Influence Of Gamma-ray Irradiation Research Articles

Modifications of optical, structural, chemical and morphological properties of molybdenum disulfide (MoS2) sputtered thin films under high dose gamma radiation

Molybdenum disulfide (MoS2) is considered to be a promising member of Transition metal dichalcogenides (TMDCs) displays significant physical and chemical peculiarities that make it promising candidate for extensive applications in nano and micro optoelectronic device applications, energy harvesting and light and gas detection devices. In the present work, we illustrated the influence of gamma ray irradiation on optical, morphological, structural and electronic peculiarities of 2D MoS2 thin films. 2D MoS2 thin films were grown by DC sputtering technique. The synthesized thin films samples were exposed to gamma radiation with 1500 kGy dose. There are significant structural and morphological alterations occur in thin films of MoS2 after exposure to gamma irradiation. From the absorption spectra Urbach energy, indirect optical band gap energy, absorption edge, and extinction coefficient were calculated. Alterations that occur in optical, structural, morphological and electronic parameters after the exposure of gamma irradiation have been corresponding with radiation instigated compositional and structural defects. The peculiarities of virgin and gamma exposed MoS2 thin films with 1500 kGy gamma-ray dose from Co-60 source were studied by UV spectrophotometer, X-ray diffraction (XRD), Rutherford Backscattering Spectroscopy (RBS), X-Ray photoelectron spectroscopy (XPS), Photoluminescence (PL) spectroscopy, Atomic Force Microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR).

Gamma radiation-induced photoluminescence in calcium phosphate glass and inhibiting effect from copper

The influence of gamma-ray irradiation on the optical properties of 50P2O5–30CaO–20Na2O glass and quaternary ones prepared with [CuO]/[Na2O] molar ratios of 0.1, 0.7 and 1.5 at fixed [P2O5]/[CaO] is reported. The glasses prepared by melting were subjected to 100 kGy Co-60 gamma ray irradiation and studied by optical transmission and photoluminescence (PL) spectroscopy. The gamma-irradiated 50P2O5–30CaO–20Na2O ternary developed a ruby-red color and showed absorption features around 425 and 500 nm attributed to oxygen hole centers. The quaternary with [CuO]/[Na2O] molar ratio of 0.1 merely showed a weak absorption feature around 425 nm, whereas the highest molar ratios did not show significant differences relative to the pristine. Analyses of band gap and Urbach energies were made to aid in evaluating radiation-induced changes. Further, the irradiated copper-free glass exhibited a distinct blue luminescence band around 415 nm (not observed prior). It was most favorably excited in the UV at 265 nm, suggesting a phosphorus electron center at its origin. Its decay kinetics appeared relatively slow with a first-order exponential decay with lifetime of 4412 (±4) μs. Conversely, such emission was not detected for the copper-containing glasses, which instead exhibited PL properties comparable to the unirradiated counterparts. Finally, the effect of heat treatment after the gamma ray exposure was evaluated. The radiation-induced color centers showed a bleaching effect whereas the new PL vanished thus supporting the defects-related origin.

Gamma ray irradiation dose dependent methanol sensing with ZnO nanoparticles

This study reports the influence of gamma ray irradiation of various doses in the range of 1–150 kGy on methanol sensing performance and adsorption kinetics of ZnO nanoparticles based sensors. ZnO nanoparticles were synthesized via sol-gel method and characterized with X-ray diffraction (XRD), transmission electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques. The results revealed that the methanol sensing performance of ZnO nanoparticles based sensor including sensitivity, response and recovery times improved by the gamma ray irradiation. Additionally, Elovich equation, Ritchie's equation and pseudo first-order model were selected to follow the methanol adsorption process. The preliminary result of the methanol adsorption kinetic studies revealed that the adsorption kinetics strongly depends on the gamma irradiation dose. Among other kinetic models investigated, the pseudo first-order equation was the best to describe the adsorption kinetics of methanol on ZnO nanoparticles up to 50 kG dose of gamma ray, as evidenced by the highest correlation coefficients. On the other hand, for higher doses than of 50 kGy of gamma irradiation, our analysis showed that Elovich equation generates a straight line that best fit to methanol adsorption data on ZnO nanoparticles.

