Narrow Results

Droplet PIXE analysis was applied to the study of radiation effects on soil ecosystem functioning. A paddy soil sample was flooded with well water to prepare soil ecosystem specimens (microcosms), and then the microcosms were chronically exposed to gamma rays at a dose rate of 1 Gy day⁻¹ for 5 days. After the final irradiation, a brownish discoloration was observed in the liquid phases of the irradiated microcosms.To clarify the factors causing the discoloration, minerals in the solutions of the microcosms were analyzed by the droplet PIXE system.Elemental profiles from the XRF spectrum showed marked iron peaks. Exposure of microcosms to gamma rays resulted in a decrease in the iron levels. Since iron is released in the form of Fe(II) from the solid soil to the liquid phase, further determination of the Fe(II) levels was performed. The percentages of Fe(II) to the total iron in the liquid phase of the irradiated microcosms were lower than those of the controls. This result may be caused by the change of Fe species from soluble Fe(II) to insoluble Fe(III) during gamma irradiation, and the Fe(III) species with a brownish color may be associated with the discoloration of the irradiated samples. The conversion from soluble to insoluble forms may also contribute the small amount of dissolved iron in the irradiated microcosms. Iron is an essential trace nutrient for plants, and thus the amount of dissolved iron is one aspect of ecosystem functioning. Effects of gamma radiation on the dissolved iron could involve a change in the soil ecosystem through the depression of iron flux in the long term.

In this paper, high purity boron carbide samples were irradiated by ${}^{60}$Co gamma radioisotope source (0.27 Gy/s dose rate) with 50, 100, 150 and 200 irradiation hours at room-temperature. The unirradiated and irradiated boron carbide samples were heated from 30${}^{\circ }$C to 1000${}^{\circ }$C at a heating rate of 5${}^{\circ }$C/min under the argon gas atmosphere of flow rate 20 ml/min. Thermogravimetric (TG) and Differential Scanning Calorimetry (DSC) were carried out in order to understand the thermodynamic kinetics of boron carbide samples. The weight kinetics, activation energy and specific heat capacity of the unirradiated and irradiated boron carbide samples were examined in two parts, T$\le$ 650${}^{\circ }$C and T$\ge$ 650${}^{\circ }$C, according to the temperature. The dynamic of quantitative changes in both ranges is different depending on the irradiation time. While the phase transition of unirradiated boron carbide samples occurs at 902${}^{\circ }$C, this value shifts upto 940${}^{\circ }$C in irradiated samples depending on the irradiation time. The activation energy of the unirradiated boron carbide samples decreased from 214 to 46 J/mol in the result of 200h gamma irradiation. The reduction of the activation energy after the irradiation compared to the initial state shows that the dielectric properties of the irradiated boron carbide samples have been improved. After the gamma irradiation, two energy barrier states depending on the absorption dose of samples were formed in the irradiated samples. The first and second energy barriers occurred in 0.56–0.80 and 0.23–0.36 eV energy intervals, respectively. The existence of two energy levels in the irradiated boron carbide indicates that the point defects are at deep levels, close to the valence band.

The modification of local structure of some commercial polyethylene terephthalate (PET) samples, gamma irradiated at different doses, was investigated by X-ray diffraction method before and after thermal treatment. Before the thermal treatment, the samples exposed to different doses of gamma radiations, does not show noticeable structural changes. However, the gamma exposure affects the thermal behavior of samples submitted to melting–cooling process. These modifications have been highlighted by X-ray diffraction, and confirmed also by thermal analysis and electron spin resonance spectroscopy.

The concentrations of forming defects during phase transitions (PTs) and elastic coefficients in the ${\text{Cu}}_{1.95}$${\text{Ni}}_{0.05}$S compound were determined based on differential thermal analysis (DTA) data $\mathrm{\Delta }{T}_y(T)$. The sample was studied under the influence of $\gamma$ irradiation (at a dose of 25 Mrad) and it was shown that the $T_y(T)$ curves coincide each other before and after irradiation. It was established that $\alpha$, $\beta$, $\gamma$ modifications are commensurate when heating the sample. A certain number of defects in S atoms at lattice sites and defects in Cu atoms (also Ni atoms) in interstitial sites of the sublattice are some of the causes of lattice rearrangement.

TlInSe₂ crystals were grown by Bridgman method. The thermal conductivity coefficient was studied in the temperature range of 80–600K, along and perpendicular to the parallelepiped sample layers. The corresponding parameters of the TlInSe₂ crystal were calculated based on the performed experiments. The results of the performed analysis have shown that the theoretical calculations and experimental results are of the same order, while the obtained and calculated values differ from each other by a factor of two. The temperature dependence of the thermal conductivity coefficient of TlIn${}_{1-x}$Dy_xSe₂ solid solutions is also studied. Moreover, effect of the gamma irradiation on the temperature dependence of the thermal conductivity of the TlInSe₂ crystals were studied.

