• Korean Chemical Engineering Research
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• 제49권2호
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• pp.151-154
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• 2011

수열 합성법과 마이크로파 가열법으로 제조한 TS-1의 촉매 성능 평가를 과산화수소수를 이용한 페놀 수산화 반응 에서 수행하였는데 아세톤과 메탄올 및 물의 세 가지 용매를 사용하여 각 용매에서의 페놀 전환율과 생성물의 선택도 변화를 관찰하였다. 수열 합성법으로 제조한 TS-1과 마이크로파 가열법으로 합성한 TS-1의 XRD, EDS, SEM, BET 흡착/탈착 시험을 통해 촉매의 특성을 비교.분석하였고 마이크로파 가열법으로 합성한 TS-1이 수열 합성으로 제조한 TS-1과 상이한 페놀 전환율과 생성물의 선택도를 보이는 이유에 대해서 설명하였다.

• Carbon letters
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• 제11권2호
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• pp.102-106
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• 2010

In this work, the effect of aminized multi-walled carbon nanotubes (NH-MWNTs) on the mechanical interfacial properties of epoxy nanocomposites was investigated by means of fracture toughness, critical stress intensity factor ($K_{IC}$), and impact strength testing, and their morphology was examined by scanning electron microscope (SEM). It was found that the incorporation of amine groups onto MWNTs was confirmed by the FT-IR and Raman spectra. The mechanical interfacial properties of the epoxy nanocomposites were remarkably improved with increasing the NH-MWNT content. It was probably attributed to the strong physical interaction between amine groups of NH-MWNTs and epoxide groups of epoxy resins. The SEM micrographs showed that NH-MWNTs were uniformly embed and bonded with epoxy resins, resulted in the prevention of the deformation and crack propagation in the NH-MWNTs/epoxy nanocomposites.

• Elastomers and Composites
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• 제30권1호
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• pp.9-19
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• 1995

To make filler loaded conducting rubber which has the excellent electronical and physical properties, CR and NBR were mixed with magnetite$(Fe_3O_4)$. From the result of the study, vulcanization characteristics shows the upgrading curve as increase in filler concentration and CR has more torque than NBR. When elongation be higher, modulus comes to decreases. Tear strength gradually decrease after showing of the maximum point when is in the 100phr in all. Resilience is not good to cause the increase in filler concentration. In the electrical properties, conductivity becomes smaller when filler concentration is increased. The increase of voltage makes an conductivity grown, but the changed rate is weak. The influence of temperature hardly changes on increasing temperature. The morphology and the distribution for a conductivity filler through SEM were better, the more filler concentration increase, the shorter the particle interval is.

• 대한화학회지
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• 제67권6호
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• pp.420-428
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• 2023

비닐화된 메조포러스 실리카와 재생 폴리에틸렌 사이에 가교결합을 도입하여 컴파운드를 제조하고 물성을 측정하였다. 메조포러스 실리카에 비닐기를 도입함으로써 비극성인 폴리에틸렌과의 가교결합을 유도할 수 있는 물질이 된다. 비닐화된 메조포러스 실리카를 합성하고 재생 폴리에틸렌과의 가교결합을 유도하여, 기존 재생 폴리에틸렌이 가지는 물성보다 더욱 향상된 재생 폴리에틸렌 복합체를 합성하였다. 또한 비닐화 된 메조포러스 실리카를 이용하였을 때, 재생 폴리에틸렌의 등급에 따라 소량 첨가하여도 가교반응이 진행되어 컴파운드의 모든 물리적 특성이 향상되었다. 비닐화된 메조포러스 실리카를 사용하여 4종의 컴파운드를 합성하였으며, 형태와 미세 구조 및 작용기는 TEM, FT-IR 및 XRD로 분석하였다. 비닐화된 메조포러스 실리카를 이용하여 재생 폴리에틸렌과 가교반응으로 3종류의 컴파운드를 배합하였다. 가교결합 유무를 확인하기 위해서 XPS, FT-IR 및 가교도 측정법으로 분석하였으며, Universal testing machine을 이용하여 인장강도, 신장율, 굴곡강도 및 굴곡 탄성율 같은 물리적 특성을 측정하였다. 그 결과, 비닐화된 메조포러스 실리카를 다양한 등급의 재생 폴리에틸렌에 적용함으로써, 기존의 재생 폴리에틸렌이 가지는 취약한 물성을 극복하였다. 비닐화된 메조포러스 실리카-재생폴리에틸렌 복합물질을 신재 폴리에틸렌에 적용한 결과, 복합 컴파운드는 상업적으로 사용할 수 있는 최선의 물성 지표를 나타내었다. 따라서 이 결과는 향후 재생 폴리에틸렌의 사용량을 증가시키고, 자원의 재순환화에 활용될 수 있을 것으로 기대된다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.1142-1146
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• 2004

