• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.162-168
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• 2010

To increase the energy conversion efficiency of dye sensitized solar cells (DSSCs), it has been widely studied how to effectively transferred the electron generated from the adsorbed dye to the $TiO_{2}$ electrode for avoiding the recombination of injected electrons and iodide ions ($I^-/I_3^-$). For the blocking of the recombination, in this study, $Al_2O_3$-coated $TiO_{2}$ electrode was prepared and applied for DSSCs. In especial, the optimal preparation conditions of $Al_2O_3$ coated onto $TiO_{2}$ porous film was proposed for higher energy conversion efficiency. As a result, the solar cells fabricated from $Al_2O_3$-coated (i.e., particle size of bohemite sol : 100 nm) $TiO_{2}$ electrodes showed superior conversion efficiency (9.0%) compared to the bare $TiO_{2}$ electrodes (7.5%).

• Korean Chemical Engineering Research
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• v.45 no.2
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• pp.117-123
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• 2007

The effect of aluminium addition to MCM-41 on product yield and carbon number distribution was investigated in the catalytic cracking of a polymer mixture, LDPE, LLDPE, and EVA copolymer, with a composition similar to that found in real agricultural film wastes. Al-MCM-41 catalyst synthesized by post-synthetic grafting method (Al-MCM-41-P) as well as Al-MCM-41 catalyst synthesized by direct sol-gel (Al-MCM-41-D). The catalytic cracking of polymer mixture was carried out in vapor phase contact as well as in liquid phase contact. The amount of acid sites increased with aluminium addition by post method as well as direct method, which was seemed to be due to Lewis acid sites. In liquid phase catalytic cracking, the yield of light hydrocarbon fraction increased with aluminium addition. The effect of aluminium addition on production of $C_5-C_{12}$ hydrocarbons over Al-MCM-41-P catalysts was greater than that over Al-MCM-41-D catalysts. In the case of vapor phase catalytic cracking, the effect of aluminium addition was smaller than that of liquid phase catalytic cracking. The selectivity to $C_{13}-C_{32}$ hydrocarbons was smaller in vapor phase catalytic cracking.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.569-574
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• 2014

We developed and evaluated a fluorescence-based optical DO sensor (OS-100, Global Optical Communication Ltd., Korea) for long-term monitoring of the dissolved oxygen concentration in waste water treatment. Fluorescent sensing membrane containing $Ru(Dpp)_3{^{2+}}$ (tris(4,7diphenyl-1, 10-phenanthroline) ruthenium(II)) was prepared with GA sol-gel matrix and coated on a quartz plate by sprayed method. Properties of sensor film exhibit deviation about ${\pm}1%$ under wide range of DO concentration from 3 to 10. The developed optical DO sensor was actually mounted in waste water from dyeing industry and successfully applied for on-line DO monitoring. Online monitoring results showed the changes of DO concentrations in wastewater treatment processes with accuracy better than ${\pm}2%$ during the 6 months measurements period in vicious environmental conditions.

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.51-54
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• 2007

By substituting Cr in inverse-spinel $Fe_3O_4,\;Cr_xFe_{3-x}O_4$ thin film samples were prepared by sol-gel spin-coating method and their structural electronic, and magnetic properties were analyzed. X-ray diffraction indicates that the lattice constant decrease with increasing Cr composition (x). This result can be explained in terms of occupation of octahedral sites by $Cr^{3+}$ ions with smaller ionic radius than that of $Fe^{3+}$ Vibrating sample magnetometry measurements on the samples at room temperature revealed that saturation magnetization ($M_s$) decrease by Cr substitution, explainable by comparing spin magnetic moment among the related transition-metal ions. A decrease of magnetoresistence effect with x was observed, similar to that of $M_s$. The coercivity of the $Cr_xFe_{3-x}O_4$ films was found to increase with x, attributed to the increase of magnetic anisotropy by the existence of octahedral $Cr^{3+}(d^3)$.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.581-588
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• 2018

