• 한국재료학회지
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• 제18권2호
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• pp.98-102
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• 2008

The ferroelectric properties of UV irradiated and non-irradiated PZT films prepared via photochemical metal-organic deposition using photosensitive precursors were characterized. Fourier transform infrared spectroscopy showed that complete removal of organic groups was possible through UV exposure of the spin-coated PZT precursor films at room temperature. The measured remnant polarization values of UV-irradiated and non-irradiated PZT films after annealing at $650^{\circ}C$ were 29 and $23\;{\mu}C/cm^2$, respectively. The UV irradiation was found to be effective for the enhancement of the <111> growth orientation and ferroelectric property of PZT film and in the direct patterning in the fabrication of micro-patterned systems without dry etching.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권10호
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• pp.465-472
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• 2002

This paper presents a study on the aging and recovery of HTV (high temperature vulcanized) silicone rubber used for outdoor insulators. UV irradiation, corona discharge and water immersion were employed as factors of the artificial aging. The effects of changes derived from these stresses on the tracking and arc resistance of silicone rubber were examined. We have investigated the aging phenomena of HTV silicone rubber by the above stresses using the surface energy calculation with contact angle measurement, solvent-extraction, and surface/volume resistivity and so on. These results showed that UV irradiation and corona discharge lead to nearly the same surface oxidation, but the percentage change of mobile low molecular weight by these stresses was different. Furthermore, the oxidized layer induced under UV irradiation restricted the recovery of hydrophobic surface. Water immersion little lowered hydrophobicity level and leaded to a loss of tracking and arc resistance. The degradation mechanism based on our results was discussed.

• Macromolecular Research
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• 제9권6호
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• pp.327-331
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• 2001

A new soluble photosensitive poly(amide-co-imide) containing p-phenylenediacryloyl moiety was synthesized and its photoreactivity was characterized. The copolymer was synthesized fromp-phenylenediacryloyl chloride, 4,4-(hexafluoroisopropylidene)diphthalic anhydride and two equivalents of bis(4-aminophenyl) ether in NMP with a subsequent chemical imidization of the resulting poly[amide$\xi$ο-(amic acid)] by acetic anhydride and pyridine. The structure and thermal properties of the polymer were characterized by spectroscopic methods and thermal analyses. The polymer was stable up to 350$\^{C}$, showed good solubility in polar aprotic solvents, and became insoluble after UV irradiation due to the[2+2] cycloaddition of phenylenediacryloyl moiety. Photoreactivity of the polymer was investigated in solution or as a film with respect to the various exposure conditions by UV/Vis spectroscopy. The photosensitivity was noticeably increased with the irradiation temperature, especially in the presense of photosensitizer. The reason for the increased sensitivity was speculated based on the flexibilization of main chain at elevated temperature. Exposure characteristic curves were obtained from the gel fraction experiments after UV irradiation. The sensitivity and contrast at 160$\^{C}$ were measured to be 293 mJ/㎠ and 1.64, respectively.

• 자연과학논문집
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• 제8권2호
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• pp.43-48
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• 1996

돌연변이원 감수성 hyper-rec type musN 돌연변이주를 recombination 과 mutation에 관여하는 유전자들이 포함된 UvsC group에 포함시켰다. 하지만, rec- 및 UV에 의한 돌연변이가 일어나지 않는 uvsC 돌연변이주와는 달리 musN은 매우 다른 성질을 나타냈다. musN은 uvsC와는 달리 mutator가 아니었다. 또한, UV 조사에 따른 selenate resistant mutation도 야생주와 비슷한 수준으로 유발되었다. 분열하는 musN 세포에서의 UV 감수성 또한 uvsC와는 달리 정상이었다. 이같은 결과는 UcsC group이 branched pathways를 갖고 있음을 나타낸다.

• Elastomers and Composites
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• 제54권3호
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• pp.252-256
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• 2019

Fullerene oxide[$C_{60}(O)_n$, ($n{\geq}1$)] was synthesized by dissolving fullerene[$C_{60}$] and 3-chloroperoxybenzoic acid in toluene under refluxing condition for 5 h. Hybrid fullerene oxide-silver nanoparticle composites were synthesized by dissolving fullerene oxide and silver nitrate[$AgNO_3$] in diethylene glycol under ultrasonic irradiation for 3 h. The synthesized hybrid nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, and ultraviolet-visible[UV-vis] spectroscopy. The catalytic activity for the reduction of various nitroanilines[NAs] was identified by UV-vis spectrophotometer. The efficiency of the catalytic reduction by the synthesized hybrid nanocomposites has an order of 4-NA > 2-NA > 3-NA.

• Elastomers and Composites
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• 제50권1호
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• pp.1-6
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• 2015

Polybutadiene rubber (BR) has been well known that its physical and chemical properties are changed when it is exposed to ultraviolet light undergoing photooxidation. In this study, photooxdiation process of BR vulcanizate was investigated using a high pressure mercury lamp used as an outdoor lighting, which has high UV radiation efficiency and reasonable cost. Discoloration and crack formation of photooxdized BR vulcanite surface were examined using an image analyzer. Change of chemical functional groups of BR vulcanite surface by photooxidation was investigated using ATR-FTIR, and variation of the crosslink density with the UV irradiation time was investigated. By increasing the UV irradiation time, the crosslink density steeply increased after a period of time and did not increase any more. Formation of hydroxyl (~OH) and carbonyl (~C=O) groups on the BR vulcanizate surface increased and the1,4-cis unit was converted to the 1,4-trans unit as the photooxidation was proceeded.

