• 제목/요약/키워드: Emission Color

검색결과 445건 처리시간 0.024초

내식성 향상을 위한 기능성 타이타늄 표면 개질 (Surface Modification of Functional Titanium Oxide to Improve Corrosion Resistance)

  • 박영주;정찬영
    • Corrosion Science and Technology
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    • 제20권5호
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    • pp.256-265
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    • 2021
  • Titanium is applied in various industries due to its valuable properties and abundant reserves. Generally, if a highly uniform oxide structure and a high-density oxide film is formed on the surface through anodization treatment, the utility value such as color appearance and corrosion inhibition efficiency is further increased. The objective of this study was to determine improvement of water-repellent property by controlling titanium oxide parameters such as pore size and inter-pore distance to improve corrosion resistance. Oxide film structures of different shapes were prepared by controlling the anodization processing time and voltage. These oxide structures were then analyzed using a Field Emission Scanning Electron Microscope (FE-SEM). Afterwards, a Self-Assembled Monolayer (SAM) coating was performed for the oxide structure. The contact angle was measured to determine the relationship between the shape of the oxide film and the water-repellency. The smaller the solid fraction of the surface, the higher the water-repellent effect. The surface with excellent hydrophobic properties showed improved corrosion resistance. Such water-repellent surface has various applications. It is not only useful for corrosion prevention, but also useful for self-cleaning. In addition, a hydrophobic titanium may open up a new world of biomaterials to remove bacteria from the surface.

UV-Vis 분광분석에 의한 전기변압기 내 절연지 열화도 측정 (Application of UV-Vis Spectroscopic Analysis for Transformer Insulating Paper Degradation)

  • 공호성;한흥구
    • Tribology and Lubricants
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    • 제35권3호
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    • pp.151-157
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    • 2019
  • Insulated oil degradation produces charged by-products, such as acids and hydro-peroxides, which tend to reduce the insulating properties of the oil. In this study, UV-vis spectroscopy measurement technology is developed and experimentally compared with other measurement methods, such as the titration method and IR spectroscopy, to validate its ability to monitor the degradation of electrical insulating paper. The degradation characteristics of the insulating paper are appropriately represented through various types of measurement methods, such as the Tan (delta) method, $CO_2$ gas production measurement, the titration method, and IR spectroscopy. The results are demonstrated to be well comparable to a change in the fluorescence emission ratio (FER), which is defined as the shift in fluorescence intensity in the measured wavelength range, and also to the chromatic ratio, which is defined as a color shift to longer wavelength ranges. The results also show that, by using UV-vis spectroscopy, it is possible to detect the degradation of the insulating paper. This study suggests that UV-vis spectroscopy can be applied as an alternative to high-performance liquid chromatography, which is the internationally recognized measurement technology for cellulose paper degradation. The FER detector is also verified to be useful as an effective condition-monitoring device for power transformers.

고 에너지 볼밀을 이용한 Blue 텅스텐산화물 나노입자의 제조와 특성 (Prepration and Properties of Blue Tungsten Oxide Nanopowders by High Energy Ball-Mill)

  • 김명재;이광석;김경남
    • 한국재료학회지
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    • 제31권1호
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    • pp.23-28
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    • 2021
  • The purpose of this study is to prepare WO3 nanopowders by high-energy milling in mixture gas (7 % H2+Ar) with various milling times (10, 30, and 60 min). The phase transformation, particle size and light absorption properties of WO3 nanopowders during reduction via high-energy milling are studied. It is found that the particle size of the WO3 decreases from about 30 ㎛ to 20 nm, and the grain size of WO3 decreases rapidly with increasing milling time. Furthermore, the surface of the particles due to the pulverization process is observed to change to an amorphous structure. UV/Vis spectrophotometry shows that WO3 powder with increasing milling times (10, 30, 60 min) effectively extends the light absorption properties to the visible region. WO3 powder changes from yellow to gray and can be seen as a phenomenon in which the progress of the color changes to blue. The characterization of WO3 is performed by high resolution X-ray diffractometry, Field emission scanning electron microscopy, Transmission electron microscopy, UV/Vis spectrophotometry and Particle size analysis.

