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Trans‐1,4‐polyisoprene (TPI) is a typical polymorphic polymer with two crystal modifications. The transition between two crystal modifications (α to β) occurs during stretching. The underlying mechanism is still under debate. In this work, the effects of crosslinking and strain rates on the crystal transition are studied. The TPI, which mainly contains α crystal (α−TPI), is crosslinked by γ‐ray radiation. The results show that crystalline morphology does not change after radiation. The melting temperature and yield stress of crosslinked α−TPI decrease with the irradiation dose. The structural evolution is studied by in situ wide‐angle X‐ray diffraction and small‐angle X‐ray scattering. During stretching, the content of β crystal (Xβ) of crosslinked α−TPI increases in the strain‐hardening region. The Xβ is lower in the sample with a higher radiation dose under the same strain. On the other hand, with increasing strain rate, the Xβ of the crosslinked sample exhibits a non‐monotonic variation. A parallel mechanical model consisting of amorphous and crystal fibrils is proposed to explain the experimental observations. [ABSTRACT FROM AUTHOR]

In this study the graphene oxide modified carbonyl iron (GO‐CI) was prepared by γ‐ray irradiation, which was added to silicone rubber composites to enhance the nuclear radiation shielding performances. X‐ray diffraction (XRD) characterization result showed the structure and morphology of the obtained GO‐CI nanocomposites. The mixture of GO/CI and the hybrid GO‐CI were individually incorporated into the vinyl‐terminated polydimethylsiloxane (Vi‐PDMS) to prepare referenced SR/GO/CI and SR/GO‐CI composites. Compared with SR/GO/CI, the SR/GO‐CI exhibited better thermal conduction and mechanical recovery properties. Moreover, the γ‐ray radiation shielding ability of SR/GO‐CI is much higher than that of pristine SR/GO/CI. CI particles are coated by GO nanosheets to increase surface area to prevent sedimentation of CI. It implies that SR‐GO/CI composite would have potential application as the radiation hardening material with thermal conductive and nuclear radiation shielding function. [ABSTRACT FROM AUTHOR]

The stability of polymer materials used in nuclear environment directly determines the life and reliability of nuclear power equipment. Poly (aryl ether ketone) (PAEK) itself exhibits excellent irradiation resistance which can be widely used. The emphasis of this study lies in designing and synthesizing three different structures of amorphous PAEKs by the solution SN2 nucleophilic polycondensation. The thermodynamic properties and structural changes of the materials under gamma‐ ray (γ‐ray) irradiation were investigated and the irradiation‐resistance mechanism was discussed. The present results illustrate that the performance can be basically stable lower than 108 Gy. Up to 1013 Gy dose, γ‐ray has little effect on the impact resistance and Young ′s modulus of the three materials, the tensile strength and elongation at break decreased with the increase of irradiation dose. No new structures were formed after irradiation, and all the three materials decomposed slightly caused by oxidized. [ABSTRACT FROM AUTHOR]

Ionizing radiation damages DNA and may lead to the development of cancer. Irradiation also generates reactive oxygen species (ROS) which cause damage to various biological molecules. Relatively low dose‐rate irradiation causes less damage. However, the damage and its effects on cell fate are difficult to evaluate. To develop a method to analyze the damage and accompanying changes in physiology in cells irradiated by γ‐rays at a relatively low dose‐rate, we used the protein array technique to quantify marker proteins involved in the stress response and the regulation of cell growth and death. This method enabled efficient analyses of many replicates of experimental data on cell lysate samples. We detected relatively small changes in the levels of these proteins in the irradiated cells. Changes in protein levels suggested ROS production and DNA damage as well as cell cycle retardation and the progression of cellular senescence. Thus, our approach shows promise for analyzing the biological effects of relatively low dose‐rate irradiation. [ABSTRACT FROM AUTHOR]

The γ‐ray resistance of epoxy network polymers was evaluated. Bisphenol A diglycidyl ether (DGEBA) was used as an epoxy oligomer, and 4,4′‐diaminodiphenylmethane (DDM), hexahydrophthalic anhydride (HHPA), and phenolic novolac (PN) were used as curing agents. The thermally crosslinked polymers were irradiated with 0–10 MGy of γ‐rays. The crosslink density as well as the glass‐transition temperature (Tg) for the DDM‐cured and PN‐cured DGEBA resins decreased upon γ‐ray irradiation; however, the elastic modulus at room temperature and the density of the resins increased. By contrast, the Tg for the HHPA‐cured DGEBA resin increased slightly and the crosslink density decreased markedly when the specimen was irradiated with γ‐rays. Among the three cured systems, the HHPA‐cured DGEBA resin exhibited the greatest amount of gas generation during irradiation. Infrared absorption spectra revealed a decrease in the number of ester bonds and an increase in the number of aliphatic and aromatic ether bonds, suggesting that new crosslinking occurred concurrently with chain scission. Overall, among the three cured systems, the PN‐cured DGEBA resin was the most stable in terms of chemical structure and physical properties under γ‐ray irradiation. [ABSTRACT FROM AUTHOR]

