Papers by Keyword: Ion Irradiation

Abstract: The irradiation embrittlement damage of reactor pressure vessel (RPV) steel is one of its primary failure mechanisms. In this work, neutron, ion and proton irradiation experiments were carried on the same commercial RPV steels with the same irradiation fluence under the same temperature of 292°C. Then the nano-indentation hardness tests were performed on the RPV steel before and after irradiation. The results show that the irradiation hardening effects are observed by means of nano-indentation technique under the above three irradiations, and the hardening features are basically the same. While the max variation and increase rate are obviously different between those irradiations. It is found that the main reason of the above differences are caused by different energies of irradiation energetic particles, resulting in different types and quantities of defects. The conclusions in this paper are helpful to select and compare different irradiation experiments to the research of RPV steels irradiation embrittlement damage.

Abstract: In the past 20 years, the phase-change memory technology has achieved rapid development, of which alloys along the GeTe-Sb₂Te₃ pseudobinary line are the most extensively researched materials. In recent years, Sb₂Te₃-based materials start to attract the attention of researchers. A recent study has shown that the Sb₂Te₃ (ST) material has a face-centered cubic (Fcc) phase which contains a high concentration of vacancies at low temperature. Due to the poor amorphous thermal stability of ST, the as-deposited film obtained by physical vapor deposition is crystalline (Fcc phase). Therefore, we proposed a vacancy control mechanism, using inert gas Ar to ion implantation of as-deposited ST films, redistributing vacancies in the as-deposited ST films. Through different doses of Ar ion implantation, we obtain amorphous ST materials with different resistivity. We find that after the injection dose reached 1 × 10¹⁶ cm^-2, the effect of continued increase in the implantation dose on the resistivity of the thin film is negligible. After ion implantation, the transition temperature of the metastable Fcc phase to the hexagonal phase (Hex) is increased, which is beneficial to improve the power consumption and endurance of the device. The ST which is injected with a dose of 1 × 10¹⁶ cm⁻² Ar ion based phase-change memory cell can perform erasing operation in 100 ns, showing low power consumption potential. Our work provides a new idea and method for the application of future defect control in phase-change memory research.

Abstract: Metallic glasses (MGs) exhibit extremely high strength and superior resistance to corrosion. They are also supposed to be resistant against displacive irradiation due to their inherent disordered structure, and thereby are viewed as potential candidates for applications in irradiation environments. However, the structures and properties evolution of metallic glasses, especially bulk metallic glasses (BMGs), under irradiation has not been fully understood up to now. In this work, the structural stability and damage characteristics of a Zr-based BMG under helium ions irradiation environment were investigated. Meanwhile, the effect of structural relaxation and crystallization on the irradiation response of the BMG was also studied. Results show that the BMG reserves the amorphous structure within the studied range of fluence, and exhibits better irradiation resistance compared to that of the crystalline alloys. In our opinion, the initial free volume concentration affects the damage morphology of the BMG, while partial crystallization will lead to significantly embrittlement under irradiation.

Abstract: In this paper, ion irradiated recycled high density polyethylene (i-HDPE_R) was investigated as modifier in bitumen. Ion irradiation process was applied to recycled HDPE (HDPE_R) in order to form strong chemical bonding between bitumen and HDPE_R polymers. Five samples were prepared with different i-HDPE_R modifier content of 1%, 3%, 5%, 7% and 9%. The effects of i-HDPE_R on the bitumen were investigated by means of morphological, chemical and physical testing program; including Fourier transform infrared spectroscopy (FT-IR) spectroscopy, conventional tests, rotational viscosity (RV) and dynamic shear rheometer (DSR) test. Tests results promote the using waste polymers in bitumen by means of ion irradiation process. The results also reveal that a gradually increment in i-HDPE_R modification leads to an increased rutting parameter which means permanent deformation in flexible pavement can be reduced by i-HDPE_R modification.

