Subjects -> METALLURGY (Total: 58 journals)
 Showing 1 - 10 of 10 Journals sorted alphabetically Acta Metallurgica Slovaca Advanced Device Materials       (Followers: 3) American Journal of Fluid Dynamics       (Followers: 47) Archives of Metallurgy and Materials       (Followers: 8) Asian Journal of Materials Science       (Followers: 5) Canadian Metallurgical Quarterly       (Followers: 20) Complex Metals       (Followers: 1) Corrosion Communications       (Followers: 5) Energy Materials : Materials Science and Engineering for Energy Systems       (Followers: 19) Handbook of Magnetic Materials       (Followers: 2) Indian Journal of Engineering and Materials Sciences (IJEMS)       (Followers: 10) International Journal of Metallurgy and Alloys       (Followers: 3) International Journal of Metals       (Followers: 6) International Journal of Minerals, Metallurgy, and Materials       (Followers: 8) International Journal of Mining and Geo-Engineering Ironmaking & Steelmaking       (Followers: 4) ISIJ International - Iron and Steel Institute of Japan       (Followers: 23) Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings)       (Followers: 2) JOM Journal of the Minerals, Metals and Materials Society       (Followers: 32) Journal of Advanced Joining Processes Journal of Central South University       (Followers: 1) Journal of Cluster Science Journal of Heavy Metal Toxicity and Diseases Journal of Iron and Steel Research International       (Followers: 7) Journal of Materials & Metallurgical Engineering       (Followers: 1) Journal of Materials Processing Technology       (Followers: 18) Journal of Metallurgical Engineering       (Followers: 2) Journal of Sustainable Metallurgy       (Followers: 3) Materials Science and Metallurgy Engineering       (Followers: 7) Metallurgical and Materials Engineering Metallurgical and Materials Transactions A       (Followers: 42) Metallurgical and Materials Transactions B       (Followers: 31) Metallurgical and Materials Transactions E       (Followers: 2) Metallurgical Research & Technology Metallurgical Research and Technology       (Followers: 6) Metallurgy and Foundry Engineering Mining, Metallurgy & Exploration Powder Diffraction       (Followers: 1) Powder Metallurgy       (Followers: 33) Powder Metallurgy and Metal Ceramics       (Followers: 7) Powder Metallurgy Progress       (Followers: 5) Rare Metals       (Followers: 1) Revista de Metalurgia Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica Revista Remetallica Russian Metallurgy (Metally)       (Followers: 4) Science and Technology of Welding and Joining       (Followers: 4) Soldering & Surface Mount Technology       (Followers: 1) Stainless Steel World       (Followers: 17) Transactions of the IMF       (Followers: 14) Transactions of the Indian Institute of Metals       (Followers: 4) Tungsten Universal Journal of Materials Science       (Followers: 1) Welding in the World       (Followers: 4) Welding International       (Followers: 7) Вісник Приазовського Державного Технічного Університету. Серія: Технічні науки
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 TungstenNumber of Followers: 0      Hybrid journal (It can contain Open Access articles) ISSN (Print) 2661-8028 - ISSN (Online) 2661-8036 Published by Springer-Verlag  [2469 journals]
• Strengthening of tungsten by coherent rhenium precipitates formed during

Abstract: Abstract Experimental data show that the accumulation of rhenium and osmium from transmutation reactions severely affect the microstructural evolution and property degradation of tungsten-based materials under neutron irradiation. Theory and modeling have confirmed that Re atom transport in W is by irradiation-produced migrating self-interstitial atoms. With this diffusion mode in operation, a specific microstructure evolution is realized when at relatively low neutron fluence the Re-rich precipitates are formed, while the void and interstitial loop population development is suppressed, affecting the mechanical properties. This research shows the effect of small coherent Re-rich precipitates on the dislocation glide under stress, investigated using the molecular dynamics approach with empirical interatomic potentials. The results are compared with an earlier simulation of void hardening in W. It is demonstrated that small coherent Re-rich precipitates of less than 6 nm diameter represent relatively weak obstacles for moving edge dislocations. The implication of these results on the interpretation of experimental results is discussed.
PubDate: 2022-03-01

• Preparation of the highly dense ceramic–metal fuel particle with
fine-grained tungsten layer by chemical vapor deposition for the
application in nuclear thermal propulsion

