• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.353-353
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• 2011

Titanium dioxide is a suitable material for industrial use at present and in the future because titanium dioxide has efficient photoactivity, good stability and low cost [1]. Among the three phases (anatase, rutile, brookite) of titanium dioxide, the anatase form is particularly photocatalytically active under ultraviolet (UV) light. In fabrication of photocatalytic devices based on catalytic nanodiodes [2], it is challenging to obtain a photocatalytically active TiO2 thin film that can be prepared at low temperature (< 200$^{\circ}C$). Here, we present the synthesis of a titanium dioxide film using TiO2 nanoparticles and sol-gel methods. Titanium tetra-isopropoxide was used as the precursor and alcohol as the solvent. Titanium dioxide thin films were made using spin coating. The change of atomic structure was monitored after heating the thin film at 200$^{\circ}C$ and at 350$^{\circ}C$. The prepared samples have been characterized by X-ray diffraction (XRD), scanning electron microcopy, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet-visible spectroscopy (UV-vis), and ellipsometry. XRD spectra show an anatase phase at low temperature, 200$^{\circ}C$. UV-vis confirms the anatase phase band gap energy (3.2 eV) when using the photocatalyst. TEM images reveal crystallization of the titanium dioxide at 200$^{\circ}C$. We will discuss the switching behavior of the Pt /sol-gel TiO2 /Pt layers that can be a new type of resistive random-access memory.

• 대한가정학회지
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• 제45권10호
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• pp.73-81
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• 2007

The purpose of this study was to increase the ultraviolet-light (UV)-cut ability of cellulose fabrics (cotton, ramie, and rayon) dyed with safflower yellow colorants. For this purpose, samples treated with UV-cut agent and tannic-acid were compared with the untreated samples after UV exposure in terms of K/S value, color changes(${\Delta}E$), SEM, and strength retention. The K/S value rapidly decreased after 28 days exposure, whereas the K/S value of the samples treated with both UV-cut agent and tannic-acid decreased to less than that of the untreated samples. In color changes, $L^*$ increased while $a^*$ and $b^*$ decreased, indicating less red and yellow character in color. This induced a change in the hue, value and chroma values. However the color change(${\Delta}E$) of the samples treated with both UV-cut agent and tannic-acid was less than that of the untreated samples. Scanning electron microscopy (SEM) pictures showed a severe degradation by exposure in all samples. Tensile strength rapidly decreased after 28 days for cotton and rayon, and after 21 days for ramie. However, the strength retention of the samples treated with UV-cut agent and tannic-acid was higher than that of the untreated samples.

• 한국진공학회지
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• 제16권2호
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• pp.145-152
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• 2007

자외선 광여기 전자현미경 (Ultraviolet - Photoelectron Emission Microscopy: UV-PEEM)을 이용하여 Si (001)과 (113) 표면에 Ge을 증착하면서 실시간으로 나노구조의 형성과 크기 및 형태 변화과정을 조사하였다. Ge은 PBEM에 부착된 e-beam 증착기를 이용하여 $450-550^{\circ}C$ 온도에서 in situ로 증착하면서 표면의 변화를 PEEM으로 관찰하였다. Ge을 ${\sim}0.4\;ML/min$의 증착율로 ${\sim}4\;ML$ 이상 두께로 증착했을 때, 두 Si 표면에서 Ge의 균일한 변형층(strained layer) 위에 island 구조가 형성되었다. 초기에 형성된 원형 모양의 island는 연속적인 Ge 증착에 따라, ripening 과정에 의해 크기가 점차 성장되었고 밀도는 감소하였으나, 형태는 원형 모양을 유지하였다. 시료 성장 후 공기 중 AFM 측정 결과, Si(001) 표면에는 dome 형태의 Ge island가 Si(113) 표면에는 윗면이 평판하고 다면의 옆면을 지닌 island 구조가 형성됨이 확인되었다. 반면에 ${\sim}0.15\;ML/min$의 낮은 증착율로 Ge을 증착했을 때, Si(113) 표면에서 원형의 Ge island가 길죽한(elongated) 형태의 나노선 구조로 변형됨이 관찰되었다. 또한, 계속적인 Ge 증착 두께를 증가시킴에 따라 표면에는 새로운 island가 형성되지 않고, 기존의 island들이 점차 길이 방향으로 크기가 증가하면서 [$33\bar{2}$] 방향으로 배열하였다. 이와 같은 Ge 나노구조의 형성과 형태 변화는 나노구조 형성과정에서 변형이완(strain relaxation)과 가원자(adatom)의 표면 동역학적 효과와 깊은 관련이 있는 것으로 분석된다.

