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1.
ABSTRACT

The results of Raman spectroscopy and electrical measurements of 40 keV boron-ion-implanted polymethylmethacrylate with ion doses from 6.25 × 1014 to 5.0 × 1016 ions/cm2 are reported for the first time. The Raman spectra recorded in the 400–3800 cm?1 range, showing the formation of new carbon–carbon bands for the as-implanted samples at higher ion doses (>1016 ions/cm2), are found to be an additional support for carbonization processes earlier revealed by slow positrons. The current–voltage dependences at 360 K testify also that the as-implanted samples examined with higher fluences (3.75 × 1016 and 5.0 × 1016 ions/cm2) have created a very thin conductive layer or conductive joints due to carbonization.  相似文献   

2.
Influence of In3+ ions on electrochemical performance of positive electrolyte for vanadium redox flow battery was investigated in this paper. The electrochemical activity and kinetics of V(IV)/V(V) redox couple can be enhanced by the addition of In3+ ions, and the optimal concentration of In3+ ions was found at 10 mM. At this condition, the oxidation peak current with 10 mM In3+ ions is 46.6 mA at a scan rate of 20 mV s?1, larger than that of pristine electrolyte (41.8 mA), and the standard rate constant is 6.53?×?10?5 cm s?1, 42 % larger than that of the pristine electrolyte (4.58?×?10?5 cm s?1). The cell using electrolyte with 10 mM In3+ ions was assembled, and the charge–discharge performance was evaluated, and the average energy efficiency increases by 1.9 % compared with the pristine cell. The improved electrochemical performance may be ascribed to that In3+ ions change the hydration state of vanadium ions in electrolyte and promote charge transfer process.  相似文献   

3.
SnO2 thin films grown on glass substrates at 300 °C by reactive thermal evaporation and annealed at 600 °C were irradiated by 120 MeV Ag9+ ions. Though irradiation is known to induce lattice disorder and suppression of crystallinity, we observe grain growth at a certain fluence of irradiation. X-ray diffraction (XRD) revealed the crystalline nature of the films. The particle size estimated by Scherrer’s formula for the irradiated films was in the range 10–25 nm. The crystallite size increases with increase in fluence up to 1×1012 ions?cm?2, whereas after that the size starts decreasing. Atomic force microscope (AFM) results showed the surface modification of nanostructures for films irradiated with fluences of 1×1011 ions?cm?2 to 1×1013 ions?cm?2. The UV–visible spectrum showed the band gap of the irradiated films in the range of 3.56 eV–3.95 eV. The resistivity decreases with fluence up to 5×1012 ions?cm?2 and starts increasing after that. Rutherford Backscattering (RBS) reveals the composition of the films and sputtering of ions due to irradiation at higher fluence.  相似文献   

4.
Makrofol-N polycarbonate was irradiated with carbon (70 MeV) and copper (120 MeV) ions to analyze the induced effects with respect to optical and structural properties. In the present investigation, the fluence for carbon and copper beams was kept in the range of 1×1011– 1×1013 ions/cm2 to study the swift heavy ion induced modifications. UV–VIS, FTIR and XRD techniques were utilized to study the induced changes. The analysis of UV–VIS absorption studies revealed that the optical energy gap was reduced by 17% on carbon irradiation, whereas the copper beam leads to a decrease of 52% at the highest fluence of 1×1013 ions/cm2. The band gap can be correlated to the number of carbon atoms, N, in a cluster with a modified Robertson's equation. In copper (120 MeV) ions irradiated polycarbonate, the number of carbon atoms in a cluster was increased from 63 to 269 with the increase of ion fluence from 0 to 1×1013 ions/cm2, whereas N is raised only up to 91 when the same polymer films were irradiated with carbon (70 MeV) ions under similar conditions. FTIR analysis showed a decrease in almost all characteristic absorption bands under irradiation. The formation of hydroxyl (? OH) and alkene (C?C) groups were observed in Makrofol-N at higher fluence on irradiation with both types of ions, while the formation alkyne end (R? C≡ CH) group was observed only after copper ions irradiation. The radii of the alkyne production of about 3.3 nm were deduced for copper (120 MeV) ions. XRD measurements show a decrease in intensity of the main peak and an increase of the average intermolecular spacing with the increase of ion fluence, which may be attributed to the structural degradation of Makrofol-N on swift ion irradiation.  相似文献   

