• Polymer(Korea)
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• v.33 no.6
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• pp.537-543
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• 2009

The direct fluorination of polymers is a heterogeneous reaction using the mixture of $F_2$ and inert gas. In general, the resulting fluorinated polymers have good barrier property chemical stability similar to those of the fluoro-polymers, and could be prepared from the simple process. In this study, the polysulfone dense films were surface fluorinated using the direct fluorination technique and gas permeability and selectivity of the prepared membranes were measured with varying both $F_2$ concentration and reaction time. The introduction of $F_2$ was confirmed by X-ray photoelectron spectroscopy (XPS), water contact angles, and atomic force microscopy (AFM). As the $F_2$ increased, the permeability decreased while the selectivities for $O_2$, $CO_2$, and He gases relative to $N_2$ increased.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1998.11a
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• pp.19-20
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• 1998

오버레이용접에 의한 표면개질기술(Weld Surfacing or Hardfacing Technology)은 내식성, 내 마모성, 또는 내열성을 갖는 합금의 용접재료를 모재 표면에 균일하게 용착(오버레이:Ovedayer)시킴으로써 목적하는 재료의 표면성질을 향상시키는 표면처리의 한 방법이으로써 1922년 Stoody가 Steel Tube에 Cr합금 분말을 충진한 용접봉을 제조하여 석유시추용 회전드릴의 선단 표면을 오버 레이 용접시켜 내마모성을 획기적으로 개선시킴으로써 이루어 졌다. 초기 오버레이 용접기술은 발전설비I 제철설비I 시벤트설비, 그리고 제지설비 등 주로 설비 부품들의 표면부 내마모성을 개선시키는 방향으로 주로 연구 개발이 이루어졌으나, 기술개발의 진전으로 탈황설비 둥의 표면부 내식성 향상, 연속주조롤 표면부의 내산화성, 내열피로성, 내마모 성 향상 둥을 위해 점차 산업전반에 널리 이용되고 있으며, 설비의 고도화 및 장수명화가 요구되 면서 본 기술의 중요성 또한 점차 부각되고 있다. 그림 1은 연강의 모재 위에 셀프쉴드플럭스코어드와이어(Self-Shield Flux Cored Wire:SS-FCW, 이하 55-FCW라 기술함)를 사용하여 오버레이 용접올 하는 장면을 도식적으로 나 타낸 것이다. 모재와 전극재인 용접봉(S5-FCW) 사이에서 아크가 발생되고, 아크열에 의해서 용접 봉 및 모재 일부가 용융되면서 모재 표면에 새로운 오버레이 표면층이 형성된다. 통상 오버레이 층의 1층 두께는 2-6mm 내외이며, 단층 혹은 다충 오버레이를 자유롭게 실시한다. 오버레이층의 물성은 아크열에 의한 모재로의 용입정도에 따라 1층부에서는 모재의 영향을 크게 받지만 오버레 이충 수가 증가된 3층부에서 부터는 전적으로 용접봉의 성분에 좌우된다. 사진 1은 연강(55-41)의 모재위에 크롬탄화물이 다량 함유된 고크롬 탄화물형 내마모재가 오버 레이된 내마모 복합강판 (wear plate)의 단면 미세조직 사진으로써 모재부와 오버레이충을 함께 보여주고 있다. 모재와 오버레이 충간의 경계면은 모재 일부가 용융된 후 웅고하면서 형성됨으로 인해서 도금이나 용사층과는 달리 매우 견고하게 결합되어 있다. 따라서 계면부의 탈락이라는 문 제점은 거의 없어 심한 응력을 받는 기계구조물 및 부품에도 본 기술은 널리 적용되고 있다. 그리고 사진 1에서 알 수 있는 바와 같이 모재와는 전혀 상이한 재료를 자유로이 선택하여 표면 유효층 일부만 오버레이시키며I 주조 및 단조가 불가능한 재료까지도 표면부에 오버레이 시킴으로 서 부품 및 설비의 제조에 있어 재료비의 절감과 제품의 수명이 획기적으로 개선될 수 있다. 그리고 최근에는 도금 빛 용사 둥과 같은 표면처리를 할 경우임의 소재 표면에 도금 및 용 사에 용이한 재료를 오버레이용접시킨 후 표면처리를 함으로써 보다 고품질의 표면층을 얻기위한 시도가 이루어지고 있다. 따라서 국내, 외의 오버레이 용접기술의 적용현황 및 대표적인 적용사례, 오버레이 용접기술 및 용접재료의 개발현황 둥을 중심으로 살펴봄으로서 아직 국내에서는 널리 알려지지 않은 본 기 술의 활용을 넓이고자 한다.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.2
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• pp.97-104
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• 2022