Influence of Gamma Ray Irradiation on the Optical Properties of Calcite and Dolomite

The class of carbonaceous chondrite meteorites has carbon in their structures, similarly to the terrestrial calcite and dolomite rocks, and contains the group =CO3 linked to Ca and/or Mg, which may be, in principle, more susceptible to the action of the spatial gamma radiation (γ-R) due to the presence of these light-atom elements. On the present work, we used a variety of optical techniques to investigate the possible effects of γ-R produced by an artificial 192Ir source in terrestrial calcite and dolomite, which may allow to understand the effect of the spatial radiation in that celestial bodies of the solar system. As a result, we verified that the γ-R irradiation caused the effect of untrapping of electrons from deep color centers, that spatially migrate to other color centers on the samples, resulting on the change of the electron energetic configuration.

Single Crystals of YAP:Yb for Ultra Short Pulse Lasers

Single crystals of yttrium orthoaluminate activated with Yb3+ ions (YAlO3:Yb) are of high interest for diode pumped high-power ultrafast lasers emitting in the spectral range around 1 µm. The major parameters of lasers achieved so far can be improved by optimizing the activator concentration and improvement of the structural and optical quality of crystals. One of the problems is occurrence of color centers giving rise to absorption bands in the visible range with tails extending to the near IR. In the present work single crystals of YAlO3:Yb were grown by the Bridgman and Czochralski methods. It is found that under the applied growth conditions absorption associated with color centers in the visible range is much lower in YAlO3:Yb crystals grown by the Bridgman method. The differences in optical quality are attributed to the growth atmosphere (Ar/H2 for Bridgman and Ar in the case of Czochralski), and to crystal cooling conditions. The influence of gamma-ray irradiation and thermal annealing on optical absorption in YAlO3:Yb grown by the two methods is studied. The lifetime of Yb3+ is measured in crystals grown by the two methods.

Influence of gamma-ray irradiation and post-annealing studies on pentacene films: the anisotropic effects on structural and electronic properties.

In this work, γ-ray irradiation effects on pentacene thin films are investigated in terms of the change in the crystallinity, and electronic structure as well as chemical states of the film. The pentacene films are γ-irradiated up to 3 kGy and then characterized using synchrotron X-ray diffraction, near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy. We found that γ-ray irradiation creates defects, resulting in a decrease of X-ray diffraction intensity both in the plane normal and in-plane directions. From angle dependent NEXAFS; the transition of C 1s to π* orbital for irradiated samples increases; suggesting that the unoccupied π* states enhance due to defects or radical formation in pentacene thin films. Additionally, the in-plane resistivity shows a decreasing trend of resistance after irradiation. This trend of increase in conductivity is also consistent with C 1s to π transition, which manifests the increase in carrier concentration. Hall effect measurements further confirmed the increase in carrier concentration as a function of dose; however, the mobility of the sample decreases as the dose rate increases due to the defects created. By post-irradiation annealing, the thin film phase diffraction intensity can be recovered. Altogether, the anisotropic studies on pentacene films disclosed that the irradiation leads to defect formation along in-plane and plane normal directions. Overall, these results suggest that pentacene is one of the robust organic electronic materials; whose structure remains mostly intact even after irradiation up to a dose of 3 kGy.

Influence of gamma ray irradiation on thermal conductivity of bismaleimide-triazine-based insulation tape at cryogenic temperature

Recent accelerator-based experiments for particle physics require the superconducting magnets that can be operated under high radiation environment. An electrical insulation tape, which is composed of polyimide film and a boron free glass fabric pre-impregnated with epoxy resin blended with bismaleimide-triazine resin, is developed to enhance the radiation tolerance for superconducting magnets. Since the thermal conductivity of insulation tape is one of key parameters that affects the coil temperature during the operation, the influence of gamma-ray irradiation on the thermal conductivity of the insulation tape is investigated with a maximum dose of 5 MGy. The thermal conductivity is measured at cryogenic temperature from 5 K to 20 K cooled by a Gifford-McMahon cryocooler. By comparing the thermal conductivity before and after the gamma ray irradiation, no significant degradation on the thermal conductivity has been observed.