• 한국입자에어로졸학회지
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• 제12권2호
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• pp.37-42
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• 2016

$CeO_2$ nanoparticles were prepared by a flame spray pyrolysis from aqueous solution of cerium nitrate. The morphology, structure crystallinity and specific surface area of as-prepared nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Telle (BET). The $CeO_2$ nanoparticles about 5 nm in diameter showed a cubic fluorite structure and polyhedral morphology. The average particle size increased as the cerium nitrate concentration increased. UV absorption performance of the as-prepared nanoparticles was measured by UV-visible spectroscopy. UV absorption of $CeO_2$ nanoparticles was more effective than that of commercial $TiO_2$ nanoparticles. Effect of dopants such as Ti and Zn to $CeO_2$ nanoparticles on UV absorption properties was also investigated. In case of $Ti/CeO_2$, and $Zn/CeO_2$ nanoparticles, they showed a little higher UV absorption values compared with $CeO_2$ nanoparticles. The as-prepared nanoparticles can be promising materials with high UV absorption value.

• Corrosion Science and Technology
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• 제19권1호
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• pp.16-22
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• 2020

It is important to realize that benzoate was intercalated into hydrotalcite (HTC-Bz) by the co-precipitation method. In this case, acrylic coating with 0.5 wt% HTC-Bz was deposited on carbon steel using the spin coating method. Next, the HTC-Bz structure was characterized by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). In fact, an ultraviolet vision spectroscopy (UV-Vis) was used to determine the benzoate content in HTC-Bz, and the UV absorption ability of HTC-Bz. Using electrochemical techniques, water contact angle measurement, and thermal-gravimetric analysis, we compared the protective properties before and after QUV test, hydrophobicity and the thermal stability of acrylic coating containing HTC-Bz. The obtained results showed that HTC-Bz with a plate-like structure was successfully synthesized; benzoate was intercalated into the interlayer of hydrotalcite with a concentration of 28 wt%. Additionally, it was noted that HTC-Bz has an UV absorption peak at 225 nm. In conclusion, the addition of HTC-Bz enhanced the UV stability, hydrophobicity and the thermal stability of acrylic coating.

• Transactions on Electrical and Electronic Materials
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• 제15권5호
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• pp.249-252
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• 2014

The aim of this work is to investigate the effect of $Ca_xSr_{2-x}$ and activator on the structural and luminescent properties of green-emitting $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ nano phosphor. Using urea as fuel and ammonium nitrate as oxidizer, $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ has been successfully synthesized, using a combustion method. The particles were found to be small, spherical and of round surface. SEM imagery showed that the phosphors particles are of nanosize. The $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ emission spectrum for 360 nm excitation showed a single band, with a peak at 490 nm, which is a green emission. The highest luminous intensity was at $1,000^{\circ}C$, which was obtained when the $Eu^{2+}$ content (y) was 0.05. The results support the application of $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor as a fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). Characteristics of the synthesized $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and photoluminescence (PL) detection.

• 펄프종이기술
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• 제34권4호
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• pp.22-29
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• 2002

This research was conducted to investigate the morphological characteristics of fine fibers produced during beating process of high yield pulp treated with ozone and the distribution of lignin in the produced fine fibers. Thermomechanical(TMP) pulp and chemithermomechanical(CTMP) pulp of spruce and CTMP of white birch were beaten to reach 200$m\ell$ CSF, and then the fine fibers were observed using ultraviolet microscope. The fine fibers produced from TMP and CTMP of spruce using treated with ozone for 15 minutes were fragments of fiber surfaces or cell corners, and most of them contained lignin. However, lignin was not observed in the fibers after 15 minutes of ozone treatment. The fine fibers produced from CTMP of white birch were broken pieces or fragments of fiber surfaces or cell corners. The lignin was observed in the fibers until 5min of ozone treatment but no lignin was observed after 5 minutes of ozone treatment. Different morphological characteristics of TMP and CTMP explained both the different morphological characteristics and the distribution of lignin observed in the fine fibers produced from the beating process of TMP and CTMP treated with ozone.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.351.2-351.2
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• 2014