5.
A. K. Nath  A. Kumar 《Ionics》2014,20(12):1711-1721
Swift heavy ion (SHI) irradiation has been used as a tool to enhance the electrochemical properties of ionic liquid-based nanocomposite polymer electrolytes dispersed with dedoped polyaniline (PAni) nanorods; 100 MeV Si9+ ions with four different fluences of 5?×?1010, 1?×?1011, 5?×?1011, and 1?×?1012 ions cm?2 have been used as SHI. XRD results depict that with increasing ion fluence, crystallinity decreases due to chain scission up to fluence of 5?×?1011 ions cm?2, and at higher fluence, crystallinity increases due to cross-linking of polymer chains. Ionic conductivity, electrochemical stability, and dielectric properties are enhanced with increasing ion fluence attaining maximum value at the fluence of 5?×?1011 ions cm?2 and subsequently decrease. Optimum ionic conductivity of 1.5?×?10?2 S cm?1 and electrochemical stability up to 6.3 V have been obtained at the fluence of 5?×?1011 ions cm?2. Ac conductivity studies show that ion conduction takes place through hopping of ions from one coordination site to the other. On SHI irradiation, amorphicity of the polymer matrix increases resulting in increased segmental motion which facilitates ion hopping leading to an increase in ionic conductivity. Thermogravimetric analysis (TGA) measurements show that SHI-irradiated nanocomposite polymer electrolytes are thermally stable up to 240–260 °C.  相似文献   

6.
A high-frequency (208 GHz) electron paramagnetic resonance (EPR) study on Mn3+ (3d4, S = 2) ions embedded in a MnMo6Se8 single crystal has been performed at 10 K. The experimental spectra reveal the presence of only one set of EPR lines from Mn3+ ions, whose magnetic axes are oriented along the crystal axes. The spin-Hamiltonian parameters are evaluated by the method of least-squares, fitting all the observed line positions simultaneously, for the three orthogonal orientations of the external magnetic field. The symmetry of the spin Hamiltonian at the site of the Mn3+ ions has been deduced from the EPR spectra.  相似文献   

7.
Bay functionalized perylene diimide substituted with pyridine isomers, (2-pyridine (2HMP-PDI), 3-pyridine (3-HMP-PDI) and 4-pyridine (4-HMP-PDI)) have been synthesized and explored for selective coloro/fluorimetric sensing of heavy transition metal ions. HMP-PDIs showed strong NIR absorption (760–765 nm) in DMF. The absorption and fluorescence of HMP-PDIs have been tuned by make use of pyridine isomers. Reddish-orange color was observed for 2-HMP-PDI (λmax = 437, 551, 765 nm) whereas 4-HMP-PDI exhibited light green (λmax = 432, 522, 765 nm). 3-HMP-PDI showed orange-yellow (λmax = 431, 524, 762 nm). The fluorescence spectra of 2-, 3- and 4-HMP-PDI showed λmax at 585, 538, 546 nm, respectively. Interestingly, HMP-PDI dyes showed selective color change (intense pink color) and fluorescence quenching for Fe3+ and Al3+ metal ions in DMF. Absorbance spectra revealed complete disappearance of NIR absorption and intensification/appearance of new peak at lower wavelength. The concentration dependent studies suggest that 4-HMP-PDI can detect up to 36.52 ppb of Fe3+ and 43.12 ppb of Al3+ colorimetrically. The interference studies in presence of other metal ions confirmed the good selectivity for Fe3+ and Al3+. The mechanistic studies indicate that Lewis acidic character of Fe3+ and Al3+ ions were responsible for selective color change and fluorescence quenching.  相似文献   

8.
ZnO thin films, irradiated by 80 MeV Ni+ ions, were analysed with the help of different characterization techniques like X-ray diffraction, optical absorption, transmission, photoluminescence (PL), electrical resistivity, photosensitivity (PS) and thermally stimulated current (TSC) measurements. Crystallinity and absorption edge were hardly affected by irradiation. PL spectrum of pristine sample showed a broad peak at 517 nm, whereas irradiated film had two emissions at 517 and 590 nm. Intensity ratio between these two emissions (I517/I590) decreased with the fluence, and finally at a fluence of 3×1013 ions/cm2, the emission at 517 nm completely disappeared. Electrical resistivity of the sample irradiated with a fluence of 1×1013 ions/cm2 drastically increased. However, on increasing the fluence to 3×1013 ions/cm2, resistivity decreased, probably due the onset of hopping conduction through defects. PS also decreased due to irradiation. TSC measurements on pristine sample could reveal only one defect level at 0.6 eV, due to interstitia1 zinc (ZnI). But, irradiation at a fluence of 1×1012 ions/cm2, resulted in three different defect levels as per TSC studies. Interestingly, the sample irradiated at a fluence of 3×1013 ions/cm2 had only one defect level corresponding to a deep donor. The possible origin of these defect levels is also discussed in the paper.  相似文献   

