Influence Of Electron Radiation Research Articles

Influence of electron radiation on the physical and mechanical properties of a nonwoven fabric made using Spunlace technology

The effect of electron radiation on the physical and mechanical properties of Sontara nonwoven fabric produced using spunlace technology has been studied. The initial raw material for the manufacture of materials using this technology, as a rule, are viscose, polyester, polypropylene and cellulose fibers. Such nonwovens are highly breathable and are therefore used in disposable surgical gowns and suits. Since radiation can be used to sterilize disposable surgical gowns, it is important to assess the resistance to ionizing radiation. It was found that the Sontara brand material is resistant to the effects of ionizing radiation - the physical and mechanical characteristics of the material (breaking load and relative elongation) in the longitudinal and transverse directions of the web do not significantly change when irradiated with absorbed doses up to 60 kGy. It should also be noted that a cloth with a basis weight of 68 g/m2 has a significant smell of strength after radiation sterilization.

Influence of electron beam irradiation on DC surface flashover of polyimide in vacuum

A satellite operates in a harsh environment including high vacuum and radiations. The vacuum-dielectric interface is the most vulnerable area to flashover discharge. Moreover, the presence of electron radiation will further decrease the flashover voltage. However, the influence of electron radiation on surface flashover remains unclear. We have performed a study on vacuum DC surface flashover during electron beam irradiation as a function of electron kinetic energy and incident direction on polyimide representative of spacecraft dielectrics. The electron radiation was accompanied by electron deposition and bombardment effects on the polyimide surface. The surface flashover voltage was experimentally found to significantly depend on the kinetic energy and incident angle of the electron beam. By calculating the trajectories of incident electron beam, we further found that the surface flashover voltages are closely connected to the irradiated area. During low energy electron beam irradiation, kinetic electrons are repelled away from the dielectric surface by the applied electric field, and deposited electrons will be dominant in the flashover process, promoting the surface flashover voltage. However, when the electron beam energy is high, kinetic electrons can overcome the applied electric field and strike the dielectric surface to generate secondary electrons, which will replace the field-emission electrons to serve as seed electrons, and initiate the flashover at a much lower applied voltage. These observations and analyses are expected to benefit the research into mitigating spacecraft discharge, and promote the knowledge of surface flashover.

Review—Promises and Challenges of In Situ Transmission Electron Microscopy Electrochemical Techniques in the Studies of Lithium Ion Batteries

In situ transmission electron microscopy (TEM) electrochemistry with high-resolution characterization of morphology and microstructure is a powerful and practical technique to observe and analyze the lithiation and delithiation process of Li ions in the cathode and anode for comprehensively understanding the performance of Li-ion batteries (LIB), the formation of a solid electrolyte interphase (SEI), and the aging process during the investigation of LIBs. This review mainly focuses on the development and achievements of in situ TEM electrochemical techniques in investigating the mechanism of LIBs in recent years. Three types of in situ TEM electrochemical holders that are used commonly in the characterization of LIBs are presented. A calculation method for quantitative determination of the lithium diffusion coefficient (DLi) in electrodes with in situ TEM electrochemical technique is also mentioned. Finally, the challenges, limitations, and future work for during application of the in situ TEM-electrochemistry technique are further discussed and reviewed from the perspective of morphology, influence of electron radiation on the decomposition of electrolyte, configuration of electrode, and determination of DLi.

Radiation-induced mobility of small defect clusters in covalent materials

Although defect clusters are detrimental to electronic and mechanical properties of semiconductor materials, annihilation of such clusters is limited by their lack of thermal mobility due to high migration barriers. Here, we find that small clusters in bulk SiC (a covalent material of importance for both electronic and nuclear applications) can become mobile at room temperature under the influence of electron radiation. So far, direct observation of radiation-induced diffusion of defect clusters in bulk materials has not been demonstrated yet. This finding was made possible by low angle annular dark field (LAADF) scanning transmission electron microscopy (STEM) combined with non-rigid registration technique to remove sample instability, which enables atomic resolution imaging of small migrating defect clusters. We show that the underlying mechanism of this athermal diffusion is ballistic collision between incoming electrons and cluster atoms. Our findings suggest that defect clusters may be mobile under certain irradiation conditions, changing current understanding of cluster annealing process in irradiated covalent materials.

In-Situ Study of Silicon Single Crystals Conductivity under Electron Irradiation

The influence of electron radiation on the properties of semiconducting silicon single crystals (Si)—both n- and p-types (currently one of the most widely applied material in the electronic technology) was studied under the electron irradiation process in-situ in air (in common conditions). Higher value of electro-conductivity (σ) during the irradiation process with respect to after irradiation was observed, which was explained by ionization and capture mechanisms resulting in the formation of non-equilibrium carriers (hole-electron pairs). The kinetics of radiation defects generation, their physical nature, temperature stability and relaxation are examined. Structural radiation defects formation: point and complexes, their influence on the silicon conductivity are considered.

Influence of electron radiation on adhesion of some polymer films to acrylic adhesives

Influence of the electron radiation on adhesion properties of the films made of low-density polyethylene, biaxially oriented polypropylene, and polyethylene terephthalate was investigated. The films were irradiated with doses of up to 500 kGy, using a high-energy electron beam. The adhesion strength of bonds between the films and acrylic adhesive was measured by means of the 180° peel-off test. For all the films, it was found that this strength increased upon irradiation with the doses of the whole range applied, which suggested that the adhesion properties of the films improved as well. Thus, the radiational modification of polymer films by means of the high-energy electron beam enables one to obtain durable bonds between the films and adhesive without necessity to modify the film surface layer with another method.