Investigation of thermal annealing effects on the optical transparency and luminescent characteristics of Eu-doped Y2O3 thin films

  • Chung, Myun Hwa;Kim, Joo Han
    • Journal of Ceramic Processing Research
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    • 제20권4호
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    • pp.431-435
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    • 2019
  • The thermal annealing effects on the optical transparency and luminescent characteristics of the Eu-doped Y2O3 thin films have been investigated. The as-deposited Y2O3:Eu films exhibited an optical band gap of 5.78 eV with a transparency of 89 % at a wavelength of 550 nm. As the annealing temperature increased from 1000 to 1300 ℃, the optical band gap and transparency of the films decreased from 5.77 to 4.91 eV and from 86.8 to 64.5 % at 550 nm, respectively. The crystalline quality of the films was improved with increasing annealing temperature. The annealed Y2O3:Eu films emitted a red-color photoluminescence (PL) with the highest emission peak near 612 nm. The PL intensity was increased with increasing annealing temperature to 1200 ℃, resulting from the improvement in the crystalline quality of the films. The PL intensity was decreased with further increasing temperature above 1200 ℃ due to the formation of Y2SiO5 phase by the reaction of the film with the quartz substrate.

더블 게이트 박막 트랜지스터를 활용한 Micro LED 디스플레이 화소 회로 설계 (Design of Pixel Circuit of Micro LED Display with Double Gate Thin Film Transistors)

  • 김태수;전재홍
    • 반도체디스플레이기술학회지
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    • 제21권1호
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    • pp.50-55
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    • 2022
  • Due to the wavelength shift problem of micro LED caused by the change of current density, the active matrix driving pixel circuit that is used in OLED cannot be applied to micro LED displays. Therefore, we need a gray scale method based on modulation of duration time of light emission. In this study, we propose the PWM-controlled micro LED pixel circuit based on CMOS thin film transistors (TFTs). By adopting CMOS inverter structure, we can reduce the number of storage capacitors from the circuit and make the operating speed of the circuit faster. Most of all, our circuit is designed to make operating speed of PWM circuit faster by adopting feedback effect through double gate TFT structure. As a result, it takes about 4.7ns to turn on the LED and about 5.6ns to turn it off. This operating time is short enough to avoid the color distortion and help the precise control of the gray scale.

고성능 유연 발광 다이오드 소자 구현을 위한 레이저 기반 페로브스카이트 소재의 재결정화 (Laser-Induced Recrystallization of Perovskite Materials for High-Performance Flexible Light-Emitting Diode)

  • 허재찬;김지은;이동규;황윤식;우유미;이한얼;박정환
    • 한국전기전자재료학회논문지
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    • 제36권3호
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    • pp.286-291
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    • 2023
  • Perovskite materials are promising candidates for next-generation optoelectronic devices owing to their outstanding external quantum efficiency, high color purity, and ability to tune the light emission wavelength. However, conventional thermal annealing processes caused the degradation of perovskite, resulting in poor optoelectronic properties and a short lifetime. Herein, we propose a laser-induced recrystallization of perovskite thin film to enhance its light-emitting properties. Laser-induced recrystallization process was performed using rapid and instantaneous laser heating, which successfully induced grain growth of the perovskite material. The laser processing conditions were thoroughly optimized based on theoretical calculations and various material analyses such as x-ray diffraction, scanning electron microscope, and photoluminescence spectroscopy.

Multiepoch Optical Images of IRC+10216 Tell about the Central Star and the Adjacent Environment

  • Kim, Hyosun;Lee, Ho-Gyu;Ohyama, Youichi;Kim, Ji Hoon;Scicluna, Peter;Chu, You-Hua;Mauron, Nicolas;Ueta, Toshiya
    • 천문학회보
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    • 제46권2호
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    • pp.36.1-37
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    • 2021
  • Six images of IRC+10216 taken by the Hubble Space Telescope at three epochs in 2001, 2011, and 2016 are compared in the rest frame of the central carbon star. An accurate astrometry has been achieved with the help of Gaia Data Release 2. The positions of the carbon star in the individual epochs are determined using its known proper motion, defining the rest frame of the star. In 2016, a local brightness peak with compact and red nature is detected at the stellar position. A comparison of the color maps between 2016 and 2011 epochs reveals that the reddest spot moved along with the star, suggesting a possibility of its being the dusty material surrounding the carbon star. Relatively red, ambient region is distributed in an Ω shape and well corresponds to the dusty disk previously suggested based on near-infrared polarization observations. In a larger scale, differential proper motion of multiple ring-like pattern in the rest frame of the star is used to derive the average expansion velocity of transverse wind components, resulting in ~12.5 km s-1 (d/123 pc), where d is the distance to IRC+10216. Three dimensional geometry is implied from its comparison with the line-of-sight wind velocity determined from half-widths of submillimeter emission line profiles of abundant molecules. Uneven temporal variations in brightness for different searchlight beams and anisotropic distribution of extended halo are revisited in the context of the stellar light illumination through a porous envelope with postulated longer-term variations for a period of 10 years.

