• 한국지진공학회논문집
• /
• 제7권3호
• /
• pp.17-22
• /
• 2003

본 연구에서는 나노기술을 이용하여 에너지 감쇠 기능을 활용한 감쇠기 개발에 대한 연구를 하였다. 유체 감쇠기를 대체하는 완충역할을 하는 미로구조를 가지는 실리카 겔 입자를 사용하였으며, 입자에 관련한 작동 유체로는 물을 사용하여 그 효과를 검증하였다. 콜로이드 감쇠기를 구현하기 인해서는 형성된 실리카 겔 입자의 표면을 유기 실리콘 매질을 이용한 소수화 코팅 처리를 하였다. 정적 하중 상태에서의 가역적 콜로이드 감쇠기에 대한 실험을 수행하였다. 콜로이드 감쇠기내 다공질 입자의 나노 유로(pore)와 다공성 입자의 직경, 다공성 입자의 구조, 그리고 대기압 상태에서 유체의 출입을 통제하기 위한 코팅처리의 분자 간 길이와 같이 여러 가지 요인의 콜로이드 감쇠기 이력현상에 대한 영향을 평가하였다. 감쇠기의 소산 에너지양과 효율에 대해서도 조사하여 유압 감쇠기 보다 뛰어난 결과를 얻었으며 콜로이드 감쇠기로 사용 가능하다는 사실을 입증하였다.

• 한국분말재료학회지
• /
• 제18권4호
• /
• pp.347-358
• /
• 2011

Two different schemes were adopted to fabricate ordered macroporous structures with face centered cubic lattice of air spheres. Monodisperse polymeric latex suspension, which was synthesized by emulsifier-free emulsion polymerization, was mixed with metal oxide ceramic nanoparticles, followed by evaporation-induced self-assembly of the mixed hetero-colloidal particles. After calcination, inverse opal was generated during burning out the organic nanospheres. Inverse opals made of silica or iron oxide were fabricated according to this procedure. Other approach, which utilizes ceramic precursors instead of nanoparticles was adopted successfully to prepare ordered macroporous structure of titania with skeleton structures as well as lithium niobate inverted structures. Similarly, two different schemes were utilized to obtain disordered macroporous structures with random arrays of macropores. Disordered macroporous structure made of indium tin oxide (ITO) was obtained by fabricating colloidal glass of polystyrene microspheres with low monodispersity and subsequent infiltration of the ITO nanoparticles followed by heat treatment at high temperature for burning out the organic microspheres. Similar random structure of titania was also fabricated by mixing polystyrene building block particles with titania nanoparticles having large particle size followed by the calcinations of the samples.

• 방사선산업학회지
• /
• 제4권4호
• /
• pp.347-352
• /
• 2010

In this study, we addressed a novel nanosized curdlan-silica complex, which is curdlan bound to silica, for the development of a sustain-releasing micro element fertilizer formulation. The complex was obtained as follow steps; First, Curdlan polymer, sodium silicate ($Na_2SiO_3$) and isopropyl alcohol were dissolved in DDW. Next the resultant solution was irradiated by $^{60}Co$ gamma-irradiator (150 TBq of capacity; ACEL, Canada). Then $MgSO_4$ was treated with the resultant solution. The obtained colloidal solution was dried by freeze dryer. Finally, we obtained a novel nanosized curdlan-silica formulation containing $MgSO_4$ from the colloidal solution. The morphology of the complex was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanosized curdlan-silica complex has a particle size ranging from 20 to 80 nm and high stability. Our results suggested that the nano-complex can be applicable to use in various sustain-releasing formulation for pesticide delivery system (PDS).

• Journal of Electrochemical Science and Technology
• /
• 제12권4호
• /
• pp.440-452
• /
• 2021

Enhancement of durability and reduction of maintenance cost of concrete, with the implementation of various approaches, has always been a matter of concern to researchers. The integration of pozzolans as a substitute for cement into the concrete is one of the most desirable technique. Silica fume (SF) and colloidal nanosilica (CS) have received a great deal of interest from researchers with their significant performance in improving the durability of concrete. The synergistic role of the micro and nano-silica particles in improving the main characteristics of cemented materials needs to be investigated. This work aims to examine the utility of partial substitution of cement by SF and CS in binary and ternary blends in the improvement of the durability characteristics linked to resistance for electrochemical corrosion using electrical resistivity and half-cell potential analysis and chloride penetration trough rapid chloride penetration test. Furthermore, the effects of this silica mixture on the compressive strength of concrete under normal and aggressive environment have also been investigated. Based on the maximum compression strength of the concrete, the optimal cement substituent ratios have been obtained as 12% SF and 1.5% CS for binary blends. The optimal CS and SF combination mixing ratios has been obtained as 1.0% and 12% respectively for ternary blends. The ternary blends with substitution of cement by optimal percentage of CS and SF exhibited decreased rate for electrochemical corrosion. The strength and durability studies were found in consistence with the microstructural analysis signifying the beneficiary role of CS and SF in upgrading the performance of concrete.

• Advances in concrete construction
• /
• 제7권2호
• /
• pp.107-115
• /
• 2019

The possibility of using a combination of mineral admixtures as a replacement for cement may reduce the $CO_2$ emission which causes global warming and climatic changes on the environment. By using the combination of different byproducts from various industries, for replacing cement in concrete leads to saving in energy and natural resources. In this article, an attempt has been made to study the mechanical and water absorption properties of concrete incorporated with combination of Fly ash (FA), Alccofine (ALC) and Collodial Nano Silica (CNS) at 7, 28 and 56 days curing period. Cement has been partially replaced by combination of FA at 25%, ALC at 10% and CNS at 0.5%, 1%, 2% and 3% with water cement ratio of 0.43. The result indicates that the incorporation of combination of FA, ALC and CNS can be very effective in improvement of mechanical and water absorption properties of concrete. The Mix with a combination of 25% FA, 10% ALC and 1% CNS is most effective in improvement of mechanical and water absorption properties as compared with all other mixes.

