• Polymer(Korea)
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• v.38 no.1
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• pp.74-79
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• 2014

Microfibrillated cellulose (MFC) was chemically modified with two different silane coupling agents (3-aminopropyltriethoxysilane and 3-mercaptopropyltriethoxysilane) and lauroyl chloride. The surface modification of MFC was confirmed by infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), and contact angle measurements. Composite paper was successfully prepared with surface modified MFC and polyamide (PA) fiber. The surface modification of MFC not only prevented aggregation of MFC but also improved adhesive property between PA fiber and surface modified MFC. It was impossible to prepare papers of only PA fiber because there is no binder to connect PA fibers. That is, surface modified MFC as a binder in PA fiber played a crucial role in making composite paper. Composite paper with silane modified MFC showed higher tensile strength and modulus than composite paper with lauroyl moiety modified MFC. The structure, morphology, and mechanical properties of composite paper were analyzed by scanning electron microscope (SEM) and universal testing machine (UTM).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.7-15
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• 2017

The purpose of this study was to evaluate the properties of recycled aggregate concrete (RAC) using low quality recycled aggregate with or without washing before usage. The recycled aggregate concrete evaluated in this study contained various amounts of low quality recycled aggregate, viz. 30%, 60% and 100%. To evaluate the performance of the recycled aggregate concrete, various test methods were employed to assess its compressive strength, absorption, surface resistance, ultrasound velocity, chloride ion resistance, etc. The properties of the RAC with 30% and 60% washed recycled aggregate were similar those of the natural aggregate. However, the properties of the RAC with 100% washed recycled aggregate were slightly lower than those of the other versions. Also, the RAC with the non-washed recycled aggregate exhibited lower performance results. The results showed that the RAC with washed recycled aggregate had similar properties to normal concrete (concrete using natural aggregate). This implies that the recycled aggregate should be washed to improve the RCA.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.24-30
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• 2013

The adsorption characteristics of cationic starches and starch-oligomers were investigated using the quartz crystal microbalance with dissipation monitoring (QCM-D). The adsorbed amount of modified starches was higher than that of cationic surfactants such as $C_{12{\sim}16}$ trimethylammonium bromide. Cationic starches did not show the tendency depending on the degree of cationic substitution and molecular weight. On the other hand, the softness of the adsorption layer increased with the molecular weight of cationic starches in a viscoelasticity terms. During the adsorption/desorption steps, the amount of adsorbed cationic surfactants was 4~9 times. On the other hand, the difference in the amount of adsorption of all the $C_1$ grafted cationic starches was just 0~50%. In addition, the rigidity of the adsorption layer of cationic surfactant in the desorption step decreased, while, that of cationic starches increased at the same condition.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.857-864
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• 2005

Dealuminated and alkali/alkaline-earth metal exchanged Y-type and ZSM-5 zeolites were prepared as catalytic materials. Comparing with the composition of starting material, the magnitude of Si/Al ratio was increased after dealumination and cation exchange process. The ratio of Si/Al on surface was appeared to be larger than that in bulk. The destruction of basic frame in catalysts observed was understood to be due to a detachment of aluminum, which results in reducing framework while increasing non-framework. This phenomenon becomes more serious with increasing time of steam treatment and even more significant for the cation exchanged catalysts. The desorption peaks of the NO-TPD profiles taken after dealumination and cation exchanged Y-type and ZSM-5 zeolites shifted to the low temperature region. It was also found that the longer the steam treatment time, the degree of shift toward low temperature region was increased. The catalytic activities are dependent on the nature of cation exchanged, the ratio of Si/Al and the ratio of framework/non-framework by a change in basic frame.

• Polymer(Korea)
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• v.36 no.6
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• pp.795-802
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• 2012

Surface modification of a hydrophobic acrylic polymer film has been performed through simple chemical treatment to give a reactive surface. 2-Triphenylstannylthioethyl acrylate was polymerized under UV-illumination with various contents of a comonomer. When the polymer film was treated with fluoride ion, thiol functional group (SH) was generated on the film surface, which was observed through infrared absorption spectroscopy. The surface was functionalized by thiol addition reaction to acrylic chromophores. The SH content on the surface was controlled with a comonomer, tris(hydroxymethyl)ethane triacrylate, and examined with UV-Vis absorbance of the chromophore attached film. Similarly, a polymer film from 2-tributylstannylthioethyl acrylate was prepared. Destannylation from the triphenylstannyl and tributylstannyl surface completed after 30 and 5 min, respectively. The SH-exposed surface was modified with an isocyanate attached chromophore within 10 min, while acrylic chromophore required 24 h.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.339-346
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• 2011

The effects of mineral admixtures on the bonding properties of cement mortar to polyolefin based synthetic fiber were evaluated. The mineral admixtures consisted of 0%, 5%, 10%, and 15% fly ash, blast furnace slag, and metakaolin in cement. Bond interactions between the cement mortar and the polyolefin based synthetic fiber were determined by Dog-bone bond tests. Bond tests of the polyolefin based synthetic fiber showed an increase in pullout load with the strength of the cement mortar. Also, the interface toughness of polyolefin based synthetic fiber in cement mortar increased as the fly ash, blast furnace slag, and metakaolin contents increased. The microstructure of polyolefin based synthetic fiber surface was examined after the pullout test to analyze the frictional resistant force according to the replacement ratio of fly ash, blast furnace slag, and metakaolin during the pullout process of polyolefin based synthetic fiber in cement mortar. The scratched of polyolefin based synthetic fibers increased with the replacement ratio of fly ash, blast furnace slag, and metakaolin. Also, the interface toughness was enhanced by adhesion forces induced by the fly ash, blast furnace slag, and metakaolin.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.190-197
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• 2000

