Comparative Study of Impact of Gamma and MeV Ion Irradiations on Electrical and Optical Properties Polystyrene/Eu2O3 Nanocomposites.

In the present study, the effect of gamma irradiation and 90 MeV carbon ion beam irradiation on electrical properties and optical of Polystyrene/Eu2O3 nanocomposites at different fluences were examined. Modified electrical and optical responses of polymer nanocomposites were investigated using Impedance, Photoluminescence and UV-VIS spectroscopies. FTIR analysis shows a reduction of various modes of molecular vibrations caused by 90 MeV carbon ion beam irradiation. The polymer nanocomposites change into a graphite-like structure upon both kinds of irradiations as evidenced by the decrease in the optical band gap. The photoluminescence emission spectra show three characteristic peaks of Eu3+ ions, when excited at 247 nm wavelength. It emits intense red light suggesting its potential for usage in LED technology. The peak intensity of PL emission spectra is enhanced after ion beam irradiation and is because of the formation new radiative combination; however, it decreases upon gamma irradiation. Dielectric responses of pristine and irradiated polymer nanocomposites were studied over the frequency range of 100 Hz to 100 kHz using LCR meter. There appears a significant improvement in the dielectric response as a result of structural changes in both types of irradiations. AFM images show that the film becomes smoother upon both types of irradiations.

Activation cross section for the (n,2n) and (n,p) reactions on 103Rh, 48Ti and 52Cr from reaction threshold up to 25 MeV energy region.

Activation and off-line γ-ray spectrometric methods were used to measure the ground and isomeric state (n,2n) reaction cross section for 103Rh at two different neutron energies. The standard 27Al (n,α)24Na reference reaction was used to normalise neutron flux. The proton beam from the 14UD BARC-TIFR Pelletron facility in Mumbai, India, was utilised to create high-energy quasi-monoenergetic neutrons via the 7Li (p,n) reaction. Statistical model calculations including the level density, pre-equilibrium and optical potential model were performed using the TALYS (ver. 1.95) and EMPIRE (ver. 3.2.3) reaction codes. In addition, because of considerable discrepancies in measured data, the literature (n,p) reaction cross section of 52Cr and 48Ti targets were examined theoretically in the present work. The measured cross sections are discussed and compared with the latest evaluated data of the FENDL-3.2b, CENDL-3.2, TENDL-2019, JENDL-5.0, and ENDF/B-VIII.0 libraries, and experimental data based on the EXFOR compilation. The theoretical investigation of the (n,2n) reaction cross section was performed for the ground and isomeric state for the first time from reaction threshold to 25 MeV energies. The experimental data corresponding to the ground, isomeric state and isomeric ratio were reproduced consistently by the theoretical calculations. The present experimental results are good with certain literature data and theoretical values.

Cross-section of (n,2n) reaction for niobium and strontium isotopes between 13.97 to 20.02 MeV neutron energies.

The activation cross-sections of 93Nb(n,2n)92Nbm and 88Sr(n,2n)87Srm reactions were measured using the activation and off-line γ-ray spectrometry technique in the neutron energy range 13.97-20.02 MeV. The present measurements have been done at the neutron energies where there are deficiencies and scarcity in the reaction cross-section data. The neutron flux was determined using the 27Al(n,α)24Na monitor reaction. The γ-ray self-attenuation effect and the low energy background neutron corrections were done in this experiment. The results of the present work were compared with the previously published data and evaluated nuclear data libraries. Theoretically, the cross-section for 93Nb(n,2n)92Nbm and 88Sr(n,2n)87Srm reactions was predicted by TALYS-1.9 nuclear code and compared with the present results.

Effect of γ-irradiation on thermal and thermoluminescence properties of polystyrene/europium (III) oxide composite film.

In the present study, polystyrene:europium (III) oxide polymer films at a ratio of 95:5 wt% were prepared using a solution casting technique. These polymeric films were irradiated with 5, 25 and 50 kGy γ-radiation doses and their thermoluminescence (TL) and thermal properties were studied as a function of radiation dose. Analysis of Fourier transform infrared spectra revealed different modes of vibration and polymer-filler interaction. Reduction of vibrational modes with radiation dose was observed. The TL glow curve intensity was observed to increase with increasing radiation dose and to become broader in the 378 K and 444 K regions. Detrapping of electrons implied by the glow curve was caused by thermally induced macromolecular motion, concurrent with ß-relaxation in polystyrene. The TL glow curve parameters were computed using a glow curve deconvolution method. Differential scanning calorimetry analysis indicated that the glass transition temperature (Tg ) increased with increase in dose, suggesting crosslinking of the polymer chain. Scanning electron microscopy analysis evidenced the change in surface morphology due to γ-irradiation.

