• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1146-1152
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• 2005

Graft copolymers were synthesized from methylcellulose(MC) and acrylic acid(AA) with active carboxyl groups in the presence of potassium persulfate($K_2S_2O_8$) initiator to enhance adsorption capacity of toxic heavy metal such as $Pb^{2+}$ and $Cu^{2+}$ from wastewater. The resulting grafted copolymers(MC-g-AA/PAA) were mixture of the graft copolymers from MC and AA(MC-g-AA) and polyacrylic acid homopolymers(PAA). The degree of palling was increased with rising concentration of monomer and initiator under the reaction conditions at $60^{\circ}C$, 3 hrs. The water insoluble property of MC-g-AA showed more than 19.7% degree of grafting. So that it could be an adsorbent of heavy metals. Adsorption characteristics of the MC-g-AA were evaluated depending on the degree of grading, pH of wastewater, adsorption time, dosage of MC-g-AA and concentration of heavy metals in the different conditions. Degree of grafting, and initial concentration of heavy metal ions increased, the adsorption amount of $Pb^{2+}$ and $Cu^{2+}$ increased, but added MC-g-AA increased, the adsorption amount per unit weight of $Pb^{2+}$ and $Cu^{2+}$ decreased. The MC-g-AA showed the high $Pb^{2+}$ and $Cu^{2+}$ adsorption amount in the range pH $4{\sim}6$. Also all of $Pb^{2+}$ and $Cu^{2+}$ ions reached in adsorption equilibrium in neighborhood 4 hours. The adsorption of heavy metals described by Freundlich isotherm, it was determined the value of l/n of $Pb^{2+}$ and $Cu^{2+}$ that 0.4294 and 0.3453, respectively.

• Current Photovoltaic Research
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• v.7 no.4
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• pp.103-110
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• 2019

Cu(In,Ga)₃Se₅ (β-CIGS) has a band gap of 1.35 eV, which is an optimum value for high solar-energy conversion efficiency. The effects of Cu and Ga content on the cell performance were investigated previously. However, the effect of Se content on the cell performance is not well understood yet. In this work, β-CIGS films were fabricated by three-stage co-evaporation of elemental sources with various Se fluxes at the third stage instead of at all stages. The average composition of five samples was Cu_1.05(In_0.59,Ga_0.41)3Se_y, where the stoichiometric y value is 5.03 and the stoichiometric Se/metal (Se/M) ratio is 1.24. We varied the Se/metal ratio in a range from 1.18 to 1.28. We found that the best efficiency was achieved when the Se/M ratio was 1.24, which is exactly the stoichiometric value where the CIGS grains on the CIGS surface were tightly connected and faceted. With the optimum Se/M ratio, we were able to enhance the cell efficiency of a β-CIGS solar cell from 9.6% to 12.0% by employing a Na₂S post deposition treatment. Our results indicate that Na₂S post deposition treatment is very effective to enhance the cell efficiency to a level on par with that in α-CIGS cell.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.99-108
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• 2018

In this paper, novel thiadiazole-thione surfactants including 5-heptyl-1,3,4-thiadiazole-2-thione (HpSDT), 5-phenyl-1,3,4-thiadiazole-2-thione (PSDT) and 5-(2-hydroxyphenyl)-1,3,4-thiadiazole-2-thione (HPhSDT) were synthesized and originally introduced as collectors in froth flotation. Microflotation tests showed that HpSDT exhibited better flotation response to malachite than PSDT and HPhSDT, as well as excellent flotation selectivity against quartz. The contact angle results inferred that the hydrophobization intensity of these collectors toward malachite was in the order as HpSDT> PSDT> HPhSDT. ${\zeta}$-potential recommended a chemisorption of HpSDT on malachite surfaces. FTIR deduced that cupric or cuprous atoms might bond with the S and N atoms of HpSDT to form a conjugated ring. XPS further gave an additional evidence that HpSDT-Cu(I) complexes were produced on malachite surfaces via combining surface Cu atoms with HpSDT's N and S atoms, with reducing surface Cu(II) to Cu (I). The tighter orientation arrangement on malachite and stronger hydrophobicity rendered HpSDT to possess better flotation affinity toward malachite than PSDT and HPhSDT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.563-566
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• 2000