Abstract: Abstract The cermet fuel element was achieved by dispersing the UO2 particles with or without tungsten (W) coating layer uniformly in the W matrix. It is considered to be a robust and secure fuel for use in nuclear thermal propulsion in the near future. In this study, the effect of deposition temperature on the densification and grain refinement of the W coating layer was investigated. A high-density (19.24 g·cm−3) W layer with a uniform thickness (~ 10 μm) and fine grains (~ 297 nm) was prepared by spouted-bed chemical vapor deposition. The prepared high-density, fine-grained W layer has the following advantages. It can prevent direct contact between fuel particles, resulting in a more uniform fuel distribution. In addition, it can decrease the reaction probability between the fuel kernel and H2, and prevent the release of fission products from the fuel kernel by extending the diffusion path at grain boundaries more efficiently. Moreover, the high-density, fine-grained W layer showed outstanding thermal and mechanical performance. Its average hardness and Young’s modulus were approximately 7 and 200 GPa, respectively. The thermal conductivity of the W film was 101–124 W·m−1·K−1 at 298–773 K. This work furthers our understanding of the potential application of the high-density, fine-grained W layer in nuclear thermal propulsion.
PubDate: 2022-03-01

• Preparation of nano-crystalline tungsten powders from gaseous WO2(OH)2

Abstract: Abstract The industrial production of tungsten powder is carried out by the reduction of tungsten oxide powder via hydrogen. In this process, the size of the W particles is limited to particle sizes larger than 100 nm. To get below this limit, alternative processes are needed. In the current work, the possibility of preparing W powder below 100 nm via a vapour phase reduction of volatile WO2(OH)2 by hydrogen was investigated. The process consists of two stages. In the first stag,e WO2(OH)2 is formed by reacting WO3 with water vapour at temperatures of 1000–1100 °C. In the second stage, WO2(OH)2 is reduced by hydrogen at about 1000 °C to form metallic tungsten. The influence of process parameters such as furnace temperature, humidity and gas flow on the WO2(OH)2 evaporation and formation of tungsten powder was investigated. The characterization of the resulting powders was performed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). By optimization of the reaction conditions, powder with a metallic tungsten content of about 70 at% besides tungsten oxides was produced with metal particle sizes down to 5 nm. Further optimization should lead to a high tungsten content and a high product yield. Due to the small particle size, applications in catalysis might be possible, although an industrial realization of the process seems unrealistic at moment.
PubDate: 2022-03-01

• Deuterium retention in chemically vapor deposited tungsten carbide
coatings and hot-rolled tungsten exposed to low-energy deuterium plasma

Abstract: Abstract Samples of chemically vapor deposited (CVD) coatings of tungsten carbides W45C55 and W60C40 and samples of hot-rolled tungsten were exposed to deuterium (D) plasma at sample temperatures ranging from 323 to 813 K, as a result of which the samples were irradiated with D ions with an energy of about 200 eV per D particle at a flux of D particles of about 1.1 × 1021 D·m−2·s−1 to a fluence of about 2 × 1024 D·m−2. The concentration of deuterium in these samples was examined by the D(3He,p)4He nuclear reaction. Based on the measured deuterium depth profiles and assuming that these profiles are determined by diffusing D atoms, the diffusion coefficients of deuterium in the CVD tungsten carbide coatings were determined. Using these diffusion coefficients, an estimate of the Arrhenius relation for the diffusion coefficients of deuterium in CVD tungsten carbide coatings was obtained: D = 2.5 × 10–3 exp(− 1.12 eV/kT) m2·s−1, where T is temperature expressed in Kelvin, and k is the Boltzmann constant. The concentration of trapped deuterium in the bulk of CVD tungsten carbide coatings is practically independent of the stoichiometry of the coatings. It decreases from about 5 × 10–2 to about 7 × 10–4 D/(W + C) with an increase in the deuterium plasma exposure temperature from 373 to 813 K. The concentration of trapped deuterium in hot-rolled tungsten, expressed in units of the D/W atomic ratio, is more than an order of magnitude lower than the concentration of deuterium in tungsten carbides, and also decreases with increasing plasma exposure temperature.
PubDate: 2022-03-01

• Z-scheme systems of ASi2N4 (A = Mo or W) for photocatalytic water
splitting and nanogenerators