Influence of gamma-ray irradiation on mechanical property of YSZ for oxygen sensors in ADS

In the accelerator driven system, oxygen sensors, on which yttria-stabilized-zirconia (YSZ) is used for the electrolyte, will be irradiated by gamma-ray in activated lead bismuth eutectic (LBE) adopted as a both coolant and spallation target. Partially stabilized zirconia, like a 3Y-YSZ, has high strength due to the stress induced phase transformation from tetragonal (T) to monoclinic (M) phase. The mechanical properties of YSZ specimens after gamma-ray irradiation, thermal aging and immersion in LBE have been investigated in terms of the fracture surface structure. In the case of 6Y and 8Y-YSZ, the 4-point bend strength did not change even after gamma-ray irradiation and thermal aging. The 3Y-YSZ, however, showed that the strength was decreased a little by the gamma-ray irradiation, thermal aging and also immersion in LBE. The XRD results indicate that in the case of 3Y-YSZ after the annealing and soaking in LBE, the pristine surface, which is not fractured and strained by bending test, shows M phase much more than the surface of as-received one. After surface polishing of 3Y-YSZ the XRD intensity of M phase increased with increasing gamma-ray dose for the pristine surface. The bend strength of irradiated 3Y-YSZ after polishing, however, did not change in this study. These results suggest that the process of gamma-ray irradiation and thermal process around 450 °C cause pre-phase transformation from T to M, which prevents the stress induced phase transformation previously.

Influence of gamma-ray irradiation on Faraday effect of Cu-doped germano-silicate optical fiber

Influence of gamma-ray irradiation on the Faraday effect of the Cu-doped germano-silicate optical fiber was investigated. The Verdet constant of the gamma-ray irradiated optical fiber at 660nm was measured to be 3.07radT−1m−1, 1.46 times larger than that of before the irradiation at total dose of 1200Gy. Cu-related radiation-induced defect centers and Cu metal particles which were reduced from Cu2+ ions by the irradiation are thought to be responsible for the increase in the Verdet constant of the optical fiber.

Influence of gamma ray irradiation on metakaolin based sodium geopolymer

Effects of gamma irradiation on metakaolin based Na-geopolymer have been investigated by external irradiation. The experiments were carried out in a gamma irradiator with 60Co sources up to 1000kGy. Various Na-geopolymer with three H2O/Na2O ratios have been studied in terms of hydrogen radiolytic yield. The results show that hydrogen production increases linearly with water content. Gamma irradiation effects on Na-geopolymer microstructure have been investigated with porosity measurements and X-ray pair distribution function analysis. A change of pore size distribution and a structural relaxation have been found after gamma ray irradiation.

Influence of gamma-ray irradiation on optical and thermal degradation of poly (ethyl-methacrylate) (PEMA) polymer

Polymer based on (polyethyl-methacrylate) (PEMA) were exposed to different doses of gamma radiation up to 100 kGy and the physical properties have been studied. The effects of gamma irradiation on the optical spectrum of PEMA films have been investigated using spectrophotometric measurements of reflectance and transmittance in the wavelength range 200-1100 nm. The structure of the sample is analyzed by X-ray diffraction technique and is found to be amorphous and partially crystalline. TGA studies revealed that the thermal stability of polyethyl methacrylate, improved after irradiation doses up to 100 kGy. On other hand driving absorption coefficient α(ω), consequently the band tail width Ee and optical band gap estimated. This behavior is believed to be associated with the generation of excess of electronic localized states. Also, Optical constants such as refractive index (n), extinction coefficient (K) have been determined using Swanepole method. Optical dispersion parameters and the dispersion parameters, such as Eo (single–oscillator energy), Ed (dispersive energy) are discussed in terms of the single-oscillator Wemple-DiDomenico model.

Gamma-ray irradiation effect on the absorption and luminescence spectra of Nd:GGG and Nd:GSGG laser crystals

Laser crystals Nd 3+:Gd 3Ga 5O 12 (Nd:GGG) and Nd 3+:Gd 3Sc 2Ga 3O 12 (Nd:GSGG) were grown by Czochralski method. The influence of gamma-ray irradiation on their absorption and luminescence spectra has been investigated. Two additional absorption (AA) bands induced by gamma-ray irradiation appear in the spectra of Nd:GGG crystal while only a very weak AA band appears for the Nd:GSGG crystal. This indicated that Nd:GSGG crystal has stronger ability to resist the color center formation by irradiation. The intensity of the excitation and emission spectra of Nd:GGG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, a luminescence strengthening effect was observed in Nd:GSGG crystal after exposure to the same irradiation dose. The results showed that the Nd:GSGG crystal is a promising candidate used under radiation environments such as in outer space.

