Search

Abstract: The absorption spectra of solvated electrons in pentanol, hexanol and octanol are measured from 22 to 200, 22 to 175 and 50 to150°C, respectively, at a fixed pressure of 15MPa, using nanosecond pulse radiolysis technique. The results show that the peak positions of the absorption spectra have a red-shift (shift to longer wavelengths) as temperature increases, similar to water and other alcohols. Including the above mentioned data, a compilation of currently available experimental data on the energy of absorption maximum (E max) of solvated electrons changed with temperature in monohydric alcohols, diols and triol is presented. E max of solvated electron is larger in those alcohols that have more OH groups at all the temperatures. The molecular structure effect, including OH numbers, OH position and carbon chain length, is investigated. For the primary alcohols with same OH group number and position, the temperature coefficient increases with increase in chain length. For the alcohols with same chain length and OH numbers, temperature coefficient is larger for the symmetric alcohols than the asymmetric ones. [ABSTRACT FROM AUTHOR]

Abstract: The absorption spectra of the hydrated electron in concentrated LiCl, LiClO4, Li2SO4, MgCl2 and Mg(ClO4)2 deuterated water solutions were measured by pulse radiolysis techniques from room temperature to 300°C at a constant pressure of 25MPa. With increasing temperature, the absorption band of the solvated electron for all solutions shifts to larger wavelengths. Whatever the temperature, shifts to shorter wavelengths of the absorption spectrum were observed as salt effects. The results on the shape and broadening of the absorption spectrum are discussed. [Copyright &y& Elsevier]

Abstract: In order to study radiation-induced fast phenomena, a new pulse radiolysis system with higher time resolution based on pulse-and-probe method was developed and utilized for practical work. A few picosecond electron beam generated from a linear accelerator, in which a laser photocathode RF-gun is introduced, was synchronized with a femtosecond laser pulse which is employed as the analyzing light. The synchronization precision between them was suppressed within 1.6ps (rms). Converting the fundamental laser into white light continuum or optical parametric amplification allows to measure in the wide wavelength from visible to infrared region. [Copyright &y& Elsevier]

Abstract: The yield of the hydrated electron in the picosecond time range has been re-evaluated with an ultrafast pulse radiolysis system using a laser photocathode RF-gun in combination with a conventional one, and a value of 4.1±0.2 per 100eV of absorbed energy at 20ps was derived. This is consistent with recent experimental results using a time correlation method [Bartels et al., J. Phys. Chem. A 104, 1686-1691 (2000)] and with Monte-Carlo calculations [Muroya et al., Can. J. Chem. 80 1367-1374 (2002)]. [Copyright &y& Elsevier]

[Display omitted] • Three amidoxime adsorbents with different chain conformations were constructed via tert -butyl hydroperoxide-initiated surface graft polymerization. • Conformational effect is a key factor affecting uranium adsorption capacity. • The linear structure of P-E-PAO had the largest adsorption capacity. • The multi-arm structure of P-E-PMGO was most affected by pH and ionic strength. • The rigid structure of P-E-PEBO had the best selectivity. The amidoxime group has received widespread attention owing to its high affinity for uranium. Since this property was discovered, various amidoxime-based adsorbents have been developed for uranium adsorption. However, the effect of chain conformation on the uranium adsorption performance (in terms of adsorption capacity, stability, selectivity, etc.) of amidoxime adsorbents has rarely been studied. Herein, three amidoxime-based adsorbents with different chain conformations (linear, multi-armed, and rigid) were constructed via tert -butyl hydroperoxide-initiated surface graft polymerization by incorporating different monomer structures. Adsorption experiments revealed that the linear structure of P-E-PAO exhibited the highest adsorption capacity owing to the highest monomer-grafting ratio; the multi-arm structure of P-E-PMGO was affected by pH and ionic strength because of the most cyclic imide dioxime structure; and the rigid structure of P-E-PEBO showed the highest selectivity owing to the most open-chain amidoxime structure. These findings are expected to have strong implications in the optimization of adsorption material designs. [ABSTRACT FROM AUTHOR]

