Effects Of High-energy Radiation Research Articles

A study of gamma-irradiated polyethylenes by temperature modulated differential scanning calorimetry

Various polyethylenes (PEs) and the effects of high-energy radiation on their structures were widely studied in the past using conventional Differential Scanning Calorimetry (DSC) measurements. In this work, we used the Temperature Modulated Differential Scanning Calorimetry (TMDSC) technique in order to obtain more information about the influence of the initial structural differences and gamma radiation on the evolution in structure and thermal properties of different polyethylenes. For this reason, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) samples were exposed to gamma radiation, in air, to a wide range of absorbed doses (up to 2400kGy). The separation of the total heat flow TMDSC signal into a reversing and non-reversing part enabled us to observe the low-temperature enthalpy relaxation (related to the existence of the “rigid amorphous phase”) and recrystallisation processes, as well as to follow their radiation-induced evolution and/or that of melting in a more revealing manner compared to the case of the conventional DSC. Consequently, our results indicate that TMDSC could improve the understanding of radiation-induced effects in polymers.

The Effects of High Energy Radiation on the Tensile Properties of Rubber Toughened Nanocomposites

Composites based on high density polyethylene (HDPE), ethylene propylene diene monomer (EPDM) and Organically Modified Montmorillonite (OMMT) clays were made by melt compounding followed by compression molding. Mechanical properties, X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to characterize the nanocomposites. The addition of clay, compatibilizer agent, Maleic Anhydride Polyethylene (MAPE) and irradiation technique, High Energy Electron Beam (EB) considerably improved the properties of nanocomposites. Tensile Strength and Modulus (MPa) were found to increase significantly with increasing clay content and decreasing as the clay content exceeds 4 vol%. The largest improvement in nanocomposite tensile properties occurred at clay loading of 4 vol% (2-8 vol%) with irradiation technique. The d spacings of the clay in nanocomposites were monitored using XRD and the extent of delamination was examined by TEM. TEM photomicrographs illustrated the intercalated and exfoliated structures of the nanocomposites with OMMT, MAPE and irradiation process.

Effects of High Energy Radiation on Mechanical Properties of PP/EPDM Nanocomposite

Nanocomposites are the materials that are created by introducing nanoparticulates that always referred to as filler into the matrix. Blends of polypropylene (PP)/ethylene propylene diene monomer (EPDM)/Montmorillonite (MMT) were treated by compatibilizer MAPP and irradiation of electron beam. The effects on mechanical properties for both samples were compared with the untreated nanocomposites. Because each samples used different portion of clay loading, the effects of clay loading on mechanical properties is also observed. The sample is characterized by using Transmission Electron Microscope (TEM), X-Ray Diffraction (XRD), tensile test and impact test.

Network characteristics of hydrogenated nitrile butadiene rubber networks obtained by radiation crosslinking by electron beam

The effects of high-energy radiation on hydrogenated nitrile butadiene rubber (HNBR) copolymer structure and properties were studied. Characterization by FTIR spectroscopy, swelling and mechanical measurements of irradiated and un-irradiated sample permit us to correlate the change in structure with properties. The modifications obtained are dependent on the radiation dose of the incident electron beam. FTIR spectroscopy in absorption mode shows that irradiation of HNBR first induces trans-vinylene bond formation and secondly small amounts of carbonyl (C O) groups. Moreover, more significant changes were observed with swelling method and mechanical behaviour showing the effect of crosslinking on the elastomer.

Band Gap Energy for SiC Thin Films Prepared By TEACO2 Laser Irradiated With Nuclear Radiation

The effect of high energy radiation on the energy gap of compound semiconductor Silicon Carbide (SiC) are viewed. Emphasis is placed on those effects which can be interpreted in terms of energy levels. The goal is to develop semiconductors operating at high temperature with low energy gaps by induced permanent damage in SiC irradiated by gamma source. TEACO2 laser used for producing SiC thin films. Spectrophotometer lambda - UV, Visible instrument is used to determine energy gap (Eg). Co-60, Cs-137, and Sr-90 are used to irradiate SiC samples for different time of irradiation. Possible interpretation of the changing in Eg values as the time of irradiation change is discussed

Band Gap Energy for SiC Thin Films Prepared By TEACO2 Laser Irradiated With Nuclear Radiation

The effect of high energy radiation on the energy gap of compound semiconductor Silicon Carbide (SiC) are viewed. Emphasis is placed on those effects which can be interpreted in terms of energy levels. The goal is to develop semiconductors operating at high temperature with low energy gaps by induced permanent damage in SiC irradiated by gamma source. TEACO2 laser used for producing SiC thin films. Spectrophotometer lambda - UV, Visible instrument is used to determine energy gap (Eg). Co-60, Cs-137, and Sr-90 are used to irradiate SiC samples for different time of irradiation. Possible interpretation of the changing in Eg values as the time of irradiation change is discussed

