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More reliable and long-term irradiation stability is essential for lubrication protection materials that served in nuclear energy equipment. In this paper, three typical commercially organic bonded solid lubricating coatings were chosen to investigate the influence of gamma (γ)-ray irradiation on microstructure and tribological behaviors. The evolution of microstructure and the changes of tribological properties for these coatings after irradiation were comparatively studied in detail. The results revealed that the crystallinity of the molybdenum disulfide (MoS 2) lubricating phase was improved and were partial oxidized in the coatings after γ-ray irradiation, resulting in the surface roughness of the coating with MoS 2 as the solid lubricating phase decreased significantly. The polytetrafluoroethylene (PTFE) lubricating phase was degraded from the long chains structure to smaller molecules after γ-ray irradiation. The results of tribological properties of the three coatings after γ-ray irradiation indicated that, for polyamide-imide-based lubricating coatings, the friction coefficient is decreased and the wear rate is increased after irradiation. For phenolic epoxy-based lubricating coating, the cross-linking effect of γ-ray irradiation predominated to improve the wear resistance and prolong the wear life of the coating. But overall, the influence of irradiation on tribological properties of three polymer-based coatings could almost be neglected duo to the changes of the microstructure in nanoscale. This work provides path and direction for design and preparation of the lubricating coatings that served in a nuclear reactor. • The crystallinity of the MoS 2 lubricating phase was improved after γ-ray irradiation • For polyamide-based coatings, the friction coefficient is decreased and the wear rate is increased after irradiation • For epoxy-based coating, the cross-linking effect of γ-ray irradiation predominated to improve the wear resistance and prolong the wear life • The degradation and cross-linking effects have occurred only in shallow surface [ABSTRACT FROM AUTHOR]

• The ionization of atoms caused by γ-ray irradiation leads to generation and accumulation of E′ centers and NBOHCs in silica film. • γ-ray irradiation results in the reductions of Si-O-Si bond angle and bond length, thus causing the densification of silica film. • The refractive index and mechanical properties firstly enhance and then reduce with the increasing absorbed dose due to the densification of silica film. • The dose-dependent surface quality, defects and mechanical properties determine the variation in laser damage threshold of silica film. γ-ray radiation effect on sol-gel silica films was investigated at different absorbed doses ranging from 10 kGy to 1000 kGy. The defect and microstructure evolutions of silica films were analyzed to understand the performance degradation behavior and mechanism of the γ-ray irradiated silica films. The cracks appear on the silica film surface and further expand at larger γ-ray absorbed dose, while surface roughness slightly decreases. During γ-ray irradiation, the thermal effect and the increased rate of diffusion-controlled process lead to the condensation of Si-OH groups and the recombination of ODCs. However, the ionization of atoms leads to generation and accumulation of E′ centers and NBOHCs. γ-ray irradiation leads to the reductions of bond lengths and bond angles of Si-O-Si groups, thus causing the densification of films. The refractive index and mechanical property firstly enhance and then reduce with the increase of absorbed dose associated with the change of silica film density. After γ-ray irradiation, the decreased contact angle and increased surface free energy indicate the reduction of anti-pollution ability of silica films. The dose-dependent surface quality, defects and mechanical properties determine the variation in laser-induced damage threshold (LIDT) of silica film. The results provide a reference to control the structural damage and performance degradation of silica films, which is very important for the research of safe operation of high-power laser facilities for inertial confinement fusion (ICF). [ABSTRACT FROM AUTHOR]

We demonstrate the reattachment of two chemically-crosslinked poly(ethylene oxide) (PEO) matrix samples prepared with the γ-ray irradiation method by a simple wetting process with a good solvent. The fractured polymer samples can be attached through chain diffusion, interpenetration into a crosslinked network, and intermixing/reentanglement. Reattached samples exhibit similar macro/microstructure and mechanical properties to those of pristine samples. This effective recovery process without any additional reactive chemicals or external stimuli highlights the importance of extending the use of simple, but fundamental, dynamic behaviors of polymer chains to obtain the desired properties as well as offering a unique and useful route toward effective healable materials. [ABSTRACT FROM AUTHOR]

