Effect of 60Co γ-irradiation on structural and optical properties of thin films of Ga10Se80Hg10

Thin films of Ga₁₀Se₈₀Hg₁₀ have been deposited onto a chemically cleaned Al₂O₃ substrates by thermal evaporation technique under vacuum. The investigated thin films are irradiated by ⁶⁰Co γ-rays in the dose range of 50–150 kGy. X-ray diffraction patterns of the investigated thin films confirm the preferred crystallite growth occurs in the tetragonal phase structure. It also shows, the average crystallite size increases after γ-exposure, which indicates the crystallinity of the material increases after γ-irradiation. These results were further supported by surface morphological analysis carried out by scanning electron microscope and atomic force microscope which also shows the crystallinity of the material increases with increasing the γ-irradiation dose. The optical transmission spectra of the thin films at normal incidence were investigated in the spectral range from 190 to 1100 nm. Using the transmission spectra, the optical constants like refractive index (n) and extinction coefficient (k) were calculated based on Swanepoel’s method. The optical band gap (E_g) was also estimated using Tauc’s extrapolation procedure. The optical analysis shows: the value of optical band gap of investigated thin films decreases and the corresponding absorption coefficient increases continuously with increasing dose of γ-irradiation.     

Effect of γ-irradiation on structural,morphological and luminescence properties of cerium-doped Y3Al5O12 nano-material

ABSTRACT

Cerium-doped yttrium aluminum garnet (YAG: Ce³⁺) nanopowder phosphors have been elaborated by sol–gel process and annealed at 900°C for 2?h. The prepared phosphors were exposed to gamma radiation, using ⁶⁰Co source, at different doses ranging from 5 to 100?kGy. The influence of γ-irradiation on the structural, morphological and luminescence properties of YAG: Ce³⁺ phosphors were investigated in detail by X-ray diffraction, ?eld emission scanning electron microscopy (FESEM), Fourier transforms infrared spectroscopy (FTIR) and photoluminescence measurements. The XRD analysis confirmed the presence of single cubic phase for all samples of YAG: Ce³⁺ nanophosphors independent of γ-rays dose. FESEM micrograph results revealed that the particles present flate-like shapes and high density of dislocation for sample irradiated at 100?kGy of γ-ray. The YAG: Ce³⁺ nanophosphors showed broad green–yellow emission band in the range of 450–700?nm with maximum intensity at 538?nm assigned to the 5d → 4f transitions of Ce³⁺ ion. The emission intensity of YAG: Ce³⁺ phosphors vary with the γ-ray irradiation and reach the maximum for sample irradiated to a dose of 25?kGy. The variation of luminescence intensity is related to the crystallite size and Ce⁴⁺ ions content in YAG host nanomaterial.     

The influence of γ-irradiation on some physical properties of chlorophyll/PMMA films

Films of poly(methylmethacrylate) PMMA doped with different concentrations of chlorophyll, from 2.5 up to 12.5 wt.%, have been prepared by casting method. Studies were carried out utilizing FT-IR, UV/vis, fluorescence, TGA and DC electrical conduction to characterize the structural, optical and thermal properties of the films before and after irradiation. Results revealed that the structural and chemical characterizations of PMMA films are affected by the addition of chlorophyll and increasing dose of γ-irradiation. FT-IR analysis revealed that the hydroxyl and carbonyl groups were responsible for the decrease of the bands intensities with increasing the dose rate up to 100 kGy. The change in these groups was attributed to competitive processes: decomposition with ester group abstraction and oxidation with formation of new oxidized carbonyls in the polymeric chains. The values of optical energy gap for the samples were decreased upon irradiation; this indicates that there is a charge transfer complexes arise between PMMA and chlorophyll. TGA analysis shows that the addition of chlorophyll to PMMA films enhances their thermal stability. The electric conduction data were interpreted on the basis of an intrachain one-dimensional interpolaron hopping model of Kuivalainen.     

Effect of γ-irradiation on optical and chemical properties of CR-39 polymer

CR-39 polymer samples were irradiated with γ-irradiation up to dose ranging from 500 to 2000 kGy. The virgin and γ-irradiated polymer samples were investigated using UV–visible spectroscopy and Fourier transform infrared (FTIR) spectroscopy. In the present work, the Urbach energy was calculated using the Urbach edge method. Also, the direct and indirect energy band gaps in virgin and γ-irradiated CR-39 polymer samples were calculated. The values of indirect energy band gap were found to be lower than the corresponding values of direct energy band gap. The decrease in the optical energy band gap with increasing γ-irradiation dose was discussed on the basis of γ-irradiation-induced modifications in CR-39 polymer. The correlation between optical energy band gap and the number of carbon atoms in a cluster with modified Tauc's equation was also discussed. The FTIR spectra show considerable changes due to γ-irradiation, indicating that the detector is not chemically stable.     