• Transactions on Electrical and Electronic Materials
• /
• 제7권4호
• /
• pp.167-172
• /
• 2006

Submicron colloidal silica coated with ceria were prepared by mixing of silica and nano ceria particles and modified by hydrothermal reaction. The polishing efficiency of the ceria coated silica slurry was tested over oxide film on silicon wafer. By changing the polishing pressure in the range of $140{\sim}420g/cm^2$ with the ceria coated silica slurries in $100{\sim}300nm$, rates, WIWNU and friction force were measured. The removal rate was in the order of 200, 100, and 300 nm size silica coated with ceria. It was known that the smaller particle size gives the higher removal rate with higher contact area in Cu slurry. In the case of oxide film, the indentation volume as well as contact area gives effect on the removal rate depending on the size of abrasives. The indentation volume increase with the size of abrasive particles, which results to higher removal rate. The highest removal rate in 200 nm silica core coated with ceria is discussed as proper combination of indentation and contact area effect.

• 한국세라믹학회지
• /
• 제41권10호
• /
• pp.766-770
• /
• 2004

구형 실리카 나노 콜로이드 입자를 이용하여 반사방지막을 제조하였다. 실리카 콜로이드 현탁액을 모세관 힘을 이용하여 기울어진 두 장의 유리판 사이에 저장한 후 위의 유리를 이동시켜 반사 방지막을 코팅하였다. 상판 유리의 이동속도가 빨라질수록 막의 두께는 감소하였고, 막의 두께 변화에 따라 광 투과율이 변하였다. SEM으로 관찰된 실리카 나노 입자는 최밀충진에 가깝게 유리 기판에 부착되어 있었으며, 이로부터 고체 입자와 기공을 포함하는 막의 유효 굴절율을 구하였다. 최대의 광투과율을 나타내는 파장과 유효 굴절율로 부터 계산한 막의 두께는 SEM 사진 및 profiler로 구한 값과 잘 일치하였다. $94.7\%$의 최대 광투과율을 얻었으며, 양면으로 코팅한다면 $97.4\%$의 투과율 즉 $1.3\%$의 반사율을 얻을 수 있는 것으로 나타났다.

• 공업화학
• /
• 제23권1호
• /
• pp.53-58
• /
• 2012

투명한 플라스틱 필름의 표면경도를 향상시키기 위하여 유-무기 하이브리드 코팅 용액을 졸-겔 공정을 이용하여 합성하였다. 무기성분으로 콜로이드 실리카와 유기성분으로 PMMA, 유-무기 성분 간의 결합력을 향상시켜 하이브리드 코팅 층의 특성을 더욱 향상시키기 위하여 실란커플링제로서 vinyl trimethoxy silane (VTMS)과 [3-(metha cryloyloxy)] propyl trimethoxy silane (MAPTMS)를 이용하였고, 알콕시 실란의 종류, 콜로이드 실리카/PMMA의 함량비 등의 반응조건에 따라 콜로이드 실리카/PMMA 졸을 합성하였다. 이러한 졸을 PET 필름에 바코팅시키고, 열경화 시켜 하드코팅막을 제조하여 물리적 화학적 특성을 조사하였다. PMMA에 비해서 하이브리드 형태에서 코팅 막의 연필경도와 기재와의 부착력이 우수하였다.

• 한국세라믹학회지
• /
• 제41권4호
• /
• pp.297-301
• /
• 2004

분무연소합성법을 이용하여 나노크기의 물라이트(3Al$_2$O$_3$$.$2SiO$_2$) 콜로이드를 제조하였다. 연소반응을 위한 산화제로서 Al(NO$_3$)$_3$$.$9$H_2O$와 환원제(연료)로서 CH$_{6}$N$_4$O를 사용하였으며, 실리카 소스로서 콜로이드 실리카를 첨가하였다. 분무된 액적들의 착화를 위해 연소반응기의 온도를 80$0^{\circ}C$로 유지하였다. 액적의 응고에 의한 액적크기 성장을 억제하기 위하여 금속 스크린 필터를 사용함으로써 액적의 개수 농도를 감소시켰으며, 에어로졸 입자의 체류시간을 2.5초로 유지하여 열 유체의 흐름을 층류로 유도하였다. 제조된 입자들의 모양은 모두 구형이었으며, 평균입자크기는 130nm이었다 XRD와 TEM 분석 결과 각각의 초미립자들은 정량화합물의 물라이트 결정성을 나타내었다.

• 한국세라믹학회지
• /
• 제48권4호
• /
• pp.312-315
• /
• 2011

The effect of slurry composition and wafer flatness on a material removal rate (MRR) and resulting surface roughness which are evaluation parameters to determine the CMP characteristics of the on-axis 6H-SiC substrate were systematically investigated. 2-inch SiC wafers were fabricated from the ingot grown by a conventional physical vapor transport (PVT) method were used for this study. The SiC substrate after the CMP process using slurry added oxidizers into slurry consisted of KOH-based colloidal silica and nano-size diamond particle exhibited the significant MRR value and a fine surface without any surface damages. SiC wafers with high bow value after the CMP process exhibited large variation in surface roughness value compared to wafer with low bow value. The CMPprocessed SiC wafer having a low bow value of 1im was observed to result in the Root-mean-square height (RMS) value of 2.747 A and the mean height (Ra) value of 2.147 A.