Copper/diamond composites were produced by the powder metallurgical method. It is known from former experiments, that there is a very weak bonding between as-received diamonds and pure copper matrix ...in the consolidated composite. Improvements in bonding strength and thermo-physical properties of the composites were achieved using atomized copper alloy with minor additions of chromium to increase the interfacial bonding in Cu/diamond composites by a thin nano-sized Cr
3C
2 layer.
This study examines the oxidation behavior of skutterudite materials fabricated using a rapid self-propagating high-temperature synthesis and pulse plasma sintering route. Pure Co4Sb12 and ...Co4Sb10.8Se0.6Te0.6 were oxidized in the air at 773 K for up to 500 h. Skutterudites modified with Se and Te had a lower oxidation resistance than that of pure Co4Sb12 and also showed a lower decomposition temperature. This changed the oxidation mechanism, as manifested by the different roles of the Sb2O3 phase during oxide scale formation and the CoSb2-like phase in the modified near-surface region. The unusual mass loss by the Co4Sb10.8Se0.6Te0.6 alloy during the first 100 h of oxidation was also revealed. Despite the evident changes at the surface of the samples, no visible grain growth was noted in both skutterudites. The electrical properties of the samples were also stable.
Traditional ways to obtain homogeneous and efficient skutterudite-based thermoelectric materials usually require long processing time. In this study thermoelectric properties of Se and Te co-doped ...CoSb3 bulk materials fabricated using a combination of self-propagating high-temperature synthesis and pulse-plasma sintering techniques were investigated. The proposed short-term fabrication route enabled synthesis of thermoelectric materials with high chemical homogeneity. Moreover, simultaneous doping with Se and Te beneficially influenced the electrical and thermal transport properties of the materials. As a result, an ultralow lattice thermal conductivity of 0.86 W m−1 K−1 has been attained while simultaneously doping and filling the voids in the skutterudite structure. The ultralow lattice thermal conductivity could be attributed to the unique lattice dynamics, enhanced point-defect, and electron-phonon scattering. Owing to these synergetic effects, a dimensionless figure of merit of 1.1 was obtained at 723 K. The findings show that combination of self-propagating high-temperature synthesis and pulse-plasma sintering techniques allow to fabricate chemically homogeneous and efficient thermoelectric materials as well as offer numerous advantages, such as time, energy efficiency, and potential scalability, to carry out large-scale production.
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•Se/Te modified skutterudites were fabricated via SHS-PPS route.•Seebeck potential mapping confirms high homogeneity of the fabricated materials.•The record low lattice thermal conductivity 0.86 W m−1 K−1 at 723 K was achieved.•Co4Sb10.8Te0.6Se0.6 sample exhibits the maximum ZT of 1.1 at 723 K.
In the DEMO power plant design, the bioshield roof above the tokamak is a steel structure with radial beams and concrete inserts. A contamination protection structure (CPS) is placed on the bioshield ...roof to protect other areas against the potential release of any radioactive materials from inside the reactor during maintenance. It also provides support to the cask, which is used to transfer the heavy blanket segments to the active maintenance facility (AMF). Herewith, the structural design of the CPS and the bioshield roof is investigated using parametrized FE models in the Ansys APDL environment.
The results of the linear static analysis show that the stress in the CPS as well as in the structure of the bioshield roof is within the acceptable range. However, linear buckling analysis shows that the CPS may lose stability due to buckling. The proposed design modifications resulted in a structure that is sufficiently strong and rigid to withstand all load conditions. The analyses revealed that the actual loads acting on the bioshield roof structure, due to the CPS and its handling structures, are lower than assumed during its preliminary design, therefore it is possible to reduce the dimensions of the bioshield roof beams and girders in the future.
Accumulation and recovery of radiation defects under/after self-ion irradiation in tungsten (W) have been investigated via decoration with deuterium (D) and scanning transmission electron microscopy ...(STEM). The deuterium was incorporated in damaged material by low-energy D plasma. The D concentration at radiation-induced defects in each sample was subsequently measured by nuclear reaction analysis allowing determination of the D concentration at depths up to 6 mu m. The total D retention was measured by thermal desorption spectroscopy. The increase of the D retention at annealing temperature of ~1000 K was not observed in the case of recrystallized W pre-irradiated with self-ions. The mechanism of recovery of radiation-induced defects in dependence on the initial intrinsic defects in W is discussed.
