Simulation study on detection efficiency of plastic scintillating fiber under γ-ray radiation

The detection efficiency of the plastic scintillating fiber (PSF) for γ-ray radiation is presented through Geant4 simulation. The incident γ-rays with energy of 100–10,000 keV are considered. Absorption efficiency and scintillating response of PSF are also obtained, and the simulated results are consistent with the theoretic ones. From simulation, the main important factor of detection efficiency in the energy range is the absorption efficiency of the scintillating material. The cross talks in a fiber array are also discussed. These results could probably provide some ways of using PSF as a γ-ray imaging detector in certain applications.     

Influence of silver nano‐additive amount on the supramolecular structure,porosity, and properties of polyacrylonitrile precursor fibers

This work examines the influence of the amount of silver nanoparticles added to polyacrylonitrile spinning solutions on their rheological properties as well as the structure and properties of the fibers produced. The influence of the amount of silver nanoparticles on the supramolecular structure of nanocomposite polyacrylonitrile precursor fibers, their porosity, as well as thermal and tensile strength properties was determined. The distribution of the nano‐ additive in fiber cross‐sections and on the surface was estimated. It was found that the addition of silver nanoparticles to polyacrylonitrile precursor fibers in an amount of up to 1.5% does not cause a decrease in the susceptibility of the fiber matter to deformation at the drawing stage. The produced fibers were characterized by an increased total volume of pores of 0.35 cm³/g and tenacity of more than 34 cN/tex. Copyright © 2009 John Wiley & Sons, Ltd.     

Polyelectrolyte Hydrogels Based on Hydrolyzed Polyacrylonitrile Fiber

Cross-linking of hydrolyzed Nitron D polyacrylonitrile fiber on exposure to ionizing radiation was studied as influenced by its concentration in the solution, dose rate, and the presence of oxygen in the system. Preparation conditions of polyelectrolyte hydrogel with maximal water absorption by radiochemical cross-linking at the minimal dose were determined.     

Effect of gamma radiation on dilute aqueous solutions and thin films of N-succinyl chitosan

N-Succinyl chitosan (N-SC) products with various degrees of substitution were synthesized by a direct reaction between chitosan and succinic anhydride. The susceptibility of the as-synthesized polymers to degradation upon their exposure to γ-ray radiation was investigated. The results were compared with the as-received chitosan. The size exclusion chromatographic results showed that chitosan and N-SC products in their dilute aqueous solution state were more subservient to degradation by γ-ray radiation than in their solid film state, despite the much less exposure to the radiation (i.e., 5-30 kGy for the solutions versus 20-100 kGy for the films). Increasing the radiation dose resulted in the rather monotonous decrease in the molecular weights of the polymers. Structural analyses of the irradiated polymers by Fourier-transformed infrared spectroscopy (FT-IR) and UV-visible spectrophotometry indicated the increase in the amount of carbonyl groups with the radiation dose. The formation of the carbonyl groups suggested that the radiolysis of chitosan and N-SC products occurred at the glycosidic linkages. In addition, FT-IR, elemental analysis and proton nuclear magnetic resonance spectroscopy (¹H NMR) results suggested that γ-ray radiation affected both the N-acetyl and N-substituted groups on the polymer chains.     

Influence of ionizing radiation on physical properties of native and chemically modified starches

Cationic and anionic starches (chemically modified) and native starch (non-modified) were exposed to electron-beam irradiation at doses of 25, 75 and 150 kGy. The increasing solubility in water, due to chain scission and creation of polar groups as already mentioned in the literature, has been confirmed using several physical methodologies. Impedance Spectroscopy (IS) on water solutions was carried out in order to calculate the relaxation parameters of the Cole–Cole model and α and β parameters of the Jones–Dole equation, which show the influence of radiation dose on increasing polarity, decreasing of molecular mass and increasing of electrostatic attraction between chains. Infra-red spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) confirm the formation of polar groups that retain water. The aim of this work was to confirm that the control of chain scission and functionalization of starches with irradiation could then be used in a future work to create nanoparticles by complex coacervation in an aqueous base.     