Indium tin oxide (ITO) has a lot of variations of its properties because it is basically in an amorphous state. Therefore, the differences in composition ratio of ITO can result in alteration of electrical properties. Normally, ITO is considered as transparent conductive oxide (TCO), possessing excellent properties for the optical and electrical devices. Quantitatively, TCO has transparency over 80 percent within the range of 380nm to 780nm, which is visible light although its specific resistance is less than $10-3{\Omega}/cm$. Thus, the solar cell is the best example for which ITO has perfectly matching profile. In addition, when ITO is used as transparent conductive electrode, this material essentially has to have a proper work function with contact materials. For instance, heterojunction with intrinsic thin layer (HIT) solar cell could have both front ITO and backside ITO. Because each side of ITO films has different type of contact materials, p-type amorphous silicon and n-type amorphous silicon, work function of ITO has to be modified to transport carrier with low built-in potential and Schottky barrier, and approximately requires variation from 3 eV to 5 eV. In this study, we examine the change of work function for different sputtering conditions using ultraviolet photoelectron spectroscopy (UPS). Structure of ITO films was investigated by spectroscopic ellipsometry (SE) and scanning electron microscopy (SEM). Optical transmittance of the films was evaluated by using an ultraviolet-visible (UV-Vis) spectrophotometer

• 한국분말재료학회지
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• 제21권2호
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• pp.119-123
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• 2014

Pt has been widely used as catalyst for fuel cell and exhausted gas clean systems due to its high catalytic activity. Recently, there have been researches on fabricating composite materials of Pt as a method of reducing the amount of Pt due to its high price. One of the approaches for saving Pt used as catalyst is a core shell structure consisting of Pt layer on the core of the non-noble metal. In this study, the synthesis of Pt shell was conducted on the surface of $TiO_2$ particle, a non-noble material, by applying ultraviolet (UV) irradiation. Anatase $TiO_2$ particles with the average size of 20~30 nm were immersed in the ethanol dissolved with Pt precursor of $H_2PtCl_6{\cdot}6H_2O$ and exposed to UV irradiation with the wavelength of 365 nm. It was confirmed that Pt nano-particles were formed on the surface of $TiO_2$ particles by photochemical reduction of Pt ion from the solution. The morphology of the synthesized Pt@$TiO_2$ nano-composite was examined by TEM (Transmission Electron Microscopy).

• Molecular & Cellular Toxicology
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• 제1권2호
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• pp.111-115
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• 2005

Ultraviolet (UV) radiation to mammalian skin is known to alter cellular function via generation of Reactive Oxygen Species (ROS), DNA damage and DNA lesions, such as pyrimidine dimmers and photoproducts, which could lead to DNA mutation if they are not repaired. In this study, we have investigated the reduction of DNA damage and of apoptosis with a particular attention to genetic effect of paeoniflorin in Normal Human Epidermal Keratinocytes (NHEK). After UVB irradiation from $10\;to\;500mJ/cm^{2}$ to NHEK, Mean Tail Moments (MTM) were increased with UVB dose increase. The greatest amount of strand breaks was induced at $500mJ/cm^{2}$ of UVB. Even at the lowest dose of UVB ($10mJ/cm^{2}$), change in MTM was detected (P<0.0001). Pretreated cell with 0.1% paeoniflorin maximally reduced the level of DNA damage to about 21.3%, compared to untreated cell. In the lower concentrations less than 0.01% of paeoniflorin, MTM had a small increase but paeoniflorin still had reductive effects of DNA damage. We measured the apoptosis suppression of paeoniflorin with annexin V flous staining kit. As we observed under the fluorescence microscopy to detect apoptosis in the irradiated cell, the fluorescence intensity was clearly increased in the untreated cell, but decreased in treated cells with paeoniflorin. These results suggest that paeoniflorin reduces the alteration of cell membranes and prevents DNA damage. Therefore, the use of paeoniflorin as a free radical scavenger to reduce the harmful effects of UV lights such as chronic skin damage, wrinkling and skin cancer can be useful to prevent the formation of photooxidants that result in radical damage.