Cosmic radiation has always been the most obvious barrier to planetary travels, especially in long-duration deep space exploration missions. Therefore, the reliability of satellite materials and the requirements of satellite miniaturization have received considerable attention. In this paper, the effect of γ-ray irradiation on the reliability of Sn50Pb49Sb1/Cu solder joints was investigated. It was found that the influence of γ-ray irradiation on the thickness and morphology of the intermetallic compound layer in Sn50Pb49Sb1/Cu was not obvious. However, the formation and growth of micro-voids and micro-cracks was observed in Pb-based solid solutions. Due to the Compton effect, the γ-ray photon could knock the electron out of its orbit, which created the energetic electron. The accumulation of dislocated atoms and lattice vacancies generated by energetic electrons could be the main factor that caused the formation of micro-voids and micro-cracks. The pull force of Sn50Pb49Sb1/Cu solder joints was reduced by 22% after being irradiated at the dose rate of 0.25 Gy(Si)/s for 960 h. Fractographic analysis showed that after irradiation, the fracture type of solder joints was still ductile but the ductility of the solder joints decreased with slightly inconspicuous dimples.

We investigated changes in the physical and chemical properties of rapeseed straw after treatment with different doses of 60 Co γ-irradiation (0 kGy-1200 kGy). Raman spectra, electron spin resonance (ESR), and nuclear magnetic resonance (NMR) analyses of the pretreated samples showed that the irradiation partially destroyed the intra- or intermolecular structure of rapeseed straw. Particle size distribution and specific surface area analyses suggested that irradiation decreased the particle size, narrowed the distribution range, and increased the specific surface area. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) curves showed that increasing the irradiated dose decreased the thermal stability of the treated rapeseed straw and increased the reactivity. Elemental analyses suggested that the oxygen content slightly increased, suggesting that oxygen in the air may be involved in the reaction. These results demonstrate that γ-irradiation can induce a series of changes in the physical and chemical properties of rapeseed straw. [ABSTRACT FROM AUTHOR]

Abstract: This investigation shows that in absence of the chemical reductant and the other protective reagents, the host–guest interaction and the molar ratio of dendrimers/Au3+ other than size and shape of the templates play an important role for the preparation of stable gold hybrid colloids by 60Co γ-ray irradiation using spherical PAMAM-G5 as nonlinear polymeric template. The hybrid colloid resultants comprised of the ordered nano-crystal and the random non-crystal part, which has been confirmed by HRTEM, display spherical structure and the polydispersity of the size distribution in the range of nanometer scale. The dendrimer/gold hybrid colloids are formed by the intramolecular and intermolecular adsorption action between PAMAM-G5 template and gold nanoparticles, respectively. [Copyright &y& Elsevier]

Silicon nitride ceramic fibers with diameter of 14μm were prepared from polycarbosilane (PCS) fibers by the γ-ray irradiation curing method. Phase, microstructure, chemical composition and tensile strength of the silicon nitride ceramic fibers were systematically investigated. The silicon nitride ceramic fibers showed an amorphous state below 1300°C, and changed from the amorphous to the α-Si3N4 crystalline state at 1400°C. The microstructures of the silicon nitride ceramic fibers were smooth and compact below 1300°C, and became rough and loose at 1400°C. The chemical composition of the silicon nitride ceramic fibers was Si, N and O. The tensile strength of the ceramic fibers reached a maximum of 1.63±0.25GPa at 1200°C, and decreased rapidly above 1300°C. [ABSTRACT FROM AUTHOR]

Abstract: Graphene nanostructures with notched edges and nanopore defects were produced by the γ-ray irradiation of the graphite oxide in polar solvents. Because of the grafting of the long polymer chains, the thickness of the graphene monolayers is shown to be significantly increased. In addition, the graphitization degree got increased in unetched regions of the irradiated graphene due to the annealing effect induced by irradiation from the Raman investigation. Spontaneously interlocking between the etching graphene and polymer matrix will be arisen with the formation of these nanostructures. The development of graphene with large contact area and nanopore volume may be of use in composites and sensors. [Copyright &y& Elsevier]

Abstract: To investigate the effect of γ-ray radiation on the microstructure of carbon fibers (CF) and graphite, the carbon fibers and graphite were irradiated by 60Co source at room temperature. X-ray diffraction results indicate that the interlayer spacing d 002 of CF and graphite decreased after irradiation. The intensity of (002) peak in CF decreased while the peak of the (002) plane in graphite becomes sharper after irradiation. Scanning electron microscopy combined with energy dispersive X-ray spectroscopy determines that γ-ray irradiation slightly improves the carbon content of CF surface layer. Compton scattering effect and heating caused by γ-ray are proposed to be responsible for the graphitization of CF and graphite. [Copyright &y& Elsevier]