• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2618-2626
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• 2010

In this paper poly (4-methyl vinylpyridinium hydroxide)/SBA-15 composite was prepared as a highly efficient heterogeneous basic catalyst by in situ polymerization method for the first time. It was characterized by XRD, FT-IR, BET, TGA, SEM and back titration using NaOH. This catalyst exhibited the excellent catalytic activities for the Knoevenagel condensation of various aldehydes with ethyl cyanoacetate. Over this catalyst, ${\alpha},{\beta}$-unsaturated carbonyl compounds were obtained in the reasonable yield at $95^{\circ}C$ in 10 - 30 min in $H_2O$ as a solvent with a 100% selectivity to the condensation products. Catalyst could be easily recycled after the reaction and it could be reused without the significant loss of activity/selectivity performance. No by-product formation, high yields, short reaction times, mild reaction conditions and operational simplicity with reusability of the catalyst were the salient features of the present synthetic protocol. Presence of $H_2O$ as a solvent was also recognized as a "green method".

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.319-319
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• 2010

칼코젠계 태양전지의 광흡수층으로 사용되는 CuInSe2은 직접천이형 반도체로 광흡수계수가 $1{\times}105cm-1$로 매우 높고, 전기광학적 안정성이 우수하여 실리콘 결정질 태양전지를 대체할 고효율 태양전지로 각광받고 있다. 광흡수층의 밴드갭 에너지가 증가하면 태양전지의 개방전압(Voc)이 증가하여 광변환 효율을 향상시킬 수 있으므로, CuInSe2에서 In의 일부를 Ga으로 치환하여 에너지 밴드갭의 변화를 주는 연구가 많이 진행되고 있다. 그러나 화합물내의 Ga 조성비가 증가하면 단락전류(Jsc), 충진률(fill factor)이 낮아져 태양전지 효율을 저하시키게 되므로 CIGS 박막의 적절한 화합물 조성비를 갖도록 최적조건을 확립하는 것이 매우 중요하다. 본 실험에서는 광흡수층 형성을 위해 Sputtering법으로 금속 전구체를 증착하고, 고온에서 셀렌화 열처리를 수행하는 Sequential process(2단계 증착법)를 이용하였다. soda-lime glass 기판에 Back contact으로 Mo를 증착하고, 1단계로 CuIn0.7Ga0.3 조성비의 타겟을 이용하여 Sputtering법으로 $0.5{\sim}2{\mu}m$ 두께의 CIG 전구체를 증착하였다. 2단계로 CIG 전구체의 셀렌화열처리를 통하여 CIGS 화합물 구조의 박막을 형성시켰다. 이때 형성된 CIGS 화합물 박막의 두께는 동일하게 함으로써, 열처리온도에 의한 박막의 구조변화를 비교하였다. 증착된 CIGS 박막은 고온 엑스선회절분석을 통해 증착 두께와 온도 변화에 따른 CIGS 층의 구조 변화를 확인하고, 동일한 증착조건으로 Buffer layer, Window layer, Grid 전극을 형성하여 태양전지셀 특성을 평가함으로써 CIGS 태양전지 광흡수층의 결정구조에 따른 광변환 효율을 비교하였다.

• Macromolecular Research
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• v.10 no.4
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• pp.187-193
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• 2002

Several methods have been used to synthesize polymer-clay nanocomposites. In-situ polymerization with clay belongs to a classical way to develop nano-structured materials, while melt intercalation is being recognized as another useful approach due to its versatility and environmentally benign character. In this research, we prepared polymer-clay nanocomposites based on the poly (methyl methacrylate) and organically modified montmorillonite via two-stage sonication process. According to the unique mode of power ultrasonic wave, the sonication during processing led to enhanced breakup of the clay agglomerates and reduction in size of the dispersed phase. Optimum conditions to form stable exfoliated nanocomposites were studied for various compositions and conditions. It was found that a novel attempt carried out in this study yielded further improvement in the mechanical performance of the nanocomposites compared to those produced by the conventional melt mixing process, as revealed by DMA, XRD and TEM. And rheological properties of nanocomposites were measured by ARES. As a result, sonicated PMMA-clay nanocomposites exhibits enhanced properties such as storage modulus and thermal stability than that of neat PMMA.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.1
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• pp.1-7
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• 2005