강한 태양 및 지자기 활동 기간 중에 아리랑 위성 1호(KOMPSAT-1)의 궤도 변화

In this paper, we analyze the orbital variation of the Korea Multi-Purpose SATellite-1(KOMPSAT-1) in a strong space environment due to satellite drag by solar and geomagnetic activities. The satellite drag usually occurs slowly, but becomes serious satellite drag when the space environment suddenly changes via strong solar activity like a big flare eruption or coronal mass ejections(CMEs). Especially, KOMPSAT-1 as a low earth orbit satellite has a distinct increase of the drag acceleration by the variations of atmospheric friction. We consider factors of solar activity to have serious effects on the satellite drag from two points of view. One is an effect of high energy radiation when the flare occurs in the Sun. This radiation heats and expands the upper atmosphere of the Earth as the number of neutral particles is suddenly increased. The other is an effect of Joule and precipitating particle heating caused by current of plasma and precipitation of particles during geomagnetic storms by CMEs. It also affects the density of neutral particles by heating the upper atmo-sphere. We investigate the satellite drag acceleration associated with the two factors for five events selected based on solar and geomagnetic data from 2001 to 2002. The major results can be summarized as follows. First, the drag acceleration started to increase with solar EUV radiation with the best cross-correlation (r

The effect of high-energy radiation on aqueous solution of Acid Red 1 textile dye

The effect of high-energy radiation on Acid Red 1 (AR1) azo-dye solution was investigated by UV–Vis spectroscopy and chemical oxygen demand (COD) measurements. Doses in the order of 10 kGy cause complete decolouration of the 10 −3–10 −4 mol dm −3 solutions; however, for complete mineralization doses higher by 1–2 order of magnitude are needed. Hydrated electrons and H atom are more effective in fading reaction, while the OH radicals have higher efficiency in mineralization. The HO 2 •/O 2 •− radical–radical anion pair is rather inefficient in fading reaction.

Space environments and effects analysis for ESA missions

The evaluation of the environments of space missions is an area of increasing importance in the spacecraft design and operation phase. The need to assess accurately the effects of high-energy radiation, plasma and micro-particles on space missions has fostered the development and use of new generation tools to cope with the increasingly demanding requirements from more challenging space missions, use of commercial devices and advanced scientific detectors. We present applications at ESA of new tools for the support of space missions including particle transport in planetary magnetic fields, applied to the INTEGRAL mission, and shielding assessments in the context of the future BepiColombo and JWST missions. Developments of other new tools or techniques, such as microscopic NIEL degradation prediction tools, will be outlined. The need of a common framework for the development of future analysis tools (Geant4-based and not) is presented.

Durability of adhesive bonding of titanium in radiation and aerospace environments

In this investigation, attempts have been made at understanding the effects of high-energy radiation, low and high temperatures on adhesive bonding of titanium (ASTM F 67–95 Grade 2). Two titanium sheets are joined by a ceramic adhesive (Resbond™ 907 GF). The service temperature of this adhesive ranges from –185 to +1290 °C and, in addition, this adhesive has excellent resistance to most acids, alkalies, solvents, corrosive agents and fire, and, therefore, is extremely useful for aerospace applications. Prior to joining, the surfaces of the titanium sheets are mechanically polished by wire brushing, cleaned by isopropanol and then modified by sodium hydroxide anodization. First, to determine the joint strength under ambient conditions, tensile lap shear test are performed according to the ASTM D 5868-95 standard. Then the joints are exposed to aggressive chemical environments. It is observed that the joint strength decreases drastically for those joints prepared without modifying the titanium surface by sodium hydroxide anodization. However, the titanium surface modified by sodium hydroxide anodization and joined are able to retain about 70% of their strength. These joints are then irradiated for 6 h at a dose rate of 37 kGy/h in the pool of a SLOWPOKE-2 nuclear reactor, which produces a mixed field of thermal and epithermal neutrons, energetic electrons and protons and gamma rays. It is observed that under this exposure, the joint strength remains almost unaffected. In order to simulate the service conditions of aerospace applications, the joints are also exposed to low temperature (−80 °C) and elevated temperature (+500 °C) for 100 h. It is observed that in these cases, the joints retained the strength of about 95% in respect to the strength of the joint tested under ambient conditions. Failures of the joints are observed as primarily cohesively within the adhesive. Therefore, this adhesive bonding of titanium is a very good candidate for structural applications in aerospace.