γ-Irradiation and synchrotron-radiation-based X-ray absorption fine-structure (XAFS) spectroscopy have been used to induce structure disorder through the interaction of γ-rays (200 kGy) with fabricated Mn-doped ZnO nanoparticles (NPs) and then to examine thoroughly the resultant structural change. The extracted electronic/fine XAFS structural parameters reflect a compositional and γ-irradiation co-dependence. The average crystal structure of samples prepared by the sol-gel method was investigated by X-ray diffraction (XRD). A detailed structural XRD data analysis was carried out by applying a Rietveld refinement using the MAUD program. XAFS spectra were collected at the Zn K-edge (9659 eV) in transmission mode and at the Mn K-edge (6539 eV) in fluorescence mode. Direct evidence of the solubility of Mn ions in the ZnO structure was demonstrated by fitting the extended-XAFS (EXAFS) signal. Near-edge XAFS (XANES) analysis provided the oxidation states of Zn and Mn ions through fingerprint XANES spectra of the sample along with those of standard compounds. Linear combination fitting showed that the most fit chemical forms of Zn and Mn in the samples are ZnO and MnO, respectively. The oxidation states of both Zn and Mn XAFS absorbers were confirmed from pre-edge fitting. The results of the magnetic measurements were explained in light of the average and electronic/local structural information obtained from XRD, XANES and EXAFS techniques. The magnetic properties of the samples translate into an induced change in the average crystal and electronic/local structures upon Mn concentration change and γ-irradiation. XRD confirmed the successful preparation of hexagonal Mn-doped ZnO NPs with a crystallite size in the range 33-41 nm. Both XRD and EXAFS analysis detected a minor amount of Mn3O4 as a secondary phase. XANES and EXAFS provided information exploring the outstanding potential of the utilized protocol for detecting precisely the presence of the secondary phase of Mn3O4, which changes with Mn content (x). Mean-square relative displacement (σ2) values extracted from the EXAFS fitting were found to grow for Zn-Zn/Mn paths demonstrating the substitution of Mn/Zn into Zn crystal sites. The EXAFS analysis explains the reasons behind the enhancement in the magnetic properties and shows that the Mn doping content at x = 0.05 produces the most local atomic disorder in ZnO NPs. There is a strong harmony among the XRD, XANES, EXAFS and magnetization behavior of the Mn-doped ZnO NPs. Maximum magnetization was acquired at an Mn content of 0.05. γ-Ray-irradiated Zn1-xMnxO NPs are recommended as optimized candidates for showing the diversity of the applications. [ABSTRACT FROM AUTHOR]

Gamma‐ray (γ‐ray) irradiation was introduced into zeolite synthesis. The crystallization process of zeolite NaA, NaY, Silicalite‐1, and ZSM‐5 were greatly accelerated. The crystallization time of NaA zeolite was significantly decreased to 18 h under γ‐ray irradiation at 20 °C, while more than 102 h was needed for the conventional process. Unexpectedly, more mesopores were created during this process, and thus the adsorption capacity of CO2 increased by 6‐fold compared to the NaA prepared without γ‐ray irradiation. Solid experimental evidence and density function theory (DFT) calculations demonstrated that hydroxyl free radicals (OH*) generated by γ‐rays accelerated the crystallization of zeolite NaA. Besides NaA, mesoporous ZSM‐5 with MFI topology was also successfully synthesized under γ‐ray irradiation, which possessed excellent catalytic performance for methanol conversion, suggesting the universality of this new synthetic strategy for various zeolites. [ABSTRACT FROM AUTHOR]