Photoluminescence and gamma-ray irradiation of SrAl 2O 4:Eu 2+and Y 2O 3:Eu 3+ phosphors

Y 2O 3:Eu 3+ phosphor is a very attractive material for use as a red phosphor in many fields. SrAl 2O 4:Eu 2+ belongs to long lasting phosphor (LLP) and it is a useful bluish-green luminescence material, which can also be a promising candidate as a simple and easy-to-use radiation detection element for visual display of two dimensional radiation distributions. In the present study, both these two kinds of phosphors were synthesized using high temperature solid state reactions. In our work, the influence of gamma-ray irradiation on the properties of these two kinds of phosphors was studied by comparing photoluminescence, brightness and the decay curve of unirradiated and gamma-ray-irradiated samples. Conclusions from the present work can be briefly summarized as follows. In irradiated samples, the brightness is decreased without sensible change in the wavelength distribution of the luminescence spectrum and in the decay kinetic upon gamma exposure. Moreover, the emission due to Eu 3+→Eu 2+ conversion in Y 2O 3:Eu 3+ phosphors was not observed in our sample after irradiation to high exposure. Also the brightness of SrAl 2O 4:Eu 2+ phosphor turned out to decrease after the exposition to ionizing radiation while the luminescence wavelength distribution remained unchanged. The reason for the effect of gamma-ray irradiation on the properties of phosphors is also discussed in the paper.

Effect of Irradiation on Adsorption Performance of Thiacalix[4]arene Impregnated Silica Adsorbent

Thiacalix[4]arene impregnated silica adsorbent, referred to as CAPS-SO2-adsorbent, exhibits excellent separation performance for Am in weak acid solution. However, in the treatment of high-level radioactive liquid waste (HLLW), the adsorbent is exposed to strong irradiation. The influence of gamma-ray irradiation on the CAPS-SO2-adsorbent's adsorption ability was investigated. Its ability to adsorb Am remained high even after irradiation. Particularly, the distribution coefficient for Am increased with increasing irradiation dose in pH 2 solution. Conversely, the distribution coefficient for Fe decreased with gamma-ray irradiation, and very low levels of Y and lanthanoids were adsorbed. Am would then be separable from HLLW even after irradiation of the adsorbent.

Effect of Irradiation on Adsorption Performance of Thiacalix[4]arene Impregnated Silica Adsorbent

Thiacalix[4]arene impregnated silica adsorbent, referred to as CAPS-SO2-adsorbent, exhibits excellent separation performance for Am in weak acid solution. However, in the treatment of high-level radioactive liquid waste (HLLW), the adsorbent is exposed to strong irradiation. The influence of gamma-ray irradiation on the CAPS-SO2-adsorbent's adsorption ability was investigated. Its ability to adsorb Am remained high even after irradiation. Particularly, the distribution coefficient for Am increased with increasing irradiation dose in pH 2 solution. Conversely, the distribution coefficient for Fe decreased with gamma-ray irradiation, and very low levels of Y and lanthanoids were adsorbed. Am would then be separable from HLLW even after irradiation of the adsorbent.

Separation of actinoids from HLW by thiacalix[4]arene compound impregnated silica ion-exchanger

If trivalent actinoids such as Am can be separated from high-level radioactive liquid waste (HLLW) generated by the PUREX process, long-term heat and radiation hazards can be significantly reduced in the disposal of this waste. This paper reports the effective separation of Am through the use of a chelating ion-exchange method that uses an octylphenyl-N,N-diisobutylcarbomoyl phosphine oxide (CMPO) or thiacalix[4]arene compound impregnated silica ion-exchanger. The separation of Cs and Sr from HLLW can be achieved using a CMPO impregnated silica ion-exchanger (CMPO-exchanger). Actinoids and lanthanoids can then be eluted from the CMPO-exchanger, with the resulting solution then treated to separate the actinoids using a thiacalix[4]arene compound impregnated silica ion-exchanger. Thiacalix[4]arene compound impregnated silica ion-exchangers have been shown to effectively separate actinoids from lanthanoids in a weak-acid solution. The influence of gamma ray irradiation on adsorption is also investigated. The adsorption of Am remains high even after irradiation of the ion-exchanger.

Mechanism of high radiation stability of electrical parameters of SmS thin films

The influence of gamma-ray irradiation on the electrical properties of thin polycrystalline films of samarium monosulfide with various crystal-lattice parameters was studied. The stability of the resistivity of films under an exposure dose in the range of D=108–109 R is explained on the basis of the existence of a channel for the relaxation of radiation-induced excitations; this channel is related to the presence of different-valence samarium ions (Sm2+ and Sm3+).