• Elastomers and Composites
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• 제53권3호
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• pp.175-180
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• 2018

Solution-styrene-butadiene rubber (SSBR) composites were manufactured using four kinds of fillers: silica-silane coated carbon black (SC-CB) hybrid, starch-SC-CB hybrid, pure silica, and pure starch. The influence of filler type on the mechanical properties of the rubber matrix was studied in this work. SC-CB was prepared by silane-graft-coating using vinyl triethoxy silane and carbon black, which enhanced the dispersion effect between the rubber matrix and the filler, and improved the mechanical properties of the compounds. The morphology of the composites was observed by field-emission scanning electron microscopy (FE-SEM). The thermal decomposition behavior of the composites was determined by thermogravimetric analysis (TGA), and the crosslinking behavior of the composites was tested using a rubber process analyzer (RPA). The hardness, tensile strength, swelling ratio, and gas transmittance rate of the composites were evaluated according to ASTM. The test results revealed that with the addition of SC-CB, the hybrid fillers, especially those blended with silica, showed a better reinforcement effect, the highest hardness and tensile strength, and stable thermal decomposition behavior. This implies that the silica-SC-CB hybrid filler has a notable mechanical reinforcement effect on the SSBR matrix. Because of self-crosslinking during its synthesis, the starch-SC-CB hybrid filler produced the most dense matrix, which improved the anti-gas transmittance property. The composites with the hybrid fillers had better anti-swelling properties as compared to the neat SSBR composite, which was due to the hydrophilicity of silica and starch.

• 한국공작기계학회논문집
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• 제14권2호
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• pp.1-7
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• 2005

In order to determine the wear Properties of PECVD ceramic coatings, wear process was evaluated using the coated pin of Falex Tribosystem. Coating materials deposited wear the TiC, TiN and Ti(CN). An experimental process was established to determine the tribological characteristics of friction and wear behavior under the variation of applied load, temperature and sliding distance by the Falex test machine. The experimental results indicate that TiN coating compared with TiC coating on e materials have e excellent friction and wear characteristics. However TiC coating compared i친 TiN coatings have a low friction coefficient with steel and good thermal stability, and Ti(CN) has the excellent anti-wear properly as well as the superiority of extreme pressure property. Compound coating compared wi simple coatings show improved tribological characteristics.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2010년도 춘계 학술논문 발표대회 1부
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• pp.219-220
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• 2010

The purpose of this study is to evaluate chloride ion attack durability of concrete structure having experienced the high temperature fire. Mechanical properties and anti chloride ion diffusivity of concrete specimens were measured which have experienced of 2 hours heating at $200{^{\circ}C},\;400{^{\circ}C},\;600{^{\circ}C},\;800{^{\circ}C}$. The coupling FE model of thermal transfer and chloride ion diffusion was built to predict the life expectancy of RC structure using the property values by a series of experiment.

• 한국세라믹학회지
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• 제40권2호
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• pp.113-117
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• 2003

To reduce the doming of the shadow mask due to thermal expansion and to prevent the color discrepancy, the electron reflecting layer with lead tungsten oxides on the electron gun side of shadow mask was formed by screen printing method and doming property was evaluated in CRT. First, the lead tungsten oxides were prepared by calcining the mixture of lead oxide and tungsten oxide above 600$^{\circ}C$. Second, the paste which has the anti-doming composition including the lead tungsten oxides was coated by screen-printing method. As a result, the doming of the shadow mask was reduced about from 30 to 45%.

• Tribology and Lubricants
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• 제10권1호
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• pp.78-88
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• 1994

For the study of chemical and mechanical properties of the synthetic and mineral oil added with two different Zn-DTPs, base and formulated oils were analyzed and compared. Kinematic viscosity and total acid number (TAN) were tested at high temperature for formulated oils. Also the oils added with different alkyl groups of Zn-DTP were tested for thermal stability and TAN changes. The 4-ball machine was used to test for the mechanical properties, such as the coefficient of friction and wear. The worn areas after sliding test were analyzed with microscope and EDX, too. From the study, mineral and synthetic oil have different effects according to the various added ratio of the primary and secondary alkyl groups of Zn-DTP. Also the temperature of test oil affected the anti-wear and friction property of the formulated oils. For synthetic oil, the primery alkyl group of Zn-DTP made better friction properties than that of secondary, while, for mineral oil, secondary alkyt group was better only at low temperature for mineral oil.