Effect of γ-ray radiation on the polyacrylonitrile based carbon fibers

To investigate the effect of γ-ray radiation on the microstructural and mechanical properties of carbon fibers, carbon fibers were irradiated by ⁶⁰Co source. The interlayer spacing d₀₀₂ of carbon fibers decreased after irradiation. The Young’s modulus and density of the fibers increased with increasing dose. The tensile strength of fibers was found to increase at low dose and decrease at high dose. Additionally, Compton scattering effect caused by γ-ray is proposed to be responsible for the structural and mechanical changes of fibers. The results indicated that γ-ray irradiation was an effective method for improving the mechanical properties and graphitization degree of polyacrylonitrile based carbon fibers.     

Spinnability of Polyacrylonitrile Gel Dope in the Mixed Solvent of Dimethyl Sulfoxide/Dimethylacetamide and Characterization of the Nascent Fibers

In this work, acrylonitrile copolymers were prepared via precipitation polymerization. The copolymer solutions prepared at various ratio of dimethyl sulfoxide and dimethylacetamide were tested to prepare the nascent fibers by one-step wet-spun method. The effect of temperature, solvent ratio, molecular weight and the solid content on the rheological properties of polyacrylonitrile gel solution in different mixed solvent were studied. It was shown that the viscosity decreased with the increase of the temperature and fluctuated with the different solvent ratio reaching the minimal value at the ratio of dimethyl sulfoxide to dimethylacetamide equal to 1.25. The crystallinity of copolymers and the structure of the nascent fiber surface also depended from the solvent ratio in polymerization. The optimum conditions for spinnability of copolymers were determined. The high-quality polyacrylonitrile precursor was achieved with the controllable range of 0.5–0.8 dtex and the toughness of polyacrylonitrile precursor was greater than 6.0 cN/dtex after the wet spinning process, while the tensile strength of carbon fiber is up to 6.25 GPa after their pre-oxidation and carbonization process.     

The radiation degradation of a nanotube-polyimide nanocomposite

The radiation degradation of a nanotube-polyimide nanocomposite was studied. Radiation chemistry was observed that was not present in the unmodified polymer or in the imbedded single-walled carbon nanotubes (SWNTs) themselves. The tensile properties were found to be improved by the addition of SWNTs in the unirradiated materials, and no deterioration in these properties with irradiation was observed. The SWNTs were found to have a detrimental effect on the optical properties however. The transparency of the composite was degraded significantly faster by electron-beam radiation than the neat polymer was. This may make the SWNT/polyimide composites unsuitable for some space applications. Electron Spin Resonance (ESR) measurements determined that the SWNTs interfere with the radical chemistry in the irradiated materials. This could be due to energy dissipation by the SWNT network, preventing the formation of radical species, or alternatively, preferential reaction or termination of radicals by the nanotubes. FT-Raman spectroscopy was found to be a very useful tool for examining SWNTs embedded at low concentrations. It revealed no signs of SWNT degradation up to 10 MGy.     

Influence of High-energy electron-beam on photocatalytic activity of TiO2 films on carbon-fiber deposited by atomic layer deposition

High-energy electron-beam with energy of 1 MeV was used for modifying surface structure of TiO₂ thin films on carbon fiber prepared by using atomic layer deposition under atmospheric pressure. TiO₂ nanoparticles (∼20 nm) on carbon fiber underwent structural modification of the surface upon electron-beam treatment, resulting in enhanced photocatalytic activity. In contrast, a thicker film of TiO₂ did not show such changes in surface structure and photocatalytic activity by electron-beam treatment. We demonstrate that electron-beam can be used for modifying surface structure of photocatalysts consisting of nanoparticles for improvement of their activity.     