Tungsten targets have been self-damaged with 20 MeV W6+ ions followed by decoration of defects with deuterium and 500 keV helium implantation. Such treatment creates a significant amount of ...irradiation-induced defects which depend on the distance from the surface. As a final step, selected samples were annealed at 1700 K for 30 min to study defect evolution at high temperature. Detailed TEM analysis, supported with quantification of microstructure, provided an insight into the effect of helium implantation on the previously established dislocation structure and its thermal stability. It was shown that helium is implanted into the material down to approximately 900 nm from the surface and creates a locally enhanced dislocation density which remained stable even after high temperature annealing. This phenomenon is opposite to annihilation of dislocations observed in the sample without helium treatment. At the same time, helium implanted zone is the source of internal stress fields which cover the whole irradiated depth. Thermal treatment releases lattice from this stress. The possible reasons of these occurrences are discussed in the light of helium interactions with vacancies and self-interstitials in the presence of dislocations which directly impacts hydrogen isotopes retention.
•500 keV He implantation creates a 930 nm deep damaged layer.•He atoms concentration and dislocation density depends on the depth.•He presence cause presence of internal stresses.•1700 K annealing cause significant changes in microstructure.•Presence of He stabilize dislocations at high temperature.
Containment structures and port configurations Bachmann, C.; Ciupinski, L.; Gliss, C. ...
Fusion engineering and design,
January 2022, 2022-01-00, 20220101, Letnik:
174
Journal Article
Recenzirano
Odprti dostop
This article describes the DEMO cryostat, the vacuum vessel, and the tokamak building as well as the system configurations to integrate the main in-vessel components and auxiliary systems developed ...during the Pre-Conceptual Design Phase.
The vacuum vessel is the primary component for radiation shielding and containment of tritium and other radioactive material. Various systems required to operate the plasma are integrated in its ports. The vessel together with the external magnetic coils is located inside the even larger cryostat that has the primary function to provide a vacuum to enable the operation of the superconducting coils in cryogenic condition. The cryostat is surrounded by a thick concrete structure: the bioshield. It protects the external areas from neutron and gamma radiation emitted from the tokamak. The tokamak building layout is aligned with the VV ports implementing floors and separate rooms, so-called port cells, that can be sealed to provide a secondary confinement when a port is opened during in-vessel maintenance.
The ports of the torus-shaped VV have to allow for the replacement of in-vessel components but also incorporate plasma limiters and auxiliary heating and diagnostic systems. The divertor is replaced through horizontal ports at the lower level, the breeding blanket (BB) through upper vertical ports. The pipe work of these in-vessel components is also routed through these ports. To facilitate the vertical replacement of the BB, it is divided into large vertical segments. Their mechanical support during operation relies on vertically clamping them inside the vacuum vessel by a combination of obstructed thermal expansion and radial pre-compression due to the ferromagnetic force acting on the breeding blanket structural material in the toroidal magnetic field.
Abstract
Single crystalline tungsten samples were irradiated by He, D, and H at room temperature, with a calculated damage level in the peak maximum up to 0.04 dpa and with He up to 0.5 dpa. The ...dislocation structure of the whole damage zone was investigated perpendicular to the irradiated surface by Transmission Electron Microscopy (TEM) under four different two-beam diffraction conditions
g
=
−200, 020, −110, 110 close to the 100 zone axis, taking bright-field kinematical images. The depth of the damage zone observed by TEM is in good agreement with the damage depth calculated by SRIM. The damage zones of the tungsten samples irradiated by He, D, H up to 0.04 dpa can be subdivided into four subzones. Significant differences in the dislocation structures between the different ion species despite comparable calculated damage levels were found at the depth close to the damage peak maximum. In this depth, the damage zone of tungsten irradiated by He consists of small dense dislocation loops (⩽3 nm) with high strain fields. Irradiation by D creates large dislocation loops with an average diameter of 15–22 nm depending on the set diffraction condition. The damage zone of H-irradiated tungsten is dominated by long dislocation lines at the depth of the damage peak maximum. No transition from dislocation loops to lines was found in the sample irradiated with He up to 0.5 dpa. This is probably due to He bubbles, which hinder the loops to aggregate into lines. This work shows that the displacement damage obtained by the irradiation of tungsten at room temperature with light ions is significantly different to tungsten irradiated to the same calculated damage level by medium to high-mass ions (Wielunska
et al
2022
Nucl. Fusion
62
096003 1).
Selenium is an effective dopant in skutterudite-based thermoelectric materials. It strongly influences thermal transport properties due to effective phonon scattering. This study proposes a ...short-term fabrication route to Se-modified CoSb3-based materials. Alloy synthesis was conducted via self-propagating high-temperature synthesis. Subsequently, pulse plasma sintering consolidated all materials. As a result, thermoelectric materials with high electrical properties homogeneity were obtained. Seebeck potential mapping showed the measured deviation of the Seebeck coefficient for all fabricated samples was between 5 and 7%. A very low thermal conductivity (1.59 W m−1 K−1, at 573 K) was achieved for the highest doped sample, and one of the lowest reported results obtained for bulk skutterudite-based thermoelectric materials ever. This resulted in a low lattice thermal conductivity (1.51 W m−1 K−1, at 573 K). This led to the highest ZT (0.27 at 623 K) for the highest doped sample.
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