• 한국균학회지
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• 제20권3호
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• pp.216-221
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• 1992

사철느타리버섯, 느타리버섯, 여름느타리버섯 형질전환주(形質轉煥珠)에서 crystal이 형성(形成) 되었으며, crystal은 물에는 녹지않고 고온(高溫)이나 ethanol에 녹으며 ethanol이 휘발되면 재결정이 이루어졌다 . crystal은 고체(固體)배지뿐 아니라 액체(液體) 배지(培地)에서도 형성(形成)되며 균사(菌絲)를 $15-25^{\circ}C$에서 배양(培養)할때 형성(形成)되나 $30-35^{\circ}C$ 에서는 형성(形成)되지 않았다. 또한 uv 를 이용(利用)하여 돌연변이(突然變異)를 유발(誘發)시켰을때도 여름느타리 버섯과 느타리버섯의 1핵(核) 균사(菌絲)에서 crystal을 형성(形成)하는 균주(菌株)를 얻었다 .

• Elastomers and Composites
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• 제57권4호
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• pp.181-187
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• 2022

CdSe-Mn nanocomposites were synthesized using a microwave method with sodium sulfite (Na₂SO₃), selenium (Se), cadmium sulfate octahydrate (3CdSO₄·8H₂O), ammonia solution (NH₃·H₂O), and manganese (II) sulfate monohydrate (MnSO₄·H₂O). We obtained CdSe-Mn-C₆₀ nanocomposites by calcining CdSe-Mn nanocomposites and fullerene (C₆₀) in an electric furnace at 700 ℃ for 2 h. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy were used to characterize the crystal structures, lattice vibrations, and surface morphologies of the products, respectively. The photocatalytic activities of the CdSe-Mn-C₆₀ nanocomposites were investigated based on the photocatalytic degradations of organic dyes such as BG, MB, MO, and RhB under ultraviolet (UV) irradiation at 254 nm. UV-visible spectrophotometry was used to confirm the degradation process.

• 대한치과기공학회지
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• 제42권2호
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• pp.113-120
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• 2020

Purpose: This study is to compare and analyze the shrinkage of the specimen after UV irradiation of UV cured resin at 5, 15, and 30 minutes. Methods: A cylindrical UV cured specimen was produced using a stainless steel mold. UV cured resin specimens were prepared in three groups: 5 minutes cured (5M), 15 minutes cured (15M), and 30 minutes cured (30M). The measurement was made in total 3rd. The measurement was made in total 3rd. The primary measurement was made after 24 hours using a digital measuring instrument. The 2nd and 3rd measurements were deposited in a constant temperature water bath and the shrinkage was measured. The measured data was calculated by referring to the ASTM C326 linear measurement calculation method. T-test and One-way ANOVA were performed to test the significance between groups. The post-test was conducted with Tukey (α=0.05). Results: When the inner diameter and the outer diameter of the three groups not placed in the water bath were compared and analyzed, the contraction was the smallest at 6.8% in the 5M group, and the contraction was the largest at 7.3% in the 30M group. In the outer diameter, the contraction of the 5M group was the smallest at 3.5%, and the contraction of the 30M group was the largest at 4.5%. Shrinkage decreased in all three groups immersed in a water bath for 3-7 days. Conclusion: In the UV cured resin specimen, the shrinkage increased as the amount of UV irradiation increased.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.571-571
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• 2012

We discovered the formation of C60 aggregates in solution by means of photoluminescence spectroscopic study on C60 in solutions. From the in-depth investigation of temperature dependence of the luminescence of C60 in toluene, benzene and CS2 solutions, we reported that the C60 aggregates are formed during cooling at the freezing temperature of these solvents. Furthermore, the C60 aggregates can be changed to stable structures by irradiating with UV pulse-laser (Nd:YAG laser, 355nm). As a consequence, we could obtain nano-scale photo-polymerized C60 clusters, which appear as round-shaped nano- scale particles in high resolution transmission electron-microscopy (HRTEM) images. However, the yield of the nano-scale C60 clusters obtained by this method is too small. So we designed and developed a system to obtain C60 cluster of macroscopic quantity by using ultrasonic nebulizer. In this system, C60 solution was vaporized to several micro-sized droplets in vacuum, resulting in the formation of C60 aggregates by evaporating solvent (toluene). The system was invented to produce nano-scale carbon clusters by the irradiation of UV light upon C60 aggregates in vacuum. We have characterized the products, C60 cluster, obtained from the system by using UV absorption spectra and HPLC spectra. Although the products have a possibility of inclusion various forms of C60 cluster, results support that the product formed from the system by using vaporizer method establishes a new method to obtain C60 cluster in macroscopic quantity. In the presentation, the details of the system and the results of characterization are reported.