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Effects of Molding Pressure and Sintering Temperature on Properties of Foamed Glass without Blowing Agent

  • Kim, EunSeok;Kim, Kwangbae;Lee, Hyeryeong;Kim, Ikgyu;Song, Ohsung
    • 한국세라믹학회지
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    • 제56권2호
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    • pp.178-183
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    • 2019
  • A process of fabricating the foamed glass that has closed pores with 8 ~ 580 ㎛ sizes without a blowing agent by sintering 10 ㎛ boron-free glass powder composed of CaO, MgO, SO3, Al2O3-83 wt% SiO2 at a molding pressure of 0 ~ 120 MPa and a sintering temperature of 750 ~ 1000℃ was investigated. To analyze the glass transition temperature of glass powder, thermogravimetric analysis-differential thermal analysis (TGA-DTA) method were used. The microstructure and pore size of foamed glass were examined using the optical microscopy and field emission scanning electron microscopy (FE-SEM). For the thermal diffusivity and color of the fabricated samples, a heat flow meter and ultraviolet-visible-near-infrared (UV-VIS-NIR)-colormetry were used, respectively. In the TGA-DTA result, the glass transition temperature of glass powder was confirmed to be 626℃. In the microstructure result, closed pores of 7 ~ 20 ㎛ were formed at 750 ~ 900℃, and they were not affected by the molding pressure and sintering temperature. However, at 1,000℃, when there was 0 MPa molding pressure, closed pores of 580 ㎛ were confirmed, and the pore size decreased as the molding pressure increased. Moreover, at a molding pressure of 30 MPa or higher, closed pores of approximately 400 ㎛ were formed. The porosity showed an increasing trend of smaller molding pressure and larger sintering temperature, and it was controllable in the range of 5.69 ~ 68.45%. In the thermal diffusivity result, there was no change according to the molding pressure, and, by increasing the sintering temperature, up to 0.115 W/m·K could be obtained. The Lab color index (CIE-Lab) results all showed a similar translucent white color regardless of molding pressure and sintering temperature. Therefore, based on the foamed glass without boron and blowing agent, it was confirmed that white foamed glass, which has closed pores of 8 ~ 580 ㎛ and a thermal diffusivity characteristic of 0.115 W/m·K, can be fabricated by changing the molding pressure and sintering temperature.

한국에서 유통 중인 산화형 염모제의 중금속 농도에 관한 연구 (A Study on Heavy Metal Concentrations of Oxidized Hair Coloring Products in Korea Market)

  • 최채만;홍미선;이윤정;김화순;김현정;김정헌;채영주
    • 대한화장품학회지
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    • 제39권3호
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    • pp.241-249
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    • 2013
  • 2012년 1월에서 10월 사이에 전국에서 유통 중인 산화형 염모제(1제) 125개 제품에서 납(Pb), 비소(As), 카드뮴(Cd), 크롬(Cr), 망간(Mn), 니켈(Ni), 구리(Cu)의 농도 측정과 국산, 수입산 및 헤나별, 성상별, 색상별로 비교해 봄으로써 이에 관련된 분야의 기초자료를 제공하고자 본 연구를 시행하였다. 분석된 전체 염모제의 평균 중금속 농도는 납 0.211 ${\mu}g/g$, 비소 0.051 ${\mu}g/g$, 카드뮴 0.008 ${\mu}g/g$, 크롬 0.954 ${\mu}g/g$, 망간 6.250 ${\mu}g/g$, 니켈 0.591 ${\mu}g/g$, 구리 0.544 ${\mu}g/g$으로 측정되었으며 납, 비소의 경우 우리나라 화장품 안전기준 등에 관한 규정에서 허용기준인 납 20 ${\mu}g/g$, 비소 10 ${\mu}g/g$보다 낮은 수치이다(식품의약품안전처 고시 제2013-24 호). 또한 헤나 염모제는 통계적으로 유의한 차이를 보였으며(p < 0.05), 납 1.264 ${\mu}g/g$, 비소 0.267 ${\mu}g/g$, 카드뮴 0.025 ${\mu}g/g$, 크롬 4.055 ${\mu}g/g$, 망간 72.044 ${\mu}g/g$, 니켈 3.076 ${\mu}g/g$, 구리 4.640 ${\mu}g/g$으로 국산 및 수입 염모제보다 높았다. 염모제의 성상별 중금속 농도는 통계적으로 유의한 차이를 보였으며(p < 0.05), 크림과 액체 타입에서 크롬이 각각 0.708 ${\mu}g/g$, 0.478 ${\mu}g/g$로 가장 높았고, 분말타입에서는 망간이 60.041 ${\mu}g/g$로 높았다. 염모제의 색상별 중금속 농도는 통계적으로 유의한 차이를 보이지 않았으며, 노란색의 경우 납, 크롬이 높은 평균 농도를 보였고, 적색과 분홍색의 염모제는 크롬, 갈색과 흑색은 망간이, 녹색은 니켈이 높은 평균 농도를 나타내었다.

