• Composites Research
• /
• v.33 no.6
• /
• pp.365-370
• /
• 2020

The icing formation at aircraft occur problems such as increasing weight of the body, fuel efficiency reduction, drag reduction, the error of sensor, and etc. The viscosity of polyurethane (PU) topcoat was measured at 60℃ in real time to set the pre-curing time. SiO2 nanoparticles were dispersed in ethanol using ultra-sonication method. The SiO2/ethanol solution was sprayed on PU topcoat that was not cured fully with different pre-curing conditions. Surface roughness of SiO2/PU nanocomposites were measured using surface roughness tester and the surface roughness data was visualized using 3D mapping. The adhesion property between SiO2 and PU topcoat was evaluated using adhesion pull-off test. The static contact angle was measured using distilled water to evaluate the hydrophobicity. Finally, the pre-curing time of PU topcoat was optimized to exhibit the hydrophobicity of SiO2/PU topcoat.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2009.11a
• /
• pp.125-126
• /
• 2009

본 연구는 수용성 폴리우레탄 코팅 제품의 문제점인 코팅층간의 끈적임 문제, 내구성 문제 등을 개선하기 위해 졸-겔법을 이용하여 구형의 실리카 나노무기입자를 제조하고, 또한 주형을 이용한 다른 모양의 나노구조체를 합성하여 수성폴리우레탄 수지에 일정 비율 혼합하여 필름을 제조하여 수성 폴리우레탄 필름 대비 물성 향상에 관한 연구이다.

• The Journal of Engineering Research
• /
• v.4 no.1
• /
• pp.119-123
• /
• 2002

3-아미노프로필기를 함유한 실리카 전구체를 물질 조성 성분, 유화제 및 촉매로 이용하여 다른 활성기를 가지는 3-머캅토프로필트리알콕시 실란, 비닐트리알콕시 실란 등과 반응시켜 여러 가지 크기의 구 입자를 제조하였다. 구는 이들 분자의 자기 조립에 의하여 형성되었으며 외부적으로 아무런 물리적, 화학적 자극을 가할 필요가 없었다. 생성되는 구의 크기는 반응 혼합물의 조성 즉 반응 혼합물에 들어 있는 3-아미노프로필기를 함유한 전구체의 양에 따라 결정되었다. 생성물에 들어 있는 3-아미노프로필기의 양은 최대 20 몰%를 넘지 않았으며, 얻어진 구의 지름은 반응물 조성에 따라 수십 nm에서 수 $\mum$에 달하였다.

• Korean Chemical Engineering Research
• /
• v.50 no.2
• /
• pp.371-378
• /
• 2012

Hydrophilic silica nanoparticles (SNPs) were treated by using 3-glycidoxypropyltrimethoxy silane (GPTMS) and then they were blended with polyurethane-urea (PUU) emulsions to obtain SNPs/PUU nanocomposite films. Thermo-mechanical properties of the nanocomposite films were investigated by varying the grafted amount of GPTMS onto SNPs and the contents of SNPs in the PUU matrix. The thermo-mechanical properties of the nanocomposite films were also compared in terms of the dispersibility of SNPs in the PUU matrix and thermal curing of the GPTMS-grafted SNPs. The maximum amount of grafted GPTMS was $1.99{\times}10^{-6}\;mol/m^2$, and which covered ca. 53% of the total SNP surface area. $^{29}Si$ CP/MAS NMR analyses with the deconvolution of peaks revealed the details of polycondensation degree and patterns of GPTMS in the surface modification of SNPs. The surface modification did not significantly affect colloidal stability of the SNPs in aqueous medium; however, the hydrophobic modification of SNPs offered a favorable effect on the dispersibility of SNPs in the PUU matrix as well as better thermal stability. XRD patterns revealed that GPTMS-grafted SNPs broadened the reduced the characteristic peak of polyol in PUU matrix. The composite films became rigid and less flexible as the SNP content increased from 5 wt.% to 20 wt.%. Particularly, Young's modulus and tensile modulus significantly increased after the thermal curing reaction of the epoxy groups in the SNPs.

• Journal of the Korean Ceramic Society
• /
• v.40 no.3
• /
• pp.286-292
• /
• 2003

In this study, new shock absorbing system was proposed using silica gel particles according to the nano-technology. For the design and real application of the proposed damper, an experimental investigations are carried out using colloidal damper, which is statically loaded. The porous matrix is composed from silica gel(labyrinth architecture), coated by organo-silicones substances, in order to achieve a hydrophobic surface. Water is considered as associated lyophobic liquid. Reversible colloidal damper static test rig and the measuring technique of the static hysteresis were described. Iufluence of the water volume and particle diameters upon the reversible colloidal damper hysteresis was investigated. Also, influence of the relaxation time on the hysteresis of the damper was investigated. As a result, the proposed new shock absorbing damper is proved as an effective one, which can be replaced for the conventional hydraulic damper.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.22 no.6
• /
• pp.291-298
• /
• 2012