Abstract: Abstract Z-scheme heterojunction catalysts have received great attention due to their efficient ability to separate electrons and holes. Here, using the first-principles calculations, we designed a series of promising two-dimensional (2D)/2D Z-scheme systems with interlayer inequivalent, including MoSi2N4/MoSi2N4, WSi2N4/WSi2N4 and MoSi2N4/WSi2N4. Molecular dynamics simulation and phonon dispersion show that they have sufficient environmental stability. The inequivalent structure between the layers caused the directional formation of built-in potentials, driving the transfer of net charge between layers, which greatly enhanced their catalytic activity. The smaller band gap and enhanced light absorption performance further revealed their perfect catalytic performance. Moreover, all they met the redox potential requirements of water splitting in a range of pH 0–7, demonstrate they are very remarkable photocatalysts for H2 evolution. More interestingly, they also have good sliding ferroelectricity, and the opposite built-in potential can be obtained by sliding between layers, which is very promising for future nanogenerators. Our works may provide new insights into energy conversion devices.
PubDate: 2022-03-01

• Hydrogen bond-mediated polyoxometalate-based metal-organic networks for
efficient and selective oxidation of aryl alkenes to aldehydes

Abstract: Abstract Selective oxidation of aryl alkenes to aldehydes is an important approach to produce industrial raw materials, in which the exploration of an efficient heterogeneous catalyst is significant but challenging. In this work, three hydrogen bond-mediated polyoxometalate(POM)-contained metal–organic networks with the formulas of [Ni(BTD)2(H2O)2]2[SiW12O40]·12H2O (1), [Ni(BTD)2(H2O)]2[SiW12O40]·6H2O (2) and [Zn(BTD)2(H2O)]2[SiW12O40]·6H2O (3) (BTD = 4H,4ʹH-[3,3ʹ-bi(1,2,4-triazole)]-5,5ʹ-diamine) were hydrothermally synthesized, in which the metal–organic fragments interact with POM clusters via abundant hydrogen bonding to extend the structure into three-dimensional supramolecular networks. To be explored as heterogenous catalysts, compounds 1–3 showed high catalytic activity and selectivity for the selective oxidation of styrene to benzaldehyde. Among them, compound 1 exhibits the highest performance with ca. 99% styrene conversion and ca. 99% selectivity of benzaldehyde in 5 h. Moreover, compound 1 displays rich substrate compatibility, recyclability and good structural stability. A series of experiments demonstrated that the high performance of compound 1 should be attributed to the synergistic effect among polyoxoanion and coordination-unsaturated metal centers in metal–organic fragments, which facilitates the activation of H2O2 and styrene substrates, thus enhancing the catalytic performance.
PubDate: 2022-01-18

• Influence of recrystallization on tungsten divertor monoblock under high
heat flux

Abstract: Abstract Extremely high heat flux reaching 20 MW·m−2 can be foreseen for the future fusion reactor. Such high heat flux would induce recrystallization of tungsten (W) material, leading to significant strength loss of tungsten material and increment of ductility at high temperature, in particular when the temperature is much higher than its ductile-to-brittle transition temperature (DBTT). In this paper, an International Thermonuclear Experimental Reactor (ITER)-like tungsten divertor monoblock is modeled, and benchmark has been done first to get consistent results with ITER. Then, the monoblock structure has been optimized in order to get a lowest possible temperature and stress during heating and cooling phase separately compared to the baseline structure. Structural analysis of two kinds of states: stress-relieved tungsten and recrystallized tungsten using finite element method has been performed, aiming at finding out the recrystallization impact on the mechanical behavior of tungsten in divertor monoblock under cyclic high heat flux. Damages due to progressive deformation and time-independent fatigue lifetime of these two states of tungsten have been assessed and compared according to criteria The Structural Design Criteria for ITER In-vessel Components. Finally, the impact of different material recrystallization temperature on mechanical behavior has been explored under stationary heat load. The result shows that after recrystallization, thermal stress of tungsten material can be released by the larger plastic deformation compared to the stress-relieved tungsten. However, it is easier for recrystallized tungsten to get damaged due to progressive deformation as well as fatigue under 20 MW·m−2 cyclic heat flux than stress-relieved tungsten because of its relatively lower yield strength and larger plastic strain, which would cause low-cycle strain fatigue. Furthermore, tungsten with lower recrystallization temperature distorts more seriously, and therefore, it can be predicted the cracks would be initiated more easily.
PubDate: 2022-01-18

