Mueller, A. v.Dorow-Gerspach, D.Balden, M.Buschmann, B....
8页
查看更多>>摘要：In the present paper, recent progress regarding additive manufacturing (AM) of pure tungsten (W) by means of laser powder bed fusion (LPBF) is discussed. In this context, several aspects are highlighted: The influence of the raw powder material characteristics on the resulting W part quality is briefly discussed, examples for complexly shaped additively manufactured W lattice structure samples are shown, the application of an additively manufactured W structure as preform for a tungsten-copper (W-Cu) composite is illustrated and thermal shock experiments on additively manufactured bulk W samples with the electron beam facility JUDITH 2 are described. The latter demonstrates that W material consolidated by means of LPBF is capable of surviving intense thermal shock loads. This is an encouraging result indicating that the thermal performance and stability of W fabricated by means of LPBF is comparable to that of conventionally fabricated W which in turn implies that the further investigation of additively manufactured W as candidate material with regard to applications in highly loaded plasma-facing components (PFCs) of future magnetic confinement thermonuclear fusion devices can be considered worthwhile. (c) 2022 Elsevier B.V. All rights reserved.
Min, Hyeong WooKo, JaehwanKim, YongheeYoon, Young Soo...
14页
查看更多>>摘要：The multilayered swaging and drawing process using raw Zr-alloy cladding is very simple, can be performed at room temperature (15-25 degrees C), and enables mass productivity. In this study, we developed a pseudo-single tube with double layers (PSTD), using a thin stainless-steel (SS316L) tube and raw Zr-alloy cladding, which is not easily accessible to a coating process. The PSTD specimens were oxidized at 900 degrees C, 10 0 0 degrees C, 110 0 degrees C, and 120 0 degrees C for 60 min at each temperature in dry air. The interface between the SS316L tube and Zr-alloy cladding was investigated using optical microscopy and scanning electron microscopy. The oxidation resistance was proven excellent through energy dispersive spectroscopy and mass change results of the oxidized PSTD specimens even though 5-6 mu m oxide layer was formed at the interface. Based on these results, it was concluded that an improved accident tolerant fuel (ATF) cladding can be produced using the swaging and drawing process. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The present work is performed to answer quantitatively the still-open question on the multi-phase interaction accompanied with phase transformation process for a U-21 at%Nb alloy via in-situ neutron diffraction (ND), which is one of the important materials for nuclear engineering (e.g., a promising metallic fuel candidate). Both the structure and micro-strain have been simultaneously revealed for all the phases including alpha-U, gamma-Nb and gamma-U. Based on Rietveld refinement analysis of in-situ ND patterns for a series temperature from RT up to 850 degrees C, the volume fraction of each phase has been quantitatively achieved as well as the lattice parameters. It is found from micro-strain analysis that the thermal-induced lattice strain for alpha-U phase is strongly anisotropic while that for gamma-Nb and gamma-U phases is isotropic. Within the multi-phase region, gamma-Nb phase possesses always the soft response while alpha-U and gamma-U phases show the hard response. There exists a phase transformation window (PTW) between the region of alpha-U and gamma-U phases, where fluctuation-like behavior appears in micro-strain response. ND pattern for the second heating at 630 degrees C is obviously different from that for the first one but similar with that at 640 degrees C, which means that the phase transformation has been facilitated. It is found that micro-strain would have a significant effect upon the phase transformation process. Those findings could provide some insight into both the fundamental understanding of multi-phase interaction accompanied with phase transformation and technological aspects including materials design and properties development through engineering the multi-phase interaction and thus phase transition process. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：In order to investigate the effect of stacking fault energy on microstructural evolution in reduced activation high entropy alloys, electron and/or Au + ion irradiation was performed to the Co-free FCC-type FeCr 0.8 Ni x Mn y ( x, y = 1, 1.3, 1.5) alloys. TEM observation of the 5%-deformed FeCr 0.8 Ni x Mn y alloys revealed the increase in the stacking fault energy with increasing both Ni and Mn concentration. In addition, FeCr 0.8 Ni 1.5 Mn 1.5 had the highest stacking fault energy, which was much higher value than that of 316SS. Furthermore, the yield strength and the elongation of deformed FeCr 0.8 Ni x Mn y also showed the Ni and Mn concentration dependence. The electron irradiation at 400 degrees C resulted in the formation of black dots, self-interstitial atom faulted loops, but no observable voids in all the FeCr 0.8 Ni x Mn y alloys. The comparison of microstructural evolution revealed less faulted loop formation and growth in FeCr 0.8 Ni 1.3 Mn 1.3 and FeCr 0.8 Ni 1.5 Mn 1.5 alloys. From these results, it is suggested that FeCrNiMn-based high entropy alloys would be developed as high irradiation resistant materials by controlling the stacking fault energy with optimized element concentration.
