Flow Channel Inserts (FCIs) are key elements in the high-temperature Dual Coolant Lead Lithium (DCLL) blanket, since they insulate electrically the flowing PbLi to avoid MHD effects and protect the ...steel structure from the hot liquid metal. SiC-based materials are main candidates for high-temperature FCIs, being a dense-porous SiC-based sandwich material an attractive option. The present work is focused on the development of such a SiC-based material.
On the one hand, in order to assess the suitability of the concept for FCIs, the main results of a stress analysis, MHD and heat transfer simulations are summarized. On the other hand, the experimental production of the SiC-based material is addressed, where the porous SiC core is manufactured from SiC powder by two different techniques: uniaxial pressing and gelcasting. The porosity is introduced using graphite spherical powder as a sacrificial template. After the production of the porous SiC core, a dense SiC coating of ˜200 μm thickness is deposited by Chemical Vapor Deposition (CVD); the coated material was tested against hot PbLi in corrosion experiments. The properties of the material in terms of thermal and electrical conductivities, flexural strength and elastic modulus were measured, with promising results for high-temperature FCIs.
Self-passivating tungsten based alloys are expected to provide a major safety advantage compared to pure tungsten, presently the main candidate material for first wall armour of future fusion ...reactors. In case of a loss of coolant accident with simultaneous air ingress, a protective oxide scale will be formed on the surface of W avoiding the formation of volatile and radioactive WO3.
Bulk WCr12Ti2.5 alloys were manufactured by mechanical alloying (MA) and hot isostatic pressing (HIP), and their properties compared to bulk WCr10Si10 alloys from previous work. The MA parameters were adjusted to obtain the best balance between lowest possible amount of contaminants and effective alloying of the elemental powders. After HIP, a density >99% is achieved for the WCr12Ti2.5 alloy and a very fine and homogeneous microstructure with grains in the submicron range is obtained. Unlike the WCr10Si10 material, no intergranular ODS phase inhibiting grain growth was detected. The thermal and mechanical properties of the WCr10Si10 material are dominated by the silicide (W,Cr)5Si3; it shows a sharp ductile-to brittle transition in the range 1273–1323K. The thermal conductivity of the WCr12Ti2.5 alloy is close to 50W/mK in the temperature range of operation; it exhibits significantly higher strength and lower DBTT – around 1170K – than the WCr10Si10 material.
In this work, a simple approach to 3D printing of carbon black based shape memory polymer nanocomposites (SMP/CB) with toughness improving capabilities during programing stage using electrical ...stimulus is reported. Conductive SMP/CB nanocomposites, consisting of commercial SMP filled with conductive CB nanoparticles, were fabricated using solvent casting and single screw extrusion processes. Subsequently, material extrusion (ME) technique was used to 3D print dog bones type IV specimens for tensile test and electrical stimulus. It was found that SMP/CB electrical conductivity can be tuned by the filler fraction. In addition, electrical current passing through SMP/CB nanocomposites causes temperature increments and changes on material strength condition. Temperature profiles at various electrical current levels are reported. Moreover, Young's modulus and toughness of the 3D printed specimens subjected and not subjected to electrical current are presented. It was observed that conductive SMP/CB specimens responded to electrical current stimulus by increasing their toughness four times higher than with no current applied during tensile test. This paper is a reference for rheological and conductive properties of SMP/CB nanocomposites fabricated by ME 3D printing process.
•For PM-Wf/W it can be said that a potential manufacturing path for Wf/W has been opened.•Wf/W on its own can’t solve the issues of heat-exhaust in the divertor of a future fusion power ...plant.•Improvements of the copper cooling structure needs to be considered.•Prototype components should be available within 5 years for application.