Environmental effects in oil palm fiber reinforced phenol formaldehyde composites: Studies on thermal, biological, moisture and high energy radiation effects

Accelerated weathering studies of untreated and treated oil palm fiber reinforced phenol formaldehyde composites and oil palm/glass hybrid fiber reinforced phenol formaldehyde composites were conducted. Thermal, water, biological and γ radiation effects on the composite properties were analysed. Mechanical properties such as tensile, flexural and impact properties of thermal and water aged samples were investigated. The extent of biodegradation and γ irradiation effects was estimated from variations in tensile and impact properties. The tensile and impact fracture mechanism and changes in fiber-matrix adhesion were studied using scanning electron microscopic analysis. The changes in the tensile and flexural stress-strain characteristics as well as deformation behaviour of aged composites are well explained by respective stress-strain curves. Mechanical performance of the composites decreased upon thermal ageing. Marked decrease in these properties of the composites is observed upon radiation ageing. However water immersion leads to an increase in strength properties in some treated composites such as on acetylation, silane, acrylonitrile grafting, isocyanate, permanganate treatment, alkali treatment etc. It is found that oil palm fiber increases the biodegradability of the composites.

High-energy radiation effects on subthreshold characteristics, transconductance and mobility of n-channel MOSFETs

The influence of 8 MeV electrons on the threshold voltage (VTH), transconductance (gm) and mobility (μ) of n-channel depletion metal–oxide semiconductor field-effect transistors (MOSFETs) irradiated at gate bias, VGS = +2, 0 and −2 V, has been studied in the dose range of 0.5–31 kGy. The measurements performed after irradiation showed considerable decrease in VTH, gm and μ. The densities of interface trapped charge (ΔNit) and oxide trapped charge (ΔNot) for irradiated devices have been estimated from the subthreshold measurements. It has been found that ΔNot is higher than ΔNit. The mobility of carriers (μ) in the n-channel was estimated from the peak transconductance (gmPeak) and it was found that μ decreased by around 68.5–73.5% after exposure to the total dose of 31 kGy. Mobility degradation coefficients due to interface traps (αit) and oxide trapped charge (αot) were estimated and it was found that the mobility degradation was mainly due to ΔNit and the effect of ΔNot was negligible.

Effect of high-energy radiation and alkali treatment on the properties of cellulose

The effect of the treatment with NaOH or tetramethyl ammonium hydroxide solutions on preirradiated cotton-cellulose was investigated. Both the radiation and the treatment with alkali solutions caused loss of weight in cellulose; however, there was a synergism, a high weight loss was observed during alkali treatment of preirradiated samples. The radiation caused scissions of the cellulose chains and during the treatment with aqueous alkaline solutions some smaller fragments dissolved, resulting in a strong absorbance of the solutions with maximum at around 268 nm. It was attributed to the absorbance of aldehyde/keto groups.

Low-Energy Electron Damage to DNA and its Basic Constituents

The DNA molecule is composed of two long strands of repeated sugar-phosphate units to which the bases are chemically linked. The two strands are held together by hydrogen bonding between the bases. It is reported that low energy (3–20 eV) electrons interacting with vacuum-dry samples of DNA can break a single strand or both. The incident electron energy dependencies of the yields of single and double strand breaks are compared with those of H- ions ejected by electron impact on thin films of the elementary constituents of DNA (i.e., H2O, bases and sugar analogues). The decay of transient anions formed on the DNA’s basic components is found to play a crucial role in producing single and double strand breaks. Since a large portion of the energy deposited by ionizing radiation first leads to the production of low energy secondary electrons, these findings provide basic knowledge necessary to understand the effects of high-energy radiation in biological cells and eventually modify these effects at the molecular level.

Mechanisms of low energy electron damage to condensed biomolecules and DNA.

It has recently been shown that 3-20 eV electron impact on vacuum-dry samples of plasmid DNA induced substantial yields of single and double strand breaks (SSBs and DSBs). These results are summarised in the present article along with those obtained from the fragmentation of elementary components (i.e. condensed H2O, bases and sugar analogues) of DNA induced by low energy electron impact under ultra high vacuum conditions. By comparing the results from these experiments, it is possible to determine fundamental mechanisms by which low energy electrons damage DNA. The decay of transient anions formed on the DNA's basic components is found to play a crucial role in producing SSBs and DSBs. Since a large portion of the energy deposited by ionising radiation first leads to the production of low energy secondary electrons, these findings provide basic knowledge necessary to understand the genotoxic effects of high energy radiation and eventually modify these effects at the molecular level.

