• Title/Summary/Keyword: Sol-gel coating

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Preparation of Silica Films by Surface Tension Control (표면장력 제어를 이용한 실리카 박막의 제조)

  • Lee, Jae-Jun;Kim, Yeong-Ung;Jo, Un-Jo;Kim, In-Tae;Je, Hae-Jun;Park, Jae-Gwan
    • Korean Journal of Materials Research
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    • v.9 no.8
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    • pp.804-809
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    • 1999
  • Silica films were prepared on Si single crystal substrates by a sol-gel process without DMF using TEOS as a starting material. Films were fabricated by spin coating technique. For films having a composition of TEOS : HCI(1:0.05mol), gelation time, the thickness of films, the formation of cracks and the microstructure of the films were investigated as a function of the molar ratio of $CH_3OH and H_2O$. With 8mol $CH_3OH$, the longest gelation time was measured to be 640hr. The thickness of the coated films was decreased with increasing content of $CH_3OH$. The films were sintered at $500^{\circ}C$ for 1hr with a heating rate of $0.6^{\circ}C$/min. The coated films showed worm-like grains and partially cracked microstructures at an amount of $CH_3OH$ 2mol and 4mol. The addition of more than 8 mole of $CH_2OH$ resulted in crack-free silica films. This suggests that crack-free films can be fabricated by controlling the surface tension energy of the sol solutions without DMF.

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Surface Modification of TiO2 Thin Films by N2 Atmospheric Plasma and Evaluation of Photocatalytic Activity (질소 상압플라즈마를 이용한 TiO2 박막의 표면개질 및 광활성 평가)

  • Lim, Gyeong-Taek;Kim, Kyung Hwan;Park, Jun;Kim, Kyoung Seok;Park, Yu Jeoung;Song, Sun-Jung;Kim, Jong-Ho;Cho, Dong Lyun
    • Applied Chemistry for Engineering
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    • v.20 no.4
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    • pp.402-406
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    • 2009
  • $TiO_2$ thin films were surface-modified with atmospheric plasma and their photocatalytic activities were evaluated. The films were deposited on glass plates by dip-coating in a $TiO_2$ sol-gel solution and sintered at various temperatures for various times. Nitrogen plasma was used for the modification and the experiments were carried out varying operational parameters such as discharge power and treatment time. Photocatalytic activity was evaluated based on the degradation efficiency of methylene blue (MB) under irradiation of UV-A and fluorescent light. According to XPS analysis, a little amount of nitrogen was found to be doped in the film surface after the modification. As a result, photocatalytic activity increased under irradiation of UV-A and fluorescent light, especially fluorescent light.

The Preparation of $TiO_2$ Coated Activated Carbon Pellets Driven by LED and Removal Characteristics of VOCs (LED구동 $TiO_2$ 코팅 활성탄소 펠렛 제조 및 VOCs 제거 특성)

  • Kim, Yesol;Kim, Do Young;Jung, Min-Jung;Kim, Min Il;Lee, Young-Seak
    • Applied Chemistry for Engineering
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    • v.24 no.3
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    • pp.314-319
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    • 2013
  • In this study, nitrogen doped $TiO_2$ ($N-TiO_2$) coated on an activated carbon pellet (ACP) was prepared using sol-gel and the solid state heat treatment of urea to improve the removal property of volatile organic compounds (VOCs). To explore the visible light photocatalytic activity of the ACP under the light emitting diods (LED), the removal property of benzene gas was characterized by gas chromatography. The SEM and BET results show that the increment of titanium tetra isopropoxide contents leads to the increased $TiO_2$ coating amount of ACP surface and decreased specific surface area. From the results of benzene gas removal, the breakthrough time of ACP10 increased about 2 times compared to that of the ACP. The improved performance was attributed to the $N-TiO_2$ coating on ACP surface, which could be more effective to remove benzene gas under the condition of LED lamp.