In the presented work, the charge state of P(VDF-TeFE)/Si-based composites obtained on the basis of nano-Si with a size of 50nm and micro-Si particles with a size of 50$\mu$m and P(VDF-TeFE) copolymer of polyvinylidenefluoride with tetrafluoroethylene from polar polymers, was investigated, the amount of filler and the effect of ionizing radiation on these properties were studied. It has been shown that the observed differences in the charge state parameters of P(VDF-TeFE)/Si composites obtained with nano- and micro-sized Si are due to the higher concentration of nanoparticles and, accordingly, the effective surface area in the composites obtained with nanosized Si, and the change in the mobility of relaxors due to the effects of construction and destruction processes that occur in the polymer matrix and at the interphase boundary after the effect of gamma radiation. The reason for the observed changes in the depolarization processes of polarized P(VDF-TeFE)/nano-Si composites after gamma radiation is the change in the ratio between the construction and destruction processes in the system.

Samples of YBa₂Cu₃O_7-δ superconducting ceramic were prepared and characterized by resistivity measurements using the four probe method and structural analysis using X-ray diffraction (XRD). XRD-patterns show the presence of orthorhombic Y-123 phase with a small fraction of secondary phase, YBa₂Cu₃O₅. Samples were irradiated with gamma (γ) rays using Co⁶⁰ source with five successive doses of 2.5 Mrad. A monotonic increase in the T_c0 value was observed for radiation dosage up to 10 Mrad. When exposed to even higher γ-doses, the T_c0 value leveled off at a saturation value or decreased. XRD-analysis shows slightly changed values of the lattice constants and a mild shift of diffraction peaks towards a lower 2θ value. These observations indicate structural changes in YBa₂Cu₃O_7-δ induced upon gamma irradiation. The present work describes our experimental findings and attempts to offer a theoretical explanation for the effects observed.

Gamma irradiation-induced chemical decomposition and related phase transformation from SnO₂ nanoparticles (NPs) to SnO have been studied using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and UV–Vis spectroscopy. XRD studies show that the SnO₂NP_S are crystalline in nature with rutile structure. Crystallinity of the NPs increases with the increase of gamma irradiation doses, which is consistent with the results of TEM. At high gamma irradiation doses, SnO phase appears from SnO₂ matrix, which pushes the SnO₂ phase toward stoichiometry. The band gap energy has been found in the range of 3.84–3.76eV, larger than the band gap of bulk SnO₂. The larger band gap is attributed due to small particle size, which is confirmed by TEM studies. Optical reflectance and band gap decrease with the increase of gamma irradiation doses due to creation of defects. This property of SnO₂ NPs makes it suitable for use in optical devices.

Lithium tetraborate (LTB) was doped with copper (0.1%) to enhance the LTB thermoluminescent (TL) properties. A graphene reducing atmosphere was used to increase the vacancies of oxygen in the crystalline structure. LTB:Cu $+$ PTFE (polytetrafluoroethylene) pellets were prepared by mixing the Li₂B₄O₇:Cu with PTFE in a 4:1 ratio. The obtained materials were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Crystals of Li₂B₄O₇ with the average size of 134nm were obtained. The presence of copper was confirmed by SEM. The TL response of LTB:Cu PTFE pellets was studied with $\gamma$ radiation by using a ${}^{60}$Co source. TTL response shows a linear behavior depending on the radiation dose. The effect of annealing time on TL glow curve was analyzed from 2h to 10h by irradiating with X-rays. The effect of mass on the TL response was studied varying the mass of the sample from 10mg to 50mg. From various heating rate studies, it was observed that the TL intensity increased when heating rate was gradually increased. The kinetic parameters were calculated by using computer deconvolution methods. The dosimetric property results showed that this material could have good potential application in a radiation dosimeter for radiation therapy treatment in the medical field.

Pt–Ni alloy with highly efficient and durable property might be of great significance for hydrogen evolution reaction (HER). Herein we present an efficient one-pot gamma irradiation method to prepare alloyed PtNi, PtNi₃ and Pt₃Ni nanoparticles with inter-crossed network structure on a large scale. The electrochemical characterization evidenced that the catalytic activity and durability of Pt₃Ni were comparable with those of commercial Pt/C for HER at the current density of 10$\mathrm{\text{mA}}\cdot {\mathrm{\text{cm}}}^{-2}$ in 0.5M H₂SO₄. We believed that the convenient and scalable gamma irradiation technique might open a way for large-scale preparation of advanced water splitting catalysts.