Carbamoylphosphate (CMPO) [CMPO analogue; 2-(diphenylphosphoryl)-N-(3-(triethoxysilyl)propyl)acetamide]silane, as a functional self-assembled molecules, grafted mesoporous silicates were prepared by simple hydrolysis and condensation reaction. Pore sized tailored mesoporous silicates such as MCM-41, SBA-15, or amorphous silica nanoparticles were adopted as host materials. The surface area of ordered mesoporous silicates was ranged from 680 $m^2/g$ to 1310 $m^2/g$ with different pore diameters that estimated to be ca. 2.3~9.1 nm by BJH method. Among the OMMs host materials, SBA-15(II) has higher loading ratio (~35 wt%) of CMPO derivative than other OMMs. Accessibility to CMPO silane functional groups in the surface of mesoporous silicas was studied by lanthanide ions sorption experiments. All of the CMPO modified OMMs favors the smaller Eu(III) and Nd(III) cations than La(III) for relative larger ionic radius.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.1
• /
• pp.24-34
• /
• 2020

This research is a study on the characteristics of OPC-slag cement using nano-silica solution (NSS) with water-weight substitution method. The new replacement method is a fundamental step to study the behavior of cement with higher NSS replacement rates than previous studies. NSS was replaced by 10%, 20%, 30%, 40%, and 50% of the mixing water weight. As a result, the mechanical and microstructural characteristics were improved. This can be summarized in two ways. First, when the NSS is replaced with mixing water, the homogeneous dispersion action of the nano-silica particles is improved. This promotes initial hydration. Second, substitution of NSS with higher density than mixing water reduces w / b. This forms a dense hydration reaction material. The new substitution method did not show any degradation of mechanical and microstructural properties as compared with the results using the powdered nano-silica particles revealed in the previous study. Therefore, it is considered that the method of weight substitution of NSS used in this study can be applied to the formulation of OPC-slag cement.

• Korean Chemical Engineering Research
• /
• v.51 no.3
• /
• pp.330-334
• /
• 2013

Mixtures of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and silica nanoparticles are coated on the surface of a silk fabrics separator. The coated separators are finally prepared by injecting an electrolyte solution and then characterized for use of lithium-ion battery separator/electrolyte. In the preparation, various contents of dibutylphthalate (DBP) as a plasticizer are used to enhance the formation of micropores within the coated membrane. The coated silk fabrics separators are characterized in terms of ionic conductivity, drenching rate, and electrochemical stability, and the charge-discharge profiles of lithium-ion batteries adopting the coated separators are also examined. As a result, the coated silk fabrics separator prepared using DBP 40~50 wt% and silica shows the superior separator properties and high-rate capability. This is due to (i) high sustainability of silk fabrics, (ii) the formation of micropores with the coated layer membrane by DBP, (iii) increase in drenching rate by silica nanoparticles to involve great enhancements in specific surface area and ionic conductivity.

• Journal of the Korean Applied Science and Technology
• /
• v.24 no.2
• /
• pp.174-181
• /
• 2007

In this study, $SiO_2/poly(ethylene-co-vinyl$ alcohol)(EVOH) hybrid coating materials with gas barrier property could be produced using sol-gel method. The biaxially oriented polypropylene (BOPP) substrate with surface pretreatment was coated with the prepared hybrid sols containing various inorganic silicate component by a spin coating method. Crystallization behavior of the hybrids was investigated in terms of analysis of X-ray diffraction and cooling thermogram from DSC experiment. From the morphological observation of the $SiO_2/EVOH$ hybrid gel, it was confirmed that there existed an optimum content of inorganic silicate precursor, Tetraethylorthosilicate (TEOS), to produce hybrid materials with dense microstructure, exhibiting uniformly dispersed silica particles with average size below 100 nm. When TEOS was added at below or above the optimum content, particle clusters with large domain were observed, resulting in phase separation. This morphological result was found to be in good agreement with that of oxygen permeability of the hybrid coated films. In the case of film coated with hybrid prepared from addition of 0.01 - 0.02mol of TEOS, a remarkable improvement in barrier property could be obtained, however, with the addition of TEOS more than 0.04 mol, the barrier property was dramatically reduced because of phase separation and micro-crack formation on the film surface.

• 한국연소학회:학술대회논문집
• /
• 2006.10a
• /
• pp.196-201
• /
• 2006

Silica(SiO2) nanoparticles are used as additives in plastics and rubbers to improve mechanical, electrical, magnetic properties and optical material. Silica nanoparticles were synthesized by the gas phase thermal oxidation of several kinds of precursors in many types of reactor. Diffusion flame reactor has some advantages compared with other types of reactors. In this study, we investigated the generation of silica nanoparticles on the effect of residence time by tetraethylothosilicate(TEOS) in a turbulent diffusion flame reactor controlled by providing reactant flowrate and reactor geometry affect particle morphology, particle size and particle size distribution. To determine the flame residence time, flame length should be determined which was examined by ICCD image. Particle size, distribution and morphology were performed with TEM.