The synthetic route and physical properties for three-ring derivatives, trans-2,3,2',3'-tetrafluoro-4-alkyl-4'-(4-alkyl-cyclohexyl)-biphenyl and 4-alkyl-cyclohexane carboxylic acid 2,3,2',3',4'-pentafluoro-biphenyl-4-yl ester are presented. They exhibit broad range nematic phases exceeding 30K and low viscosity of nematic liquid crystal mixtures containing these materials. Their viscosity is compared with that of homologues with a lateral isothiocyanate group and show large negative dielectric anisotropies. The threshold voltage $V_{th}$ was low enough to be operated at a driving voltage of 5V. Our novel LC compounds are suitable materials for the improvement of dielectric anisotropy of vertical align liquid crystal displays (VA-LDCs).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.249.1-249.1
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• 2015

Quantum dots (QDs) are attracting growing attention for photovoltaic device applications because of their unique electronic, optical and physical properties. Lead sulfide (PbS) QDs are one of the most widely studied materials for the devices and known to have size-tunable properties. In this context, we investigated the relationship between the size of PbS QDs and two synthesizing conditions, a concentration of ligand, oleic acid in this work, and injection temperature. The inverted colloidal quantum dot solar cells based on the heterojunction of n-type zinc oxide layer and p-type PbS QDs were also fabricated. The size of the QDs and cell properties were observed to depend on both the QD synthesizing conditions, and hence the overall efficiency of the cell could vary even though the size of QDs used was same. The QD synthesizing conditions were finally optimized for the maximum cell efficiency.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.609-611
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• 2004

Sodium salt of photoluminescent Eu-containing polyoxometalate (Eu-POM) was newly synthesized and its chemical structure and physical properties characterized. The Eu-POM was unstable outside the pH range 5.5-8.5, and a pH just over 7 gave the best yield. We have investigated the photoluminescent properties of Eu-POM with changing the reactants ratio of heteropolytungstate and $EuCl_3{\cdot}6H_2O}$. The Eu-POM was characterized by UV/Vis, FT-IR, $^1H$-NMR, PL and XPS. Eu-POM emits orange light of 590nm when excited with the light of 280nm. Furthermore, we made dodecyltrimethylammonium (DDTA) salt of Eu-POM (Eu-POM/DDTA) by exchange of the counter cation. The Eu-POM/DDTA is soluble in common organic solvents, while Eu-POM is only soluble in water. And it emits reddish orange light of 625nm when excited with light of 250nm.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1163-1168
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• 2019

Hydrodynamic properties have been investigated for promising extraction systems: $0.05mol\;L^{-1}$ solutions of di(N-ethyl-4-ethylanilide) of 2,2'-bipyridine-6,6'-dicarboxylic acid, di(N-ethyl-4-fluoroanilide) of 2,6-pyridinedicarboxylic acid and di(N-ethyl-4-hexylanilide) of 2,2'-bipyridine-6,6'-dicarboxylic acid in meta-nitrobenzotrifluoride (F-3) or trifluoromethylphenyl sulfone (FS-13) diluents. To evaluate the perspectives for their use as extraction mixtures at the final stage of the nuclear fuel cycle, the change in density, viscosity, surface tension, and phase separation rate under irradiation with accelerated electrons was studied. The concentrations of extractants in the irradiated mixtures have been determined and the radiation-chemical yields have been calculated. Irradiation significantly decreases the phase separation rate at the stages of extraction and back extraction for all the studied systems. The viscosity of the DYP-7 solution in FS-13 increase above the values suitable for its use in extraction processes.

• Bulletin of the Korean Chemical Society
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• 제35권4호
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• pp.1091-1097
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• 2014

Tageteserecta flower like zinc oxide nanostructures composed of hexagonal nanorods were synthesized via sonochemical method at room temperature. The synthesized nanomaterials exhibited wurtzite hexagonal phase structure with the single crystalline nature. The diameter of the individual nanorods that constitute the flower shaped zinc oxide structures is in the range of 120-160 nm. The sonication time effectively determined the morphological properties of the prepared materials. The catalytic activity of prepared zinc oxide nanostructures towards N-formylation reactions were evaluated without any surface modification and the nanostructures exhibited good reaction yield with the prompt recyclability behavior.

• 농업과학연구
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• 제46권1호
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• pp.205-217
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• 2019

The aim of this study was to identify land resources because food production and supply in North Korea have been at risk due to variations in its seasonal climate. More than three-fifths of the soils are locally derived from the weathering of granitic rocks or various kinds of schists developed from crystalline rocks. Well-developed reddish brown soils derived from limestone are found in the North Hwanghae province and in the southern part of the South Pyeongan province. Additionally, a narrow strip of similarly fertile land runs through the eastern seaboard of the Hamgyong and Kangwon Provinces. The loss of clay particles and organic matter are major causes of degradation in the soil physical and chemical properties in North Korea. 75% of the areas converted from forests became croplands, and 69% of the land converted to croplands came from forests. The net forest loss was quite small from the 1990s to the 2000s. However, deforestation in areas with a slightly lower elevation and gentler slope between 1997 and 2014 led to severe soil erosion resulting in a drastic change in the physical and chemical properties of the soil which influenced cropland stability and productivity. Therefore, the drastic changes in land cover as well as in the physical and chemical properties of the soil caused by various geographical features have seriously influenced the productivity of crops in North Korea.