1,177 research outputs found

    Longitudinal distribution of the fish fauna in the river Ganga from Gangotri to Kanpur

    Get PDF
    Fish fauna of the river Ganga from Gangotri to Kanpur consisted of 140 fish species from 9 orders and 25 families; 63 fish species from 6 orders and 12 families in the mountain section (MS), while 122 species from 9 orders and 25 families in the Plains section (PS) of Upper Ganga. Cypriniformes and Cyprinidae were most species rich order and family in both sections. Forty six fish species primarily Cypriniformes and Siluriformes are common to both sections, only 17 in MS and 76 in PS. Orders Tetradontiformes, Osteoglossiformes and Clupeiformes were present in PS only. The taxonomic richness in the MS was low compared to PS. Probably motility and physiological requirements in respect of tolerance for temperature restrict faunal elements

    Thermoluminescence studies in swift heavy ion irradiated aluminum oxide

    Get PDF
    Thermoluminescence (TL) of combustion-synthesized aluminum oxide bombarded with 120 MeV swift Au9 + ions in the fluence range of 1 à 1011 - 2 à 1013 ions cm- 2 has been studied at room temperature. Two TL glows-a well-resolved one with peak at ⼠623 K(Tg2) and another unresolved one at ⼠513 K (Tg1)-are recorded at a heating rate of 10 K s- 1. It is found that the TL intensity increases with the fluence up to 1 à 1013 ions cm- 2 and then decreases with increase in fluence. Also, the prominent glow peak temperature (Tg2) is found to be shifted towards the lower temperature region, while the TL intensity increases with the increase in ion fluence. In the case of heat-treated samples, the TL intensity is observed to be enhanced further. However, in the case of samples heat-treated beyond 973 K, the TL intensity is found to be decreased with the increase in heat treatment. The glow curves are analyzed by the glow curve deconvolution technique and trap parameters are estimated and discussed in this paper. © 2008 Elsevier Ltd. All rights reserved

    SHI induced thermoluminescence properties of sol-gel derived Y2O3:Er3+ nanophosphor

    Get PDF
    Nanocrystalline erbium doped yttrium oxide (Y2O3:Er3+) was synthesized by the sol-gel technique using citric acid as complexing agent. The synthesized samples were characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM) techniques for phase-purity and microstructure. Er3+ doped Y2O3 crystallizes in cubic phase with an average crystallite size of 24.3 nm. The pellets of Y2O3:Er3+ were irradiated with 100 MeV swift Si8+ ions with fluence in the range of 3×1011 - 3×1013 ions cm-2. Three well resolved thermoluminescence (TL) glows with peaks at ~422, 525 and 620 K were observed in Er3+ doped Y2O3 samples. It was observed that the TL intensity was found to increases with increasing Er3+ concentration up to 0.4 mol% in Y2O3 and thereafter it decreases with further increase of Er3+ concentration. Also, the intensity of low temperature TL glow peak (~422 K) increases with increasing ion fluence up to 1×1012 ions cm-2 and decreases with further increase of ion fluences. The TL trap parameters were calculated by glow curve shape method and the deconvoluted glows were exhibit of second order kinetics. Copyright © 2015 VBRI press. - See more at

    Ion Beam Induced Cubic To Monoclinic Phase Transformation of Nanocrystalline Yttria

    Get PDF
    Sol gel derived nanocrystalline yttria pellets are irradiated with 120 MeV Ag9+ ions for fluence in the range 1 � 1012–3 � 1013 ions cm2 . Pristine and irradiated samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. XRD pattern of pristine Y2O3 nanocrystal reveal cubic structure. A new XRD peak at 30.36� is observed in pellet irradiated with 1 � 1013 ions cm2 . The peak at 30.36� is corresponding to ð4 0 � 2Þ plane of monoclinic phase. The diffraction intensity of ð4 0 � 2Þ plane increases with Ag9+ ion fluence. Raman spectrum of pristine pellet show bands corresponding to cubic phase. And, ion irradiated sample show new peaks at 410, 514 and 641 cm1 corresponding monoclinic phase. HR-TEM and SAED pattern of ion irradiated sample confirmed the presence of monoclinic phase. Hence, it is confirmed that, 120 MeV Ag9+ ions induce phase transformation in nanocrystalline Y2O3

    Ion beam induced luminescence studies of sol gel derived Y2O3:Dy3+ nanophosphors

    Get PDF
    Pure and Dy3+ doped Y2O3 are prepared by sol-gel technique. The samples are annealed at 900 °C to obtain crystalline phase. X-ray diffraction (XRD) patterns confirm cubic phase of Y2O3. The crystallites size is calculated using Scherrer formula and is found to be in the order of 29.67 nm. The particles are found to be spherical in nature and their sizes are estimated to be 35 nm by scanning electron microscope (SEM) technique. Online ionoluminescence (IL) spectra of pure and Dy3+ doped Y2O3 are recorded with 100 MeV Si8+ ions with fluence in the range 0.375-6.75×1013 ions cm-2. Undoped samples do not show IL emission for any of the fluence explored. Four prominent IL emissions with peaks at 488, 670, 767 nm and a prominent pair at 574 and 584 nm are observed in Dy3+ doped samples. These characteristic emissions are attributed to luminescence centers activated by Dy3+ ions due to 4F9/2→6H15/2, 4F9/2→6H11/2, 4F9/2→6H9/2+6H11/2 and 4F9/2→6H13/2 transitions respectively. Further, it is found that IL intensity at 574 nm decays rapidly with ion fluence. A broad and weak photoluminescence (PL) emission with peak at ~485 nm and a strong emission at 573 nm are observed in ion irradiated Y2O3:Dy3+. It is found that PL intensity increases with ion fluence up to 3×1010 ions cm-2 and then it decreases with further increase of ion fluence. This may be attributed to lattice disorder produced by dense electronic excitation under swift heavy ion irradiation. © 2015 Elsevier B.V

