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RISS 인기검색어
- 검색키워드
- 저자 : Thube, Dilip R. (검색결과 5 건)
- 무료
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Thube, Dilip R.,Kang, Suk-Min,Ryu, Ho-Jin 한국암반공학회 2009 Geosystem engineering Vol.12 No.2
An efficient blue-green phosphor, $Sr_4Al_{14}O_{25}:Eu^{2+}$, $Dy^{3+}$, was prepared by solid-state synthesis method. $B_2O_3$ was used as a flux for the synthesis of phosphor materials. The different mol % of $B_2O_3$ was employed during the synthesis. X-ray powder diffraction (XRD) confirmed the formation of $Sr_4Al_{14}O_{25}:Eu^{2+}$, $Dy^{3+}$ phosphor in an orthorhombic phase. The synthesized phosphor materials were further investigated by XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence studies. The phosphor, $Sr_4Al_{14}O_{25}:Eu^{2+}$, $Dy^{3+}$ shows broad band ultraviolet (UV) excited luminescence in the blue-green region (${\lambda}_{max}$= 491 nm) due to the transition from the $4f^65d^1$ to the $4f^7$ level of the $Eu^{2+}$ ion. The phosphor material with 75 mol % $B_2O_3$ shows high brightness and long persistent luminescence whereas the phosphor material without $B_2O_3$ shows no emission and persistence of luminescence.
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Calcium Aluminate Phosphor Supported $TiO_2$ Nanoparticles
김진환,강석민,류호진,Thube, Dilip R.,Kim, Jin-Hwan,Kang, Suk-Min,Ryu, Ho-Jin 한국자원리싸이클링학회 2009 資源 리싸이클링 Vol.18 No.4
희토류 원소를 기반으로한 알루미늄산 형광체에 담지된 산화티탄은 졸겔방법 으로 제조되었다. 이렇게 제조된 산화티탄 나노입자의 재료물성을 분석하기 위해 XRD, FT-IR, DRS UV-Vis, TEM 측정을 실시하였다. 형광체에 담지된 산화티탄 입자의 소결 전후의 XRD분석결과는 600도 이상의 온도에서 아나타제에서 루틸로 상변화가 일어나지 않았다. 600도 이상의 온도에서 지속적인(장시간) 열처리 후에도 형광체에 담지된 산화티탄이 결정화도가 높은 아나타제로 존재 하는 것은 형광체 지지체와 담지된 산화티탄의 서로 다른 결정입계에 의하여 결정성장과 상변화에 필요한 치밀화가 억제되기 때문으로 판단된다. DRS측정결과 형광체에 담지된 산화티탄은 산화티탄이 없는 형광체에 비하여 보다 긴 장파로 쉬프트한 것은 밴드갭 에너지의 환원을 나타낸다. 이러한 형광체에 담지된 산화티탄의 FT-IR 스펙트럼은 피크의 위치가 더 높은 파수로 이동하였다. 이것은 산화티탄 입자와 지지체 사이의 공유결합이 관계하기 때문 이라 판단된다. TEM 이미지는 형광체 지지체에 다른 입자 크기로 담지되어 있는 산화티탄의 분산, 결정화 및 입자 형상을 나타낸다. Rare earth based calcium aluminate phosphor ($CaAl_2O_4:Eu^{2+}$, $Nd^{3+}$) supported $TiO_2$ nanoparticles are synthesized by using sol-gel method, which are further characterized using powder X-ray diffraction (XRD), fourier transform infrared (FT-IR), diffuse reflectance UV-Visible spectroscopy (DRS UV-Vis) and transmission electron microscopy (TEM). The XRD pattern of as-prepared and sintered phosphor supported $TiO_2$ does not show the tendency to change the crystal structure from anatase to rutile phase up to $600^{\circ}C$. This indicates that the phosphor support might inhibit the densification and crystallite growth by providing dissimilar boundaries. The diffuse reflectance spectral (DRS) measurements showed shift towards longer wavelength indicating reduction in the band-gap energy as compared to free $TiO_2$. The FT-IR spectra of phosphor supported $TiO_2$ nanoparticles show shift in the peak positions to lower wavelengths. This indicates that the $TiO_2$ nanoparticles are not free, but covalently bonded to the phosphor support. TEM micrographs show presence of crystalline and spherical $TiO_2$ nanoparticles (8 - 15 nm diameter) dispersed uniformly on the surface of phosphor.