• A review of late-stage tungsten fuzz growth

Abstract: Abstract Tungsten will be used as the plasma-facing divertor material in the International Thermonuclear Experimental Reactor (ITER) fusion reactor. Under high temperatures and high ion fluxes, a ‘fuzz’ nanostructure forms on the tungsten surface with dramatically different properties and could contaminate the plasma. Although simulations and experimental observations have provided understanding of the initial fuzz formation process, there is debate over whether tungsten or helium migration is rate-limiting during late-stage growth, and the mechanisms by which tungsten and helium migrations occur. Here, the proposed mechanisms are considered in turn. It is concluded that tungsten migration occurs by adatom diffusion along the fuzz surface. Continual helium migration through the porous fuzz to the tungsten bulk is also required for fuzz growth, for continued bubble growth and rupture. Helium likely migrates due to ballistic penetration, although diffusion may contribute. It is difficult to determine the limiting process, which may switch from helium penetration to tungsten adatom diffusion above a threshold flux. Areas for further research to clarify the mechanisms are then considered. A greater understanding of the fuzz formation mechanism is key to the successful design of plasma-facing tungsten components, and may have applications in forming porous tungsten catalysts.
PubDate: 2022-01-12

• Effects of Zr/Mo addition on He bubble formation in Y2O3-added W alloys

Abstract: Abstract To improve the mechanical properties of the Y2O3-added W alloy, Mo and Zr were independently added to a sample of W-Y2O3. In this study, the effects of minor additions of elemental Mo and Zr on He bubble formation in the Y2O3 added W alloys were investigated at 773 K, 973 K, and 1173 K, where the maximum irradiation fluence of the samples using 5 keV He ions was 1.8 × 1021 He m−2. He bubbles were observed at all temperatures for both alloys; however, the irradiation fluences at which He bubbles could be observed differed at each temperature. With increase in irradiation temperature, the He irradiation fluence for which the formation of He bubbles could be observed decreased. At the relatively low temperature of 773 K, the void swelling in the W-Mo-Y2O3 and W-Zr-Y2O3 alloys was slightly lower than that of W-Y2O3 alloy. However, at high temperature of 973 K and 1173 K, the He irradiation resistances of both W-Mo-Y2O3 and W-Zr-Y2O3 were worse than that of W-Y2O3. The addition of Zr enhanced the interaction between vacancies and He, enhancing the formation of He bubbles. However, the addition of Mo coarsened the Y2O3 particles, reducing the suppression of vacancy cluster formation due to the dispersion of Y2O3 particles. It is, therefore, necessary to fully consider mechanical properties and T-retention in addition to the irradiation resistance of He to select an alloy as the plasma-facing material for fusion applications.
PubDate: 2022-01-12

• Composition design of high yield strength points in single-phase
Co–Cr–Fe–Ni–Mo multi-principal element alloys system based on
electronegativity, thermodynamic calculations, and machine learning

Abstract: Abstract A method which combines electronegativity difference, CALculation of PHAse Diagrams (CALPHAD) and machine learning has been proposed to efficiently screen the high yield strength regions in Co–Cr–Fe–Ni–Mo multi-component phase diagram. First, the single-phase region at a certain annealing temperature is obtained by combining CALPHAD method and machine learning, to avoid the formation of brittle phases. Then high yield strength points in the single-phase region are selected by electronegativity difference. The yield strength and plastic deformation behavior of the designed Co14Cr30Ni50Mo6 alloy are measured to evaluate the proposed method. The validation experiments indicate this method is effective to predict high yield strength points in the whole compositional space. Meanwhile, the interactions between the high density of shear bands and dislocations contribute to the high ductility and good work hardening ability of Co14Cr30Ni50Mo6 alloy. The method is helpful and instructive to property-oriented compositional design for multi-principal element alloys.
PubDate: 2022-01-03

• Heteropolyacids supported on hierarchically macro/mesoporous TiO2:
efficient catalyst for deep oxidative desulfurization of fuel