Formation of optical color and fluorescence centers in polytetrafluoroethylene under γ-irradiation

Fluorescent properties and colors of polytetrafluoroethylene (PTFE) samples were studied as functions of absorbed dose of γ-radiation at a temperature above the melting temperature of the crystallites (327°C) in the dose range 0.2–0.8 MGy. The samples were irradiated at low pressure (10^–6 Torr) in glass ampuls and at atmospheric pressure in a chamber purged with argon. Samples in ampuls acquired an off-white tint and fluoresced weakly. The fluorescence intensity increased slowly as the radiation dose increased from 0.2 to 0.6 MGy and decreased at 0.8 MGy. Samples irradiated in the chamber fluoresced more strongly and acquired colors that changed from gray (0.2 MGy) to dark-brown (0.8 MGy). Color centers were formed only in the sample surface layer. Their appearance was associated with the adsorption of particles of an unknown nature from the environment. The argon-purged samples turned white upon removing their surface layer (50 μm). The intensity and shape of fluorescence bands emitted by these samples remained essentially unaltered, i.e., depended weakly on the absorbed dose in the range 0.2–0.8 MGy.     

Correlating the TL response of γ-irradiated natural quartz to aluminum and hydroxyl point defects

This paper investigates the relationship between Al- and OH-related point defects with the thermoluminescent (TL) response of natural quartz sensitized with high doses of γ radiation and heat-treatments. For this, specimens from a single crystal were progressively irradiated with doses of ⁶⁰Co from 2 to 50 kGy. After each step of sensitization, the absorption bands related to [AlO₄]⁰, [AlO₄/H]⁰, [H₄O₄]⁰ and Li-dependent OH point defects were measured by optical absorption and infrared (IR) spectroscopy. The sensitization of the 280 °C TL peak increased up to 15 kGy and then its intensity remained constant. The absorption intensity at 470 nm increased with γ doses suggesting a progressive creation of [AlO₄]⁰ acting as recombination centers for the sensitized peak. At the same time, the TL intensity of the 90 °C peak decreased with the accumulated dose. This effect was not related to the saturation in the number of recombination centers because both [H₄O₄]⁰ and [AlO₄]⁰ bands were increasing after 50 kGy. Compared to the as-received condition, it was found that IR bands associated with [AlO₄/H]⁰ and Li-dependent OH decreased with the effect of heat-treatments. The precursor for [AlO₄]⁰ is [AlO₄/Li]⁰ and the Li species dislodged from [AlO₄/Li]⁰ and Li-dependent OH centers play an important role in the sensitization process.     

Fluence rate linear response limit of a scintillators to γ-rays

Scintillation detectors based on LSO, CeF and PbWO are the main candidates for measuring γ-rays in a mixed γ/n pulsed radiation field with high intensity. An experiment using the Lissajous figure method to study the high fluence rate response behavior of three kinds of commonly used scintillators is introduced in this paper. The result shows that the fluence rate linear response limit of LSO and CeF is 1.9×10¹⁹ and 2.1×10¹⁸MeV/(cm²·s), respectively, and the PbWO scintillator still maintains linear response when the fluence rate of γ-ray is up to 2.0 × 10²⁰ MeV/(cm²·s).     

Radiation-induced changes in electrical conductivity and structure of BaPbO3 after γ-irradiation

Several barium plumbate (BaPbO₃) solid samples, made from PbO and BaCO₃ powder by chemistry liquid-phase coprecipitation, were investigated before and after γ-irradiation. The solid samples were irradiated by a ⁶⁰Co γ-irradiation source whose dose rate is about 0.7?kGy per hour. The irradiation times were 0, 72, 144, 216, 288 and 360?h. Then, the four-probe method, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to indicate the changes in electrical conductivity and microstructure of BaPbO₃ after γ-irradiation. The XRD results indicated that the content of PbO was reduced as the irradiation dose was increased and eventually vanished from the surface of samples. However, there was no new obvious substance phase found from the XRD atlas. It seems that the PbO transformed into nearly amorphous Pb₅O₈. The conjecture could be proved by the results of annealing experiment and SEM. The XPS results seem to show that the microstructure of BaPbO₃ was slightly changed.     