• Corrosion Science and Technology
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• 제4권1호
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• pp.33-38
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• 2005

Some feasibility studies are conducted to produce an advanced ceramic coating, which reveals superior chemical and mechanical strength, on metal base structure used in chemical plant. This advanced coating on metallic frame can replace ceramic delivery pipe and reaction chamber used in chemical plant, which are operated in hi-temperature and corrosive/erosive environment. An dual spraying is adopted to reduce the residual stress in order to increase the coating thickness and the residual stress is estimated by in-situ manner. Then new methodology is tried to form special coating of yttrium aluminum garnet(YAG), which reveals hi-strength and low-creep rates at hi-temperature, superior anti-corrosion property, hi-stability against Alkali-Vapor corrosion, and so on, on iron base structure. To verify the formation of YAG during thermal spraying, XRD(X ray diffraction) technique was used.

• 멤브레인
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• 제31권6호
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• pp.434-442
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• 2021

Poly(vinylidene fluoride) (PVDF) 막은 내구성 및 열적·화학적 안정성 등의 물성은 우수하나 소수성이 커서 수투과도가 낮고 단백질 및 유기물에 의한 막오염이 쉽게 발생한다. 본 연구에서는 PVDF 막의 내오염성을 개선시키고자 바이오 기능성 물질인 𝛽-cyclodextrin (𝛽-CD)을 PVDF 막 구조 내에 분산 함침시킨 PVDF/𝛽-CD 혼합기질 비대칭막을 상변환법을 통해 제조하고, 𝛽-CD 함침량에 따른 순수 투과 유속(PWF) 측정과 BSA 용액을 대상으로 한 막여과 실험을 수행하여 내오염성 특성을 평가하였다. 이 결과 PVDF 고분자 매질 내에 𝛽-CD를 함침시키면 막의 친수성을 증가시켜 접촉각을 감소시키고 이로 인해 내오염성을 향상시킬 수 있었다. 𝛽-CD 함침량이 2 wt%인 도프용액을 사용하여 제조된 PVDF/𝛽-CD 혼합기질 비대칭막의 PWF는 64 L/m²·h, BSA 배제도는 95%를 나타내었으며, 𝛽-CD를 첨가하지 않고 제조된 pristine PVDF 막에 비해 투과 유속 향상성이 최대 80%에 달해 𝛽-CD를 첨가시킴으로서 PVDF 막의 내오염성을 증가시킬 수 있었다.

• 한국재료학회지
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• 제31권1호
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• pp.8-15
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• 2021

Transparent, photocatalytic, and self-cleaning TiO2 thin film is developed by TiO2 sol-gel coating on glass and polycarbonate (PC) substrates. Acetyl acetone (AcAc) suppresses the precipitation of TiO2 by forming a yellowish (complex) transparent sol-gel. XPS analysis confirms the presence of Ti2p and O1s in the thin films on glass and PC substrates. The TiO2-sol is prepared by stabilizing titanium (IV) isopropoxide (TTIP) with diethylamine and methyl alcohol. The addition of AcAcsilane coupling solution to the TiO2-sol instantaneously turns to yellowish color owing to the complexing of titanium with AcAc. The AcAc solution substantially improves the photocatalytic property of the TiO2 coating layer in MB solutions. The coated TiO2 film exhibits super hydrophilicity without and with light irradiation. The TiO2 thin film stabilized by adding 8.7 wt% AcAc shows the highest photo-degradation for methylene blue (MB) solution under UV light irradiation. Also, the optimum photocatalytic activity is obtained for the 8.7 wt% AcAc-stabilized TiO2 coating layer calcined at 450 ℃. The thin-films on glass exhibit fast self-cleaning from oleic acid contamination within 45 min of UV-light irradiation. The appropriate curing time at 140 ℃ improves the anti-fogging and thermal stability of the TiO2 film coated on PC substrate. The watermark-free PC substrate is particularly beneficial to combat fogging problems of transparent substrates.