Abstract: Abstract The fabrication of polyoxometalates (POMs)-modified TiO2 catalysts with connected pore structure has attracted great interests due to its prominent effect on mass transfer and catalytic oxidation activity. Here, we report a series of hierarchically macro/mesoporous (M/m) phosphotungstic acid (HPW)/TiO2 composites, which are fabricated by colloidal crystal template method and applied as deep desulfurization catalyst in fuel oil. As-synthesized hierarchical HPW/TiO2 composite is interconnected by ordered macroporous channel with disordered mesoporous embedded on pore walls. Moreover, Keggin-type HPW is homogeneously dispersed on the TiO2 matrix. Hierarchical macro/mesoporous HPW/TiO2 shows an excellent catalytic performance, the removal rate for dibenzothiophene in model fuel reaches 99% under the optimum conditions. This high performance of the three-dimensional ordered macropores (3DOM) HPW/TiO2 can be attributed to its hierarchically porous which is highly beneficial for the mass transfer during the catalytic process. Moreover, the used catalyst could be regenerated by centrifugation and only slight decreasing of the catalytic activity after five cycles.
PubDate: 2021-12-18

• Preparation of tungsten–iron composite oxides and application in
environmental catalysis for volatile organic compounds degradation

Abstract: Abstract Emission of volatile organic compounds has important influence on complex air pollution and human health. In this paper, a series of tungsten–iron composite oxides with different proportions and preparation methods were synthesized and first used for catalytic combustion of chlorobenzene and toluene, as typical polluting gas sources. These WO3-based solid catalytic materials were systematically characterized by modern analytical methods, and the results showed that there was strong electron interaction between W and Fe elements in the composite oxides, and the presence of a certain amount of tungsten oxide inhibited the crystallization of iron oxide, and vice versa, which were beneficial to the uniform dispersion of tungsten–iron components into each other and the improvement of redox properties. Compared with single-component oxide, the formation of tungsten–iron composite oxide affected the micro-structure, improved the specific surface area and optimized the pore structure of materials. The performance test results showed that the tungsten–iron composite oxide (FeWO4–0.5Fe2O3, molar ratio of tungsten and iron was 1/2) prepared using citric acid-based sol–gel method was the optimal, and its catalytic degradation efficiency could reach 90% for chlorobenzene and 83% for toluene at 320 °C, and maintain at least 60 h without obvious deactivation, with high selectivity to the formation of HCl and CO2.
PubDate: 2021-12-17

• A polyoxometalate based electrochemical sensor for efficient detection of
L-cysteine

Abstract: Abstract L-cysteine (L-cys), as an important sulfur-containing amino acid, plays an indispensable role in biological systems. Too low and excessively high ratio of L-cys will cause harm to the function of human organs. Therefore, it is very necessary to develop efficient methods to detect it in multifarious samples. This paper has built an electrochemical sensor by combining Keggin-type polyoxometalate (PMo9V3) and cobalt tetrasulfonate (II) phthalocyanine (CoTsPc) on indium tin oxide electrodes using the layer-level self-assembly technology for efficiently detection of L-cys. The assembly process and surface morphology of the modified electrode was characterized by ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope, and atomic force microscopy. The conditions of electro-catalysed oxidation of L-cys were optimized by cyclic voltammetry, and the kinetic electrochemical parameters were also evaluated by electrochemical impedance spectra. Furthermore, the sensing performance of the modified electrode was explored using amperometry. The proposed electrochemical L-cys sensor was found to have superior sensing performance with a range of linear response of 2.5 × 10–7 to 1.7 × 10–4 mol·L−1 and 1.7 × 10−4 to 39.5 × 10−4 mol·L−1, the detection limit of 1.0 × 10–7 mol·L−1 (signal/noise = 3), and satisfactory anti-interference ability. Consequently, the fabricated sensor has the potential to be applied in laboratory practices for L-cys deterimination in commercial drinks.
PubDate: 2021-12-17

• Selective laser melting of lanthanum oxide-reinforced tungsten composites:
microstructure and mechanical properties

Abstract: Abstract In this study, La2O3 nanoparticles were introduced into the tungsten (W) matrix to optimize the microstructure and properties of pure W. The W-La2O3 composites with different mass ratios of La2O3 were manufactured by selective laser melting (SLM). The result showed that the average grain sizes for W-1 wt% La2O3 and W-2 wt% La2O3 were reduced by more than 51.3% compared with that of pure W, and the defects obviously decreased. The microhardness and compressive strength of the SLM W-2 wt% La2O3 sample reached 455 HV and 2194 MPa, respectively. The toughness of the SLM W-2 wt% La2O3 sample also improved significantly. One main reason was that the La2O3 nanoparticles provide many heterogeneous nucleation sites to refine the grains. The other main reason was that La2O3 nanoparticles formed into dislocation loops, which hindered the movement of dislocations and then increased the strength further. This research provided a new method to improve the mechanical properties of SLM W by introducing La2O3 nanoparticles to achieve fine-grains strengthening and Orowan strengthening.
PubDate: 2021-12-17