Material issues pose a significant challenge for future fusion reactors like DEMO. When using materials in a fusion environment a highly integrated approach is required. Damage resilience, power exhaust, as well as oxidation resistance during accidental air ingress are driving issues when deciding for new materials. Neutron induced effects, e.g. transmutation adding to embrittlement is crucial to material performance. Here advanced materials, e.g. Wf/W or W/Cu, Wf/Cu composites allow the step towards a fusion reactor. Recent developments in the area of multi-fibre powder-metallurgical Wf/W mark a possible path towards a component based on standard tungsten production technologies. Field assisted sintering technology is used as production route to achieve 94% dense materials. Initial mechanical tests and micro-structural analyses show potential for pseudo-ductile behavior of materials with a reasonable (30%) fibre fraction. In the as-fabricated condition samples showed step-wise cracking while the material is still able to bear rising load, the typical pseudo-ductile behavior of a composite. Yttria is used as the interface material in order to allow the energy dissipation mechanisms to become active. Wf/W as plasma facing material contributes here to advanced material strength and crack resilience even with a brittle matrix embrittlement, while W/Cu, Wf/Cu composites at the coolant level allow for higher strength at elevated cooling temperatures. In addition to the use of pure tungsten it is demonstrated that tungsten-based self-passivating alloys can also be used in the composite approach.
A subclass of dynamical systems with a time rate of change of acceleration are called Newtonian jerky dynamics. Some mechanical and acoustic systems can be interpreted as jerky dynamics. In this ...paper we show that the jerk dynamics are naturally obtained for electrical circuits using the fractional calculus approach with order γ . We consider fractional LC and RL electrical circuits with 1 ⩽ γ < 2 for different source terms. The LC circuit has a frequency ω dependent on the order of the fractional differential equation γ , since it is defined as ω ( γ ) = ω 0 γ γ 1 - γ , where ω 0 is the fundamental frequency. For γ = 3 / 2 , the system is described by a third-order differential equation with frequency ω ~ ω 0 3 / 2 , and assuming γ = 2 the dynamics are described by a fourth differential equation for jerk dynamics with frequency ω ~ ω 0 2 .
The energy transfer at room temperature between Tb3+ and Eu3+ ions sorbed onto SrTiO3 powders is investigated, using Time-Resolved Laser-induced Fluorescence Spectroscopy (TRLFS). Several published ...works deal with the energy transfer between two lanthanide ions in co-doped matrices but it is the first time that transfer processes between two lanthanide ions sorbed on a solid surface is reported. The results show that the energy transfer between sorbed Tb3+ and Eu3+ ions on strontium titanate is a non-radiative process and follows a dipole–dipole type interaction. Moreover, the higher the acceptor ions Eu3+ concentration, the more efficient the energy transfer.
It is shown that no energy migration between the Tb3+ donor ions occurs. A formalism based on the model of Inokuti–Hirayama is used and allows one to fit the non-exponential Tb3+ fluorescence decay. It is thus possible to evaluate the critical radius (R0) of the influence sphere of the sorbed Tb3+ ions. According to the previous works, two sorption sites are considered for the sorbed rare-earth. The calculated radii are similar to those obtained for other couples of donor–acceptor lanthanide ions reported in the literature.
The field of energy harvesting has drawn an increased amount of interest due to the rapid development of wireless sensors and self-powered devices. Currently, there is limited information regarding ...the impact of coupling both thermal and mechanical excitations in a single material and its energy harvesting capabilities. This paper demonstrates the use of Lead Zirconate Titanate (PZT) as a coupled thermal and mechanical energy harvesting device. PZT ceramic was subjected to different thermal and mechanical loading conditions. Under pure mechanical cycling the sample consistently generated the least power output averaging less than 200 nW. An increase in power output was observed under mechanical cycling and higher temperatures. A peak power of 500 nW was seen under both, thermal cycling, as well as under coupled thermal-mechanical cycling. This study demonstrated the feasibility to harvest different waste energies from a single device.
•Tungsten alloys were investigated for their deuterium retention at an implantation temperature of 100°C.•The “heavy alloy” HPM 1850 retains similar amounts as pure tungsten.•The self-passivating ...alloy W10Cr0.5Y retains 10 times more.