The 3‐aminopropyltriethoxysilane (APS) grafted aramid fibers were prepared by γ‐ray irradiation and chemical treatment to improve the interfacial properties between aramid fibers and epoxy matrix. The functionalization process of aramid fibers was investigated by scanning electron microscopy, X‐ray photoelectron spectroscopy, and Fourier transform infrared spectrum. After grafted with APS, the surface roughness of aramid fibers increased obviously, and the element content and composition of functional groups changed significantly in the modification process. Dynamic contact analysis indicated the wettability, and surface free energy of the fibers were greatly improved after the APS treatment. Monofilament pull‐out measurement showed that the interfacial shear strength of aramid fiber reinforced composite increased by 51.03%, from 36.33 to 54.87 MPa after the surface modification. Moreover, benefited from the appropriate radiation and the APS grafting, the functionalization process did not damage fiber tensile strength. [ABSTRACT FROM AUTHOR]

The photoluminescence and thermoluminescence characteristics of rare earths (Dy or Ce) activated LiCaBO3 phosphors have been studied. Phosphors were synthesized by modified solid state synthesis. The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and thermoluminescence (TL) for structural, morphological and luminescence studies. Dy3+ activated LiCaBO3 shows emission at 486 and 577 nm due to 4 F9/2 → 6H15/2 and 4 F9/2 → 6H13/2 transition, respectively, whereas the PL emission spectra of Ce3+ activated LiCaBO3 phosphor shows a broad band peaking at 432 nm, which is due to the transition from 5d level to the ground state of the Ce3+ ion. The thermoluminescence study was also carried out for both these phosphors for γ-ray irradiation and carbon beam irradiation. Linearity was studied for a 0.4-3.1 Rad dose γ-rays. Linear behaviour over this dose range was observed. Gamma ray-irradiated phosphors were shown to be negligible fading upon storage. All the samples were also studied for 75 MeV C5+ ion beam exposure in the range of 3.75 × 1012 - 7.5 × 1013 ion cm-2 fluence. In addition to this, trapping parameters of all the samples were also calculated using Chen's peak shape method. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SbBiTe alloys have been some of the most efficient thermoelectric materials near room temperature. Here we synthesized a complete nanocomposite using γ-ray irradiation, in which Au/AuTe2 nanoparticles are dispersed uniformly without aggregation in the Sb1.6Bi0.4Te3 matrix. The lattice thermal conductivity was significantly reduced mainly due to the increased number of interfaces for phonon scattering between the nanoparticles and the matrix phase, thereby resulting in clear enhancement of dimensionless figure of merit ( ZT). The maximum ZT value of the Au/AuTe2 nanoparticle-supported Sb1.6Bi0.4Te3 nanocomposite was 1.01 at 423 K, which is about 18% higher than the maximum ZT value of Sb1.6Bi0.4Te3. [ABSTRACT FROM AUTHOR]

We investigated the possibility of preprimed storage of an artificial lung (AL), aiming at facilitating its emergency use. Test ALs, consisting of a special microporous hollow fiber membrane made of polyolefin in which direct blood-gas contact was completely eliminated, were preprimed with saline solution, sterilized by γ-ray irradiation, and evaluated after 1–3 months of storage at room temperature. A small amount of bubble was noted in the priming solution after storage in some ALs, which most likely originated from the air dissolved in the priming solution or persisted in the liquid compartment at priming. Although the preprimed solution contained several polyolefin-breakdown products due to irradiation, including ethyl alcohol, n- and t-butyl alcohol, acetone, and carbon dioxide, the levels of these substances were at concentrations known to be not toxic. Endotoxin concentration was negligible. In SEM observation, no perceptible microstructural change was observed in the hollow fibers after preprimed storage. Maximum tensile stress and ultimate elongation of the hollow fiber in the test ALs were reduced by approximately 20% and 3%, respectively, from those of the control AL. The influence of preprimed storage on gas-exchange function was examined in a venoarterial bypass animal study using a goat. Oxygen transfer function was well preserved whereas carbon dioxide removal function was slightly lowered according to the storage term in the stored ALs compared with those of a nonpreprimed control AL. On the basis of these results, we conclude that preprimed storage of the AL with γ-ray sterilization is basically feasible and realistic. [ABSTRACT FROM AUTHOR]

This research examines the effect of γ-ray irradiation at different temperatures (room temperature and 250°C) and atmospheric conditions (air and N2) on the electrical and mechanical characteristics of thermoplastic polyimide (TPI) insulated and sheathed coaxial cable, which is designed for high-temperature, radioactive use. It was found that the TPI insulated and sheathed coaxial cable had good radiation resistance at 250°C under N2, γ-ray irradiation of 75 MGy under air and electron beam irradiation of approximately 100 MGy under He. It was also found that both crosslinking and crystallization of TPI was accelerated by the synergistic effect of heat and γ-ray irradiation. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (2): 1–9, 1997 [ABSTRACT FROM AUTHOR]