Papers by Keyword: Irradiation

Abstract: Recently peaceful use of the nuclear energy and radioactive nuclides has increased the radiation pollution factor in the world and radiation safety problems have become actual ones. The development of the nuclear power engineering, protection and processing of radioactive wastes of nuclear reactors, the use of radioactive isotopes in national economy, nuclear explosion, industrial wastes and etc. may cause the radioactive pollution of the environment. In the case of such pollution the environment as well as living organisms are exposed to radioactive radiation (a-, b-, γ- etc.). Radioactive substances emit radioactive rays and as their decay time varies for natural and artificial radioactive substances the time of their environmental effect ranges from some years to million years.

Abstract: Sapphire crystals grown by an improved Kyropoulos-like method were irradiated by gamma rays and electrons in this paper. Thermoluminescence (TL) and optical stimulated luminescence (OSL) properties of sapphire were studied. TL glow curves of sapphire were varied within the room temperature to 500°C at a heating rate of 10min•s-1. The OSL spectra wavelength covered were from 200nm to 700nm. There was a new peak at 220°C, which was produced by the irradiation of gamma rays and electrons. Two broad bands at 330nm and 410nm were found in the luminescence spectra, which were due to transitions of two charge states of an anion vacancy defect, corresponding to F+ and F color centers, respectively.

Abstract: Heavy ion tracks recorded in dielectric materials were found to have a width of 5-10 nm using SEM. Heavy ion beams were used for irradiation of Polymers and Muscovite mica to create Ion Track Filters (ITFs) using UNILAC facility at Darmstadt, Germany. The electrochemically etched pores of ITFs used would act as a template. The simple principle of electroplating is used to create heterostructures. The rate of deposition of metallic film depends upon current density, inter-electrode distance, cell voltage, electrolyte concentration and temperature etc. The use of ITFs looks quite promising in the fabrication of micro and nanostructures. The morphology of such structures produced through electrochemical methods and replicas of etched tracks in ITFs have been investigated in detail. The efficacy of the technique was tested for growth of quantum dots, fibers, cones, whiskers, micro and nano wires. A 3-dimensional ensemble of Cu-Se was grown electrochemically using ITF of Makrofol-KG. Replication of etched pores in ITFs has been used to develop microtubules. Presently, we are engaged to develop quantum dots, nanorods and nanowires of copper, iron and bismuth using Anodic Alumina Membranes (AAM), Polycarbonate ITFs and Reverse Micelle technique. The preliminary results of our investigations will be presented at NADPA-2008.

Abstract: An Ag-Ce-TiO2 composite film was prepared by incorporating Ag in the Ce-TiO2 films with an impregnation method through photoreduction. The bactericidal activity of the Ag-Ce-TiO2 composite film and the effect of deposition of silver and doping cerium in the different irradiations on the antibacterial performance were assessed against Escherichia coli (E. coli). TIhrough characterization of X-ray diffraction (XRD), X-ray photoelectronic spectra (XPS) and UV/VIS diffusive reflectance spectra (DRS), it was found that the Ag-Ce-TiO2 composite film was composed of predominant anatase titania, cerium oxides (in the form of Ce2O3/CeO2) and silver nanoparticles. Moreover, the bactericidal activity of the Ag-Ce-TiO2 composite film and the effect of deposition of silver and doping cerium in the different irradiations on the antibacterial performance were assessed against Escherichia coli (E. coli). The results show that the Ag-Ce-TiO2 composite film has much higher antibacterial efficiency than that of glass and pure TiO2 film either in the room light or in the dark. Therefore, this composite film is promising in applications of antimicrobial and self-clean technologies.

Abstract: Positron annihilation lifetime (PAL) spectroscopy，photo-induced current transient spectroscopy (PICTS) and thermally stimulated current (TSC) have been employed to study the formation of compensation defects and their evolvement under iron phosphide (IP) ambience or pure phosphide (PP) ambience. In the formation of IP SI-InP, the diffusion of Fe atoms suppresses the formation of some open-volume defects. As to PP SI-InP, VInH4 complexes dissociate into acceptor vacancies VInHn(n-3)(n=0,1,2,3), which compensate residual donor type defects and make the sample semi-insulating. Electron irradiation-induced deep level defects have been studied by TSC in PP and IP SI-InP, respectively. In contrast to a high concentration of irradiation-induced defects in as-grown and PP annealed InP, IP SI-InP has a very low concentration of defects.

