• Polymer(Korea)
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• v.39 no.2
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• pp.300-310
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• 2015

In this study, we modified silica nanoparticles with N-[3-(trimethoxysilyl)propyl]ethylenediamine (TPED) silane coupling agent, which has one primary and one secondary amino groups in a molecule, to introduce amino groups on the silica surface. After modification of silica, we used 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) to introduce methacrylate groups by Michael addition reaction. We found about 30% of N-H groups on the TPED modified silica surface reacted with acrylate groups of AHM compared to about 85% of reaction between N-H groups of pure TPED with acrylate groups of pure AHM. This lower degree of Michael addition reaction for heterogeneous reaction between N-H groups on the solid TPED modified silica and liquid AHM compared to homogeneous reaction between pure liquid TPED and pure liquid AHM may be caused by lower mobility of grafted amino groups of TPED moiety and higher steric hindrance caused by solid silica particles.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.292-299
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• 2012

We made 8 wt% silica dispersion system with fumed silica and photo curable acrylic monomer by beads mill process. These dispersions could be applied in organic/inorganic hybrid coating systems. These dispersions could be applied in organic/inorganic hybrid coating systems. The 4 species of photo curable acrylic monomer which was presence of hydroxyl group, different solubility parameter, and different molecular size were used in the silica dispersions. Stability of polar solvent, isopropyl alcohol, in silica dispersions was investigated. We investigated the stability of silica dispersions by using steady-state and dynamic rheology. As the monomer has hydroxyl group increased in mono and binary monomer silica dispersions, they showed non flocculated stable sol (loss modulus (G")> storage modulus (G')). When polar solvent IPA was added into slightly flocculated silica dispersions, they changed to non flocculated stable sol.

• Elastomers and Composites
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• v.44 no.1
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• pp.22-33
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• 2009

Recently, elastomer-nanocomposites reinforced with low volume fraction of nanofillers have attracted great interest due to their fascinating properties. The incorporation of nanofillers, such as, layered silicate clays, carbon nanotubes, nanofibers, calcium carbonate, metal oxides or silica nanoparticles into elastomers improves significantly their mechanical, thermal, dynamic mechanical, barrier properties, flame retardancy, etc. The properties of nanocomposites depend greatly on the chemistry of polymer matrices, nature of nanofillers, and the method in which they are prepared. The uniform dispersion of nanofillers in elastomer matrices is a general prerequisite for achieving desired mechanical and physical characteristics. In this paper, current developments in the field of elastomer nanocomposites reinforced with layered silicates, silica, carbon nanotubes, nanofibers and various other nanoparticles have been addressed.

• Polymer(Korea)
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• v.38 no.2
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• pp.257-264
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• 2014

In this study, we modified silica nanoparticles with bis[3-(trimethoxysilyl)propyl]ethylenediamine (BTPED) silane coupling agent, which has two secondary amino groups in a molecule, to introduce amino groups on the silica surface. After modification of silica, we used acrylate group containing 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) to introduce polymerizable methacrylate groups by Michael addition reaction. We used Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA) and liquid and solid state cross polarization magic angle spinning (CP/MAS) nuclear magnetic resonance spectroscopy (NMR) to understand the reactions between N-H groups of BTPED modified silica surface and acrylate groups of AHM monomer. We confirmed Michael addition reaction between BTPED modified silica and AHM completed in 2 hr reaction time. We also found increased methacrylate group introduction with increase of mol ratio of the acrylate group of AHM to N-H group of BTPED modified silica by increase of C=O peak area of measured FTIR spectra. These results were also supported by EA and solid state $^{13}C$ and $^{29}Si$ NMR results.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1197-1205
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• 2018

UV protection cosmetics belong to functional cosmetics and contain organic or inorganic UV blocking pigments. The inorganic UV blocking pigments are mainly zinc oxide and titanium dioxide. It is known that inorganic UV blocking pigment has a diameter of 60 to 100 nm and has good blocking ability of UVA and UVB. Also, it has high inactivity against sunlight including UV and is excellent in safety. In addition, it is not absorbed or accumulated on the skin like organic pigments and does not cause skin irritation or allergy. In this study, mica, a plate-shaped inorganic pigment, nanosized titanium dioxide, an UV blocking material, and hydrophobic silica were surface-treated with surfactants. And then, titanium dioxide nanoparticles and silica were physically adsorbed on the mica by non-chemical mutual attraction due to differences in charge. Thereafter, the mica complex was surface-treated with silane to prepare a hydrophobic UV blocking pigment complex. The plate-shaped UV blocking composite improves the cohesiveness of a general nanoparticle material titanium dioxide, enhances UV blocking effect due to uniform dispersion, and can greatly improve dispersion stability in cosmetic formulations by surface treatment with hydrophobic property. The surface charge of the pigment was evaluated by zeta potential. The properties of the UV blocking pigment complex were evaluated by FE-SEM, XRD, FT-IR and UV-VIS.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.70-70
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• 2011

표면처리는 전기적, 물리적, 화학적 처리방법 등을 통해 보호표면을 생성시킴으로서 재료의 외관미화, 내마모성, 전기절연, 전기전도성 부여 등의 폭넓은 목적을 달성시키고자 하는 일련의 조작을 말한다. 최근 스마트 휴대폰으로 대표되는 이동통신기기 산업의 빠른 성장으로 인하여 이들 기기를 보호하기 위한 표면 처리기술도 함께 발전하고 있다. 그중 대표적인 것이 나노기술을 융합한 보호막 도장기술이다. 나노입자를 분산하거나 나노상(phase)을 융합하여 제품의 표면에 보호막을 도장하는 기술이며, 그 주된 목적은 내 스크래치, 내 부식 등의 물리 화학적 보호기능을 수행하도록 층(layer)을 형성하는 것이다. 본 연구에서는 제조된 실리카 나노입자와 유기물을 사용하여 휴대폰 케이스에 도장막을 형성하였고, Scratch, Wear, hardness Test등의 분석을 통하여 유무기 하이브리드 도장막의 특성을 평가하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.338-338
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• 2012

