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RISS 인기검색어
- 검색키워드
- 저자 : Kurugundla Gopi Krishna (검색결과 3 건)
- 무료
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Krishna, Kurugundla Gopi,Bharat, L. Krishna,Yu, Jae Su Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.2
<P><B>Abstract</B></P> <P>The Sr<SUB>3</SUB>SiO<SUB>5</SUB>: Ce<SUP>3+</SUP>/Dy<SUP>3+</SUP> phosphors were prepared via a citrate assisted sol-gel method. The prepared samples were characterized by X-ray diffraction pattern, scanning electron microscopy, Fourier transform infrared spectroscopy and fluorescence spectroscopy. When excited with near-ultraviolet (NUV) (360nm) irradiation, the photoluminescence emission spectra showed a broad band blue emission of Ce<SUP>3+</SUP> ions combined with the sharp emission peaks of Dy<SUP>3+</SUP> ions. Energy transfer occurred between the Ce<SUP>3+</SUP> and Dy<SUP>3+</SUP> ions and it increased with the increase of Dy<SUP>3+</SUP> ion concentration. The luminescence properties of the prepared phosphor materials could be adjusted by changing the concentration ratio of the Ce<SUP>3+</SUP> and Dy<SUP>3+</SUP> ions. The prepared phosphor materials also exhibited good thermal stability.</P>
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Bharat, L. Krishna,Krishna, Kurugundla Gopi,Yu, Jae Su Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.699 No.-
<P><B>Abstract</B></P> <P>Ca<SUB>2</SUB>AgZn<SUB>2</SUB>V<SUB>3</SUB>O<SUB>12</SUB> self-activated vanadate phosphors were synthesized via a citrate assisted sol-gel method. The phase formation of the garnet structure was verified by X-ray diffraction (XRD) and Rietveld refinement analyses. From XRD patters, it is clear that the prepared samples were crystallized in cubic phase with a space group Ia 3 ¯ d (230). The photoluminescence excitation spectrum showed a broad band in the UV region and a broad emission spectrum was observed in the wavelength range of 400–750 nm. The doping of transition metal ion (Nb<SUP>5+</SUP>) in the vanadium site changed the luminescence properties. Doping of Nb<SUP>5+</SUP> ions increased the VO bond length from 1.7016 to 1.7148 Å which causes the increase in luminescence intensity and the red shift of emission spectrum. The increase in the luminescence intensity may also be attributed to the emission from Nb<SUP>5+</SUP> ions. The thermal stability of the materials was measured and the activation energy was found to be 0.254 eV. The luminescence decay time was also measured and the values were found to be 158 and 154 μs for undoped and doped samples, respectively. The prepared phosphors exhibited a greenish yellow emission under UV excitation, indicating that they can be potential candidates for the application in UV-based WLEDs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The self-activated Ca<SUB>2</SUB>AgZn<SUB>2</SUB>V<SUB>3</SUB>O<SUB>12</SUB> vanadate phosphor was prepared via a sol-gel method. </LI> <LI> The prepared phosphors exhibited a greenish yellow emission under UV excitation. </LI> <LI> The doping of Nb<SUP>5+</SUP> ions in the vanadium site changes the luminescence properties. </LI> <LI> The red shift in the emission spectrum is due to the increase in VO bond length. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Mohan Reddy Pallavolu,Kurugundla Gopi Krishna,Goli Nagaraju,P.S. Srinivasa Babu,Sangaraju Sambasivam,ADEM SREEDHAR 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.116 No.-
Development of structurally stable transition metal-oxides and cost-effective biomass-based carbon materials have attracted considerable attention in the fabrication of hybrid supercapacitors. In this work, we designed spinal copper-doped cobalt oxide (Cu-Co3O4 ) nanoboxes decorated functionalized-carbon nanotubes (f-CNTs) as hybrid redox-type material and agriculture crop-waste derived mesoporous activated carbon as capacitive-type electrode for high-performance hybrid supercapacitors. Structural properties reveal that the Cu-Co3O4 has a cubic spinel structure and Raman spectra results confirm the presence of f-CNTs. The hybrid composite material demonstrates superior redox behavior with excellent structural durability. The hybrid electrodes exhibit maximum specific capacity of 130.7 mAh g−1 at 0.5 A g−1 with 86.7 % capacitance retention over 10,000 cycles. Besides, the crop waste-derived activated carbon demonstrates high surface area (1549 m2g-1), mesoporous characteristics and excellent capacitive behavior. The high voltage hybrid supercapacitor is further fabricated with Cu-Co3O4 @F-CNTs as battery-type and biomass-derived activated carbon as capacitive-type electrodes, which demonstrate high energy density of 30.8 Wh kg−1 at 5972 W kg -1 power density. The augmented results indicate that the hybrid composites with biomass-derived carbon materials pave the way for design of eco-friendly energy storage applications.
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