• 제목/요약/키워드: nanosilica

검색결과 46건 처리시간 0.025초

Modified Chloroprene Rubber를 이용한 Primer 제조 및 특성평가 (Characterization of Modified Chloroprene Rubber by Nanosilica as a Primer)

  • 임경은;정부영;천정미;최민지;천제환
    • 접착 및 계면
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    • 제19권1호
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    • pp.1-4
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    • 2018
  • 본 연구에서는 부착력 향상 및 모바일 기기용 toluene-free 프라이머를 제조하기 위해 클로로프렌 고무 (CR)에 실리카 나노입자를 분산시켜 CR/silica 복합체를 제조하였다. CR/silica 복합체는 FT-IR, SEM, EDS 등을 이용하여 물성을 평가하였다. SEM을 통해 실리카 나노입자의 함량이 4 phr일때 가장 균일하게 분산되어 있는 것을 확인하였다. 접촉각과 연필경도측정을 통해 실리카 함량이 증가할수록 소수성을 띠는 것과, 연필경도가 증가함을 나타내었다. 부착력 결과 역시 실리카 함량이 4phr일때 가장 높았으며, 실리카가 함유되지 않은 P-0에 비해 50% 증가함을 확인하였다.

Effect of pozzolans on mechanical behavior of recycled refractory brick concrete in fire

  • Nematzadeh, Mahdi;Baradaran-Nasiri, Ardalan;Hosseini, Mehdi
    • Structural Engineering and Mechanics
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    • 제72권3호
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    • pp.339-354
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    • 2019
  • Reusing building materials and concrete of old buildings can be a promising strategy for sustained development. In buildings, the performance of materials under elevated temperatures is of particular interest for determining fire resistance. In this study, the effect of pozzolan and aggregate type on properties of concrete exposed to fire was investigated. In doing so, nanosilica with cement-replacement levels of 0, 2, and 4% as well as silica fume and ultrafine fly ash with cement-replacement levels of 0, 7.5, and 15% were used to study effect of pozzolan type, and recycled refractory brick (RRB) fine aggregate replacing natural fine aggregate by 0 and 100% was utilized to explore effect of aggregate type. A total of 126 cubic concrete specimens were manufactured and then investigated in terms of compressive strength, ultrasonic pulse velocity, and weight loss at $23^{\circ}C$ and immediately after exposure to 400 and $800^{\circ}C$. Results show that replacing 100% of natural fine aggregate with recycled refectory brick fine aggregate in the concretes exposed to heat was desirable, in that it led to a mean compressive strength increase of above 25% at $800^{\circ}C$. In general, among the pozzolans used here, silica fume demonstrated the best performance in terms of retaining the compressive strength of heated concretes. The higher replacement level of silica fume and ultrafine fly ash pozzolans in the mixes containing RRB fine aggregate led to a greater weight loss rate, while the higher replacement level of nanosilica reduced the weight loss rate.

불소계면활성제를 함유한 초친수 코팅액의 제조 및 방담 방오 특성 (Preparation of superhydrophilic coating solutions containing fluorosurfactants and characterization of their antifogging and antifouling properties)

  • 이수;임선문;황헌
    • 한국응용과학기술학회지
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    • 제34권3호
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    • pp.525-535
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    • 2017
  • 내열성이 우수하며, 태양광 모듈의 유리 표면에 방담성(antifogging) 및 방오성(antifouling)을 동시에 부여하여 효율을 향상시키기 위한 친수성 코팅액을 제조하기 위해 초친수성과 우수한 방담효과를 나타내는 Tween 20과 데카플루오로부탄과 폴리에틸렌글리콜 성분으로 구성된 불소계면활성제 수용액에 방오성 부여를 위하여 나노실리카를 분산하였다. 고온 처리에서 나노실리카의 함량에 따른 방담 효과는 모든 코팅액이 우수하였으나, 방오 효과는 나노실리카의 함량이 6 wt%일 때부터 나타났다. 불소계면활성제의 함량이 증가할수록 초기 접촉각이 증가하며 방담 효과도 500회 wiping까지 잘 유지되었다. 방오 효과 역시 불소계면활성제의 함량에 상관없이 우수하여 불소계면활성제의 적절한 첨가량은 0.1 wt%이상 이면 충분하였다. AFM 결과로부터 불소계면활성제가 0.1 wt%에서 0.3 wt%가 첨가된 경우 코팅 표면의 프랙탈구조가 확실히 나타나 방오성 향상에 기여하였다. 코팅된 유리의 투과도는 불소계면활성제가 0.1 wt% 첨가된 TL-1의 경우가 가장 높았으며 더 많은 양의 불소계면활성제를 첨가할 경우 오히려 투과도 향상은 미미하였다. 이러한 결과는 앞의 AFM 결과에서 나타난 표면 조도가 높으며 프랙탈구조 형성도 잘 일어난 TL-1 코팅액의 결과와 잘 일치하는 것이다.

Two step lithography와 나노 실리카 코팅을 이용한 초발수 필름 제작 (Fabrication of Superhydrophobic Film with Uniform Structures Using Two Step Lithography and Nanosilica Coating)

  • 유채린;이동원
    • 센서학회지
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    • 제28권4호
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    • pp.251-255
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    • 2019
  • We propose a two-step lithography process to minimize edge-bead issues caused by thick photoresist (PR) coating. In the conventional PR process, the edge bead can be efficiently removed by applying an edge-bead removal (EBR) process while rotating the silicon wafer at a high speed. However, applying conventional EBR to the production of desired PR mold with unique negative patterns cannot be used because a lower rpm of spin coating and a lower temperature in the soft bake process are required. To overcome this problem, a two-step lithography process was developed in this study and applied to the fabrication of a polydimethylsiloxane (PDMS) film having super-hydrophobic characteristics. Following UV exposure with a first photomask, the exposed part of the silicon wafer was selectively removed by applying a PR developer while rotating at a low rpm. Then, unique PR mold structures were prepared by employing an additional under-exposure process with a second mask, and the mold patterns were transferred to the PDMS. Results showed that the fabricated PDMS film based on the two-step lithography process reduced the height difference from 23% to 5%. In addition, the water contact angle was greatly improved by spraying of hydrophobic nanosilica on the dual-scaled PDMS surface.