9.
Erbium–nitrogen codoped zinc oxide nanowires of ytterbium-doped are prepared by thermal evaporation and ion implantation methods. Ytterbium ions are doped into nanowires at a fluence of (0, 1, 3, 5, and 9) × 1015 cm?2. Microstructural and optical properties of specimen are investigated by X-ray diffractometer, absorption spectra, Raman, and upconversion photoluminescence examinations. Upconversion photoluminescence emissions at 550 nm and 660 nm are obtained under 980-nm light excitation. Both intensities of green and red peaks are enhanced by the introduction of ytterbium ions. When ytterbium ion fluence is 5 × 1015 cm?2, light emission intensity reaches maximum value. The energy transfer and cross-relaxation processes are responsible for the change of emission intensity.  相似文献   

10.
Gd2O3:Eu3+ (4 mol%) co-doped with Bi3+ (Bi = 0, 1, 3, 5, 7, 9 and 11 mol%) ions were synthesized by a low-temperature solution combustion method. The powders were calcined at 800°C and were characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), Fourier transform infrared and UV–Vis spectroscopy. The PXRD profiles confirm that the calcined products were in monoclinic with little cubic phases. The particle sizes were estimated using Scherrer’s method and Williamson–Hall plots and are found to be in the ranges 40–60 nm and 30–80 nm, respectively. The results are in good agreement with TEM results. The photoluminescence spectra of the synthesized phosphors excited with 230 nm show emission peaks at ~590, 612 and 625 nm, which are due to the transitions 5D07F0, 5D07F2 and 5D07F3 of Eu3+, respectively. It is observed that a significant quenching of Eu3+ emission was observed under 230 nm excitation when Bi3+ was co-doped. On the other hand, upon 350 nm excitation, the luminescent intensity of Eu3+ ions was enhanced by incorporation of Bi3+ (5 mol%) ions. The introduction of Bi3+ ions broadened the excitation band of Eu3+ of which a new strong band occurred ranging from 320 to 380 nm. This has been attributed to the 6s2→6s6p transition of Bi3+ ions, implying a very efficient energy transfer from Bi3+ ions to Eu3+ ions. The gamma radiation response of Gd2O3:Eu3+ exhibited a dosimetrically useful glow peak at 380°C. Using thermoluminescence glow peaks, the trap parameters have been evaluated and discussed. The observed emission characteristics and energy transfer indicate that Gd2O3:Eu3+, Bi3+ phosphors have promising applications in solid-state lighting.  相似文献   

11.
Photoluminescence studies of pure and Dy3+, Eu3+ doped Sr2CeO4 compounds are presented by oxalate precipitation method for solid state lighting. The prepared samples also characterized by XRD, SEM (EDS) and FTIR spectroscopy. The pure Sr2CeO4 compound displays a broad band in its emission spectrum when excited with 280 nm wavelength, which peaks centered at 488 nm, which is due to the energy transfer between the molecular orbital of the ligand and charge transfer state of the Ce4+ ions. Emission spectra of Sr2CeO4 with different concentration of Dy3+ ions under near UV radiation excitation, shows that intensity of luminescence spectra is found to be affected by Dy3+ ions, and it increases with adding some percentages of Dy3+ ions. The maximum doping concentration for quenching is found to be Dy3+?=?0.2 mol % to Sr2+ions. The observed broad spectrum from 400 to 560 nm is mainly due to CT transitions in Sr2CeO4 matrix and some fractional contribution of transitions between 4F9/26H15/2 of Dy3+ ions. Secondly the effect of Eu3+ doping at the Sr2+ site in Sr2CeO4, have been studied. The results obtained by doping Eu3+ concentrations (0.2 mol% to 1.5 mol%), the observed excitation and emission spectra reveal excellent energy transfer between Ce4+ and Eu3+. The phenomena of concentration quenching are explained on the basis of electron phonon coupling and multipolar interaction. This energy transfer generates white light with a color tuning from blue to red, the tuning being dependent on the Eu3+ concentration. The results establish that the compound Sr2CeO4 with Eu3+?=?1 mol% is an efficient “single host lattice” for the generation of white lights under near UV-LED and blue LED irradiation. The commission internationale de I’Eclairage (CIE) coordinates were calculated by Spectrophotometric method using the spectral energy distribution of prepared phosphors.  相似文献   