• PDA from self-aggregation of dopamine successfully wrap the surface of CeO 2. • PDA significantly improved the compatibility between SR and CeO 2. • Both CeO 2 and PDA@CeO 2 can keep the irradiated SR's mechanical properties. • Both CeO 2 and PDA@CeO 2 decreased the radiation induced crosslinking of SR. • The mechanism of PDA@CeO 2 reducing the radiation damage of SR was clarified. With the widespread use of nuclear science and technology, slowing down the aging of polymers in a radiation environment has become a matter of great concern. In this work, cerium dioxide (CeO 2) and CeO 2 encapsulated with dopamine (PDA@CeO 2) were selected as special fillers to prepare the silicone rubber (SR) composites, and their radiation resistance were investigated by comparing the mechanical properties and thermal performance before and after irradiation. The interfacial bridge formed by PDA results in a greater elongation at break for PDA@CeO 2 /SR5.0 (770.0 ± 33.6 %) than for CeO 2 /SR (686.0 ± 15.0 %). After irradiation with γ-rays, the retention of elongation at break of both CeO 2 /SR0.1 and PDA@CeO 2 /SR0.1 were larger than SR. Furthermore, PDA@CeO 2 /SR0.1 showed an impressive retention of 90.5 ± 2.7 % of the tensile strength retention after exposure to an absorbed dose of 200 kGy. The disparity in crosslink density prior to and following irradiation indicated that both CeO 2 and PDA@CeO 2 were efficacious in reducing radiation crosslinking within the SR. An electron paramagnetic resonance spectrometer and an ultraviolet lamp (UV-EPR) were used to observe in real time the free radical scavenging ability of CeO 2 and PDA@CeO 2 inside the SR. These results indicated that CeO 2 and PDA@CeO 2 was expected to prevent further chain reactions in silicone rubber by scavenging free radicals generated in SR, thus improving the radiation resistance of SR. [ABSTRACT FROM AUTHOR]

Abstract: Two histidine-containing natural dipeptides, carnosine and anserine (β-alanyl-1-methyl-l-histidine), have been examined for their antioxidant and radioprotective abilities. Pulse radiolysis studies indicated the antioxidative properties of carnosine and anserine aqueous solutions at different pH. The rate constants for the reaction OH radical with carnosine at neutral pH were determined to be 5.3×109 M−1 s−1 at 300nm, and 4.1×109 M−1 s−1 at 400nm, respectively. Carnosine and anserine also protected plasmid pUC18 DNA from X-ray radiation-induced strand breaks as evidenced from the studies by agarose gel electrophoresis. Carnosine showed higher protective efficiency under the experimental conditions. Our data demonstrated that carnosine and anserine may play an important role in the maintenance of the antioxidant system. [Copyright &y& Elsevier]

Abstract: In the present work, laser photolysis techniques have been used to study the transient species of silybin (abbreviated as SLB) in ethanol solutions. It has been demonstrated that the exposure of silybin to 248nm excimer laser gives rise to monophotonic ionization with a high quantum yield. The transient species have been identified, and a series of related kinetics parameters have also been obtained. For the sake of comparison, we approached the problem using another way to reduce silybin, i.e. attack of solvated electrons, esol −, produced in pulse radiolysis. The rate constant for reaction of esol − was determined to be 3.8×109 dm3 mol−1 s−1 at 720nm, which is consistent with 4.6×109 dm3 mol−1 s−1, obtained by laser photolysis. [Copyright &y& Elsevier]

Abstract: Measurements of primary g-values (at ∼10−7 s after the initial ionizing event) of , OH and H2O2 were extended to the very high linear energy transfer (LET) region (∼700eV/nm) near the Bragg peak. Heavy ions (4He2+, 12C6+, 20Ne10+, 28Si14+, 40Ar18+ and 56Fe26+) of energies up to 28GeV were provided by the Heavy Ion Medical Accelerator in Chiba (HIMAC) of the National Institute of Radiological Sciences (NIRS) in Chiba, Japan. Energies of the ions were decreased down to about 10MeV/u for 4He2+ using an energy absorber made of polymethylmethacrylate (PMMA) plates in order to vary the LET values. Beam was visualized after passing through the energy absorber using agarose gel of aqueous solution containing methyl viologen and sodium formate in order to determine how long ions can penetrate into water. Based on the information of the penetration depth of ions in samples, much attention was paid to dose correction and LET evaluation. The obtained data were plotted as a function of (Z eff/β)2 also instead of LET in order to discuss effects of physical track structures on product yields, resulted in better universality. [Copyright &y& Elsevier]