The effect of CuO and CuO-B $i_2$ $O_3$ additives on microwave dielectric properties of (P $b_{0.45}$C $a_{0.55}$)[F $e_{0.5}$N $b_{0.5}$)$_{0.9}$S $n_{0.1}$] $O_3$were investigated to decrease the sintering temperature for usage of Low Temperature Co-firing Ceramics (LTCC). The (P $b_{0.45}$C $a_{0.55}$)[F $e_{0.5}$N $b_{0.5}$)$_{0.9}$S $n_{0.1}$] $O_3$ceramics was sintered at 11$65^{\circ}C$. In order to decrease the sintering temperature, CuO and Cuo-B $i_2$ $O_3$ were added in the (Pb,Ca)[(Fe,Nb)Sn] $O_3$ with CuO-B $i_2$ $O_3$. For the addition of 0.4 wt.% CuO, the sintered density and the dielectric constant of the ceramics were revealed the maximum values of the 6.06g/c $m^2$ and 83 respectively and temperature coefficient of resonance frequency ($\tau$$_{f}$) shifted to the positive value. As increasing B $i_2$ $O_3$to the (Pb,Ca)[(Fe,Nb)Sn] $O_3$ with CuO-B $i_2$ $O_3$with 0.2 wt.% CuO, the sintered density, the $\varepsilon$$_{r}$ and the Q was decreased, and $\tau$$_{f}$ was minimized at 0.2 wt.% CuO, and 0.2 wt.% B $i_2$ $O_3$. For this composition, dielectric properties were $\varepsilon$$_{r}$ of 81, Q. $f_{0}$ of 4400 GHz, and $\tau$$_{f}$ of 5 ppm/$^{\circ}C$ at sintering temperature of 100$0^{\circ}C$. the relationship between the microstructure and properties of ceramics was studied by X-ray diffraction(XRD), scanning electron microscopy(SEM).copy(SEM).oscopy(SEM).copy(SEM).EM).

• Bulletin of the Korean Chemical Society
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• v.26 no.5
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• pp.781-785
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• 2005

A fast and reliable method for the selective separation and preconcentration of $Cu^{2+}$ ions using homogeneous liquid-liquid extraction was developed. A new $\alpha$-dioxime derivative (2H-1,4-benzothioazine-2,3(4H)dionedioxime, Dioxime I) was synthesized and investigated as a suitable selective complexing ligand for $Cu^{2+}$ ions. Zonyl FSA (FSA) was applied as a phase-separator agent under the slightly acidic pH conditions. Under the optimal experimental conditions ([FSA] = 3.2% w/v, [THF] = 19.5% v/v, [Dioxime I] = 1.9 ${\times}\;10^{-3}$ M, and pH = 4.7), 10 ${\mu}g\;of\;Cu^{2+}$ in 5.2 mL aqueous phase could be extracted quantitatively into 80 $\mu$L of the sedimented phase. The maximum concentration factor was 65-fold. The limit of detection of the proposed method was 0.005 ng $mL^{-1}$. The reproducibility of the proposed method, on the 10 replicate measurements, was 1.3%. The influence of the pH, type and volume of the water-miscible organic solvent, concentration of FSA, concentration of the complexing ligand and the effect of different diverse ions on the extraction and determination of $Cu^{2+}$ ions were investigated. The proposed method was applied to the extraction and determination of $Cu^{2+}$ ion in different synthetic and natural water samples.

• Transactions of Materials Processing
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• v.10 no.7
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• pp.565-572
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• 2001

It is well known that a multicomponent $Zr_{4l.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ bulk metallic glass alloy shows good bulk glass forming ability due to its high resistance to crystallization in the undercooled liquid state. DSC and XRD have been performed to confirm the amorphous structure of the master alloy. To investigate the mechanical properties and deformation behavior of the bulk metallic $Zr_{4l.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ alloy, a series of compression tests has been carried out at the temperatures ranging from $351^{\circ}C$ to $461^{\circ}C$at the various initial strain rates from $2{\times}10^4s^1$ to $2{\times}10^2s^1$. Three types of nominal stress-strain curves have been identified such as linear stress-strain relationship meaning fracture at maximum stress, plastic deformation including stress overshoot and steady-state flow, plastic deformation without stress overshoot depending on the strain rate and test temperature. Also DSC analysis for the compressed specimens was carried out to investigate the change of structure, thermal stability and crystallization behavior for the various test conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.282-285
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• 2003

Single crystal $CuAlSe_2$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $410\;^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $CuAlSe_2$ source at $680\;^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $CuAlSe_2$ thin films measured with Hall effect by van der Pauw method are $9.24{\times}10^{16}\;cm^{-3}\;and\;295\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CuAlSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;=\;2.8382\;eV\;-\;(8.68\;{\times}\;10^{-4}eV/K)T^2/(T\;+\;155\;K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $CuAlSe_2$ have been estimated to be 0.2026 eV and 0.2165 eV at 10 K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the $\Delta$so definitely exists in the ${\Gamma}_5$ states of the valence band of the $CuAlSe_2$. The three photocurrent peaks observed at 10 K are ascribed to the $A_1-$, $B_1-$, and $C_1$-exciton peaks for n = 1.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.404-405
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• 2011