查看更多>>摘要：Thorium-uranium dioxide nanofibers were prepared in a three-step process. Green composite microfibers were electrospun from solutions composed of Th(IV) and U(VI) acetylacetonate complexes in different molar ratios, polyvinylpyrrolidone, and acetone/ethanol mixed solvents. The second step converted the green composite fibers by calcination in the air to mixed Th/U oxide fibers. In the final step, the heat treatment under forming gas provided the nanofibers with diameters of 28 -46 nm composed of solid solutions ThxU1-xO2 ( x = 1, 0.75, 0.5, 0.25, 0). The XRD and STEM-EDS analyses of the prepared Th/U mixed oxide nanofibers attested to their atomic homogeneity. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Study of the water-plutonium oxide interaction is of fundamental importance in the corrosion of plutonium materials. In the present work, we report the results of adsorption and dissociation of water molecules on the alpha-Pu 2 O 3 (111) surface with ab-initio molecular dynamics (AIMD) simulations. We identify the stable adsorption configuration of water dimer on the alpha-Pu 2 O 3 (111) surface. Also, we find that one water molecule in the dimer can dissociate into hydrogen atom and hydroxyl group, and the reaction energy barrier is calculated to be 0.21 eV using climbing image nudged elastic band (CINEB) method. Electronic structure analysis shows a strong interaction between the dissociated hydrogen atom and the surface oxygen atom. Moreover, AIMD simulations at 300K and 600K confirm that the hydrogen-bonding interaction within the water clusters including dimer and trimer, as well as the hydrogen-transfer reaction, facilitates the dissociation of water clusters on the alpha-Pu 2 O 3 (111) surface. The obtained results can provide a way to understand the corrosion of plutonium enhanced by moisture. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The design of radiation-tolerant polycrystalline materials has been mainly based on the control and manipulation of grain boundaries (GBs) that leads to annihilation of point defects at grain-boundary neighborhoods thus resulting in the formation of defect denuded zones. Nanocrystalline materials are potential candidates providing large density defect sinks for individual point defects and small highly mobile defect clusters (DCs). Using the in-situ irradiation transmission electron microscopy (TEM) technique, this study not only experimentally revealed the coalescence of small glissile DCs at/near GB and their subsequent annihilation at grain-boundary, but also provide insight into defect cluster dynamics. The small DCs were found to be transported to grain-boundary neighborhoods where they can annihilate by the onedimensional loop hop or Burgers-vector rotation mechanism to GBs, considered as the main contribution to the long-range flux of interstitials to GB sinks. This process had marked effects on the morphology of the irradiated microstructure in nanocrystalline iron, limiting the length of DC strings and reducing the coalescence of DCs into large clusters (dislocation loops).(c) 2022 Published by Elsevier B.V.