• In-situ transmission electron microscopy observation of the evolution of
dislocation loops and gas bubbles in tungsten during H2+ and He+ dual-beam

Abstract: Abstract Dislocation loop and gas bubble evolution in tungsten were in-situ investigated under 30 keV H2+ and He+ dual-beam irradiation at 973 K and 1173 K. The average size and number density of dislocation loops and gas bubbles were obtained as a function of irradiation dose. The quantitative calculation and analysis of the migration distance of 1/2  $$\langle{111}\rangle$$  loops at low irradiation dose indicated that the main mechanism of the formation of  $$\langle{100}\rangle$$  loops should be attributed to the high-density helium cluster inducement mechanism, instead of the 1/2  $$\langle{111}\rangle$$  loop reaction mechanism. H2+ and He+ dual-beam irradiation induced the formation of  $$\langle{100}\rangle$$  loops and 1/2  $$\langle{111}\rangle$$  loops, while increasing the irradiation temperature would increase  $$\langle{100}\rangle$$  loop percentage. The percentage of  $$\langle{100}\rangle$$  loops was approximately 18.6% at 973 K and increased to 22.9% at 1173 K. The loop reaction between two 1/2  $$\langle{111}\rangle$$  loops to form a large-sized 1/2  $$\langle{111}\rangle$$  loop was in-situ observed, which induced not only the decrease of the number of 1/2  $$\langle{111}\rangle$$  loops but also the significant increase of their sizes. The  $$\langle{100}\rangle$$  loops impeded the movement of dislocation line and tended to escape from it instead of being absorbed. With the increase of irradiation dose, the yield strength increment ( $$\Delta {\sigma }_{\mathrm{l}\mathrm{o}\mathrm{o}\mathrm{p}}$$ ) caused by the change of loop size and density increased first and then decreased slightly, while the yield strength increment ( $$\Delta {\sigma }_{\mathrm{b}\mathrm{u}\mathrm{b}\mathrm{b}\mathrm{l}\mathrm{e}}$$ ) caused by the change of bubble size and density always increased. Meanwhile, within the current irradiation dose range, $$\Delta {\sigma }_{\mathrm{l}\mathrm{o}\mathrm{o}\mathrm{p}}$$ was much larger than $$\Delta {\sigma }_{\mathrm{b}\mathrm{u}\mathrm{b}\mathrm{b}\mathrm{l}\mathrm{e}}$$ .
PubDate: 2021-12-01
DOI: 10.1007/s42864-021-00104-7

• Microstructures and mechanical properties of Ta–Nb–Zr–Ti–Al
refractory high entropy alloys with varying Ta/Ti ratios

Abstract: Abstract The refractory high entropy alloys (RHEAs) containing disordered body-centered cubic (BCC) and ordered BCC (B2) structures often exhibit high strength but low ductility at room temperature, even in the compressive tests. In this study, (Ta25-xNb25Zr25Ti25+x)95Al5 (x = 0, 5, 10) RHEAs are fabricated to investigate the compositional dependence of the microstructures and mechanical properties. All the three alloys exhibit a single BCC structure at the as-cast and solution-treated states, while the basket weave-like microstructures consisting of cuboidal and strip-like phases are formed after aging at 600 °C. The microstructure of the aged alloys is sensitive to the compositions: only disordered BCC1 + BCC2 dual phases are observed in the (Ta25Nb25Zr25Ti25)95Al5 alloy; additional B2 phases are formed by replacing 5 at% Ta with Ti; a complex microstructure containing BCC1 + BCC2 + B2 + Omega phases are identified in the (Ta15Nb25Zr25Ti35)95Al5 alloy. Although replacing Ta with Ti results in a reduction of compressive yield strength from 1762 to 1243 MPa, the fracture strain is greatly enhanced from 7.3 to 44.3%, indicating that the strength-ductility balance can be tuned to a large extent in this RHEA system.
PubDate: 2021-12-01
DOI: 10.1007/s42864-021-00111-8