In this article, electrochemical investigation of the transfer reaction of ionizable cefotiam (CTM), an antibiotic molecule across a polarized water/1,2-dichloroethane (water/1,2-DCE) interface was studied. Ion partition diagram providing the preferred charged form of CTM in either water or 1,2-DCE phase was established via the voltammetric evaluation of the transfer process of differently charged CTM species depending upon the pH variation of aqueous solutions. Thermodynamic information including the formal transfer potential and formal Gibbs transfer energy values in addition to important pharmacokinetics including partition coefficients of ionizable CTM were also evaluated. In particular, the current associated with the transfer of CTM present at pH 3.0 aqueous solution proportionally increased with respect to the CTM concentration which was further used for developing CTM sensitive ion sensor. In order to improve the portability and convenient usage, a single microhole interface fabricated in a supportive polyethylene terephthalate film was used of which hole was filled with a polyvinylchloride-2-nitrophenyloctylether (PVC-NPOE) gel replacing 1,2-DCE, a toxic organic solvent. A dynamic range of $1-10{\mu}M$ CTM was obtained.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.562-572
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• 2005

Statement of problem : Titanium is widely used as an implant material lot artificial teeth. Also, studies on surface treatment to form a fine passive film on the surface of commercial titanium or its alloys and improving bioactivity with bone have been carried out. However, there is insufficient data about the biocompatibility of the implant materials in the body. Purpose: The purpose of this study was to examine whether the precipitation of apatite on titanium metal is affected by surface modification. Materials and methods: Specimens chemically washed for 2 minute in a 1:1:1.5 (in vol%) mixture of 48% HF 60% $HNO_3$ and distilled water. Specimens were then chemically treated with a solution containing 97% $H_2SO_4$ and 30% $H_2O_2$ at $40^{\circ}C$S for 1 hour, and subsequently heat-treated at $400^{\circ}C$ for 1 hour. All specimens were immersed in the HBSS with pH 7.4 at $36.5^{\circ}C$ for 15 days, and the surface were examined with TF-XRD, SEM, EDX and XPS. Also, commercial purity Ti specimens with and without surface treatment were implanted in the abdominal connective tissue of mice for 4 weeks. Conventional aluminium and stainless steel 316L were also implanted for comparison. Results and conclusions : The results obtained were summarized as follows. 1. An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a $H_2SO_4$ and $H_2O_2$ solution. The average roughness was $2.175{\mu}m$ after chemical surface treatment. 2. The amorphous titania was subsequently transformed into anatase by heat treatment at $400^{\circ}C$ for 1 hour. 3. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was $46.98{\mu}m$ in chemically-treated Ti, and 52.20, 168.65 and $100.95{\mu}m$ respectively in commercial pure Ti, aluminum and stainless steel 316L without any treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.337-337
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• 2014

투명 전도성 산화물(transparent conductive oxide: TCO) 박막은 높은 투과율과 낮은 비저항 덕분에 LCD (liquid crystal display), PDP (plasma display panel), OLED (organic light emitting display) 등 평판 디스플레이에 널리 사용되고 있다. 현재 양산되고 있는 ITO (indium tin oxide)는 90% 이상의 높은 투과율과 우수한 전도성으로 인해 TCO 박막 가운데서 디스플레이 산업에서 가장 널리 쓰이고 있다. 그런데, ITO의 인듐산화물에 의한 간질성 폐렴(interstitial pneumonia)의 유발 위험이 있다든가, 인듐의 매장량이 적어 원자재 가격이 비싼 단점도 가지고 있다. 이에 최근 ITO를 대체할 수 있는 TCO물질로 많은 연구가 이루어지고 있는데, 특히 AZO (aluminum-doped zinc oxide)는 그 중 대표적인 대체물질로서 독성이 없고 가격도 저렴하여 많은 관심이 증폭되고 있다. 현재 AZO는 sol-gel 방법이나 CVD (chemical vapor deposition) 또는 스퍼터링 방법 등으로 증착되고 있다. 본 연구에서는 두 개의 이종타겟(hetero target)을 장착한 대향 타겟 스퍼터링(facing target sputtering: FTS) 장치를 사용하여 AZO 박막을 제작한다. 기존의 여러 증착법과 달리, FTS 장치는 두 타겟 사이에 형성되는 플라즈마 내의 ${\gamma}$-전자를 구속하게 되며, 낮은 가스 압력에서 고밀도 플라즈마가 생성되어 빠른 증착 속도와 안정적인 방전을 유지한 상태에서 박막을 증착할 수가 있다. 또한 기판과 플라즈마가 이격되어 있어 높은 에너지를 갖는 입자들의 기판 충돌을 억제할 수 있는 장점들을 갖는다. 이종 타겟인 ZnO와 Al2O3를 사용하고 각 타겟에 인가되는 파워 변화를 통해 AZO 박막 내 Al2O3의 성분비를 조절하였다. ZnO 타겟의 증착 파워를 100 W로 고정할 경우, Al2O3 타겟의 증착 파워가 (50~90) W으로 실험을 하였으며, Al2O3 타겟의 증착 파워가 70 W일 때 AZO 박막의 Al2O3 성분비는 2.02 wt.%이며 박막의 비저항 값은 $5{\times}10^{-4}{\Omega}{\cdot}cm$로 최소값을 보였다. 이러한 비저항의 변화는 파워에 따른 AZO 박막의 캐리어 이동도(Hall mobility)와 캐리어의 농도(Carrier Concentration)의 변화와 밀접한 관계가 있음을 보여주며, 특히 AZO 박막의 캐리어 농도와 캐리어 이동도는 AZO 박막을 형성하고 있는 결정립의 크기에 의존하는 것이 X-선 회절 패턴과 SEM으로부터 확인되었다. 특히, 본 연구에서는 두 개의 이종 타겟(hetero target) Al2O3와 ZnO를 장착하고 각각의 파워를 변화시켜 도핑 량을 조절할 수는 대향 타겟 스퍼터링(FTS: facing-target sputtering) 방법을 이용하여 제작된 AZO 박막에 대해 전기적, 광학적 및 구조적 특성을 분석하고 ITO의 대체물로서의 가능성을 검토하고자 한다.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.939-944
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• 1997