Aging Effect on the Antimicrobial Activity of Nanometal (Au, Ag)-Titanium Dioxide Nanocomposites (Aging 효과에 따른 나노메탈(Au, Ag)-이산화티탄 복합체의 항균 활성도)

  • Park, Hye-Rim;Lee, Sang-Wha;Yoo, In-Sang
    • Applied Chemistry for Engineering
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    • v.23 no.3
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    • pp.293-296
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    • 2012
  • Nanocomposites were fabricated as titanium dioxide ($TiO_2$) doped with nanometals (Au, Ag) by sonochemical reduction method and sol-gel method in order to investigate their antimicrobial activities. Then, the antimicrobial activity of the resulting samples was compared by the measurement of colony numbers survived on the agar plate incubated for 24 h after the loading E. coli on the solid-state media with the nanocomposites. The initial antimicrobial activity of the metal (Au, Ag)-doped $TiO_2$ was higher than that of the pristine $TiO_2$. Afterwards the nanocomposite samples were kept at $4^{\circ}C$ for a long time and the aged samples exhibited the different antimicrobial activity. With the elapse of aging times, Ag-doped $TiO_2$ with $TiO_2$ coating ($Ag-TiO_2$@$TiO_x$) exhibited the higher antimicrobial activity than those of $Ag-TiO_2$and $Au-TiO_2$. The $TiO_2$ coating on the $Ag-TiO_2$ may prevent the oxidation of Ag nanometals and stabilize colloidal nanocomposites.

Electrochemical Characteristics of Anode-supported Solid Oxide Fuel Cells (연료극 지지형 고체산화물 연료전지의 전기화학적 특성)

  • Yoon Sung Pil;Han Jonghee;Nam Suk Woo;Lim Tae-Hoon;Hong Seong-Ahn;Hyun Sang-Hoon;Yoo Young-Sung
    • Journal of the Korean Electrochemical Society
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    • v.4 no.2
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    • pp.58-64
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    • 2001
  • YSZ ($8mol\%$ yttria-stabilized zirconia)-modified LSM $(La_{0.85}Sr_{0.15}MnO_3)$ composite cathodes were fabricated by formation of YSZ film on triple phase boundary (TPB) of LSM/YSZ/gas. The YSZ coating film greatly enlarged electrochemical reaction sites from the increase of additional TPB. The composite cathode was formed on thin YSZ electrolyte (about 30 Um thickness) supported on an anode and then I-V characterization and AC impedance analyses were performed at temperature between $700^{\circ}C\;and\;800^{\circ}C$. As results of the impedance analysis on the cell at $800^{\circ}C$ with humidified hydrogen as the fuel and air as the oxidant, R1 around the frequency of 1000 Hz represents the anode Polarization. R2 around the frequency of 100Hz indicates the cathode polarization, and R3 below the frequency of 10 Hz is the resistance of gas phase diffusion through the anode. The cell with the composite cathode produced power density of $0.55\;W/cm^2\;and\;1W/cm^2$ at air and oxygen atmosphere, respectively. The I-V curve could be divided into two parts showing distinctive behavior. At low current density region (part I) the performance decreased steeply and at high current density region (part II) the performance decreased gradually. At the part I the performance decrease was especially resulted from the large cathode polarization, while at the part H the performance decrease related to the electrolyte polarization.

Magnetic Properties of Cr-Doped Inverse Spinel Fe3O4 Thin Films (Cr 치환된 역스피넬 Fe3O4 박막의 자기적 특성)

  • Lee, Hee-Jung;Choi, Seung-Li;Lee, Jung-Han;Kim, Kwang-Joo;Choi, Dong-Hyeok;Kim, Chul-Sung
    • 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 $Cr^{3+}(d^3)$.

An Experimental Study of Synthesis and Characterization of Vanadium Oxide Thin Films Coated on Metallic Bipolar Plates for Cold-Start Enhancement of Fuel Cell Vehicles (연료전지 차량의 냉시동성 개선을 위한 금속 분리판 표면의 바나듐 산화물 박막 제조 및 특성 분석에 관한 연구)

  • Jung, Hye-Mi;Noh, Jung-Hun;Im, Se-Joon;Lee, Jong-Hyun;Ahn, Byung-Ki;Um, Suk-Kee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.6
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    • pp.585-592
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    • 2011
  • The enhancement of the cold-start capability of polymer electrolyte fuel cells is of great importance in terms of the durability and reliability of fuel-cell vehicles. In this study, vanadium oxide films deposited onto the flat surface of metallic bipolar plates were synthesized to investigate the feasibility of their use as an efficient self-heating source to expedite the temperature rise during startup at subzero temperatures. Samples were prepared through the dip-coating technique using the hydrolytic sol-gel route, and the chemical compositions and microstructures of the films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy. In addition, the electrical resistance hysteresis loop of the films was measured over a temperature range from -20 to $80^{\circ}C$ using a four-terminal technique. Experimentally, it was found that the thermal energy (Joule heating) resulting from self-heating of the films was sufficient to provide the substantial amount of energy required for thawing at subzero temperatures.