Influence of γ-irradiation on the non-isothermal decomposition of calcium-gadolinium oxalate

Thermal decomposition of co-precipitated unirradiated and irradiated Ca-Gd oxalate has been studied by adopting differential thermal analysis (DTA) and thermogravimetric (TG) techniques. The reaction occurs through two stages corresponding to the decomposition of gadolinium oxalate (Gd-Ox) followed by that of calcium oxalate (Ca-Ox). The kinetic parameters for both the stages are calculated by using solid state reaction models and Coats-Redfern's equation. The co-precipitation as well as irradiation alter the DTA peak temperatures and the kinetic parameters of Ca-Ox. The decomposition of Gd-Ox follows the two dimensional Contracting area ( R 2 ) mechanism, while that of Ca-Ox follows the Avrami-Erofeev ( A 2 ) mechanism ( n =2), which are also exhibited by the co-precipitated and irradiated samples. Co-precipitation decreases the energy of activation and the pre-exponential factor of the individual components but the reverse phenomenon takes place upon irradiation of the co-precipitate. The mechanisms underlying the phenomena are explored.     

Gamma induced changes in the structural and optical properties of Makrofol LS 1–1 polycarbonate

ABSTRACT

Samples from sheets of the polymeric material Makrofol LS 1–1 have been exposed to gamma radiation in the dose range 10–250?kGy. The modifications induced in Makrofol samples due to gamma irradiation have been studied through different characterization techniques such as intrinsic viscosity as a measure of the average molecular mass, Fourier Transform Infrared spectroscopy FTIR, refractive index and color difference studies. The results indicate that the crosslinking dominates at the dose range 50–250?kGy. The crosslinking reported by viscosity measurements is supported by the trend of the function groups present in the sample with the gamma dose. Also, the increase in intrinsic viscosity indicating an increase in the average molecular mass was associated with an increase in the refractive index. Additionally, the non-irradiated Makrofol samples showed significant color sensitivity towards gamma irradiation. The color intensity ΔE, which is the color difference between the non-irradiated sample and those irradiated with different gamma doses, increased (0–5.56) with increasing the dose up to 250?kGy, convoyed by an increase in the red and yellow color components.     

Effect of γ-irradiation on the transport and structural properties of polycrystalline Bi1.2 Pb0.33 Sr1.54 Ca2.06 Cu3 O10+δ superconductor

The effect of γ-irradiation on the transport and structural properties of polycrystalline Bi_1.2 Pb_0.33 Sr_1.54 Ca_2.06 Cu₃ O_10+δ superconductor, synthesized by nitrate route is studied. The sample has been irradiated by γ-ray upto a dose 400 MR using a ⁶⁰Co isotope source of 2 kCi strength with a dose-rate of 6.26 Gy/min. Its X-ray diffraction pattern, resistivity–temperature behaviour as well as elemental and morphological analyses using scanning electron microscope have been examined before and after the irradiation. It is observed that the normal state resistivity increases as the dose is increased. The transition width of the sample is found to get broadened with the increasing dose. Using the theories of Aslamazov–Larkin and Maki–Thompson, we present an analysis of the excess conductivity of our sample and the effect of γ-irradiation on it. It is found that the coherence length of the sample gets increased with the increase of the irradiation dose.     

Quasi-static response and texture evolution of α- and γ-RDX: a comparative study

In this paper, we undertake a comparative study of the stress–strain response and slip activity of α- and γ-polymorph of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) under pressure loading using a rate-dependent single-crystal plasticity model. Texture evolution studies are performed to further understand the effects of the dominant slip systems. The simulations indicate that the difference in elastic moduli and lattice parameters for α- and γ-RDX lead to different elastic–plastic constitutive response in the two polymorphs. γ-RDX exhibits more plastic slip compared to α-RDX for loading on (1 1 1) plane and the two polymorphs have different sets of dominant slip systems. We observe that the high-pressure slip system (0 0 1)[0 1 0] that is determined using molecular dynamics simulations is the most dominant slip system for this orientation. Whereas, for loading on (2 1 0) plane, α-RDX has marginally higher plastic slip than γ-RDX, though the same slip system is dominant for both the polymorphs. The texture evolution for loading on (1 1 1) and (2 1 0) planes follow the path towards the most dominant slip systems for both the polymorphs. We predict that the larger plastic slip in γ-RDX for loading on (1 1 1) plane might play an important role in understanding the reduced sensitivity for shock loading on (1 1 1) plane, when compared to (2 1 0) for which γ-RDX has lesser plastic slip, and (1 0 0) which is purely elastic.     