The tungsten “heavy alloy” HPM 1850, a liquid-phase sintered composite material with two weight percent Ni and one weight percent Fe, as well as the self-passivating tungsten alloy W-10Cr-0.5Y, a high temperature oxidation resistant alloy with 10 weight percent of Cr and 0.5 weight percent of Y, were investigated with respect to their deuterium retention. The samples were deuterium loaded in an electron cyclotron resonance plasma up to a fluence of 1025m−2. The deuterium retention was then investigated by Nuclear Reaction Analysis and by Thermal Desorption. In HPM 1850 the observed deuterium amount was similar to pure tungsten, however the outgassing behaviour during thermal desorption was considerably faster. In W-10Cr-0.5Y the released deuterium amount during thermal desorption was about one order of magnitude higher; by comparison of nuclear reaction analysis and thermal desorption this was attributed to deeper diffusion of deuterium into the bulk of the material.
•Advanced tungsten-based smart alloys are being developed for future fusion power plant•Smart alloys will be used as plasma-facing components and as a passive safety measure in case of ...accident.•First direct comparative test of smart alloy and pure tungsten under identical plasma and accidental conditions was made.•Smart alloys featured similar sputtering as that of pure tungsten during plasma exposure.•Smart alloys demonstrate the 3-fold suppression of oxidation during the simulated accident as compared to pure tungsten.
In case of an accident in the future fusion power plant like DEMO, the loss-of-coolant may happen simultaneously with air ingress into the vacuum vessel. The radioactive tungsten and its isotopes from the first wall may become oxidized and vaporized into the environment. The so-called “smart” alloys are under development to suppress the mobilization of oxidized tungsten. Smart alloys are aimed at adjusting their properties to environment. During regular operation, the preferential sputtering of alloying elements by plasma ions should leave almost pure tungsten surface facing the plasma. Under accidental conditions, the alloying elements in the bulk will form an oxide layer protecting tungsten from mobilization.
The first direct comparative test of pure tungsten and smart alloys under identical plasma conditions was performed. Tungsten–chromium–titanium alloys were exposed simultaneously with tungsten samples to stationary deuterium plasma in linear plasma device PSI-2. The ion energy and the temperature of samples corresponded well the conditions at the first wall in DEMO. The accumulated fluence was 1.3 × 1026 ion/m2. The weight loss of pure tungsten samples after exposure was ΔmW = 1000–1150µg. The measured weight loss of sputtered smart alloy sample ΔmSA = 1240µg corresponds very well to that of pure tungsten providing experimental evidence of good resistance of smart alloys to plasma sputtering.
Plasma exposure was followed by the oxidation of alloys at 1000°C accomplishing the first test of these new materials both in a plasma environment and under accidental conditions. Compared to pure tungsten, smart alloys featured the 3-fold suppression of oxidation. Plasma exposure did not affect the oxidation resistance of smart alloys. At the same time, the self-passivation of the protective layer did not occur, calling for further optimization of alloys.
Purpose
Shape memory polymer (SMP) is capable of recovering its original shape from a high degree of deformation by applying an external stimulus such as thermal energy. This research presents an ...integration of two commercial SMP materials (DiAPLEX and Tecoflex) and a material extrusion (ME) printer to fabricate SMP parts and specimens. The material properties such as Young’s modulus of the specimens was examined as a process output. Furthermore, stress-strain curve, strain recovery, instant shape-fixity ratio, long-term shape-fixity ratio and recovery ratio of SMP specimens during a thermo-mechanical cycle were investigated.
Design/methodology/approach
The ME fabrication settings for the SMP specimens were defined by implementing a design of experiments with temperature, velocity and layer height as process variables.
Findings
It was found, according to main effect and iteration plots, that fabrication parameters have an impact on Young’s modulus and exist minimum iteration among variables. In addition, Young’s modulus variation of DiAPLEX and Tecoflex specimens was mostly caused by velocity and layer height parameters, respectively. Moreover, results showed that SMP specimens were able to recover high levels of deformation.
Originality/value
This paper is a reference for process control and for rheological properties of SMP parts produced by ME fabrication process.
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