• Macromolecular Research
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• 제10권6호
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• pp.311-317
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• 2002

The quantitative analysis of polymer micelles consisting of amphiphilic block copolymers was carried out by small-angle neutron scattering (SANS). The block copolymers, made of poly(2-ethoxyethyl vinyl ether-b-2-hydroxyethyl vinyl ether)(poly(EOVE-b-HOVE)), exhibited a sharp morphological transition from a homogeneous solution to a micelle structure with increasing temperature. This transition is accompanied by a formation of spherical domains of poly(EOVE) with a radius around 200 $\AA$. The variations of the size and its distribution of the domains were investigated as a function of polymer concentration and temperature. The validity of SANS analysis, including the wavelength- and incident-beam-smearing effects of the SANS instrument, was examined with a pre-calibrated polystyrene latex.

• Bulletin of the Korean Chemical Society
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• 제6권6호
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• pp.344-347
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• 1985

Perovskite type oxides of $SrTiO_3,SrZrO_3,and\;SrTi_{1-x}Zr_xO_3$ have been systematically synthesized at $1250^{\circ}C$and $1550^{\circ}C$ with specimens containing additions of up to x=0.9 of zirconium by solid state reactions and characterized by X-ray diffraction. X-ray diffraction studies showed that the compound $SrTi_{1-x}Zr_xO_3$ has cubic structure. The lattice paramters of $SrTi_{1-x}Zr_xO_3$ solid solutions obey the Vegard's law and fairly large increase in volume can acompany the formation of this solution with increasing Zr content(X). Assuming the lattice constants of perovskite type compounds $A(B_{1-x}B'_x)O_3$where $B_{1-x}B'_x$ is $Ti_{1-x}Zr_x$, to be a linear function of the ionic radii of B and B' ions, the disordered ion pair of $Ti^{4+}$and $Zr^{4+}$ was verified from the lattice constants of a series compounds varying x=0,0.05, 0.25, 0.5, 0.75, 0.9, and 1.0 with known isovalent pairs.

• 한국분말재료학회지
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• 제6권4호
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• pp.314-319
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• 1999

The solid state reaction by mechanical alloying(MA) generally proceeds by lowering the free energy as the result of a chemical reaction at the interface between the two adjacent layers. However, Lee et $al.^{1-5)}$ reported that a mixture of Cu and Ta, the combination of which is characterized by a positive heat of mixing of +2kJ/mol, could be amorphized by mechanical alloying. This implies that there exists an up-hill process to raise the free energy of a mixture of pure Cu and la to that of an amorphous phase. It is our aim to investigate to what extent the MA is capable of producing a non-equilibrium phase with increasing the heat of mixing. The system chosen was the ternary $Cu_{30}Ta_{ 70-x}Mo_ x$ (x=35, 10). The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-K $\alpha$ radiation, thermal analysis, electron diffraction and TEM micrographs. In the case of x=35, where pure Cu powders were mixed with equal amount of pure Ta and Mo powders, we revealed the formation of bcc solid solution after 150 h milling but its gradual decomposition by releasing fcc-Cu when milling time exceeded 200 h. However, an amorphous phase was clearly formed when the Mo content was lowered to x=10. It is believed that the amorphization of ternary $Cu_{30}Ta_{60}Mo_{10}$ powders is essentially identical to the solid state amorphization process in binary $Cu_{30}Ta_{70}$ powders.

• 대한화학회지
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• 제9권4호
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• pp.179-184
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• 1965