Effect of cobalt-60 gamma radiation on the determination of uranium(IV) in phosphoric acid solutions of uranium(iv) oxide

The effect of ⁶⁰Co γ-radiation on aerated and deaerated phosphoric acid solutions of uranium(IV) oxide (UO₂) was studied as a function of temperature, concentration of UO₂, and radiation dose rate. The effect was measured in terms of the radiolytic yield of uranium(VI),Gu_VI. For solutions of high initial UO₂ concentration, Gu(VI) is largest for the aerated solutions at 25°; it is lowest for the deaerated solutions at 140°. The Gu(VI) is lower for the solution of low initial UO₂ concentration than for any of the solutions of high initial UO₂ concentration. At the high starting UO₂ concentration, the initial Gu(VI) values are always higher than the succeeding values; this effect is attributed to the depletion of oxygen originally present in the solution. Gamma radiation causes an error in the determination of the stoichiometry of UO₂; the error is a function of the radiation dose. This error can be minimized by excluding oxygen from solutions of UO₂ and by keeping the initial UO₂ concentration as low as possible.     

Synthesis and efficiency of a chelating fiber for preconcentration and separation of trace Au(III) and Pd(IV) from solution samples

A novel poly(acryl-benzoylamidrazone-acryl-benzoylhydrazine) chelating fiber was synthesized simply from nitrilon (polyacrylonitrile fiber). The structure of the chelating fiber was verified with the help of FT-IR spectrum. The parameters influencing the efficiency of the fiber for concentrating trace amounts of Au(III) and Pd(IV) were investigated in detail. Trace Au(III) and Pd(IV) were enriched and separated from real sample solutions and detected using inductively coupled plasma atomic emission spectrometry (ICP-AES) with satisfactory results. The experiments show that the method is rapid, precise, simple and convenient to use.     

Temperature-dependence of mechanical and morphological properties of ultra-high molecular weight polyethylene cross-linked by electron beam irradiation

Cross-linking of ultra-high molecular weight polyethylene was performed with electron-beam irradiation in the range of radiation dose from 12 to 96 Mrad under nitrogen. Dry gel films and melt films were used as specimens. Two kinds of cross-linked specimens could be kept at 200°C for a prolonged time in an undeformed state and this tendency was independent of radiation dose. The elongation of the gel films hampered the heat-resistant effect and the drawn specimens were broken at temperatures lower than 175 °C. The elongation of the melt films could not be realized, because of a marked fixation of chains in the fiber network, even at a dose of 12 Mrad.     

Standards and regulations for radiation processing industry in China

To understand the current status and development tendency of radiation processing industry in China, and to know the relationship between the perfecting of standard systems and the increasing of throughput of this industry, a brief introduction on Chinese standards and regulations is given in this paper. Typical documents for setting up and operating an irradiation facility for radiation processing, either a gamma-ray or an electron-beam facility, are introduced in detail. A comparison is made between some of the international standards and those corresponding Chinese national standards. The consideration of development of Chinese standards and regulations indicates a positive tendency for this industry.     

新型含季铵基腈纶纤维的制备

以商品级腈纶为基体,二甲氨基丙胺(Ⅰ)为胺化剂,经胺化反应制得含叔胺基的腈纶纤维(1)。以溴辛烷(Ⅱ)为季铵化试剂对1进行季铵化改性,制得新型的含季铵基的腈纶纤维(2),其结构经IR和EDS表征。较佳的胺化反应条件为:以乙二醇为溶剂,Ⅰ的体积分数为30%,于118℃反应3 h。较佳的季铵化反应条件为:以乙醇为溶剂,Ⅱ.的体积分数为10%,于70℃反应6 h。     

Liquid carbon dioxide as a solvent for the radiation polymerization of ethylene

The usefulness of liquid carbon dioxide as a solvent for polymerization of ethylene was studied. The effect of liquid carbon dioxide on the polymerization was investigated under conditions of the pressure of 400 kg./cm.² over the temperature range 20–45°C. by using γ-radiation and AIBN as initiators. The infrared spectrum of the polymers showed that carbon dioxide had little effect on the polymer structure. The polymers contained no combined carbon dioxide and only small amounts of vinylidene unsaturation. The methyl content of the polymers was 0.5–4.0 CH₃/1000C. The polymer yield and molecular weight were found to be decreased by the addition of carbon dioxide in both polymerization by γ-radiation and AIBN. The number of polymer molecules formed per unit time increased with the content of carbon dioxide in the γ-ray polymerization, and was constant in the case of AIBN. The advantages of the use of liquid carbon dioxide as a solvent in this polymerization were also considered from the viewpoints of the continuous process, the separation of polymer, the stability of carbon dioxide to radiation, and commercial applications.     