This study investigated the characteristics for the optimal concentration of addition of the mixing solution through the corn husk pulverization and surface modification of biomass byproducts adding mixed solution between ESO and silane. And surveyed the specific surface area, water absorption, particle size and physical properties of bio- degradable plastic sheet. The specific surface area was 1.105 m²/g, particle size was the highest at 19 ㎛. The impact strength, tensile strength, elongation and hardness of plastic sheet showed the highest at the 1% concentration among the mixing solutions. The flexural strength and modulus was high according to the increasing the mixing solution. The results above showed that it was the best the adding 1% of mixed solution after silane treatment of corn husks for its manufacture as a bio-based plastic sheet.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.85-92
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• 2002

When the United Nation classified as Korea is the one of the water deficit country. The consensus was made that the water is the one of the precious national resources. Government increases their R/D budget trying to get more clean water bodies. For instances, 'Sustainable Water Resources Development' project is the one of major title in '21 Century Frontier Research project and there are several small research projects are undergoing by the Ministry of Agriculture and KARICO. However, when the environmental preservation issue has been get more emphasis, construction of the Surface Dam met the blockage from the environmentalists due to the problem of the their water buried area. Since the most fitting site for surface dam had been used in the past, some engineer move their focus on modification of the existing Dam's height to enlarge its capacity or dredging the bottom of the reservoir recently However dredging evoke water quality problem in return by accumulated materials at the bottom. Last year the Dong Gang Dam plan has been canceled by environmental problem in water buried area of the reservoir. With the point of this view, ground water gets more focus for the one of the useful alternative for clean water bodies. Underground dam technique which had widely applied once in the early nineteen eighties by the KARICO and attenuated due to engineering insufficiency. The technique is newly studied with the advanced engineering technique. Still groundwater usage rate in Korea is much lower comparing with the advanced countries and has many rooms to develop. Wells, under ground dam and radial collector wells are typical facilities up to now. There is little application in Korea for the Recharge Dam, which had been widely used in the advanced countries. The Recharge Dam is technique to conjunct surface water and groundwater body together, This technique had developed to increase groundwater recharge at the beginning This research is the result of the study on the possibility of the development of the new technology, Groundwater Reservoir' which was modified from Recharge Dam. Groundwater Reservoir is like a deep artificial lakes trenched in hard rock aquifer to get groundwater. The advantage of the Groundwater Reservoir is followings 1) It can be developed at the plains area, not in the deep valley 2) Huge water body can be developed without dam 3) Small buried area comparing surface water dam makes the least environmental effect. 4) Trenching cost can be substitute by the income of the selling rock debris 5) Outfit of the reservoir can be modified to match with the site prospect 6) Rock debris can be used as constructing materials 7) It can be used as groundwater recharge system when the heavy rains comes 8) The reservoir looks like scenery lake with huge clean water bodies.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.111-116
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• 2022

Recently, building structures tend to be super high-rise and large-scale with the development of concrete technology. When high-rise building is constructed of reinforced concrete structure, it has a disadvantage that its own weight increases. Light weight aggregate(LWA) was developed to compensate for these shortcomings. Manufacturing concrete using these light weight aggregates has the advantage of reducing the self weight of the reinforced concrete structure, but has a disadvantage in that the strength of the concrete is reduced. In this study, an experimental study was conducted to investigate the strength characteristics of hardened cement according to the presence or absence of surface coating of lightweight aggregates. As a result, in terms of compressive strength, the surface-coated lightweight aggregate exhibited higher strength than the uncoated lightweight aggregate. Also, it was considered that this is because the interfacial voids of the surface coated lightweight aggregate mixed cement hardened body were filled with blast furnace slag fine powder particles.

• Advances in nano research
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• v.12 no.6
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• pp.605-616
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• 2022

We prepared two samples of ultrafine ferrihydrite (FH) nanoparticle ensembles of quite a different origin. First is the biosynthesized sample (as a product of the vital activity of bacteria Klebsiella oxytoca (hereinafter marked as FH-bact) with a natural organic coating and negligible magnetic interparticle interactions. And the second one is the chemically synthesized ferrihydrite (hereinafter FH-chem) without any coating and high level of the interparticle interactions. The interparticle magnetic interactions have been tuned by modifying the nanoparticle surface in both samples. The coating of the FH-bact sample has been partially removed by annealing at 150℃ for 24 h (hereinafter FH-annealed). The FH-chem sample, vice versa, has been coated (1.0 g) with biocompatible polysaccharide (arabinogalactan) in an ultrasonic bath for 10 min (hereinafter FH-coated). The changes in the surface properties of nanoparticles have been controlled by XPS. According to the electron microscopy data, the modification of the nanoparticle surface does not drastically change the particle shape and size. A change in the average nanoparticle size in sample FH-annealed to 3.3 nm relative to the value in the other samples (2.6 nm) has only been observed. The estimated particle coating thickness is about 0.2-0.3 nm for samples FH-bact and FH-coated and 0.1 nm for sample FH-annealed. Mössbauer and magnetization measurements are definitely shown that the drastic change in the blocking temperature is caused by the interparticle interactions. The experimental temperature dependences of the hyperfine field hf>(T) for samples FH-bact and FH-coated have not revealed the effect of interparticle interactions. Otherwise, the interparticle interaction energy E_int estimated from the hf>(T) for samples FH-chem and FH-annealed has been found to be 121k_B and 259k_B, respectively.

