Gamma Irradiation of Fluorocarbon Polymers

Several fluorocarbon polymers were irradiated with Co⁶⁰ gamma radiation at doses up to 10²² ev/g. The polymers studied included polytetrafluoroethylene, polytrifluoroethylene, polychlorotrifluoroethylene, a copolymer of tetrafluoroethylene with hexafluoropropylene, and several rubbery vinylidene fluoride copolymers. G-values were measured for volatile products, for free radicals detected by electron spin resonance, and, in the case of polychlorotrifluoroethylene, for scissions. The course of degradation or crosslinking was followed by zero-strength-time and tensile-strength measurements. It was found that for polytetrafluoroethylene and its hexafluoropropylene copolymer the presence of air-accelerated scission drastically. The mechanism of the radiation-induced changes is discussed in terms of free-radical intermediates.     

Effect of Gamma Irradiation on the Electrical Properties of Single-Crystal Corundum

The effect of gamma irradiation on the electrical properties of single-crystal corundum is studied. The conductivity of corundum as a function of gamma dose is found to pass through a minimum. The results are discussed in terms of the known models. The dielectric losses in irradiated corundum vary with temperature in a complex manner and pass through a maximum. This behavior is interpreted under the assumption that losses are mainly due to relaxation processes or conduction, depending on temperature. The activation energies of conduction and polarization are determined, and the likely mechanisms of dielectric losses are discussed.     

Effect of Gamma Irradiation on the Electrical Properties of Synthetic Quartz Crystals

The effect of gamma irradiation on the electrical conductivity, dielectric losses, and dielectric permittivity of synthetic quartz crystals was studied in a broad temperature range (295–670 K). The conductivity of the crystals was shown to exhibit Arrhenius behavior above 420 K and power-law behavior (T ^1/4) below 420 K. These findings are interpreted as evidence that, at elevated temperatures, thermally activated transport prevails, whereas at low temperatures, the dominant mechanism of conduction is hopping transport. The conductivity of quartz passes through a maximum at a gamma dose of about 10⁶ rad. Gamma irradiation slightly reduces the activation energy for low-temperature conduction, whereas the high-temperature activation energy remains virtually unchanged.     

Hydrolitic Stability of Aluminophosphate Glasses with Radioactive Waste Simulators under Gamma Irradiation

Radiochemistry - The effect of γ-irradiation with a dose of 62 MGy on the stability in water of two types of sodium aluminophosphate glasses was studied: glasses of a simple composition (GS)...     

60 Coγ射线辐照对硅泡沫材料压缩性能的影响

为了给60 Coγ辐照条件下硅泡沫垫层的构型设计和工艺优化提供依据,本工作通过材料辐照实验、力学实验和扫描电子显微镜观察等方法,研究了60 Coγ射线辐照对硅泡沫材料压缩性能的影响,探索了辐照条件下硅泡沫材料的损伤机理,并在此基础上建立了辐照环境条件下多孔硅泡沫材料压缩性能的预测模型,给出了材料压缩模量和断裂应变随辐照剂量的变化规律.结果表明:γ辐照对材料压缩性能的影响较为明显,在预压缩量较低的情况下,辐照后硅泡沫材料力学性能呈先升后降的趋势;当预压缩量超过50％时,辐照后硅泡沫材料力学性能呈先陡后缓的下降趋势.预压缩量为30％、辐照剂量为300 kGy时,硅泡沫材料的拉伸强度和剪切强度分别增加了69％和84％;而辐照剂量增大到1000 kGy时,其值分别下降了47％和50％.结合材料宏观性能和细观结构的分析认为,γ辐照引起的交联反应和降解反应是造成硅泡沫材料力学性能改变的主要原因.     

Gamma Ray Irradiation Effects on Electrical Transport and Microwave Properties of BISCO Superconducting Films

High-T _c Superconducting films of Bi–Sr–Ca–Cu–O (2:2:1:2) have been synthesized by spray pyrolysis of nitrate precursors onto yttria stabilized zirconia (YSZ). -ray irradiation of the sample, was carried out using a ⁶⁰Co source of 10³ Ci strength for several hundreds of hours; the dose received by the samples was 80 K rad/hr. Superconducting properties such as critical transition temperature (T _c), resistivity (R), critical current density (J _tc). Voltage-time relaxation (V _t) and microwave induced dc voltage were investigated as a function of temperature down to 77 K after -ray irradiation. -ray irradiation was found to have practically no effect on its structural modification and on the critical transition temperature. However, transport critical current density (J _tc) increased. The increase of pinning energies with irradiation suggests that these changes in properties are dominated by radiation-induced randomly distributed mobile oxygen defects in the films. An appreciable decrease in the microwave-induced dc voltage at 77 K was also observed after irradiation which suggests that the mobile defects are clustered at the major defect region and reduce the total number of weak links. These results suggests that oxygen defects induced by -ray irradiation of BISCO films act as important and major pinning centers which is responsible for the enhancement of J _tc and reduction of microwave induced dc voltage.     