Hydrogel of Radiation-Induced Cross-Linked Hydroxypropylcellulose

Hydroxypropylcellulose (HPC) hydrogel being a material of natural origin, combines the properties of a polymer, which make up the network, with biodegradability. In this report the effects of high energy radiation on the ether of cellulose-HPC are presented. The polymer irradiated in its solid state or in dilute aqueous solution underwent mainly degradation, induced by the cleavage of glycosidic bonds in its main chain. Irradiation of HPC in aqueous solutions at moderate concentrations resulted in the formation of hydrogels. Chemical cross-links bond the chains of polymer, turning it to an insoluble macroscopic gel. We have found that in addition to concentration, dosage and dose rate can affect the results of irradiation. Electron beam irradiation gave higher gel fraction, up to 90%, than gamma irradiation, which has a maximum gel fraction of 65%. Swelling of the cross-linked hydrogels was related to the density of cross-links and was the highest at low irradiation doses. HPC hydrogels displayed thermally reversible character in their swelling. The volume of gel underwent continuous deswelling with an increase of the solution temperature, with the deswelling rate increasing rapidly over 40°C. At elevated temperatures the hydrogel collapsed, lost its transparency and changed color to translucent white. This transition was fully reversible when the gel was placed in the medium of low temperature. The hydrogel demonstrated superior mechanical properties. Despite of the stable three-dimensional cross-linked network, the gels underwent biodegradation under controlled conditions when enzyme was used.

Effects of gamma irradiation on the stress relaxation of drawn ultrahigh molecular weight polyethylene

Effects of high energy radiation on stress relaxation behavior of unoriented ( λ =1) and oriented ( λ =9) ultrahigh molecular weight polyethylene (UHMWPE) were investigated. As in a previous study, the stress relaxation is interpreted in terms of a model that consists of two thermally activated processes acting parallel. The first process is related to crystal and the second to the amorphous fraction. Application of the two-process model enabled separate studying of the influence of irradiation on viscoelastic behavior of these two fractions.

Degradation of poly(2-hydroxyethyl methacrylate) by gamma irradiation

Electron Spin Resinance (ESR) spectroscopy has been utilised to examine the effect of high energy radiation on poly(2-hydroxyethyl methacrylate) PHEMA. Radiation chemical yields ( G-values) for radicals were 1.7 and 1.2 for γ-irradiation at 77 K and ambient temperature, respectively. The ESR spectra at 77 and 300 K were simulated. The ESR spectrum at 77 K is a combination of six types of radicals ·CH 3, ·CH 2CH 2OH, COOCHCH 2OH, ·COO-, -CH- and ·CHO. However, after room temperature irradiation, the spectrum is a combination of methacrylate main chain scission radical and -CH-. The high stability of this radical at room temperature indicates the system is very rigid as a result of hydrogen bonding from the inherent side chain structure and radiation induced crosslinking due to labile hydrogen atoms in the side chain.

High energy radiation effects on halogenated butyl rubbers

The effect of high energy radiation on halogenated butyl rubbers was studied using electron spin resonance and nuclear magnetic resonance spectroscopies and gas chromatography. During high energy irradiation, most of the radicals were found to be generated on the halogenated isoprene units. A higher radiation yield for scission was observed in chlorinated butyl rubber than in brominated butyl rubber. This is due to the ready abstraction of hydrogen from the main chain by the chlorine radicals to give main-chain radicals which are known to contribute to scission in butyl rubbers. However, in both polymers, crosslinking predominates over scission up to a limiting dose.

Effects of high energy radiation on group III–V compound semiconductors

The determination of the properties of compound semiconductors exposed to radiation from the environment is relevant because this exposure triggers optically induced degradation mechanisms which introduce strong non-radiative recombination centers. Two different III–V compound materials were studied: indium phosphide and indium gallium arsenide, both with interesting properties and well suited to optoelectronic applications. A highly doped InP:Sn (3 × 10 18 cm −3) substrate was exposed in different experiments to high energy electrons (3.8 MeV) and γ-rays (0–3.8 MeV) and annealed at room temperature and 473 K. Photoluminescence (PL) analyses showed a significant effect of radiation as well as of heat treatments on InP properties. Thick (3 μm) In 0.4Ga 0.6As epitaxial layers grown on a multistage strain-relief buffer system produced on GaAs substrates were exposed to the same irradiation doses employed for InP. It was expected these layers would not perform well after irradiation since they were grown on mismatched substrates. Nevertheless PL measurements indicated that In x Ga 1−x As was not affected by the γ-ray irradiation doses employed in this work, while it was quite sensitive to electron irradiation although almost complete recovery was possible after heat treatment.