사파이어 ($Al_2O_3$)는 높은 밴드갭 에너지 (~19.5 eV)를 가진 물질로서 우수한 내마모성, 강도, 전기 절연성 및 안정한 화학적 특성을 갖고 발광다이오드 기판, 보석재료 등 각종 산업 및 기술적 분야에서 널리 사용되고 있다. 특히, 플립칩 발광다이오드 구조의 경우 광추출효율을 향상시키기 위해 높은 투과도를 갖는 사파이어 기판이 요구되어 왔으며, 지금까지 건식/습식식각방법을 이용한 사파이어 표면에 마이크로 크기의 심한 거칠기 또는 요철이 형성된 나노크기의 격자구조를 형성시키는 연구가 진행되어 오고 있다. 그 중, 나노 크기의 격자구조는 공기에서 반도체 기판까지 선형적인 유효굴절률 분포를 갖기 때문에 표면에서 생기는 Fresnel 반사 손실을 줄일 수 있다. 이러한 구조를 형성하기 위해서는 식각 마스크가 필요한데, 형성 방법으로 레이저 간섭 리소그래피, 전자빔 리소그래피, 나노임프린트 리소그래피 등이 있으나, 비싼 가격과 복잡한 공정 절차 등의 단점을 지니고 있다. 따라서 본 연구에서는 식각 마스크 패턴을 위해, 보다 저렴하고 간단한 실리카 나노구 및 열적응집 금 나노 입자를 이용하였다. 양면 폴리싱 c-plane 사파이어 기판을 사용하였고, 단일 층의 주기적인 실리카 나노구를 기판 표면에 스핀코팅에 의해 도포한 후 유도결합플라즈마 식각 장비를 이용하여 식각하여 주기적인 패턴을 갖는 렌즈모양의 격자구조를 형성하였다. 그리고 주기적으로 형성된 격자 위에 열 증착기를 이용하여 금 박막을 증착한 후 급속열적어닐닝(rapid thermal annealing)을 이용하여 열처리함으로써 비주기적인 금 나노입자를 형성시켰다. 형성된 금 나노패턴을 이용하여 동일한 조건으로 식각함으로써 광대역 및 전방향성 높은 투과도를 갖는 원뿔 모양의 사파이어 나노구조를 제작하였다. 제작된 샘플의 패턴 및 식각 형상은 전자현미경을 사용하여 관찰하였으며, UV-vis-NIR 분광광도계 (spectrophotometer)를 사용하여 투과율을 측정하였다. 렌즈 모양 표면 위에 원뿔모양의 나노구조를 갖는 사파이어 기판은 일반적인 사파이어 기판보다 향상된 투과율 특성을 보였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.59-66
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• 2003

A novel application of nano-technology in the field of engineering, called colloidal damper, is investigated. This device is complementary to the hydraulic damper, having a cylinder-piston construction. Particularly for colloidal damper, the hydraulic oil is replacedby a colloidal suspension, which is consisted from a nano-porous matrix with controlled architecture and a lyophobic fluid. In this experimental work, the porous matrix is composed from silica gel, with labyrinth architecture, coated by organo-silicones substances in order to achieve a hydrophobic surface. Water is considered as associated lyophobic fluid. The colloidal damper test rig and the measuring technique of the hysteresis are described. the influence of the hydrophobicity level upon the colloidal damper hysteresis is investigated, for silica gels with similar pores distribution. A certain desired shape of the hysteresis can be achieved by employing mixture of silica gels with different level of hydrophobicity and/or architecture. With these results, it is believed that the proposed damper can be designed and be applied to the desired structure.

• Analytical Science and Technology
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• v.23 no.3
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• pp.233-239
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• 2010

Pure macroporous silica matrix using a template of polystyrene (PS) was prepared by the sol-gel method. Macroporous Ag-$SiO_2$ composite materials, which were homogeneously dispersed with Ag particles in the macropores, were successfully fabricated. The pure porous silica had ordered pore sizes of 100 nm and 200 nm, which was adjusted under consideration of the template size. The macroporous Ag-$SiO_2$ composite showed the ideal ordered distribution of the pore in case of the adding of 3 wt% $AgNO_3$ under consideration of controlling of the pore size as well as microstructural observation of $AgNO_3$concentration. The macroporous Ag-$SiO_2$ composites had ordered 100 nm and 200 nm pores, and the Ag particles within the matrix showed the size of 15~20 nm.

• Tribology and Lubricants
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• v.25 no.6
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• pp.404-408
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• 2009

In this paper, the relationship between the material removal rate and the interfacial mechanical properties at particle-surface contact situation, which can be seen in an abrasive machining process using micro/nano-sized particles, was discussed. Friction and stiffnesses were measured experimentally on an atomic force microscope (AFM) by using colloidal probes which have a silica colloid particle in place of tip to simulate a particle-flat surface contact in an abrasive machining process. From the experimental investigation and theoretical contact analysis, the interfacial contact properties such as lateral stiffness of contact, friction, the material removal rate were presented with respect to some of material surfaces and the relationship between the properties as well.