韓國産 酸性白土類 및 日本産 白土를 1NKCI 溶液으로 처리한 후 그 瀘液의 pH를 측정하므로써 그들의 酸性度를 결정하였다. 또 $KCI,\;NaCI,\;BaCI_2,\;Pb(NO_3)_2$ 및 $CuSO_4$ 들의 中性鹽溶液이 酸性度에 미치는 영향을 조사한 결과 위의 적은 順으로 그 영향이 작음을 알았고 이것은 $K^+>Na^+>Ba^{++}>Pb^{++}>Cu^{++}$의 順으로 Lyotrope 系列과 일치하였다. 그리고 cation 吸着후에 白土로부터 용출되는 $Al_2O_3$ 및 $Fe_2O_3$를 측정한 결과 溶出量이 酸性度에 대략 비례함을 알았다. 이 결과는 白土類의 酸性原因이 cation 交換에 의해서 1차적으로 생긴 HCI이 白土固體와 反應하여 溶出한 鹽化物이 加水分解를 일으켜 2차적으로 HCI을 형성한다는 小林, 山本들의 설명과 일치한다. 鹽基性 및 酸性色素의 水溶液에서 白土의 色素吸着率을 측정한 결과 酸性色素는 酸性度와 무관계하며 吸着되지 않았으나 鹽基性色素의 吸着率은 酸性度에 비례함을 보았다. 鹽基性色素吸着후의 pH는 固體酸의 酸性度에 비례하였으며 色素吸着率에도 비례하였으므로 鹽基性色素吸着은 中性鹽의 吸着메카니즘과 동일하다고 보았다. 本 實驗결과로부터 固體酸의 水溶液에서의 酸性原因, 色素吸着 메카니즘을 考察하게 되었다.

• 청정기술
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• 제26권4호
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• pp.286-292
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• 2020

본 연구는 Cu/CeO2-X 촉매의 저온 CO 산화 활성에 미치는 영향을 촉매의 구조적 특성, 반응 특성을 통해 확인하였다. 사용된 촉매는 습윤 함침법으로 제조되었으며, 각기 다른 소성온도(300~600 ℃)에서 형성된 CeO2 (지지체)를 이용하여 Cu (활성금속)를 담지함으로써 Cu/CeO2-X 촉매를 제조하였다. 제조된 Cu/CeO2-X 촉매는 저온 CO 산화 활성을 평가하였다. 125 ℃에서 Cu/CeO2_300 촉매는 90% 이상의 활성을 나타냈으며, CeO2의 소성온도가 증가됨에 따라 활성이 점차 감소하여, Cu/CeO2_600 촉매는 65%를 나타냈다. 다음으로 촉매의 물리/화학적 특성을 Raman, BET, XRD, H2-TPR, XPS 분석으로 확인하였다. XPS 분석 결과, CeO2-X의 소성온도가 낮을 수록 불안정한 Ce3+ 종(비 화학양론 종) 비율이 증가하였다. 증가된 Ce3+종은 Cu와 결합함으로 써 치환결합을 형성하였으며 Raman 분석의 CeO2 peak 변화와 H2-TPR 분석의 치환결합 구조의 환원 peak를 통해 확인하였다. 결과적으로 Cu와 CeO2의 치환 결합 형성은 촉매의 redox 특성 및 저온 CO 산화 활성을 증진시켰다고 판단된다.

• Membrane and Water Treatment
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• 제14권1호
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• pp.27-33
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• 2023

In previous studies, solely ferric (Fe³⁺) and calcium (Ca²⁺) ions were commonly used for removal of PO₄-P (considered as T-P in this study) in wastewater via chemical precipitation. Herein, the removal of total phosphorus (T-P) in wastewater was performed using various mineral and lime dissolved solutions. The dissolution kinetics of different minerals (feldspar, olivine, elvan, illite, sericite, and zeolite) and lime was compared and used their solutions for T-P removal of real wastewater. The highest T-P removal (almost 90%) was obtained by the lime dissolved solution and followed by zeolite, illite, feldspar, and others. We observed a significant co-relationship (R of 0.96) between the amount of initial Ca²⁺ and T-P removal. This was induced by formation of hydroxyapatite-like mineral via Ca-P precipitation reaction at high pH solution. Furthermore, additional removal of suspended solid (SS) and chemical oxygen demand (COD) was achieved by only lime dissolved solution. Finally, the lime-feldspar dissolved solutions were prepared at different ratios (10-50%), which showed a successive T-P removal up to two times by samples of 40 and 50%.