Abstract: Hyperthermia using ferrofluid with alternating current (AC) magnetic field, which is the principal method we try to use in this study, where chitosan was used as a surfactant agent. Irradiation of Co-60 plays multi-function roles on the syntheses of chitosan-coated nanoparticles. Optimal conditions for synthesizing magnetic nanoparticles have been successfully found by the Taguchi method in which the dominated quality characteristic was SAR.

Abstract: Carbon atoms are always present in Fe-based materials, either as impurities even in high purity samples or as an intrinsic constituent in steels. Density Functional Theory calculations have been performed to study the interaction between C atoms and vacancies (V) in α-Fe. We find that the formation of VCn complexes is energetically favourable for n ≤ 3, with VC2 being the most stable one. The energy gain corresponding to the clustering reaction VCn-1 + C → VCn depends mainly on the strength of C-C covalent bonds. The vacancy diffusivity is shown to be significantly modified by the formation of vacancy-carbon complexes, exhibiting non-Arrhenius behaviour. Effective vacancy diffusion coefficients in α-Fe are calculated as a function of temperature and carbon content using a simplified thermodynamic model. The results are discussed in detail in the limiting case of excess of C with respect to vacancies.

Abstract: Neutron irradiation is known to have a considerable impact on the mechanical characteristics and the behaviour of materials and components. The distribution of residual stresses is one of the properties affected by irradiation. However, because of the difficulties in performing measurements in radioactive components, not many experimental data have to date been collected. At the High Flux Reactor (HFR) of the European Commission’s Joint Research Centre (JRC), a facility has been developed for residual stress measurements in steel specimens subjected to longterm irradiation. The objective of this development was to establish the neutron radiation induced changes in the residual stresses around welds in test pieces representative of the core shroud of boiling water reactors. Residual Stress measurements on such double-V butt welds in stainless steel plates after irradiation exposure have been performed by neutron diffraction using this facility. The comparison with measurements in non-irradiated companion specimens [1] showed that irradiation changed the distribution of residual stresses. The results suggested that the impact of irradiation varied with the distance of the test location from the specimen surface. On the basis of currently measured data we could not draw definitive conclusion about the influence of neutron dose and irradiation duration upon the stress modification.

Abstract: A material capsule system including a main capsule, a fixing, a control, a cutting, and a transport system was developed for an irradiation test of non-fissile materials in HANARO. This capsule system has been actively utilized for the various material irradiation tests requested by users from research institutes, universities, and the industries. Based on the accumulated irradiation experience and the user’s sophisticated requirements, the instrumented capsule technologies for a more precise control of the irradiation temperature and fluence of a specimen were developed in HANARO. 6,000 specimens from domestic research institutes, nuclear industry companies and universities, were irradiated in HANARO for 54,000 hours by using the developed capsule irradiation system. Recently, development of new instrumented capsule technologies for an IP/OR irradiation test and a high temperature irradiation test has been performed in HANARO for relevant ongoing R&D for the international Gen IV Program. New irradiation technologies are also under development for the production of new functional materials including superconductor and optical/electrical materials.

Abstract: The aim of this paper is to give a short review on cluster dynamics modeling in the field of atoms and point defects clustering in materials. It is shown that this method, due to its low computer cost, can handle long term evolution that cannot, in many cases, be obtained by Lattice Kinetic Monte Carlo methods. Indeed, such a possibility is achieved thanks to an important drawback that is the loss of space correlations of the elements of the microstructures. Some examples, in the field of precipitation and irradiation of metallic materials are given. The limitations and difficulties of this method are also discussed. Unsurprisingly, it is shown that it goes in a very satisfactory way when the objects are distributed homogeneously. Conversely, the source term describing the primary damage under irradiation, by nature heterogeneous in space and time, is tricky to introduce especially when displacement cascades are produced.