• Analytical Science and Technology
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• v.20 no.4
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• pp.279-288
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• 2007

We have studied a method for the preparation of $ACF/TiO_2$ composites involving the penetrationof titanium n-butoxide (TNB) solution into activated carbon fiber. It was focused on the characterization of $TiO_2$ formed in prorous carbon was which increased with surface functional groups by hydrochloric acid treatment. The conversion of TNB to $TiO_2$ for the acid treatment effect must be important for the preparationof $ACF/TiO_2$ composites. From the characterization of surface properties, both the BET surface area and the total pore volume decreased as the distribution of $TiO_2$ on the activated carbon fiber surfaces after acid treatments.The changes in XRD pattern showed the typical anatase type on $ACF/TiO_2$ composite for the sample named FT, FT1 and FT2 treated with 0.05, 0.1 and 0.5 M, respectively. However, XRD patern of FT3 treated with 0.5M showed mixed amatase-rutile structure. According to the results of SEM micrographs, the titanium complexe particles were irregularly distributed around carbon. And some large clusters were found when an amount of acid treatment increased. The EDX results of $ACF/TiO_2$ composites showed the presence of C, O and P with strong Ti peaks. Finally, the excellent photocatalytic activity of the $ACF/TiO_2$ composites between relative concentration($c/c_o$) of MB (methylene blue) and UV irradiation time could be attributed to the both effects between photocatalysis of the formation of titania complexes and adsorptivity of the activated carbon fiber.

• Elastomers and Composites
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• v.35 no.1
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• pp.63-70
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• 2000

Zinc plated steel tire cords were subjected to RF plasma etching of argon, followed by plasma polymerization coating of acetylene or butadiene in order to enhance adhesion to rubber compounds. Plasma polymerization was carried out under optimized conditions of 10 W, 30 sec, 30 mTorr for acetylene and butadiene gas, while plasma etching was performed at 90W, 10min and 30mTorr. The adhesion of tire cords was evaluated via Tire Cords Adhesion Test (TCAT) and the failure surfaces of the tested samples were analyzed by SEM. Polymer coating by plasma polymerization was also characterized by FT-IR, Alpha-Step and dynamic contact angle analyzer in order to elucidate the adhesion mechanism.

• Elastomers and Composites
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• v.35 no.1
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• pp.53-62
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• 2000

Zinc plated steel tire cords were treated with RF plasma polymerization coating of acetylene or butadiene in order to enhance adhesion to rubber compounds. Plasma polymerization was carried out as a function of plasma power, treatment tune and gas pressure. In order to maximize adhesion, argon plasma etching was performed, with carrier gas such as argon, nitrogen and oxygen, while the adhesion of tire cords was evaluated via TCAT. Best results were obtained from a combination treatment of argon etching (90 W. 10 min, 30 mTorr) and acetylene plasma polymerization coating (10 W, 30 sec, 30 mTorr) with argon carrier gas (25/5:acetylene/argon). These samples exhibited a pull out force of 285N which is comparable to that obtained from the brass plated tire cords (290N).

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.115-120
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• 2017

In recent, it is worldwide issued that nanoscale science and technology as a solution have supported to increase the sensing performance in carbon nanotube based biosensor system. Containing material chemistry in various nanostructures has formed their high potentials for stabilizing and activating biocatalyst as a bioreceptor for medical, food contaminants, and environmental detections using electrode modification technologies. Especially, the large surface area provides the attachment of biocatalysts increasing the biocatalyst loading. Therefore, nano-scale engineering of the biocatalysts have been suggested to be the next stage advancement of biosensors. Here, we would like to study the electrical mechanism depending on the exposure methods (soaking or dropping) to the sample solution to the assembled carbon nanotubes (CNTs) on the gold electrodes of biosensor for a simple and highly sensitive detection. We performed various experiments using polar and non-polar solutions as sampling tests and identified electrical response of assembled CNTs in those solutions.