• Journal of Welding and Joining
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• 제31권1호
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• pp.58-64
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• 2013

The following results were obtained, microstructures and tensile properties in arc brazed joints of DP(dual phase) steel using Cu-5.3wt%Sn insert metal was investigated as function of brazing current. 1) The Fusion Zone was composed of ${\alpha}Fe+{\gamma}Cu$ and Cu23Sn2. The reason for the formation of these solid solutions. Despite, Fe & Cu were impossible to solid solution at room temperature. It's melting & reaction to something of insert metal & Base Metal (DP Steel) by Arc. Brazing Process has faster cooling rate then Cast Process, Supersaturated solid solution at room temperature. 2) The increase Hardness of Fusion Zone was directly proportional to the rise of welding current. Because, ${\alpha}Fe+{\gamma}Cu$ phase (higher hardness than the Cu23Sn2.(104.1Hv < 271.9Hv)) Volume fraction was Growth, due to increasing the amount of base metal melting by High current. 3) The results of tensile shear test by Brazing, All specimens happen to fracture in Fusion Zone. On the other hand, when Brazing Current increasing tend to rise tensile load. but it was very small, about 26-30% of the base metal. 4) The result of fracture analysis, The crack initiate at Triple Point for meet to Upper B.M/Under B.M/Fusion Zone. This Crack propagated to Fusion zone. So ruptured by tensile strength. The Reason to in the fusion zone fracture, Fusion zone by Brazing of hardness (strength) was very lower then the base metal (DP steel). In addition the Fusion Zone's thickness in triple point was thin than the base metal's thickness in triple point.

• 설비공학논문집
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• 제10권1호
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• pp.11-21
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• 1998

A numerical study is made on the ice-formation for water flow inside a stenotic tube. The study takes into account the interaction existing between the laminar flow and the stenotic port in the circular tube. In the solution strategy, the present study is substantially distinguished from the existing works In that the complete set of governing equations in both the solid and liquid regions are resolved. In a channel flow between parallel plates, the agreement of predictions and available experimental data is very good. Numerical results are mainly obtained by varying the height and length of a stenotic shape and additionally for several temperatures of the wall and inlet of tube. The results show that the shape of stenotic port has the great effect on the thickness of the solidification layer in the tube. As the height of a stenosis grows and the length of a stenosis decreases, the ice layer thickness near the stenotic port is thinner due to backward flow caused by the sudden expansion of water tunnel. It is also found that the ice layer becomes more fat In accordance with Reynolds number and the temperature of the wall and inlet of tube decreased.

• 대한화학회지
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• 제32권5호
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• pp.464-475
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• 1988

Fe(Ⅲ) 및 Mn(Ⅱ)과 p-aminoazobenzene 및 그 유도체가 반응하여 형성된 착물들에 대하여 가시-자외선 및 적외선 분광광도법과 전기전도도방법을 이용하여 용매의 효과, donor의 염기도와 착물형성에 미치는 영향을 조사하였다. 그 결과 착물의 조성비, 안정도 상수 및 몰흡광계수를 구하여 van't Hoff식으로부터 ${\Delta}H^{\circ}$, ${\Delta}G^{\circ}$ 및 ${\Delta}S^{\circ}$를 계산하였으며 반응성과 등속도관계를 고려하여 반응속도와 평형조절인자를 알게 되었다.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3835-3839
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• 2013

A new synthesis route for Pt nanoparticles by direct electrochemical reduction of a solid-state Pt ion precursor ($K_2PtCl_6$) is demonstrated. Solid $K_2PtCl_6$-supported polyethyleneimine (PEI) coatings on the surface of glassy carbon electrode were prepared by simple mixing of solid $K_2PtCl_6$ into a 1.0% PEI solution. The potential cycling or a constant potential in a PBS (pH 7.4) medium were applied to reduce the solid $K_2PtCl_6$ precursor. The reduction of Pt(IV) began at around -0.2 V and the reduction potential was ca. -0.4 V. A steady state current was achieved after 10 potential cycling scans, indicating that continuous formation of Pt nanoparticles by electrochemical reduction occurred for up to 10 cycles. After applying the reduction potential of -0.6 V for 300 s, Pt nanoparticles with diameters ranging from $0.02-0.5{\mu}m$ were observed, with an even distribution over the entire glassy carbon electrode surface. Characteristics of the Pt nanoparticles, including their performance in electrochemical reduction of $H_2O_2$ are examined. A distinct reduction peak observed at about -0.20 V was due to the electrocatalytic reduction of $H_2O_2$ by Pt nanoparticles. From the calibration plot, the linear range for $H_2O_2$ detection was 0.1-2.0 mM and the detection limit for $H_2O_2$ was found to be 0.05 mM.