Thin films of vanadium oxide(VO/sub x/) were deposited by r.f. magnetron sputtering from V₂O/sub 5/ target with oxygen/(oxygen+argon) partial pressure ratio of 0% and 8% and in situ annealed in vacuum at 400℃ for 1h and 4h. Crystal structure, chemical composition, molecular structure, optical and electrical properties of films were characterized through XRD, XPS, RBS, FTIR, optical absorption and electrical conductivity measurements. The films as-deposited are amorphous, but 0%O₂ films annealed for time longer than 4h and 8% O₂ films annealed for time longer than 1h are polycrystalline. As the oxygen partial pressure is increased the films become more stoichiometric V₂O/sub 5/. When annealed at 400℃, the as-deposited films are reduced to a lower oxide. The optical transmission of the films annealed in vacuum decreases considerably than the as-deposited films and the optical absorption of all the films increases rapidly at wavelength shorter than about 550nm. Electrical conductivity and thermal activation energy are increased with increasing the annealing time and with decreasing the oxygen partial pressure.

• Advances in materials Research
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• v.1 no.2
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• pp.161-168
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• 2012

Nanoflake composite multi core-shell $SrFe_{12}O_{19}/Fe_3O_4$/PEG/Polypyrrole was synthesized by in situ polymerization method. In this paper, the fabrication of $SrFe_{12}O_{19}$ nanoflake is as first core by solgel method. Then fabricated a shell layer from magnetic nanoparticles of $Fe_3O_4$, which synthesized by coprecipitation technique, onto the $SrFe_{12}O_{19}$ nanoflake. Polyethylene glycol (PEG) as a polymer layer and as second shell was coated onto the before core-shell. Than core-shell $SrFe_{12}O_{19}/Fe_3O_4$/PEG was used as template for the preparation of $SrFe_{12}O_{19}/Fe_3O_4$/PEG/Polypyrrole composite. Final composite has a conductive property among $4.23{\times}10^{-2}Scm^{-1}$ and magnetic property about $M_s$=2.99 emu/g. Also final composite in soluble at organic solvent such as DMF and DMSO and has a flake structure. Conductivity and magnetic property respectively determine by four-probe instrument and vibrant sample magnetometer (VSM), morphology and article size determined by FE-SEM, TEM and XRD.

• Economic and Environmental Geology
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• v.30 no.6
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• pp.531-541
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• 1997

Unconsolidated sediments of Youngjong Island were investigated to consider the vertical distribution of clay minerals and their origin. At least three sedimentation units can be recognized by color, magnetic susceptibility, and pH. X-ray diffraction analysis of clay size fraction reveals that illite is the most abundant phase (52.06%), and chlorite (27.16%), kaolinite (16.92%), smectite (3.86%) occur next to it. Detailed XRD study suggests that illitic materials contain fairly large amount of ordinary muscovite derived from the mica schist in Youngjong Island and adjacent area. The relative amount of kaolinite and chlorite is less than those of samples from estuary mouth of several rivers that flow to Yellow Sea and South Sea. Especially smectite content of the present sample is much higher than those of estuary sediments. These indicate that the unconsolidated sediments of tidal-flat deposit in Youngjong Island are largely affected by marine influence and partly affected by sediment in influx from China. However, some degree of source of this unconsolidated sediments is inland origin from adjacent estuary sediment and in situ or nearby weathered materials.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3218-3224
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• 2012