12.
High-frequency (236 GHz) electron paramagnetic resonance (EPR) studies of Fe3+ ions at 255 K are reported in a Sn1?x Fe x O2 powder with x = 0.005, which is a ferromagnetic semiconductor at room temperature. The observed EPR spectrum can be simulated reasonably well as the overlap of spectra due to four magnetically inequivalent high-spin (HS) Fe3+ ions (S = 5/2). The spectrum intensity is calculated, using the overlap I(BL) + (I(HS1) + I(HS2) + I(HS3) + I(HS4)) × exp(?0.00001B), where B is the magnetic field intensity in Gauss, I represents the intensity of an EPR line (HS1, HS2, HS3, HS4), and BL stands for the baseline (the exponential factor, as found by fitting to the experimental spectrum, is related to the Boltzmann population distribution of energy levels at 255 K, which is the temperature of the sample in the spectrometer). These high-frequency EPR results are significantly different from those at X-band. The large values of the zero-field splitting parameter (D) observed here for the four centers at the high frequency of 236 GHz are beyond the capability of X-band, which can only record spectra of ions with much smaller D values than those reported here.  相似文献   

13.
Low-temperature (40 K) photoluminescence (PL) measurements were used to follow the defect formation induced in the 4H-SiC epitaxial layer by irradiation with 200 keV H+ and 800 keV C+ in the fluence range of 5×109–3.5×1012 ions/cm2. After irradiation, the PL spectra show the formation of some sharp lines, called “alphabet lines”, located in the wavelength range of 425–443 nm, due to the recombination of excitons at structural defects induced by ion beams. The analysis of luminescence line intensity versus ion fluence allows us to mark two different groups of peaks, namely the P1 group (e, f and g lines) and the P2 group (a, b, c and d lines). The normalised yield of P1 group lines increases with ion fluence and reaches a maximum value, while the normalised yield of P2 group lines exhibits a threshold fluence and then increases until a saturation value is reached. These different trends indicate that, while the P1 group lines are related to the primary defects created by ion beams (interstitial defects, vacancies), the P2 group lines can be associated with some complex defects (divacancy, antisites). The trends are similar for irradiation with H+ and C+ ions; however, the defect formation occurs in the fluence range of 5×109–1011 ions/cm2 for C+ irradiation and 1011–4×1012 ions/cm2 for H+ irradiation. Taking into account the different values of energy deposited in elastic collision, a dependence on the ion type was found: the C+ ion results in being less effective in defect production as a higher defect recombination occurs inside its dense cascade.  相似文献   

14.
Single crystal of La3Ga5.5Ta0.5O14 (LGT) containing intentionally 0.5 % of Ho3+ and 1 % of Yb3+ was grown by the Czochralski method. Examination of chemical composition of the grown crystal revealed that luminescent holmium and ytterbium ions are preferably retained in the melt and their actual concentrations are 0.12 and 0.24 %, respectively. Spectroscopic investigation performed encompassed IR host absorption spectra and Raman spectra at room temperature, optical absorption and luminescence spectra of Ho3+ and Yb3+ at room temperature and at 5 K, and luminescence decay curves at room temperature. It was found that all spectral bands recorded show important inhomogeneous line broadening. This feature was attributed to structural disorder inherent to the crystal lattice in which pentavalent Ta5+ ions occupy octahedral Ga(1) sites together with trivalent Ga3+ ions. Despite small concentrations of luminescent ions, the occurrence of nonradiative interaction that feeds the 5I6 and 5I7 levels of Ho3+ ions by transfer of an excitation from the 2F5/2 level of Yb3+ ions was evidenced. Based on examination of spectroscopic parameters evaluated, it was concluded that LGT:Ho, Yb may be considered as a potential intermediate-gain laser active material able to emit infrared radiation from the 5I7 → 5I8 transition of Ho3+ around 2 micrometres upon laser-diode pumping into Yb3+ absorption band.  相似文献   

15.
Samples of polystyrene (PS) have been irradiated with 64Cu (50 and 120 MeV) and 12C (70 MeV) ion beams (fluence=1011 to 1013 ions cm?2) in order to study the induced modifications using UV‐VIS and FTIR spectroscopy. UV spectra of irradiated samples reveal that the optical band gap decreases from 4.36 to 1.46 eV in PS. The decrease in optical band gap is more pronounced with the Cu‐ion beam due to high electronic energy loss as compared to the C ion beam. The effect of low energy (50 MeV) Cu ions on the optical properties of PS is larger than that due to high energy (120 MeV) Cu ions. The correlation between the optical band gap and the number of six member carbon rings inside the largest carbon clusters embedded in the network of polystyrene is discussed. FTIR spectra reveal the formation of hydroxyl, alkene, and alkyne groups in the Cu‐ion irradiated PS. Changes in the intensity of the absorption bands on irradiation with C‐ion relative to pristine samples have also been observed and are discussed.  相似文献   