Electrosorption Behavior of $TiO_2$/Activated Carbon Composite for Capacitive Deionization (축전식 이온제거에 대한 $TiO_2$/Activated Carbon 화합물의 전기흡착 거동)

  • Lee, Jeong-Won;Kim, Hong-Il;Kim, Han-Joo;Park, Soo-Gil
    • Applied Chemistry for Engineering
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    • v.21 no.3
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    • pp.265-271
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    • 2010
  • Desalination effects of capacitive deionization (CDI) process was studied using $TiO_2$/activated carbon electrode. In order to enhance the wettability of electrode and decrease a electrode resistance, $TiO_2$ was coated on activated carbon. By means of $TiO_2$ coating on activated carbon, electric double layer to adsorption content in CDI process was increased. It was identified from TEM, XRD, and XPS that the activated carbon based on $TiO_2$ composite was fabricated successfully by means of sol-gel method. As a results of cyclic voltammetry and impedance, it was identified that $TiO_2$/activated carbon electrode has more electric double later capacitance and less diffusion resistance than activated carbon. Also charge-discharge and ion conductivity profiles showed that the ion removal ratios of $TiO_2$/activated carbon electrode in NaCl electrolyte of $1000\;{\mu}S/cm$ more increased about 39% than that of activated carbon. In conclusion it was possible to identify that the carbon electrode coated $TiO_2$ as electrode material was more effective than raw carbon electrode.

Structural and Electrical Properties of La0.7Sr0.3MnO3 Thin Films for Thermistor Applications (서미스터로의 응용을 위한 La0.7Sr0.3MnO3 박막의 구조적, 전기적 특성)

  • Lim, Jeong-Eun;Park, Byeong-Jun;Yi, Sam-Haeng;Lee, Myung-Gyu;Park, Joo-Seok;Kim, Byung-Cheul;Kim, Young-Gon;Lee, Sung-Gap
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.35 no.5
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    • pp.499-503
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    • 2022
  • La0.7Sr0.3MnO3 precursor solution were prepared by a sol-gel method. La0.7Sr0.3MnO3 thin films were fabricated by a spin-coating method on a Pt/Ti/SiO2/Si substrate. Structural and electrical properties with the variation of sintering temperature were measured. All specimens exhibited a polycrystalline orthorhombic crystal structure, and the average thickness of the specimens coated 6 times decreased from about 427 nm to 383 nm as the sintering temperature increased from 740℃ to 830℃. Electrical resistance decreased as the sintering temperature increased. In the La0.7Sr0.3MnO3 thin films sintered at 830℃, electrical resistivity, TCR, B-value, and activation energy were 0.0374 mΩ·cm, 0.316%/℃, 296 K and 0.023 eV, respectively.

Fabrication of LiDAR-detectable Plate-type Black Materials and Application in Hydrophilic Paints (라이다 센서에 인지되는 판상형 검은색 소재의 제조 및 친수성 도료로의 응용)

  • Jiwon Kim;Minki Sa;Chan-Gyo Kim;Ha-Yeong Kim;Yeon-Ryong Chu;Suk Jekal;Chang-Min Yoon
    • Journal of Adhesion and Interface
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    • v.24 no.3
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    • pp.95-99
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    • 2023
  • In this study, LiDAR-detectable black materials are synthesized by coating and reduction of titanium dioxide onto plate-type natural mica, which evaluated practical LiDAR verification. In detail, black TiO2@Mica materials are fabricated by utilizing a sol-gel reaction to coat titanium dioxide onto natural mica, followed by reduction using sodium tetrahydridoborate. Subsequently, Black TiO2@Mica materials are dispersed in hydrophilic transparent varnish and sprayed onto the glass substrate to assess applicability as paints. As a result, Black TiO2@Mica-based paints exhibit true blackness (L*=12.1) and a higher NIR reflectance (30.2 R%). In addition, it was confirmed that as-synthesized Black TiO2@Mica materials are successfully recognized by a LiDAR sensor. This phenomenon is attributed to Fresnel's reflection law, in which light reflection occurs at the interface between natural mica and titanium dioxide with different refractive indices. In this regard, the findings of the study are expected to contribute to the potential utilization of LiDAR-detectable materials in various fields such as autonomous vehicles, robotics, and drones.