通过辐射交联提高PLA/纤维复合材料的耐热性能

通过热加工的方法制备了一系列含三烯丙基异氰脲酸脂(TAIC)的PLA/纤维复合材料,并在氮气保护下用γ射线诱导发生辐射交联反应.通过热变形温度实验表明辐射交联后,复合材料的热变形温度(HDT)都有提高,特别是当纤维质量分数超过20%时,即使在很小的吸收剂量下,复合材料的HDT从60℃左右大幅提高到120℃以上.HDT的提高只与纤维的含量有关而与纤维种类无关.凝胶抽提与红外光谱实验结果表明,复合材料在辐射后所形成的复杂交联结构,可能是导致其HDT大幅提高的重要原因.     

高平均分子量聚丙烯腈的制备、性能和应用

介绍了高平均分子量聚丙烯腈的主要制备方法，如混合溶剂自由基聚合、水相悬浮聚合、反相浮液聚合、离子聚合、紫外光辐射聚合等。还根据高平均分子量聚丙烯腈的性能探讨了其在高性能碳纤维前驱体聚丙烯腈原丝和高强高模中空纤维过滤膜方面的应用。     

Phase distribution of the products of radiation and postradiation distillation of cellulose

A comparison of the postradiation dry distillation of cellulose and its distillation in the mode of electron-beam radiation heating has shown that irradiation reduces the yield of char and water. Preirradiation of cellulose at doses of 0.2–2.2 MGy stimulates a monotonic increase in the proportion of total organic products in the condensate distilled off during postradiation dry distillation, reducing the proportion of water by one third. Effective distillation of cellulose in the radiation heating mode is observed at a dose rate above ∼1 kGy/s. The condensate distilled off at 1.5–2.5 kGy/s is composed of organic compounds by ∼90% and is characterized by a high density (up to 1.33 g/cm³) and a high refractive index (up to 1.4690).     

Radiation-induced crosslinking of polyacrylonitrile fibers and the subsequent regulative effect on the preoxidation process

To investigate the radiation effect on polyacrylonitrile (PAN) fibers as well as on the preoxidation process, PAN fibers were irradiated by γ-rays at room temperature at 50–500 kGy in vacuum and then were thermally oxidized in air. Gel fraction determination indicated that γ irradiation led to the predominant crosslinking of PAN fibers, with G values (the number of event per 100 eV absorbed) of G(X)=0.28 and G(S)=0.16 for chain crosslinking and scission, respectively. It was found that irradiation caused a slight change in the crystal structure and tensile strength at low dose. Radiation led to a reduction of the onset temperature of cyclization reaction and moderated the exothermic behavior. The density of the PAN fibers after thermal oxidation was used to evaluate the preoxidation extent. It was proven that radiation could significantly accelerate the preoxidation process and consequently shortened the preoxidation time. Radiation crosslinking may have potential application in the production of PAN-based carbon fibers.     

Thermal behaviour of poly(dimethylsiloxane) hybrid silicas prepared by radiation grafting

This paper reports our investigation regarding the thermal properties of new polymer-silica hybrid materials obtained by radiation grafting. The polymer poly(dimethylsiloxane),bis(3-aminopropyl)terminated is γ-grafted on a silica gel surface. The thermal behaviour of γ-grafted hybrid materials reveals remarkable differences compared to the thermal behaviour of physically adsorbed polymers. These differences allow us to assess the ability of γ-rays to produce a polymer chemically bonded on a silica surface. The chemical bonds formed by irradiation give to the polymer a high conformational stability confirmed by DTA analysis.