16.
《光谱学快报》2013,46(4):401-420
Abstract

A spectrophotometric method for the determination of titanium(IV) is described. It is based on the extraction of titanium(IV) as an ion‐associated complex, formed between the titanium(IV)–thiocyanate anion and the cetyltrimethylammonium (CTMA), cetylpyridinium (CP), or tetradecyldimethylbenzylammonium (TDMA) cation in chloroform or dichloromethane. Optimum conditions for the extraction and spectrophotometric determination of titanium(IV) by all extractants were determined. The effect of chloride ions on the extraction was also examined. In their presence the systems studied were most sensitive. The apparent molar absorptivities of the complex, at 420 nm, and limit of detection, in the presence of chloride ions, were (6–7) × 104 L mol?1 cm?1 and 20–35 ng Ti(IV) mL?1, respectively, depending upon the reagent used. Titanium determination was feasible in the presence of many foreign ions. The ratios of titanium(IV) and CTMA, CP or TDMA determined by Job's method were 1:2. The validity of the method was tested on bauxite and aluminum alloy samples. The values determined were in good agreement with the certified values.  相似文献   

17.
This report discusses the preparation and microstructure of Co/Ni co-doped MgGa2O4 nanoparticles. The nanoparticles with the size of 20–55 nm were synthesized by sol-gel method. The phase and crystallinity were confirmed by X-ray powder diffraction (XRD) pattern. The particle size was estimated according to XRD data and transmission electron microscopy. The electronic structure was studied using X-ray photoelectron spectroscopy (XPS). The XPS studies showed that Ga3+ ions possess tetrahedral and octahedral sites of spinel structure and the inverse degree (two times of the fraction of tetrahedral Ga3+ ions) has increased with the increase of the doping concentration of Co2+ and Ni2+ ions. For Co/Ni co-doped MgGa2O4, two broad absorption bands of 350~500 and 550~700 nm were observed in the absorption spectra. The broad band at 350~500 nm was assigned to the combination of the absorption of octahedral Co2+ and Ni2+ ions, whereas the absorption band at 550~700 nm is mainly due to tetrahedrally coordinated Co2+ ions and octahedrally coordinated Ni2+ ions.  相似文献   

18.
Polyvinylidene difluoride (PVDF)–lithium bis(oxalato)borate (LiBOB) solid polymer electrolytes (SPEs) have been prepared by solution casting. The highest ionic conductivity achieved is 3.4610?3 S cm?1. Electrochemical potential window of the SPEs is found around 4.7 V. Interaction between PVDF and LiBOB is studied systematically. The changes of C–C, CF2, and CH2 vibration modes with an emerging shoulder are analyzed. At higher salt content, this shoulder becomes more prominent peak at the expense of CF2 vibration mode. This suggests the possible Li+?F coordination. Deconvolution of IR spectra region from 1750 to 1850 cm?1 has been carried out to estimate the relative percentage of free ions and contact ions. The finding is in good agreement with conductivity and XRD results. When more salt is present, the number of free ions percentage increases and the Full width at half-maximum (FWHM) of (110) plane is broadening. The Li+?F interaction breaks the folding patterns of polymer chain and enhances amorphousness domain.  相似文献   

19.
The present work is devoted to investigation of optical absorption in pure and neodymium-doped YAlO3 (YAP) single crystals in the spectral range 0.2–1.1 μm induced by the influence of 12C ions irradiation with energy 4.50 MeV/u (MeV per nucleon) and a fluence 2 × 109 cm?2 or of 235U ion irradiation with energy 9.35 MeV/u and a fluence 5 × 1011 cm?2. The induced absorption in the case of 12C ions irradiation is caused by recharging of point growth defects and impurities under the radiation influence. After irradiation by 235U ions with fluence 5 × 1011 cm?2 the strong absorption rise is probably caused by contribution of the lattice destruction as a result of heavy ion bombardment.  相似文献   

20.
Defects induced in Y3Al5O12 single crystals by swift heavy ions are investigated by X-ray diffraction (XRD) and atomic force microscopy. The irradiation was performed at GANIL with 561 MeV 51Cr, 466 MeV 128Te, and 957 MeV 208Pb ions. The XRD data reveal that the lattice strain increases with increasing electronic stopping power, whereas the hillock parameters (height and diameter) are not influenced by the electronic stopping power. According to our experimental data, for the same mean electronic stopping power, the hillock parameters are more pronounced for the lower range in contrast to swelling measurements. The experimental data show a strong increase in the hillock parameter at higher fluence, indicating the amorphization of Y3Al5O12 single crystals.  相似文献   

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