Abstract: Water radiolysis has been investigated with heavy ions having energies up to 28GeV provided from the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). Beams of 4He2+, 12C6+, 20Ne10+, 28Si14+, 40Ar18+ and 56Fe26+ with respective energies of 150, 400, 400, 490, 500 and 500MeV/u corresponding LET values of 2.2, 13, 30, 54, 92 and 183eV/nm, respectively, were taken for the irradiation. The LET changes in sample solutions can be neglected due to their high energies for the irradiation of 1-cm cells. Primary g values have been determined for three important products, hydrated electron (e− aq), hydroxyl radical (·OH), and hydrogen peroxide (H2O2) as track segment yields (differential yields) under the conditions of neutral pH. With increasing LET, the g values of e− aq and ·OH decrease from 2.4 and 2.6 in 4He2+ radiolysis to 0.9 and 1.1 (100eV)−1 in 56Fe26+ radiolysis, respectively. It was also found that the primary g value of e− aq is smaller than that of ·OH for any type of ion beam. For the 12C6+ beam, other energies such as 290, 220, 135MeV/u were taken for the irradiation to investigate the effects of type or atomic number of ions on the measured yields. Furthermore, effects of dissolved oxygen on enhancement of H2O2 production have also been investigated with aerated NaNO3 solutions. The presence of dissolved oxygen caused 15–35% enhancement in H2O2 yields for all beams. In addition, the results of the present work were compared with reported track segment yields. [Copyright &y& Elsevier]

Abstract: The absorption spectra of solvated electrons in 1-propanol and 2-propanol have been investigated from 22 to 270°C at a fixed pressure of 7MPa, by using both nanosecond pulse radiolysis and laser photolysis techniques. The results show that, even up to supercritical conditions, it is still possible to measure unambiguously the absorption spectra of solvated electron in these two propanols. The peak positions of the absorption spectra show a red-shift (shifts to longer wavelengths) as temperature increases, similar to water and other alcohols, but the temperature efficiency, dE max/dT, of 1-propanol is larger than that of 2-propanol. In addition, in clear contrast to that of pulse radiolysis, in laser photolysis experiments, an increase in the maximum absorbance of the absorption spectra of solvated electron with temperature up to ∼200°C is attributed to the increase of absorbance (CTTS absorption band) of I− anion at 248nm with increasing temperature. [Copyright &y& Elsevier]

Abstract: γ-Radiolysis and pulse radiolysis of phenol in aqueous solution up to supercritical condition have been carried out. G-values of phenol consumption and product formation have been determined. While dihydroxybenzenes were major products at room temperature, multi-ring compounds and benzene were formed above 300°C. This indicates reaction mechanism was changed above 300°C, where phenoxyl radical plays a predominant role. This is supported by the observation of phenoxyl radical in pulse radiolysis. In supercritical water, the G-values increased with decrease of density. [Copyright &y& Elsevier]

Abstract: A product analysis study of γ-irradiated benzophenone aqueous solutions from room temperature to 400°C has been carried out by the combination of a flow irradiation system and a liquid chromatographic method. At room temperature, the main decomposition products are phenol and hydroxybenzophenone isomers. In high temperature and supercritical water solutions, 9-fluorenone appears as an important product and the G-value of benzophenone consumption depends significantly on the water density under supercritical conditions. [Copyright &y& Elsevier]