Cu(InGa)$Se_2$ (CIGS) 박막 태양전지의 저가 및 대면적화를 위한 양산화 공정인 two-step process (sputter/selenization) 공정에서는 sputtering으로 형성한 metal precursor stack을 $H_2$ Se gas를 이용하여 selenization하는 공정을 주로 이용한다. 하지만 이러한 selenization 공정은 유독한 $H_2$ Se gas를 이용해야 한다는 점과 긴 시간 동안 열처리를 해야 하는 단점을 가지고 있다. 이에 metal precursor stack 위에 Se 막을 우선 증착하고, Rapid Thermal Process (RTP)를 이용하여 selenization하는 방법이 현재 많은 관심을 끌고 있다. 본 논문에서는 sputtering 이후 RTP를 이용한 CIGS 흡수층 제작에 대한 선행연구의 일환으로 co-evaporator 장비를 이용하여 다양한 구조의 precursor를 제작하고 RTP 조건에 따른 selenization 효과를 연구하였다. Co-evaporator를 이용하여 CIGS, CIG/Se, CuGa/In/Se, In/CuGa/Se 4가지 구조의 precursor stack을 Mo coated soda lime glass 위에 제작하였다. 이때 amorphous 상태의 precursor stack을 만들기 위하여 기판에 열은 가하여 주지 않았으며, 각각의 stack 구조에서 가지고 있는 Cu, In, Ga, Se의 총량을 동일하게 유지하기 위하여 각 stack의 증착 시간을 동일하게 유지하였다. Selenization을 위한 RTP 조건은 550, $600^{\circ}C$ 각각에 대하여 1, 5, 10분으로 split을 진행하였다. Precursor stack의 증착 후 관찰한 XRD 결과는 비정질 상태를 잘 나타내었으며, SEM 결과 CIGS precursor stack을 제외한 나머지 구조의 stack에서는 In 박막의 surface roughness로 인하여 박막의 평탄화가 좋지 않음을 확인하였다. CIGS precursor stack의 경우, RTP 온도와 시간 split와 상관없이 결정화가 잘 이루어졌으나 grain의 성장이 부족하였다. 이에 비하여 CIG/Se, CuGa/In/Se, In/CuGa/Se 구조의 precursor stack의 경우, $550^{\circ}C$ 열처리에서는 InSe의 결정상이 관찰 되었으며 $600^{\circ}C$, 5분 이상 열처리에서 CIGS 결정상이 관찰되었다. 이러한 결과는 Se이 metal 원소들과 함께 있는 CIGS 구조에 비하여 metal precursor stack 위에 Se을 증착한 stack 구조들의 경우는 CIGS 결정을 형성하기 위해 Se이 metal 층들로 확산되어 반응을 하여야 하므로 상대적으로 많은 열에너지가 필요한 것으로 이해할 수 있으며, RTP를 이용한 selenization 공정으로 CIGS 박막 태양전지의 흡수층 형성이 가능함을 확인하였다.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.2
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• pp.127-138
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• 2014

As increasing concerns about potential risks and hazards in children's products, the laws and regulations for heavy metals and phthalate retardants contained in the children's products have been reinforced in many countries. Especially, in Korea, environment and health laws and regulations for children's products was declared in 2009. This study was researched in terms of contents and migration of phthalates and heavy metals in 124 children's products sold in the Korean market. The results for contents of heavy metals showed that 123 products contained different 14 heavy metals depending on kinds of products. As the results of migration by sucking, the heavy metals in the products such as black, plastic dolls, wood toys, and bottom mat for swimming were transferred into extraction solution. Ba, Cu, Zn, and Sn were transferred from most of these products into the extraction solution and Co, Ni and Pb were additionally transferred into several products. As the results of migration through a skin, while Ba, Cu, and Zn were transferred from most products containing the heavy metals, as for accessories, Cr, Ba, Ni, Zn, and Cu were migrated. The results of contents of phthalates presented that 21 products contained DBP, DEHP and DINP. Only 2 products showed the migration of DEHP by sucking. DEHP in most products were transferred and DBP for 2 products and DINP for 7 products were migrated.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.360.2-360.2
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• 2016

CuSn thin films were fabricated by rf magnetron co-sputtering method on the Si(100) substrate for evaluation of the antibacterial effect. The co-sputtering process was performed with different rf powers and sputtering times to regulate the thickness of the films and relative atomic ratio of Cu to Sn. The physicochemical properties of the CuSn thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES), Optical microscope (OM), 4-point probe, and antibacterial test. An antibacterial test was conducted with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as changing contact times between CuSn fillms and bacteria suspension. We compared to the crystalline structures of films before sterilization and after sterilization by XRD measurement. The changes of oxidation states of Cu and Sn and the chemical environment of films before and after antibacterial test were investigated with high resolution XPS spectra in the regions of Cu 2p, Cu LMM, and Sn 3d. After antibacterial test, the morphology of the films was checked with an OM images. The electrical properties of the CuSn films such as surface resistance and conductivity were measured by using 4-point probe.