Abstract: The irradiation effects of a new nickel-base alloy (Ni-17Mo-7Cr) has been investigated by using 1 MeV Xe²⁰⁺ and 7 MeV Xe²⁶⁺ ions irradiation with displacement damage range from 0.33 to 6.6 dpa. The transmission electron microscopy and nanoindentation were employed to study respectively the microstructural evolution of thin-foil specimens and nanoindentation hardness changes of bulk specimens. In case of 0.33 dpa, high number density of nano-scale black spots were observed in thin-foil specimens. High-resolution transmission electron microscopy images revealed that these black spots are some rounded solute clusters and dislocation loops. As far as the ion dose of 3.3 and 6.6 dpa, the black spots were replaced with linear-like defects which were proved to be some Ni, Mo and Cr-enrichment regions. In addition, nanoindentation results for bulk specimens showed an evident hardening phenomenon in irradiated Ni-17Mo-7Cr alloys, compared to the unirradiated specimen. The irradiation induced defects may be responsible for the hardening of Ni-17Mo-7Cr alloys.

Abstract: Oxide dispersive steel is a promising material for next nuclear reactors generation. Performance of this material in nuclear reactor can be modeled by means of irradiation by swift Bi ions, which are typical nuclear fusion products. Radiation damage results in microstructure alternation leading to formation of micro and macro stresses that influence the material performance. The residual stress state of ferrite matrix of the steel is investigated by XRD methodic and dependence on the irradiation dose is analyzed.

Abstract: A hybrid model of microstructural evolution of a coupled multi–field system that is subjected to ion irradiation is presented. Materials exposed to low energy ion irradiation experience a wide range of radiation effects, e.g. surface roughening and chemical segregation. The hybrid model combines Monte Carlo methods and a phase field model to simulate the kinetic and radiation-induced processes that lead to radiation induced chemical segregation with associated phase transformations of a binary system by differential diffusivity.

Abstract: One of the strategies for enhancing the detection sensitivity of etched nuclear track-based biosensors uses the cladding of track walls with enzymes and the subsequent enrichment of charged enzymatic reaction products in the confined volume of the narrow tracks. For sensing two different bio-molecule types simultaneously, the tracks can be separated into two adjacent compartments by inserting a membrane in between them. The recipe for membrane formation is outlined. If the same enzyme is inserted into both compartments, the sensing accuracy can greatly be enhanced, as compared to etched tracks without membranes, due to a different underlying sensing mechanism. Such sensors act as frequency filters, which is useful for sensors operating in electrosmog-rich ambient.

Abstract: The effect of irradiation with heavy ions Ne, Ar, and Kr of various energies on the structure and properties of ceramic barium cerate doped with neodymium and annealed in air at 650°C for 7 hours is studied. It is noted that blistering was observed on cerate surface during its irradiation by low energy Ne ions, whereas it was not observed under low-energy Ar and Kr ions irradiation. Irradiation of the cerate with high energy ions caused partial amorphization of the irradiated surface of the material, while the structure of the non-irradiated surface did not change. In addition, the irradiated surface of the cerate endured solid-phase structural changes. Thus, upon high-energy ions irradiation in the range of Ne, Ar, Kr the cerate surface resembled the stages of spherulite formation - nucleation, growth (view of cauliflower), formation of spherulitic crust, respectively. The increase in water molecules release and reduction of molecular oxygen release from the barium cerate, irradiated by high-energy ions is found during vacuum constant rate heating. It is concluded that cerates undergo changes to the distances significantly exceeding the ion ranges in these materials. Features of high-energy ions influence on thermal desorption of carbon dioxide from cerates show, apparently, the formation of weakly bound carbonate compounds on the cerate surface in the irradiation process.

Abstract: We have found that deposited film can be crystallized without the post-annealing treatment but with the simultaneous ion-irradiation during sputter-deposition at very low substrate temperature. The present paper reviews the low temperature crystallized TiNi films deposited by the above technique. An RF magnetron sputtering apparatus equipped with separate confocal sources as well as with a heating and ion-irradiating system for substrates was used to make the films crystalline. Without using the ion-irradiating system, the films deposited on ambient-temperature substrate have been amorphous. However, crystallized film is deposited even at 353 K of substrate temperature with using the system. Appropriate ion-irradiation is considered to be help to crystallize the film at low substrate temperature. Broad and doublet X-ray diffraction profile of the film, which was diffracted from B19’ and/or R phase, was recorded between 42 degree to 45 degree in 2 theta. The crystallized film deposited on a polyimide sheet was cut into the shape of a double-beam cantilever and the ends of the two beams were connected to an electrical power supply. The cantilever shows a repeatable two-way motion by electrical cycle of 0.1 Hz at room temperature.