The films of zeolite X on the surface of metal sieve were prepared by continuous crystallization method. It is known that the growth of zeolite crystal on the surface of metal is mainly dependent on the surface composition of metal sieve. In the present work, the zeolite nuclei could be easily formed as Cr content on the metal surface was removed by acid treatment. In order to investigate the proedure growing of zeolite crystal by the continuous crystallization method, the composition of zeolite X($6.36Na_2O-Al_2O_3-5.3SiO_2-190.8H_2O$)was supplied every 12hour. Then the mechanism and inter-relationship between the metal surface and nucleation are investigated. The results show that as the content of silica increases in the gel mixture, the nuclei of zeoilite are easily formed on the metal surface. Also, it was confirmed that the particle of zeolite stuck on the metal surface continues the linear growth. The particles are combined by the reaction of polycondensation, and finally become the shape of crystal. The sample synthesized by the film type was confirmed as zeolite X by the analyses of SEM and XRD.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.18-22
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• 2006

Effects of V substitution of Fe on the magnetic properties of $Fe_3O_4$ have been investigated by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), conversion electron Mossbauer spectroscopy (CEMS), and vibrating sample magnetometry (VSM) measurements on sol-gel-grown films. XRD data indicates that the $V_xFe_{3-x}O_4$ films maintain cubic structure up to x=1.0 with little change of the lattice constant. Analyses on V 2p and Fe 2p levels of the XPS data indicate that V exist as $V^{3+}$ mostly in the $V_xFe_{3-x}O_4$ films with the density of $V^{2+}$ ions increasing with increasing V content. Analyses on the CEMS data indicate that $V^{3+}$ ions substitute tetrahedral $Fe^{3+}$ sites mostly, while $V^{2+}$ ions octahedral $Fe^{2+}$ sites. Results of room-temperature VSM measurements on the films reveal that the saturation magnetization for the x=0.14 sample is larger than that of $Fe_3O_4$, while it becomes smaller than that of $Fe_3O_4$ for $x{\geq}0.5$. The coercivity of the $V_xFe_{3-x}O_4$ films is found to increase with x, attributed to the increase of anisotropy by the substitution of $V^{2+}(d^3)$ ions into the octahedral sites.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.34-39
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• 2006

Pure and Fe-doped CuO thin-film and powder samples were prepared using a sol-gel method. Undoped CuO films exhibited monoclinic structure and p-type electrical conductivity $(\~10^{-2}\;{\Omega^{-1}\;cm^{-1}$ due to copper deficiency. On the other hand, CuO: Fe films were found to be insulating and Li doping on the films led to a restoration of p-type conductivity and a ferromagnetic hysteresis behaviour at room temperature. The observed properties far the CuO : Fe, Li films can be explained in terms of hole creation by substitution of $Li^+$ for $Cu^{2+}$ sites and mediation of long-range interactions between $Fe^{3+}$ ions by the $Li^+$-induced defect states. CuO: Fe powders exhibited a ferromagnetism at room temperature with its strength being dependent on post-annealing temperature. Mossbauer measurements on the CuO: Fe films and powders revealed that the octahedral $Cu^{2+}$ sites are mostly substituted by $Fe^{3+}$ ions.