• 멤브레인
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• 제24권4호
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• pp.301-310
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• 2014

본 연구에서는 제조된 유무기 나노복합막의 치수안정성, 수소이온 전도능력 및 전기화학성능을 향상시키기 위하여 실리카 나노입자를 선정하였다. 이를 위하여, 소수성 실리카(Aerosil$^{(R)}$ 812, Degussa)와 친수성 실리카(Aerosil$^{(R)}$ 380, Degussa)를 각각 술폰화 폴리아릴렌 에테르 술폰(SPAES) 고분자 매트릭스에 도입하였다. 이들 실리카 입자들은 비이온성 분산제인(Pluronics$^{(R)}$ L64)을 사용함으로써 SPAES 매트릭스에 고르게 분산시킬 수 있었다. 실리카 함량은 최종 제조된 고분자의 미세 구조 및 특성에 중요한 영향을 미치게 된다. 따라서, 본 연구에서는 과량의 실리카가 도입된 나노 복합막의 특성을 연구하기 위하여, 실리카의 함량을 5 wt%까지 증가시켰다. 이를 통하여 소수성 실리카가 포함된 나노복합막이 실리카가 도입되지 않은 SPAES막에 비하여, 더 낮은 수소이온 전도도에도 불구하고, 29% 더 높은 전기화학 성능을 나타내는 것을 관찰하였으며, 이는 같은 소수성을 가지고 있는 촉매층과의 접합성 향상에 따른 것으로 나타났다. 이외의 나머지 복합막들 또한 실리카가 도입되지 않은 SPAES막에 비하여 높은 성능을 나타냈다.

• Elastomers and Composites
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• 제55권1호
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• pp.26-39
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• 2020

The physical properties of silica-filled SBR compounds (WSBR) prepared using silica-SBR wet masterbatches (WMB) were systematically investigated to understand the effect of the surface treatment of silica on the reinforcement performance of SBR. Treatment of silica with bis(triethoxysilylpropyl)tetrasulfide (TESPT) in the liquid phase, followed by mixing with an SBR solution and recovery by water stripping, easily produced silica-SBR WMB. However, insufficient surface treatment in terms of the amount and stability of the incorporated TESPT led to considerable silica loss and inevitable TESPT elution. Pretreatment of silica in the gas phase with TESPT and another organic material that enabled the formation of organic networks among the silica particles on the surface provided hydrophobated silica, which could be used to produce silica-SBR WMB, in high yields of above 99%. The amount and type of organic material incorporated into silica greatly influenced the cure characteristics, processability, and tensile and dynamic properties of the WSBR compounds. The TESPT and organic material stably incorporated into silica increased their viscosity, while the organic networks dispersed on the silica surface were highly beneficial for reducing their rolling resistance. Excessive dosing of TESTP induced low viscosity and a high modulus. The presence of connection bonds formed by the reaction of glycidyloxy groups with amine groups on the silica surface resulted in physical entanglement of the rubber chains with the bonds in the WSBR compounds, leading to low rolling resistance without sacrificing the mechanical properties. Mixing of the hydrophobated silica with a rubber solution in the liquid phase improved the silica dispersion of WSBR compounds, as confirmed by their low Payne effect, and preservation of the low modulus enhanced the degree of entanglement.

• Elastomers and Composites
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• 제53권3호
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• pp.109-123
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• 2018

The effect of the silica content on the state and properties of silica-filled styrene-butadiene rubber/butadiene rubber (SBR/BR) compounds containing coupling and dispersion agents was evaluated by varying the content of silica from 50 to 120 phr. Bis-[(triethoxysilyl)propyl] tetrasulfide (TESPT) and zinc 2-ethylhexanoate (ZEH) were used as the coupling and dispersion agents, respectively. The maximum silica content in the pristine material was 80 phr, which increased to 120 phr upon the addition of TESPT and ZEH. The incorporation of TESPT considerably improved most of the rubber properties due to its coupling action and the suppression of silica flocculation, while further addition of ZEH resulted in additional improvements. The properties of the rubber compounds with different silica contents can be fully explained either by an enhancement of the rubber-silica interactions or by their deterioration due to an excessive amount of silica aggregates.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.151-152
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• 2023

This study investigates the effect of nano-silica and nano-calcite on the hydration properties and mechanical performance of limestone calcined clay cement (LC³) paste. The pastes were synthesized by replacing limestone with nano-silica and nano-calcite in order to enhance the mechanical properties in both early and late stages of hydration. The nano-calcite enhanced the strength of LC³ pastes at 1 day of hydration, however, the strength decreased compared to the ordinary LC³ pastes afterwards due to excessive amount of carboaluminate produced in the pastes. On the other hand, nano-silica improved the mechanical properties of LC³ pastes at all ages of hydration. This is mainly due to the nucleation effect and pozzolanic reaction of nano-silica, affecting the early age and late ages of hydration, respectively. The nucleation effect of both nanomaterials were confirmed by the analysis of hydration heat, supporting the enhanced early age strength of nanomaterial incorporated LC³ pastes. Furthermore, the dense matrix was shown in the pore size distribution, and the increased C-S-H due to the pozzolanic reaction evidence the improved compressive and splitting tensile strength of nano-silica incorporated LC³ pastes.