The large-scale synthesis and the stabilization of noble metal nanocatalysts with ultrasmall sizes are crucial to their practical application. Herein, Pd, Au, and Pt nanoparticles (NPs) are in situ embedded on boron nitride nanosheets (BNNSs) via the reduction of precursor salts induced by 60Co γ-irradiation, which is a mature technique widely used in industry. The reduction mechanism was elucidated by pulse radiolysis experiments. In comparison with other BN substrates like hexagonal BN (h -BN), BNNSs had not only large surface area of 263 m2 g−1, but also abundant hydroxyl groups produced during the sonicated exfoliation, resulting in ultrasmall sizes, large loading amounts, and uniform distribution of the anchored NPs. The particle sizes of the loaded Pd, Au, and Pt NPs were measured to be 2.9, 3.1, and 3.0 nm, respectively. As a consequence, in the model reaction of 2-nitroaniline reduction, the Pd-, Au- and Pt-BNNSs composite nanocatalysts showed much higher catalytic activities than those composites loading the corresponding NPs on other BN substrates. Particularly, most of the 2-nitroaniline could be reduced within merely 40 s when using Pd-BNNSs as catalysts, performing a rate constant of 1.1 × 10−1 s−1. The number of hydroxyl groups on BNNSs support as well as the catalytic performance of the corresponding NPs-loaded BNNSs composites could be improved by extending the sonicated exfoliation time, because more NPs were loaded and the hydroxyl groups were also proved to play an important role in enhancing the catalytic activity. Moreover, Pd-BNNSs catalysts still displayed prominent activity even after five cycles owing to the high stability of BNNSs and their strong affinity for PdNPs. This work not only demonstrates BNNSs as ideal supports to load noble metal NPs for catalysis, but also reveals the feasibility to synthesize and in situ embed ultrasmall noble metal NPs on BNNSs via γ-irradiation. γ-Radiation-induced reduction achieved facile loading of noble-metal nanoparticles on BNNSs as ideal supports for extraordinary catalytic activity and excellent reusability. [Display omitted] • BNNSs with hydroxyl groups, prepared from sonicated exfoliation, were suitable to load noble metal nanoparticles (NPs). • Noble metal NPs of Pd (Au or Pt) were in situ embedded on BNNSs by facile γ-radiation-induced reduction. • The reduction mechanism was elucidated by pulse radiolysis experiments. • NPs loaded on BNNSs possessed the smaller sizes and higher loading amounts, compared with those on other BN substrates. • NPs-loaded BNNSs showed excellent catalytic activity and reusability for 2-nitroaniline reduction. [ABSTRACT FROM AUTHOR]

• BCN was successfully modified by silane coupling agent. • The mechanical properties of SR were enhanced by BCN after irradiation. • BCN decreased the radiation crosslinking of SR. • BCN lessened the gas generated by SR side chain after irradiation. • The mechanism of BCN to improve the radiation resistance of SR was explained. The developing nuclear technology has increased the need for radiation-resistant and shielding materials. It is crucial to study the radiation resistance of polymers in order to prevent safety incidents brought on by the degradation of polymer performance in a nuclear environment. In this work, γ-aminopropyltriethoxy silane (KH550) was successfully grafted onto carbon-doped boron (BCN) to obtain modified BCN (BCN-KH550), then BCN-KH550 was added in silicone rubber and refined and vulcanized. The elongation at break of silicone rubber composite doped with 0.3 phr BCN-KH550 can retain (54 ± 2)% of the initial value. The addition of BCN and BCN-KH550 both increases the initial decomposition temperature of the irradiated SR. The radiation caused changes in crystallinity and glass transition temperature (T g) were measured using differential scanning calorimetry. The difference T g of BCN-KH550/SR0.3 before and after irradiation is 0.9 °C higher than that of SR. It is supposed that BCN protects the side group of SR during irradiation through differential thermogravimetric analysis curve and gas phase infrared spectra of the irradiation-induced gas products. BCN and BCN-KH550 can lower the hydrocarbon, CO 2 and CO production by side chain breakdown in both air and nitrogen atmospheres. The presence of BCN and BCN-KH550 decrease the radiation crosslinking of SR. The outcomes demonstrate that BCN-KH550 can reduce the effects of γ-radiation crosslinking on SR by declining side chain decomposition. [ABSTRACT FROM AUTHOR]

This article investigated the solubility of platinum group metals (PGMs) in sodium borosilicate glass and its effect on the viscosity and electrical conductivity of melts. The role of PGMs in the viscosity and electrical conductivity of melts was examined using the rotating cylinder method and impedance spectroscopy, respectively. Moreover, XRD, XPS, and SEM were used to measure the phase compositions, valence states, and microstructures, respectively, of the glass samples with different PGMs contents. The results showed that the solubility of Pd and Rh in sodium borosilicate glass was estimated to be less than 110 ppm by weight. The higher concentrations of Pd and Rh resulted in Pd-rich and Rh-rich inclusions in the glass matrix, which eventually agglomerated to form metallic Pd, Rh and Rh 2 O 3. The evolution of viscosity and electrical conductivity with different temperatures followed the Arrhenius equation with a fairly good linear relationship between ln η and ln κ. • The solubility of PGMs in borosilicate glass was less than 110 ppm by weight. • The aggregation and crystallization trends of PGMs in glass were investigated. • The temperature dependence of viscosity and conductivity of glass melts obeyed Arrhenius equation at high temperature region. • The viscous/electrical activation energy of glass melts containing 0–1 wt% PGMs was calculated. • The impact of PGMs concentration on the structure of PGMs aggregates had a nonlinear threshold effect. [ABSTRACT FROM AUTHOR]