Effect of Gamma Irradiation on Dynamics of Charge Exchange Processes between Single Trap and Nanowire Channel

In the present study, transport properties and single trap phenomena in silicon nanowire (NW) field‐effect transistors (FETs) are reported. The dynamic behavior of drain current in NW FETs studied before and after gamma radiation treatment deviates from the predictions of the Shockley–Read–Hall model and is explained by the concept taking into account an additional energy barrier in the accumulation regime. It is revealed that dynamics of charge exchange processes between single trap and nanowire channel strongly depend on gamma radiation treatment. The results represent potential for utilizing single trap phenomena in a number of advanced devices.     

Effect of Gamma Irradiation on the Magnetothermoelectric Properties of Extruded ZrO2-Modified Bi0.85Sb0.15

Inorganic Materials - Electrical and thermal properties of extruded unmodified and ZrO2-modified Bi0.85Sb0.15 samples have been studied as functions of gamma dose at temperatures from ~77 to 300 K...     

Effect of Gamma Irradiation on the Electrical Properties of Vitreous SiO<Subscript>2</Subscript>

The effect of gamma irradiation on the electrical properties of vitreous SiO₂ is studied at temperatures from 290 to 720 K and gamma doses from 10² to 5 × 10⁷ Gy. The activation energy of conduction in the samples studied is shown to be unaffected by gamma irradiation. The conductivity of vitreous silica is a nonlinear function of gamma dose, with a minimum near 10⁵ Gy. Temperature-dependent conductivity data attest to a change in conduction mechanism around 400 K: the data are well fitted by a power-law function at lower temperatures and by an exponential at higher temperatures.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 7, 2005, pp. 834–840.Original Russian Text Copyright © 2005 by Abdukadyrova.     

Effects of Doping, Gamma Irradiation, and Annealing on the Temperature Dependence of the Photocurrent through Bismuth Titanate Crystals

The separate and combined effects of doping, annealing, and gamma irradiation on the temperature-dependent photocurrent through nominally undoped and doped sillenite-type crystals were investigated between 77 and 300 K. The results were interpreted using a band-structure model describing the recombination processes involved in terms of deep slow and fast recombination centers (r- and s-centers) and shallow traps. The electron transitions to recombination centers were shown to be controlled by the trap levelE _t. The thermal stability of radiation-induced defects was assessed.     

Generation of Random Gamma Variates from the Two-Parameter Gamma

An algorithm has been developed capable of generating random gamma variates from any two-parameter gamma form with arbitrary parameters. The algorithm, shown to be both accurate and computationally efficient, is given as a FORTRAN IV function routine. Extensions are also made to the generation of random deviates from other useful probability density functions.     

Theoretical Foundations of Gamma–Gamma Method of Detection of Explosives

Theoretical calculations of the spectra of gamma radiation scattered by trinitrotuluene and by substances that are close to trinitrotuluene in terms of density and composition are presented. From the results of calculations, requirements that must be satisfied by a method of detection and identification of different explosives and a device to implement the method are formulated.     

玻璃的辐照效应及耐辐照改性研究进展

航天科技、核医学、核能工业和绿色建筑的发展对使用在辐射环境中的玻璃提出了越来越高的要求。玻璃在辐射环境中会发生微观结构变化和宏观性质改变,耐辐照玻璃是一种在高能射线或粒子辐照后可见光区透过率下降较小,能保持物理化学性能稳定的特种玻璃。阐述了玻璃的辐照效应研究现状,介绍了玻璃耐辐照改性的研究进展及挑战,并提出了值得关注的新趋势。     

Simulation of Arbitrary Gamma Distributions

Two simulation procedures for arbitrary gamma distributions are compared. Both procedures depend on closed form approximations to the cumulative gamma distributions, but one procedure appears to yield considerably more accurate results than the other. Tables are given which allow this procedure to be easily applied.     

Inference on the Gamma Distribution

This study develops inferential procedures for a gamma distribution. Based on the Cornish–Fisher expansion and pivoting the cumulative distribution function, an approximate confidence interval for the gamma shape parameter is derived. The generalized confidence intervals for the rate parameter and other quantities such as mean are explored. The proposed generalized inferential procedures are extended to construct prediction limits for a single future measurement and for at least p of m measurements at each of r locations. The performance of the proposed procedures is evaluated using Monte Carlo simulation. The simulation results show that the proposed procedures are very satisfactory. Finally, three real examples are used to illustrate the proposed procedures. Supplementary materials for this article are available online.