• 한국농공학회논문집
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• 제62권4호
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• pp.23-31
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• 2020

Recently, meteorological disasters have been increasing by climate change, excessive rainfall, and landslide. The purpose is to develop new fabric concrete that can prevent and recover from damages because some of areas are vulnerable to meteorological disaster. Specifically, this technology can minimize time and space constraint when repairing the concrete structure and installing a formwork. The structure of fabric concrete is a mixture of fabric concrete and a high-speed hardened cement, Silica sand, wollastonite mineral fiber, fabric material and waterproof PVC fabric. In this study, the ratio of mechanical properties and durability of the fabric concrete mixture was evaluated by deriving the binder: silica sand mix ratio of the fabric concrete mixture and substituting part of the cement amount with wollastonite mineral fiber. Best binder in performance evaluation: Silica sand mix ratio is 6: 4 and the target mechanical performance and durability are the best when over 15% wollastonite binder is replaced by silicate mineral fiber.

• Macromolecular Research
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• 제17권10호
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• pp.776-784
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• 2009

N,N-dimethyldodecylamine (tertiary amine)-modified MMT (DDA-MMT) was prepared as an organically modified layered silicate (OLS), after which styrene-butadiene rubber (SBR) nanocomposites reinforced with the OLS were manufactured via the latex method. The layer distance of the OLS and the morphology of the nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By increasing the amount of N,N-dimethyldodecylamine (DDA) up to 2.5 g, the maximum values of torque, tensile strength and wear resistance of the SBR nanocomposites were increased due to the increased dispersion of the silicate layers in the rubber matrix and the increased crosslinking of the SBR nanocomposites by DDA itself. When SBR nanocomposites were manufactured by using the ternary filler system (carbon black/silica/OLS) to improve their dynamic properties as a tire tread compound, the tan $\delta$(at $0^{\circ}C$ and $60^{\circ}C$) property of the compounds was improved by using metal stearates instead of stearic acid. The mechanical properties and wear resistance were increased by direct substitution of calcium stearate for stearic acid because the filler-rubber interaction was increased by the strong ionic effect between the calcium cation and silicates with anionic surface. However, as the amount of calcium stearate was further increased above 0.5 phr, the mechanical properties and wear resistance were degraded due to the lubrication effect of the excessive amount of calcium stearate. Consequently, the SBR/organoclay nanocomposites that used carbon black, silica, and organoclay as their ternary filler system showed excellent dynamic properties, mechanical properties and wear resistance as a tire tread compound for passenger cars when 0.5 phr of calcium stearate was substituted for the conventionally used stearic acid.

• 한국세라믹학회지
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• 제25권3호
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• pp.237-242
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• 1988

Float 공법에 의한 국산 Soda-lime-silica 판유리를 대상으로하여 그의 이온교환 거동에 대하여 연구하였다. 효과 분석으로는 $K^+$ 이온의 침투깊이, 표면층에 형성된 압축응력의 크기, 압축응력층의 두께, $K^+$이온 교환량 및 밀도변화 등을 조사하였다. 본 연구에서 표면층의 최대 압축응력값은 43$0^{\circ}C$-8h 및 45$0^{\circ}C$-6h의 열처리 조건하에서 59.8kg/$Cm^2$이며, 확산을 위한 활성화 에너지는 17.0Kcal/mole이었다. 한편, 과도한 이온교환 열처리 조건하에서는 응력이완 현상을 나타냄을 알 수 있었다.

• Current Photovoltaic Research
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• 제4권3호
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• pp.124-129
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• 2016

Recently industry has voiced a need for optimally designing the production process of low-cost, high-quality ingots by improving productivity and reducing production costs with the Czochralski process. Crystalline defect control is important for the production of high-quality ingots. Also oxygen is one of the most important impurities that influence crystalline defects in single crystals. Oxygen is dissolved into the silicon melt from the silica crucible and incorporated into the crystalline a far larger amount than other additives or impurities. Then it is eluted during the cooling process, there by causing various defect. Excessive quantities of oxygen degrade the quality of silicone. However an appropriate amount of oxygen can be beneficial. because it eliminates metallic impurities within the silicone. Therefore, when growing crystals, an attempt should be made not to eliminate oxygen, but to uniformly maintain its concentration. Thus, the control of oxygen concentration is essential for crystalline growth. At present, the control of oxygen concentration is actively being studied based on the interdependence of various factors such as crystal rotation, crucible rotation, argon flow, pressure, magnet position and magnetic strength. However for methods using a magnetic field, the initial investment and operating costs of the equipment affect the wafer pricing. Hence in this study simulations were performed with the purpose of producing low-cost, high-quality ingots through the development of a process to optimize oxygen concentration without the use of magnets and through the following. a process appropriate to the defect-free range was determined by regulating the pulling rate of the crystals.

• 공업화학
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• 제10권2호
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• pp.237-241
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• 1999

니켈을 알루미나와 실리카 담체에 담지 한후 CFC-113 ($CF_2Cl$-$CFCl_2$)을 수소 기류 중에서 3FCl ($CF_2$=CFCl, CFC-1113)로 하는 환원반응을 실시하였다. 실리카나 알루미나의 경우 모두 활성이 급격히 저하하였으며 니켈의 함량이 증가할수록 저하속도는 현저하였다. 그러나 선택성은 80% 수준을 유지하면서 변하지 않았다. 알루미나 상에 동과 리티움을 니켈과 동시에 담지 시켰을 시는 활성과 선택성이 크게 개선되었다. 그러나 과량의 리티움의 증가는 활성과 선택성을 모두 저하시켰다. 담체로 실리카를 사용한 경우에는 활성이 급격히 저하되었는데, 이는 반응중 생성 된 HF가 Silica와 반응, $SiF_4$로 증발됨으로서 표면적이 큰 실리카 담체의 손실 또는 알카리 금속의 첨가로 인한 활성점의 감소에 의한 것으로 보여 진다.