• BCN was surface modified with two silane coupling agents. • Composites exhibited excellent properties before and after gamma irradiation. • The performance of composites can be improved by improving the interfacial compatibility. • Modified BCN could weaken oxidative degradation of EP under γ irradiation. Polymer matrix composites reinforced with boron nitride (BN) have attracted much attention in the nuclear industry due to their attractive properties. Nevertheless, the performance of such composites largely depends on matrix–filler interactions. Herein, carbon-doped boron nitride (BCN), modified by two silane coupling agents, was used to fabricate epoxy composites, and the effect of gamma irradiation on the properties of epoxy resin composites was investigated. The research showed that the modified BCN/epoxy composites prepared herein exhibited excellent mechanical and thermal properties before and after gamma irradiation. The tensile strength of the composites increased up to 63.1 MPa at 0.5 wt % loadings compared to neat epoxy (54.7 MPa). After irradiation at 900 kGy, the tensile strength of the composites was 32.5% higher than that of neat EP. This improvement was ascribed to the excellent compatibility of the modified BCN and epoxy. Moreover, the char yield and the glass transition temperature significantly increased with incorporation of modified BCN before and after irradiation. The mechanism for the enhanced performance was that the barrier consisting of BN protected the matrix from further oxidative degradation. This study suggested that functionalized BN more effectively enhanced epoxy properties before and after irradiation. [ABSTRACT FROM AUTHOR]

Solvatochromic shift of 4,4′-bpyH in aqueous solutions at elevated temperatures up to supercritical conditions and in various organic solvents with different dielectric constants, is investigated by pulse-radiolysis technique. 4,4′-bpyH shows a stronger solvent–solute interaction in water than in organic solvents, perhaps due to the hydrogen bond between 4,4′-bpyH and water. At 380 °C, local density augmentation, namely ρ local – ρ bulk , in supercritical water becomes 280 kg m −3 ( ρ bulk = 208 kg m −3 ), and the density enhancement factor is 8.9. Density fluctuation maximizes when ρ bulk is around 120 kg m −3 . Density inhomogeneity decreases as temperature rises, but is still remarkable at 400 °C. [ABSTRACT FROM AUTHOR]

• The mechanical property and T g of the EP were improved by introducing h -BN. • The low contents of h -BN were favorable to enhance the radiation resistance of EP. • h -BN could weaken oxidative degradation of EP under γ irradiation. • h -BN endowed the EP with excellent neutron shielding by absorbing neutrons. Improving the radiation resistance of epoxy resin (EP) is pivotal for the reliability of equipment and the safety of facilities in the nuclear industry. Hexagonal boron nitride (h -BN) is attractive in the preparation of radiation-resistant materials due to its good radiation stability and neutron shielding capability. In this work, h -BN/EP composites with enhanced radiation resistance were fabricated by solution blending. The tensile strength and thermal properties of the composites after γ-ray and neutron irradiation were investigated. The results showed that the addition of h -BN improved the mechanical property and the glassy transition temperature of the resin. The presence of low-level h -BN was favorable to enhance the radiation resistance of EP. As for composites with the 0.05% mass percentage of h -BN, the absorbed dose required to decrease relative tensile strength by 50% was about 300 kGy, which was higher than that of neat EP. The intrinsic mechanism of radiation resistance was attributed to the oxygen barrier effect as investigated by XPS and EPR. Then, benefiting from the absorbing neutrons capability of boron atoms, an addition of 0.55% h -BN to the EP resin could reduce the neutron transmittance of the resin by 5.6%. This study demonstrates that the blending with h -BN can increase the radiation-resistant property of EP resin, meanwhile augmenting the neutron shielding ability. [Display omitted] [ABSTRACT FROM AUTHOR]