    Synthesis characterization and luminescence studies of gamma irradiated nanocrystalline yttrium oxide

    Get PDF
    Nanocrystalline Y2O3 is synthesized by solution Combustion technique using urea and glycine as fuels. X-ray diffraction (XRD) pattern of as prepared sample shows amorphous nature while annealed samples show cubic nature.The average crystallite size is calculated using Scherrer's formula and is found to be in the range 14–30 nmfor samples synthesized using urea and 15–20 nm for samples synthesized using glycine respectively. Field emissionscanning electron microscopy (FE-SEM) image of 1173 K annealed Y2O3 samples show well separated sphericalshape particles and the average particle size is found to be in the range 28–35 nm. Fourier transformed infrared (FTIR) and Raman spectroscopy reveals a stretching of Y–O bond. Electron spin resonance (ESR) shows V− center, O2 − and Y2+ defects. A broad photoluminescence (PL) emission with peak at ~386 nm is observed when the sample is excited with 252 nm. Thermoluminescence (TL) properties of γ-irradiated Y2O3 nanopowder are studied at a heating rate of 5 K s−1 . The samples prepared by using urea show a prominent and well resolved peak at ~383 K and a weak one at ~570 K. It is also found that TL glow peak intensity (Im1) at ~383 K increases with increase in γ-dose up to ~6.0 kGy and then decreases with increase in dose. However, glycine used Y2O3 shows a prominent TL glow with peaks at 396 K and 590 K. Among the fuels, urea used Y2O3 shows simple and well resolved TL glows. This might be due to fuel and hence particle size effect. The kinetic parameters are calculated by Chen's glow curve peak shape method and results are discussed in detai

    Optical absorption and thermoluminescence studies in 100MeV swift heavy ion irradiated CaF 2 crystals

    Get PDF
    Pure and Ytterbium (Yb) doped Calcium fluoride (CaF2) single crystals were irradiated with 100 MeV Ni7+ ions for fluences in the range 5 × 1011–2.5 × 1013 ions cm−2. The irradiated crystals were characterized by Optical absorption (OA) and Thermoluminescence (TL) techniques. The OA spectra of ion irradiated pure CaF2 crystals showed a broad absorption with peak at ∼556 nm and a weak one at ∼220 nm, whereas the Yb doped crystals showed two strong absorption bands at ∼300 and 550 nm. From the study of OA spectra, the defect centers responsible for the absorption were identified. TL measurements of Ni7+ ion irradiated pure CaF2 samples indicated a strong TL glow with peak at ∼510 K. However, the Yb doped crystals showed two TL glows at ∼406 and 496 K. The OA and TL intensity were found to increase with increase of ion fluence upto 1 × 1013 ions cm−2 and thereafter it decreased with further increase of fluence. The results obtained are discussed in detail

    Synthesis characterization and luminescence studies of 100 MeV Si 8+ ion irradiated sol gel derived nanocrystalline Y2O 3

    Get PDF
    Nanoparticles of pure yttrium oxide (Y2O3) have been prepared by sol gel method. The powder X-ray diffraction (PXRD) pattern of as synthesized sample showed the amorphous nature. The as synthesized Y2O3 powders are annealed at 500, 600, 700, 800 and 900 °C for 2 h. Y2O3 powder heat treated for 600 °C showed cubic phase and the crystallite sizes are found to be ∼13 nm. Fourier transformed infrared spectroscopy (FTIR) revealed absorption with peaks at 3434, 1724, 1525, 1400, 847, 562 and 465 cm−1. Photoluminescence (PL) of 100 MeV Si8+ ion irradiated samples shows emission with peaks at 417, 432, 465 nm. It is found that PL intensity increases with increasing in ion fluence up to ∼3 × 1012 ions cm−2 and then decreases with further increase in ion fluence. A well resolved thermoluminescence (TL) glow with peak at ∼430 K (Tm1) and an unresolved TL glow with peak at ∼538 (Tm2), 584 K (Tm3) are observed in ion irradiated samples

    Luminescence studies of 100Â MeV Si8+ ion irradiated nanocrystalline Y2O3

    Get PDF
    Combustion synthesized Y2O3 revealed cubic structure and the average cry stallite size is found to be 32.73 nm. FTIR spectra revealed YeO, OH stretching and CeO bending bonds. Y2O3 pellets are irradiated with 100 MeV Si8þions in the fluence range 11010 to 11014ions cm2. PL of irradiated samples shows emission with peaks at 417, 432, 465 nm. Y 2O3 shows a prominent well resolved TL glow with peak at 403 K (Tm1) and a weak TL peak at 461 K (Tm2). TL intensity in the present work increases up to about 11011ions cm2 there after it decreases. The TL kinetic parameters are calculated by glow peak shape method. Activation energy and frequency factors are found to in the range of w1.6 eV andw 1018 s1 respectively
    • …
    corecore