Lateral Compression Behavior of High-Strength and High-Elastic-Modulus Fibers and Influence of Environment.

In this paper, we describe the quasi-static lateral compression tests of high-strength, high-elastic-modulus fibers. The fibers examined were γ-alumina fiber (Altex) by Sumitomo Chemical Co., Ltd., two types of carbon fibers by Mitsubishi Rayon Co., Ltd., and four types of aramid fibers by Du Pont and Teijin Ltd. Special attention was paid to environmental influences such as water absorption and electron or ultraviolet radiation on the lateral compression behavior of aramid fibers. A specially designed testing machine (load range:0.1mN-5N, accuracy:0.02mN) that enables mechanical testing, including fatigue of microelements, was employed. Using the testing machine, lateral compression of fibers whose diameter ranged from 7 to 17 μm was achieved with sufficient precision. The transverse compression behavior of carbon fibers and alumina fiber exhibited brittle nature:most of the load-displacement curve followed the elastic deformation, with a final catastrophic fracture into small pieces. However, that of the aramid fibers showed a more ductile nature:the very early stage of the load-displacement curve was elastic, and the rest was plastic. The final catastrophic fracture observed in ceramic and carbon fibers did not occur with a large amount of plastic deformation. The influence of electron radiation on the transverse elastic modulus of aramid fibers was not observed. However, water absorption or ultraviolet radiation lowered the transverse elastic modulus. The fiber surface was closely examined using an atomic force microscope, and the influence of environment on surface degradation and deformation behavior is discussed.

Microscopic and Mesoscopic Evaluations of Materials. Lateral Compression of High Strength and High Elastic Modulus Fibers and Influences of Environments.

This paper describes the quasi-static lateral compression tests of high-strength, high-elastic-modulus fibers. The fibers examined were γ-alumina fiber (Altex) by Sumitomo Chemical Co. Ltd., two types of carbon fibers by Mitsubishi Rayon Co. Ltd., and four types of aramid fibers by du Pont and Teijin Ltd. Special attention was paid to the environmental influence of water absorption, electron or ultraviolet radiation on lateral compression behavior of aramid fibers. The mechanical testing machine employed was a specially designed testing machine (load range : 0.1mN∼5N, accuracy : 0.02 mN), which enables mechanical testing including fatigue of microelements. By using the testing machine, the lateral compression of fibers whose diameter ranged from 7 to 17 μm was achieved with sufficient precision. The lateral compression behavior of the carbon fibers and ceramic fiber exhibits brittle nature : most of load-displacement curve follows the elastic deformation, with a final catastrophic failure into small pieces. However, that of the aramid fibers shows more ductile nature : a very early stage of load-displacement curve is elastic, and the rest is plastic. Final catastrophic fracture that is observed in ceramic and carbon fibers do not occur, with large amount of plastic deformation. The influence of electron radiation on the transverse elastic modulus of aramid fibers is negligible. However, water absorption as well as ultraviolet radiation lowers the transverse elastic modulus. The fiber surface was closely examined by using an atomic force microscope, and the influence of environment on surface degradation and deformation behavior is discussed.

Influence of Electron Radiation on Tensile and Impact Fracture Mechanism of Carbon/PEEK Composite.

An investigation has been carried out concerning the influence of electron radiation on tensile and impact fracture as well as compression after impact (CAI) behavior of carbon fiber reinforced thermoplastic matrix composite (AS-4/PEEK), having a quasi-isotropic stacking sequence of [0°/±45°/90°]2s. Specimens were irradiated in air with electron energy of 1.5 MeV, resulting in total absorbed dose of 1000 Mrad. The tensile strength was higher in irradiated specimens than nonirradiated ones. The impact tests were carried out by a falling weight tester. Impact induced delamination was observed with a scanning acoustic microscope (SAM). The delamination area was evaluated by the subtraction method. Impact-load-induced delamination area was increased by electron radiation. However, no influence of electron radiation on CAI strength was observed. The fracture surface was closely examined using a scanning electron microscope, and the fracture mechanisms were discussed.

Influence of Electron Radiation and Temperature on the Cyclic, Matrix Dominated Response of Graphite-Epoxy

The effects of electron radiation and elevated temperature on the matrix dominated, cyclic response of standard T300/934 and a chemically modified T300/934 graphite-epoxy are characterzed. Both materials were subjected to 1.0 x 1010 rads of 1.0 MeV electron ir radiation, under vacuum, to simulate 30 years in geosynchronous orbit. Cyclic tests were performed at room temperature (75°F/24°C) and elevated temperature (250°F/121 °C) on 4-ply unidirectional laminates to characterize the effects associated with irradiation and elevated temperature. Both materials exhibited energy dissipation in their response at elevated temperature. The irradiated modified material also exhibited energy dissipation at room temperature. The combination of elevated temperature and irradiation resulted in the most severe effects in the form of lower proportional limits, and greater energy dissipation. Dynamic-mechanical analysis demonstrated that the glass transition temperature, Tg, of the standard material was lowered 70°F (39°C) by irradiation, whereas the Tg of the modified material was lowered 50°F (28°C) by irradiation. Thermomechanical analysis showed the occurrence of volatile products generated upon heating of the irradiated materials.