Measurement of neutron induced 86Sr(n, 2n)85Sr reaction cross sections at different neutron energies.

The cross-sections for 86Sr (n, 2n)85Sr reaction are measured at neutron energies 19.44 ±â€¯1.02 MeV and 16.81 ±â€¯0.85 MeV wherein there is scarcity of data. The standard neutron activation analysis technique and offline gamma ray spectroscopy have been employed for measurement and analysis of the data. The results are compared with experimental data available in EXFOR database, JEFF-3.3, JENDL-4.0, TENDL-2017 and ENDF/B-VIII.0 evaluated data. The theoretical prediction was incorporated using nuclear modular codes TALYS 1.8 and EMPIRE 3.2.2. A detailed comparative study of experimental results with the theoretical models and various major evaluations has been presented.

Proton Beam Induced Modification of Luminescence Properties of Polystyrene/Al2O3 Polymer Nanocomposites.

Polystyrene polymer (PS)/Al2O3 nanocomposite films were synthesized from PS:Al2O3 (1-x):x mixtures (x = 3 wt%) via solution casting method. These nanocomposite films were exposed to 5 MeV proton beam of different fluences. The proton beam induced changes in optical and luminescence properties of PS and PS:Al2O3 films have been investigated using FTIR, UV-visible, Photoluminescence and thermoluminescence studies. FTIR studies concede reduction in the peak intensity due to doping of Al2O3 and proton irradiation. The UV-visible spectra show shifting of absorption edge with increasing fluence. This can be attributed to creation of conjugated system of bonds. The band gap of PS and 3 wt% Al2O3 doped PS is observed to be 4.38 eV and 4.34 eV, respectively, whereas the band gaps of proton irradiated 3 wt% Al2O3 doped PS films are found to be 4.28 eV and 4.23 eV at the fluences of 1 × 1012 ions/cm2 and 1 × 1013 ions/cm2, respectively. The photoluminescence emission spectra show three peaks, wavelength at 411 nm, 435 nm and 462 nm corresponding to the PS in violet-blue region when excited with near UV wavelength of 380 nm. The intensity of emission peaks was found to increase with increasing fluence. The thermoluminescence curves of PS/Al2O3 were analysed using glow curve deconvolution method (GCD). The increase in TL peak intensity of the glow curve was observed as fluence increase.

Measurement of 232Th and 238U neutron capture cross-sections in the energy range 5-17 MeV.

The neutron capture cross sections of 232Th and 238U at the average neutron energies of 5.08 ±â€¯0.17, 8.96 ±â€¯0.77, 12.47 ±â€¯0.83, and 16.63 ±â€¯0.95 MeV have been measured by using the activation technique and off-line γ-ray spectroscopy. The 232Th and 238U were irradiated with neutrons produced from the 7Li(p, n) reaction using the proton energies of 7, 11, 15 and 18.8 MeV from the 14UD BARC-TIFR Pelletron facility in Mumbai, India. Detailed covariance analysis was also performed to evaluate the uncertainties in the measured cross-sections. The excitation function of the 232Th(n, γ) and 238U(n, γ) reactions were calculated using the theoretical model code TALYS-1.9. The experimental and theoretical results from the present work were compared with the ENDF/B-VII-1 and JENDL-4.0 nuclear data libraries and were found to be in good agreement.

Effect of γ-irradiation on optical properties of Eu2 O3 -doped polystyrene polymer films.

In the present study, europium (III) oxide (Eu2 O3 )-doped polystyrene (PS) polymer films were synthesized using a solution-casting technique for different filler levels. These films were irradiated with 5, 25 and 50 kGy γ doses and characterized using various techniques, viz. X-ray diffraction (XRD), and UV-visible and photoluminescence (PL) spectroscopies as a function of composition level and radiation dose. The UV-visible spectra indicated a decrease in the optical direct band gap of composite films with increasing concentrations of dopant and radiation dose. The band gaps of composites obtained using Tauc's equation were found to be 4.38, 4.37, 4.36 and 4.34 eV for 0, 1, 3 and 5% Eu2 O3 -doped PS respectively, while the band gaps of 5% Eu2 O3 -doped PS polymer films irradiated with 5, 25 and 50 kGy were found to be 4.30, 4.26 and 4.21 eV, respectively. Photoluminescence (PL) emission spectra showed the characteristic peaks of Eu3+ at 595 nm, 612 nm and 617 nm with an excitation wavelength of 247 nm. The intensity of characteristic peaks of Eu3+ was observed to increase with increasing filler concentration, while it was found to decrease with increasing radiation dose. The polymer under study may be useful in accidental dosimetry. As photoluminescence studies are carried out after a gap of 200 h from irradiation and PL emission of γ-irradiated polymer yielded 10 times emission when compared with non-irradiated polymer.