Experimental Investigation of Electrochemical Corrosion and Chloride Penetration of Concrete Incorporating Colloidal Nanosilica and Silica Fume

  • Garg, Rishav;Garg, Rajni;Singla, Sandeep
    • Journal of Electrochemical Science and Technology
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    • 제12권4호
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    • pp.440-452
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    • 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.

Study of strength and microstructure of a new sustainable concrete incorporating pozzolanic materials

  • Grzegorz Ludwik Golewski
    • Structural Engineering and Mechanics
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    • 제86권4호
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    • pp.431-441
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    • 2023
  • The aim of this paper is to present a new sustainable ternary and quaternary binder by partially replacing ordinary Portland cement (OPC) with different percentages of supplementary cementitious materials. The motivation is to reduce our dependency on OPC to reduce CO2 emission and carbon foot print. As the main substitute for the OPC, siliceous fly ash was used. Moreover, silica fume and nanosilica were also used. During examinations the main mechanical parameters of concrete composites, i.e., compressive strength (fcm) and splitting tensile strength (fctm) were assed. The microstructure of these materials was also analysed. It was found that the concrete incorporating pozzolanic materials is characterized by a well-developed structure and has high values of mechanical parameters. The quaternary concrete containing: 80% OPC, 5% FA, 10% SF, and 5% nS have shown the best results in terms of good strength parameters as well as the most favourable microstructure, whereas the worst mechanical parameters with microstructure containing microcracks at phase interfaces were characterized by concrete with more content of FA additive in the concrete mix, i.e., 15%. Nevertheless, all concretes made on quaternary binders had better parameters than the reference one. It can be stated that sustainable concrete incorporating pozzolanic materials could be good substitute of ordinary concretes.

Investigating the effect of using three pozzolans (including the nanoadditive) in combination on the formation and development of cracks in concretes using non-contact measurement method

  • Grzegorz Ludwik Golewski
    • Advances in nano research
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    • 제16권3호
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    • pp.217-229
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    • 2024
  • This paper presents results of visual analysis of cracks formation and propagation of concretes made of quaternary binders (QBC). A composition of the two most commonly used mineral additives, i.e. fly ash (FA) and silica fume (SF) in combination with nanosilica (nS), has been proposed as a partial replacement of the cement. The principal objective of the present study is to achieve information about the effect of simultaneous incorporation of three pozzolans as partial replacement to the OPC on the fracture processes in concretes made from quaternary binders (QBC). The modern and precise non-contact measurement method (NCMM) via digital image correlation (DIC) technique was used, during the studies. In the course of experiments it was established that the substitution of OPC with three pozzolans including the nanoadditive in FA+SF+nS FA+SF+nS combination causes a clear change of brittleness and behavior during fractures in QBCs. It was found that the shape of cracks in unmodified concrete was quasi-linear. Substitution of the binder by SCMs resulted in a slight heterogeneity of the structure of the QBC, including only SF and nS, and clear heterogeneity for concretes with the FA additive. In addition, as content of FA rises throughout each of QBC series, material becomes more ductile and shows less brittle failure. It means that an increase in the FA content in the concrete mix causes a significant change in fracture process in this composite in comparison to concrete with the addition of silica modifiers only.

PAI 유/무기 하이브리드코일의 곡률변화에 따른 AC 및 DC 절연파괴 특성 (Insulation Breakdown Properties of AC and DC according to Curvature Variation of PAI Organic/Inorganic Hybrid Coils)

  • 박재준
    • 전기학회논문지
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    • 제65권10호
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    • pp.1721-1726
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    • 2016
  • 4-types of coils were prepared by coating with polyamideimide (PAI) organic/inorganic hybrid. One type was made with original PAI vanish and the other 3-types were made of double layers, that was to say, high flexural PAI layer and high anti-corona PAI/nanosilica (15 wt%) layer. Drying temperature (T/D) were $220^{\circ}C$, $240^{\circ}C$, and $260^{\circ}C$, respectively and rectangular type coil for high-voltage rotating machine was used. DC and AC electrical breakdown tests were carried out in order to study the insulation properties according to T/D temperature and coil curvature (5, 15, and $25mm{\Phi}$). As the curvature increased, electrical breakdown voltage decreased and as T/D temperature decreased, electrical breakdown voltage increased.

Corrosion resistant self-compacting concrete using micro and nano silica admixtures

  • Jalal, Mostafa
    • Structural Engineering and Mechanics
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    • 제51권3호
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    • pp.403-412
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    • 2014
  • In this paper, enhancement of corrosion and chloride resistance of high performance self compacting concrete (SCC) through incorporating nanosilica into the binder has been investigated. For this purpose, different mixtures were designed with different amounts of silica fume and nano silica admixtures. Different binder contents were also investigated to observe the binder content effect on the concrete properties. Corrosion behavior was evaluated by chloride penetration and resitivity tests. Water absorption and capillary absorption were also measured as other durability-related properties. The results showed that water absorption, capillary absorption and Cl ion percentage decreased rather significantly in the mixtures containing admixtures especially blend of silica fume and nano silica. By addition of the admixtures, resistivity of the SCC mixtures increased which can lead to reduction of corrosion probability.