Anions such as C $l^{[-10]}$ , N $O_3$$^{[-10]}$ , S $O_4$$^{2-}$, P $O_4$$^{3-}$, and organic anions, that do not become a part of the clay mineral crystal lattice, are of considerable interest in soils which are a potential sink caused by acid rain. In this paper, elution of native sulfate and breakthrough curves (BTC) were obtained from miscible displacement of non-specifically or specifically adsorbed anions through non-saturated or saturated Bt soil of Chungwon series. The shape and position of the BTC's could be affected by adsoprtion and ion exchange onto the soil particle surfaces. Measured BTC's for oxalic acid under unsaturated and saturated conditions showed that less pore volumes were required to displace the native S $O_4$$^{2-}$S from the soil column, and that maximum detection limit of oxalic acid reached earlier than under unsaturated. The retarded BTC's to the righthand side could be attributed by different adsorption behavior of each anion, although BTC's may be influenced by the smaller order of velocity change. The alternate breakthrough and elution curves show the rapid approach to the maximum detection limit of C/Co = 1, compared to progressive tailing of elution curve to reach to C/Co = 0. The probable explanation for asymmetric elution patterns for both anion is that the anion was selectively adsorbed on the positively charged soil surface from the solution passing in the soil column. On the other hand, the variations of pH in effluent showed that pH was increased to 7 in the first 6 pore volume and then gradually decreased to pH 4.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.145-151
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• 2006

The molecular assembly of p-iodo-phenyl octadecyl ether (I-POE), p-iodo-phenyl docosyl ether (I-PDE) and a binary mixture of these two molecules on graphite has been studied using a scanning tunneling microscope. Each molecular system self-assembles on the graphite surface to form a stable monolayer with a head-to-tail configuration. For the binary system, the I-POE and I-PDE molecules do not mix on the surface, preferring instead to form isolated monolayer domains. Here, the I-POE molecules are preferentially adsorbed on the graphite surface, due to the effects of alkyl chain length and the functional group on the monolayer structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.470-470
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• 2011

반도체 집적회로의 고집적화 및 고성능화를 위한 기본 소자(MOSFET)의 미세화 및 단위공정의 물리적 한계를 극복하기 위한 다양한 연구가 진행되고 있다. 그 중 다양한 나노입자를 이용한 나노소자 제작 연구가 활발하게 이루어지고 있다. 하지만 이러한 나노입자를 이용한 나노소자의 제작에 있어서 원하는 위치의 나노입자의 배열과 정렬의 어려움을 겪고 있다. 이를 위해서 본 연구에서는 자기조립특성을 가지는 DNA 분자와 CdSe/ZnS 나노입자들의 표면 기능화를 통해서 상호 결합시키는 실험을 하였다. DNA 분자를 형틀로 이용하여 CdSe/ZnS 나노입자를 선택적 배열하고 전자 소자화하기 위해서는 CdSe/ZnS 나노입자의 표면 기능화가 필수적이다. 이를 위하여 무극성인 CdSe/ZnS 나노입자들과 DNA 분자의 phosphate backbone의 음전하와의 경합 특성을 향상시키기 위하여 이들 나노입자의 표면을 양전하로 치환하는 실험을 수행하였다. Core 나노입자인 CdSe 나노입자를 제작한 다음에 CdSe 보다 높은 band gap을 가지고 lattice mismatch가 적은 ZnS 로 shell 층을 형성하는 2-step 방법을 이용하여 합성한 CdSe/ZnS 나노입자를 무극성 용매인 chloroform 용액 0.5 ml에 분산시키고 DMAET 0.3 ml 와 Methanol 0.1 mg/ml를 이용하여 리간드들을 바꿔주고 과잉된 리간드인 DMAET를 제거하기 위해 Methanol로 3차례 세척한 다음 증류수에 용해시키는 실험을 하였다. 나노입자 기능화 과정 이후 기능화 여부를 판단하기 위하여 FT-IR spectroscopy 와 zeta potential 측정을 통하여 나노입자 표면의 변화와 전위를 측정하였다.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.207-212
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• 2010

Purpose: Rigid gas permeable (RGP) contact lenses, based on fluorosilicone acrylate, were treated with plasma in air. Methods: The chemical compositions were analyzed by using X-ray photoelectron spectroscopy (XPS), the surface morphology and roughness of RGP contact lenses were observed by using atomic force microscopy (AFM), and the wettability changes were estimated by wetting angle measurement. Results: As the contact lenses were treated by the plasma, the F contents decreased significantly, and the O and Si contents increased on the surface. The number of oxygen-containing hydrophilic radicals (C-O and Si-O) increased greatly, the hydrophobic surface decreased, and the wetting angle increased. But the C-O bonds created with exchange of the fluorine did not increase a wettability. The surface compositions were not remarkably changed for the 6 months after plasma treatment, but the wetting angle increased again. Conclusions: It was considered that the improved wettability of the RGP contact lenses of high fluorine content after plasma treatment was affected by the activation of surface, the increase of Si-O, and the decrease of hydrophobic surface.