Interaction of deep impurities with radiation defects in n-Si at γ-irradiation

This work presents the results of research on peculiarities of radiation defect formation in single crystal n-Si, doped by deep level impurities (Cu, Ni, Ir, Rh, Pt and Au), at irradiation by γ-quanta of ⁶⁰Co. A property of γ-irradiation to create only vacancies and self-interstitial atoms is used to understand the nature of deep levels with participation of these impurities and primary elemental radiation defects. The role of covalence radii and diffusion coefficients in efficiency of radiation defect formation is discussed.     

The Recoilness Emission and Reception of γ-Gravitons in Laboratory and Cosmic Conditions

The theoretical consideration of the sponteneous emission of γ-gravitons by excited nuclei lead us to the conclusion about the principle possibility of γ-graviton detection from cosmic and laboratory sources. The γ-graviton astronomy and geophysics can give new information about cosmic and geophysical processes.     

Changes in the thermoelectric response of vitreous carbon due to the irradiation by γ-rays

In order to study variations in the thermoelectric properties, some commercial glassy carbon samples were subjected to a sequence of steps consisting of a combination of irradiation with γ-rays produced by radioisotopes ⁶⁰Co, and hydrogen adsorption when the samples were put in an over pressured atmosphere of this gas. With this procedure it was possible to observe that the irradiation decreases the electrical conductivity of glassy carbon samples and the hydrogenation changes the sign of Seebeck coefficient. The material initially is an n-type semiconductor, but with hydrogenation changes to p-type semiconductor. X-ray diffraction analysis showed that the hydrogenated vitreous carbon is more amorphous than the pristine material and the γ-rays irradiation produces changes in the crystallite size and shape.     

Influence of γ-irradiation on the optical and electrical properties of Se(0.85) Te(0.15) films

Abstract

Se_(0.85) Te_(0.15) films were prepared by thermal evaporation under vacuum on glass substrate. The optical and electrical properties of as deposited and irradiated Se_(0.85) Te_(0.15) films with different γ-doses are reported.

The optical constants (absorption coefficient (α), extinction coefficient (k), refractive index (n) and dielectric constants (?, ?) of unirradiated and irradiated films were calculated. The value of allowed direct optical energy gap of Se_(0.85) Te_(0.15) films increased from 1.47 eV. to 1.72 eV. with increasing the γ-doses to 2.5 Mrad. The irradiated films have lower resistivity than those as deposited films (unirradiated). The activation energy (ΔE) increases from 0.72 eV. to 0.86 eV. with increasing γ-doses to 2.5 Mrad.     

Structural investigation of bismuth borate glasses under the influence of γ-irradiation through ultrasonic studies

The ultrasonic velocity and attenuation measurements for different compositions of irradiated heavy metal oxide (HMO) borate glasses xBi₂O₃ (1−x) B₂O₃ (where x=0.25, 0.30, 0.35, 0.40, 0.45) has been investigated at room temperature (303 K) using pulse echo overlap method. The elastic moduli, Debye temperature, Poisson's ratio and other acoustical parameters have been obtained from experimental data. Structural changes after irradiation have been investigated by using FTIR spectroscopy and ultrasonic studies. As the changes are strongly dependent on the internal structure of the absorbing substance, in the present investigation ultrasonic velocities before and after γ-irradiation in bismuth borate glasses are measured as a function of composition, from which the structural changes in the network former B₂O₃ and modifier Bi₂O₃ due to irradiation are obtained.     

Influence of γ-irradiation on the optical parameters of 4-tricyanovinyl-N,N-diethylaniline thin films

Thin films of 4-tricyanovinyl-N,N-diethylaniline (TCVA) were prepared by thermal evaporation technique. The spectral and the optical parameters have been investigated by using the spectrophotometric measurements of both transmittance and reflectance at normal incidence of light in the wavelength range 200–2500 nm. The effect of γ-irradiation on the optical parameters was investigated. It was observed that the increase in γ-irradiation dose caused an increase in the value of absorption index and a shift in the spectrum towards higher wavelengths. Therefore, the value of the optical band gap has decreased from 1.45 eV for as-deposited film to 1.39 eV for film exposed to γ-ray dose of 150 kGy and Urbach tail increased. On the other hand, the dispersion parameters of TCVA films were increased with the increase of the irradiation dose.