Investigation of (n, p), (n, 2n) reaction cross sections for Sn isotopes for fusion reactor applications.

The compound Nb3Sn possess superconductivity at suitable temperatures, therefore, it is best suited to be used in the toroidal coils of superconducting magnets which holds the fusion plasma and confine it inside the reactor core. The neutron induced reaction cross-sections are required from threshold to 20MeV for different isotopes of Tin (Sn). Since limited data is available for the reactions with the Sn isotopes. Therefore, we have optimized the (n, p) and (n, 2n) reaction cross-sections for all possible Sn isotopes from threshold to 20MeV with modified input parameters in the nuclear reaction modular codes EMPIRE-3.2.2 and TALYS-1.8. These codes account for the major nuclear reaction mechanisms, including direct, pre-equilibrium, and compound nucleus contributions. The present results from 116Sn(n,p)116mIn, , 117Sn(n,p)117mIn, 118Sn(n,2n)117mSn,120Sn(n,2n)119mSn and 124Sn(n,2n)123mSn reactions calculated with nuclear modular codes: TALYS - 1.8, EMPIRE - 3.2.2 were compared with EXFOR data, systematics proposed by several authors and with the existing evaluated nuclear data library ENDF/B-VII.1, as well. The results from the present study can be used for the future development of ITER devices as well as to upgrade the nuclear model codes.

Modification of Optical, Structural and Dielectric Properties of MeV Ions Irradiated PS/Cu Nanocomposites.

In order to study structural, thermal, optical and dielectric behaviors of composites, the films of Cu/polystyrene nanocomposites were synthesized at different concentrations of Cu-nanoparticles. These polymer nanocomposites were irradiated with carbon (85 MeV) and silicon (120 MeV) ions at different fluences. The samples were characterized using different techniques viz: X-ray diffraction, UV-visible spectroscopy, differential scanning calorimetry, and impedance gain phase analyzer. A noticeable increase in the intensity of X-ray diffraction peaks was observed after irradiation with 120 MeV Si-ions, which may be attributed to radiation-induced cross-linking in polymer. Optical properties like band gap was estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength region 200-800 nm. It was found that the band gap value shifted to lower energy (from 4.38 eV to 3.40 eV) on doping with silver nanoparticles and also upon irradiation. Differential scanning calorimetry analysis revealed an increase in the glass transition temperature upon irradiation, which may be attributed to cross linking of polymer chain due to ion beam irradiation which is also corroborated with XRD analysis. Dependence of dielectric properties on frequency, ions and filler concentration was studied. The results revealed the enhancement in dielectric properties after doping nanoparticles and also upon irradiation. It was observed that the effect of Si-beam is more effectual than the C-beam because of large electronic energy loss of heavy ion.

Optical and dielectric properties of ion beam irradiated Ag/polymethyl methacrylate nanocomposites.

Changes in the dielectric, optical, structural and thermal properties of PMMA/silver nanocomposites of different concentrations of silver nanoparticles (5%, 10%, 15%) due to swift heavy ion irradiation were studied by means of impedance gain phase analyzer, UV-visible spectroscopy, X-ray diffraction and differential scanning calorimetry. Samples were irradiated with 120 MeV Si-ions at fluences of 1 x 10(11), 1 x 10(12) ions/cm2. Dependence of dielectric properties on frequency, ion beam fluence and filler concentration was studied. The results revealed the enhancement in dielectric properties after dopping nanoparticles and also upon irradiation. Optical properties like band gap was estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength region 200-800 nm. It was found that the band gap value shifted to lower energy (from 4.58 eV to 3.21 eV) on doping with silver nanoparticles. Differential scanning calorimetry analysis revealed a decrease in the glass transition temperature upon irradiation, which may be attributed to scissioning of polymer chain due to ion beam irradiation which is also confirmed with XRD analysis.