Excimer-Based White Phosphorescent OLEDs with High Efficiency

  • Yang, Xiaohui;Wang, Zixing;Madakuni, Sijesh;Li, Jian;Jabbour, Ghassan E.
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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    • pp.1520-1521
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    • 2008
  • There are several ways to demonstrate white organic light emitting diodes (OLEDs) for displays and solid state lighting applications. Among these approaches are the stacked three primary or two complementary colors light-emitting layers, multiple-doped emissive layer, and excimer and exciplex emission [1-10]. We report on white phosphorescent excimer devices by using two light emitting materials based on platinum complexes. These devices showed a peak EQE of 15.7%, with an EQE of 14.5% (17 lm/W) at $500\;cd/m^2$, and a noticeable improvement in both the CIE coordinates (0.381, 0.401) and CRI (81). Devices with the structure ITO/PEDOT:PSS/TCTA (30 nm)/26 mCPy: 12% FPt (10 nm) /26 mCPy: 2% Pt-4 (15 nm)/BCP (40 nm)/CsF/Al [device 1], ITO/PEDOT:PSS/TCTA (30 nm)/26 mCPy: 2% Pt-4 (15 nm)/26 mCPy: 12% FPt (10 nm)/BCP (40 nm)/CsF/Al [device 2], and ITO/PEDOT:PSS/TCTA (30 nm)/26 mCPy: 2% Pt-4: 12% FPt (25 nm)/BCP (40 nm)/CsF/Al [device 3] were fabricated. In these cases, the emissive layer was either the double-layer of 26 mCPy:12% FPt and 15 nm 26 mCPy: 2% Pt-4, or the single layer of 26mCPy with simultaneous doping of Pt-4 and FPt. Device characterization indicates that the CIE coordinates/CRI of device 2 were (0.341, 0.394)/75, (0.295, 0.365)/70 at 5 V and 7 V, respectively. Significant change in EL spectra with the drive voltage was observed for device 2 indicating a shift in the carrier recombination zone, while relatively stable EL spectra was observed for device 1. This indicates a better charge trapping in Pt-4 doped layers [10]. On the other hand, device 3 having a single light-emitting layer (doped simultaneously) emitted a board spectrum combining emission from the Pt-4 monomer and FPt excimer. Moreover, excellent color stability independent of the drive voltage was observed in this case. The CIE coordinates/CRI at 4 V ($40\;cd/m^2$) and 7 V ($7100\;cd/m^2$) were (0.441, 0.421)/83 and (0.440, 0.427)/81, respectively. A balance in the EL spectra can be further obtained by lowering the doping ratio of FPt. In this regard, devices with FPt concentration of 8% (denoted as device 4) were fabricated and characterized. A shift in the CIE coordinates of device 4 from (0.441, 0.421) to (0.382, 0.401) was observed due to an increase in the emission intensity ratio of Pt-4 monomer to FPt excimer. It is worth noting that the CRI values remained above 80 for such device structure. Moreover, a noticeable stability in the EL spectra with respect to changing bias voltage was measured indicating a uniform region for exciton formation. A summary of device characteristics for all cases discussed above is shown in table 1. The forward light output in each case is approximately $500\;cd/m^2$. Other parameters listed are driving voltage (Bias), current density (J), external quantum efficiency (EQE), power efficiency (P.E.), luminous efficiency (cd/A), and CIE coordinates. To conclude, a highly efficient white phosphorescent excimer-based OLEDs made with two light-emitting platinum complexes and having a simple structure showed improved EL characteristics and color properties. The EQE of these devices at $500\;cd/m^2$ is 14.5% with a corresponding power efficiency of 17 lm/W, CIE coordinates of (0.382, 0.401), and CRI of 81.

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