Uniform and well dispersed metal sulfide semiconductor nanoparticles incorporated into matrices of alginate biopolymer are prepared by using a facile in situ method. The reaction was accomplished by impregnation of alginate with divalent metal ions followed by reaction with thioacetamide. XRD analysis showed that the nanoparticles incorporated in the polymer matrix were of cubic structure with the average particle diameter of 1.8 to 4.8 nm. Field emission scanning electron microscopy and high resolution transmission electron microscopy images indicated that the particles were well dispersed and distributed uniformly in the matrices of alginate polymer. FT-IR spectra confirmed the presence of alginate in the nanocomposite. The crystalline nature and thermal stability of the alginate polymer was found to be influenced by the nature of the divalent metal ions used for the synthesis. The proposed method is considered to be a simple and greener approach for large scale synthesis of uniform sized nanoparticles.

• Korea-Australia Rheology Journal
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• v.18 no.2
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• pp.103-107
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• 2006

Organic-inorganic composite of polyaniline and barium titanate (PANI-$BaTiO_3$) was synthesized via an in-situ oxidation polymerization of aniline in the presence of barium titanate ($BaTiO_3$) nanoparticles dispersed in an acidic medium. Barium titanate has large electric resistance and relatively high dielectric constant which is one of the essential properties for its electrorheological (ER) applications. The microstructure and composition of the obtained PANI/$BaTiO_3$ composite were characterized by SEM, FT-IR and XRD. In addition, we also employed a rotational rheometer to investigate the rheological performance of the ER fluids based on both pure PANI particle and PANI/$BaTiO_3$ composite. It was found that the composite materials possess much higher yield stresses than the pristine PANI due to unique dielectric properties of the inorganic $BaTiO_3$ particles. Finally, we also examined dynamic yield stress by analyzing its extrapolated yield stress data as a function of electric field strengths. Using the critical electric field strengths deduced, we further found that the universal yield stress equation collapses their data onto a single curve.

• Progress in Superconductivity
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• v.4 no.2
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• pp.153-156
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• 2003

We have studied fabrication of $MgB_2$ thin film on $SrTiO_3$ (001) and r-cut $A1_2$$O_3$ substrates by rf magnetron sputtering method using and $ MgB_2$ single target and two targets of Mg and B, respectively. Based on P -T phase diagram of $MgB_2$ and vapor pressure curves of Mg and B, a three-step process was employed. B layer was deposited at the bottom to enhance the film adhesion to the substrate. Secondly, co-sputtering of Mg and B was done. Finally, Mg was sputtered on top to compensate fur the loss of Mg during annealing. Subsequently, $MgB_2$ films were in-situ annealed in various conditions. The sample fabricated using the three-step process showed $T_{c}$ of 24 K and formation of superconducting $MgB_2$ phase was confirmed by XRD spectra. In case of co-sputtering deposition, $T_{c}$ depended on annealing time and argon pressure. However, those made by single-target sputtering showed non-superconducting behavior or low transition temperature, at best.est.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.12
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• pp.1003-1010
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• 2000

Thin films of vanadium oxide(VOx) have been deposited by r.f. magnetron sputtering from V$_2$O$\_$5/ target in gas mixture of argon and oxygen. Crystal structure, surface morphology, chemical composition, molecular structure and optical properites of films in-situ annealed in O$_2$ambient with various heat-treatment conditions are characterized through XRD, SEM, AES, RBS, RTIR and optical absorption measurements. The films annealed below 200$\^{C}$ are amorphous, and those annealed above 300$\^{C}$ are polycrystalline. The growth of grains and the transition of vanadium oxide into the higher oxide have been observed with increasing the annealing temperature and time. The increase of O/V ratio with increasing the annealing temperature and time is attributed to the diffusion of oxygen and the partial filling of oxygen vacancies. It is observed that the oxygen atoms located on the V-O plane of V$_2$O$\_$5/ layer participate more readily in the oxidation process. Also indirect and direct optical band gaps were increased with increasing the annealing temperature and time.