of the membrane along with a considerable reduction in the number of surface defect. As the polymeric silica sol enclosed the colloidal silica sol with spherical particles during the SRFF method, the separation-layer-coated silica membrane showed a denser surface than the intermediate layer. Moreover, the silica membranes showed high hydrogen gas permeability of $(6.63-9.21){\times}10^{-5}mol{\cdot}m^{-2}{\cdot}s^{-1}{\cdot}Pa^{-1}$ with low $H_2/N_2$ perm-selectivity (2.9-3.1) at room temperatures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.967-972
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• 2004

Hardness and surface property of coated gel materials are considerably different according to kinds(particle size/stabilized ion) of colloidal silica(CS), kinds of silanes, content ratio of silane versus CS, and reaction degree in sol solution. We report the properties of sol-gel coating materials in which the factors of reaction are kinds of CS, contents ratio of CS and MTMS, and reaction time of sol. The contact angles of the coated films obtained from the mixed CS system showed a little good relationship with MTMS content increase to those from HSA CS reaction system and the change of contact angle didn't have much effect on reaction time of sol. In the coating films obtained from HSA CS reaction system, the surface was much rough in case of that the content MTMS decreased and the reaction of sol kept long. The surface roughness of films obtained from the mixed CS reaction system showed similar tendency, though its degree was a little different. In synthesis of sol-gel coating materials, we could identify that choice of CS kinds and content ratio of CS and silane were important and it was desirable the reaction time of sol is not long.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.82-85
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• 2004

Colloidal Silica(CS) HSA/2327과 methyltrimethoxysilane(MTMS), 1034A와 tetramethoxysilane(TMOS)/MTMS 간의 졸겔 반응조건이 코팅도막의 특성에 미치는 영향을 조사하기 위하여 CS종류, CS 대비 TMOS/MTMS의 함량비, 반응시간 등을 달리하여 졸을 합성하고, 합성된 졸을 slide glass에 코팅한 후 $300^{\circ}C$에서 경화시킨 도막의 특성들을 조사하였다. HSA/2327/MTMS에 의한 졸로부터 제조된 코팅도막은 졸 반응시간 의존성이 거의 없으며 반응초기부터 접촉각이 상당히 안정되어 있고 특히 낮은 MTMS 함량을 가진 졸들이 더욱 안정된 표면물성을 보였다. 1034A/TMOS/MTMS에 의해서 제조된 코팅도막은 적절한 소수성의 형성과 표면조도의 향상과 더불어 안정된 접촉각 양상을 나타내었다. 표면거칠기는 HSA/2327 혼합 CS계에 의해서는 반응시간이 길고 MTMS 함량이 높아질 때 비교적 표면조도가 나빠지는데 반응시간과 더불어 약간씩 증가하는 경향을 보였다. 1034A CS계에서는 반응시간과 MTMS 함량의 조건에 영향을 받지 않고 표면조도와 균질성이 우수하였다.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.129-132
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• 2009

Monodisperse ZnS colloidal particles with precisely specified diameters over a broad size range were synthesized by controlled aggregation. Sub-10nm ZnS seed crystals were first nucleated at ambient temperature and then grown at an elevated temperature, which produced large polydisperse colloidal particles. Subsequent rapid thermal quenching and heating processes induced a number of secondary nucleations in addition to growing the large polydisperse microparticles which were finally removed by centrifugation and discarded at the completion of the reaction. The secondary nuclei were then aggregated further at elevated temperatures, resulting in colloidal particles which exhibited a nearly monodisperse size distribution. Particle diameters were controlled over a wide size range from 50 nm to 1 μm. Mie simulations of the experiment extinction spectra determined that the volume fraction of the ZnS is 0.66 in an aggregated colloidal particle and the colloidal particle effective refractive index is approximately 2.0 at 590 nm in water. The surface of the colloidal particles was subsequently coated with silica to produce ZnS@silica core-shell particles.