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Effect of B2O3 on the Photoluminescence Properties of Sr4Al14O25:Eu2+, Dy3+ Phosphor
류호진,Dilip R. Thube,강석민 한국자원공학회 2009 Geosystem engineering Vol.12 No.2
An efficient blue-green phosphor, Sr4Al14O25: Eu2+,Dy3+, was prepared by solid-state synthesis method. B2O3 was used as a flux for the synthesis of phosphorous materials. The different mol % of B2O3 was employed during the synthesis. X-ray powder diffraction (XRD) confirmed the formation of Sr4Al14O25:Eu2+,Dy3+ phosphor in an orthorhombic phase. The synthesized phosphorous materials were further investigated by XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence studies. The phosphor, Sr4Al14O25:Eu2+,Dy3+ shows broad band ultraviolet (UV) excited luminescence in the blue-green region (λmax= 491 nm) due to the transition from the 4f65d1 to the 4f7 level of the Eu2+ ion. The phosphorous material with 75 mol % of B2O3 shows high brightness and long persistent luminescence whereas the phosphorous material without B2O3 shows no emission and persistence of luminescence. An efficient blue-green phosphor, Sr4Al14O25: Eu2+,Dy3+, was prepared by solid-state synthesis method. B2O3 was used as a flux for the synthesis of phosphorous materials. The different mol % of B2O3 was employed during the synthesis. X-ray powder diffraction (XRD) confirmed the formation of Sr4Al14O25:Eu2+,Dy3+ phosphor in an orthorhombic phase. The synthesized phosphorous materials were further investigated by XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence studies. The phosphor, Sr4Al14O25:Eu2+,Dy3+ shows broad band ultraviolet (UV) excited luminescence in the blue-green region (λmax= 491 nm) due to the transition from the 4f65d1 to the 4f7 level of the Eu2+ ion. The phosphorous material with 75 mol % of B2O3 shows high brightness and long persistent luminescence whereas the phosphorous material without B2O3 shows no emission and persistence of luminescence.
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고분자전해질 연료전지용 20% Pt/C 캐소드 촉매 제조 및 산소환원반응 평가
김진환 ( Jin Hwan Kim ),강석민 ( Suk Min Kang ),Dilip. R. Thube,류호진 ( Ho Jin Ryu ) 대한금속재료학회 ( 구 대한금속학회 ) 2009 대한금속·재료학회지 Vol.47 No.7
In order to commercialize Polymer Electrolyte Fuel Cell (PEFC), the cathode catalyst such as Platinum supported Carbon (Pt/C) need to have a high activity of Oxygen Reduction Reaction (ORR). In this study, the 20% Pt/C was synthesized using the chemical reduction method while the crystallinity of Platinum (Pt) particles were controlled under heat treatment conditions. The activity of synthesized Pt catalysts was evaluated using electrochemical measurement. Compared with the i(ORR) at 0.8 V of 20% Pt/C heat-treated at 500℃ and the 20% Pt/C that were not heated and commercial 20% Pt/C, the i(ORR) at 0.8 V of 20% Pt/C heat-treated at 500℃ was 9.5 and 1.7 times higher than those of the 20% Pt/C and commercial 20% Pt/C that were not heated. It was considered that the crystallinity and particle size affect the ORR activity of the Pt/C catalysts.
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화학환원법(化學還元法)을 이용(利用)해 제조(製造)한 20% Pt/C 캐소드 촉매(觸媒)의 열처리(熱處理)에 따른 산소환원반응(酸素還元反應) 평가(評價)
김진환,강석민,류호진,Kim, Jin-Hwan,Kang, Suk-Min,Thube, Dilip.R.,Ryu, Ho-Jin 한국자원리싸이클링학회 2009 資源 리싸이클링 Vol.18 No.5
The 20% Pt/C catalysts were synthesized using the chemical reduction method for polymer electrolyte fuel cell cathode and were heat-treated in the temperature range from 300 to $600^{\circ}C$. The oxygen reduction reaction of the catalysts was evaluated using the electrochemical measurement. The oxygen reduction reaction of the heat-treated Pt/C at $300^{\circ}C$ had high catalytic activity and the oxygen reduction reaction current of that was 2 times than that of non-heat treatment catalyst. It is considered that the change of the crystallinity and particle size by heat treatment could increase the catalytic activity. 고분자전해질 연료전지용 캐소드 촉매로서 화학환원법을 이용하여 20% Pt/C 제조하고 다양한 온도($300-600^{\circ}C$)열처리하여 산소환원반응을 평가하였다 $300-400^{\circ}C$에서 열처리한 20% Pt/C가 높은 산소환원반응 활성을 나타냈으며, 특히 $300^{\circ}C$에서 열처리한 촉매를 0.6V에서의 정전위를 측정한결과, 열처리하지 않은 촉매에 비해서 산소환원 반응 활성정도가 2배 높게 나타났다. TEM 및 XRD 분석을 이용하여 조사한 결과, 열처리 온도가 높아짐에 따라서 백금 입자 크기가 커지고 결정화도가 증가하는 것을 확인하였다. 이러한 결과에서 산소환원반응 활성을 위한 백금의 입자 크기와 결정화도가 $300^{\circ}C$에서 최적화되는 것으로 판단된다.
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