• 대한화장품학회지
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• 제30권2호
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• pp.167-172
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• 2004

피부 활성 물질로 넓이 알려져 있는 vitamin C (L-Ascorbic acid)는 콜라겐 생합성 촉진과 강한 항산화 작용으로 피부 항노화 및 주름 개선 효과 있을 뿐만 아니라 멜라닌 세포 활성 억제, 자외선 차단, 상처치유 등의 효능을 갖고 있다. 그러나 물성 면에서 피부 자극과 수분 및 공기, 빛에 불안정하여 쉽게 산화된다는 단점을 갖고 있다 이러한 문제점을 해결하기 위해 많은 연구가 진행되어 왔고, 그 결과 다양한 vitamin C 유도체가 개발되었다. 그러나 아직까지도 vitamin C의 불안정한 물성을 해결하면서 그 자체의 효능을 피부에 적용시키기에는 미흡한 점이 많다는 평을 받고 있다. 본 연구에서는 이러한 vitamin C의 불안정한 물성을 개선시키고 그 효능을 피부에 적용시킬 수 있는 vitamin C 유도체를 개발하기 위해, 피부 친화성이 우수한 스핑고지질류 중 하나인 phytosphingosine을 이용하여 산염기 반응에 의한 vitamin C의 OH기와 phytosphingosine의 -NH$_2$이온 결합시킨 새로운 vitamin C 유도체인 phytosphingosine ascorbate (SP-VC)를 합성하였다. 이렇게 합성된 phytosphingosine ascorbate (SP-VE)는 원소 분석(C58.3 : H9.3 : N2.8 : 029.5) 및 mass spectrosocopy (Maldi TOF-MS), UV/vis spectra (268.5nm), $^1$H NMR, FT-IR, 열분석 (m.p=154$^{\circ}C$), HPLC 등을 통하여 구조 및 물성을 확인하였다 또한 효능면에서는 우선적으로 phytosphingosine ascorbate(SP-VC)의 항균 및 항산화 효과를 확인하였다. 이러한 결과를 토대로 vitamin C와 phytosphingosine의 효능을 동시에 갖으며 불안정한 물성과 자극을 개선시킬 것이라 예상되는 새로운 소재를 합성하였다.

• Corrosion Science and Technology
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• 제13권5호
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• pp.178-185
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• 2014

Alloy 617 is considered as a candidate Ni-based superalloy for the intermediate heat exchanger (IHX) of a very high-temperature gas reactor (VHTR) because of its good creep strength and corrosion resistance at high temperatures. Helium is used as a coolant in a VHTR owing to its high thermal conductivity, inertness, and low neutron absorption. However, helium inevitably includes impurities that create an imbalance in the surface reactivity at the interface of the coolant and the exposed materials. As the Alloy 617 has been exposed to high temperatures at $950^{\circ}C$ in the impure helium environment of a VHTR, the degradation of material is accelerated and mechanical properties decreased. The high-temperature strength, creep, and corrosion properties of the structural material for an IHX are highly important to maintain the integrity in a harsh environment for a 60 year period. Therefore, an alloy superior to alloy 617 should be developed. In this study, the mechanical and high-temperature corrosion properties for Ni-Cr alloys fabricated in the laboratory were evaluated as a function of the grain boundary strengthening and alloying elements. The ductility increased and decreased by increasing the amount of Mo and Cr, respectively. Surface oxide was detached during the corrosion test, when Al was not added to alloy. However the alloy with Al showed improved oxide adhesive property without significant degradation and mechanical property. Aluminum seems to act as an anti-corrosive role in the Ni-based alloy.