查看更多>>摘要：In order to better understand and predict the behavior of noble metal fission products in molten salt reactor (MSR), the distributions of( 99)Mo, Ru-103, Rh-105 and Te-132 between molten salt, graphite and GH3535 alloy were investigated using gamma-ray spectroscopy. Experimental results showed that (99) Mo, Ru-103, Rh-105 and Te-132 mainly settle at the bottom of molten salt in the form of metallic particles, and the flow of molten salt can easily make the settled metallic particles suspend in molten salt. In addition, Mo-99, Ru-103, Rh-105 and Te-132 tend to be deposited more on GH3535 than on graphite, and the deposition behavior of 99Mo is particularly sensitive to the oxidation-reduction state of molten salt, which might be used as a redox indicator for the fuel salt of MSR. More importantly, the deposition characteristics provide new ideas for the separation and extraction of medical isotope 99Mo from MSR in the future. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：Incident neutrons in irradiated W can cause the formation of solid transmutation elements, of which Rhenium (Re) is the most abundant. We apply the phase-field method to investigate the clustering and growth of the Re-rich precipitate in irradiated W based on the spinodal decomposition mechanism, and their effects on the mechanical and thermal properties of W. Needle-like precipitates are reproduced and comparable to experimental observations. We then vary the irradiation dose and temperature to study their influences on the microstructure evolution of the Re-rich precipitate. Simulation results show that the average diameter, the number density, and the coverage rate of the precipitates significantly increase with the increase of the irradiation doses but slightly increase with the increase of the temperature. The effects of the Re-rich precipitate on the mechanical and thermal properties of W are also investigated. Results show that the Vickers hardness increase and the thermal conductivity degrade due to the forma-tion of the Re-rich precipitate, especially at high irradiation doses. Conventional simulation methods can hardly handle the effect of the needle-like precipitates on the mechanical and thermal properties. In this work, we compare these two properties by using needle-like precipitates and circular precipitates. Our re-sults clearly show that the needle-like precipitates give a better consistency with experimental results of the Vickers hardness increase, and reveal the anisotropic ability of the heat transfer in neutron-irradiated W. The current results can provide a systematic understanding of the Re clustering behavior from the microstructure evolution to its influences on the mechanical and thermal properties of W materials.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Zr alloys are commonly used materials for in-core components of pressurized water reactors. The evolution of defects in Zr under irradiation conditions will directly contribute to the degradation of reactor components. For a better understanding of the evolution process of defects in Zr, a multiscale simulation was performed to study the diffusion behavior of radiation-induced point defects. Because the existing potentials cannot accurately describe the energy differences of stable states self-interstitial atoms (SIAs) in Zr, an embedded atom method potential that can exactly reproduce the energy difference between metastable states and ground states, and the binding energy of divacancy of Zr, was first developed by fitting a potential to point defect properties calculated by density functional theory and other basic crystal properties. Based on the constructed potential, molecular dynamics (MD) and kinetic Monte Carlo simulations were conducted to investigate the migration of point defects. We determined several frequent migration paths of SIAs by kinetic study, which is rarely reported in previous MD studies. The SIA exhibits obvious anisotropic diffusion characteristics at low temperatures ( < 600 K). The most frequent migration path for SIAs is the jump between the two nearest basal octahedral (BO) sites in the basal plane, which means that SIAs diffuse faster along the basal plane than along the c axis. It is found that diffusion within the basal plane tends to be two-dimensional (2D) diffusion rather than 1D diffusion, and there is a significant correlation effect for diffusion of SIAs along the basal plane. Additionally, the existence of trivacancy-SIA complex was found in the process of divacancy migration, which can inhibit divacancy migration. Monovacancies and divacancies exhibit anisotropic diffusion characteristics in the considered temperature range Divacancies have a much faster diffusion rate than monovacancies in the present MD simulation and can easily dissociate at high temperatures ( > 900 K). The rapid migration of the divacancies may contribute to the formation of vacancy dislocation loops. These results are meaningful to understand the evolution process of radiation-induced defects.(c) 2022 Elsevier B.V. All rights reserved.
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