• Recent progress of vanadium-based alloys for fusion application

Abstract: Abstract Low-activation vanadium alloys, with the reference composition of V–4Cr–4Ti have been considered as one of the most promising candidate materials for structural components such as the blanket in future fusion reactors, thanks to their excellent neutron irradiation resistance, superior high-temperature mechanical properties, and high compatibility with liquid lithium blankets. The self-cooled liquid lithium blanket using structural materials of vanadium alloys is an attractive concept because of the high heat transfer and high tritium breeding capability. After more than 2 decades of research, technological progress has been made in reducing the number of critical issues for application of vanadium alloys to fusion reactors. In this paper, the recent research and development activities of vanadium alloys are summarized, including significant progress achieved on fabrication technology and composition optimization, coating and corrosion, improved understanding of irradiation effects upon microstructure and material properties, retention of hydrogen isotopes, as well as advancements in joining and welding. In particular, the fact that recent products from China, Japan, US and France showed similar properties which meant the fabrication technology has been almost standardized.
PubDate: 2021-12-01
DOI: 10.1007/s42864-021-00107-4

• Neutron irradiation effects on mechanical properties of ITER specification
tungsten

Abstract: Abstract In this contribution, we present the results of recent neutron irradiation campaign performed in the material test reactor BR2 (Belgium) on pure tungsten. We have applied various irradiation conditions and sample geometry to assess the effect of neutron irradiation on hardness, bending, tensile and fracture mechanical properties. The investigated material is a commercially pure tungsten plate fabricated according to the international thermonuclear experimental reactor (ITER) specification for the application in the divertor plasma-facing components. The neutron irradiation covers a large span of temperatures and damage doses, ranging from 600 to 1200 °C and 0.1–1 dpa. The obtained mechanical properties were analyzed to deduce the shift of the ductile to brittle transition temperature (DBTT) applying bending, tensile and fracture toughness-testing procedures. Then, a correlation of the fracture toughness with the change of the hardness was established. The obtained results are compared with the already published results on another ITER specification grade produced in the form of a rod. The presented and discussed results show that the performance of the compared grades in terms of the irradiation-induced embrittlement is similar, and that the irradiation in the high-temperature region (600–800 °C) causes a considerable DBTT shift already at 0.2–0.5 dpa.
PubDate: 2021-12-01
DOI: 10.1007/s42864-021-00105-6

• He bubble-driven growth of W fuzz during the interaction between H2/He
plasmas and W materials

Abstract: Abstract The tungsten (W) material as the divertor of fusion reactors is exposed to low-energy and high-flux He/H isotope irradiation, leading to the growth of fuzz layers. The W fuzz growth does not show any dependence on the plasma irradiation devices used; however, it is strongly dependent on He+ fluence and energy, irradiation temperature, and impurity level. When the incident He ions collide inside the dense fuzz layers with the extremely high specific area, their mean free path can be up to 690 nm. Up to now, the He bubble-driven W fuzz growth process is not entirely understood; however, it can be closely related to the surface bursting of He bubbles in the W surface layer and W surface erosion by He+ implantation. The formation of He bubbles can be attributed to the solute He diffusion into defects or bubbles, which is strongly affected by the temperature and He+ fluence. The W fuzz grows over the W surface, where the micro-stress caused by He bubbles in the W surface layer acts as the driving force. The W fuzz layer inhibits He+ implantation into W bulk, and provides an entire protection against the He+ erosion into W bulk beneath the fuzz layer. In this review article, the current status of experiment and theory are presented, and some of the remaining issues are discussed.
PubDate: 2021-12-01
DOI: 10.1007/s42864-021-00096-4

• Micron-scale ultrathin two-dimension zirconia nanosheets towards enhancing
anticorrosion performance of epoxy coatings

Abstract: Abstract Polymer nanocomposite coatings have attracted great interest in the anticorrosion fields due to their excellent properties. Nanofillers are necessary to achieve high anticorrosion performance of the polymer coating. Herein, we report a wet-chemical template strategy to prepare large-size ZrO2 nanosheets, in which the Zr4+ ions are anchored on the surface of a graphene oxide template via electrostatic adsorption, followed by a thermal treatment process to remove graphene. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images show that the size and thickness of as-prepared ZrO2 nanosheets are more than 2 μm and ~ 4.5 nm, respectively. The micron-scale ultrathin two-dimension (2D) ZrO2 nanosheets, for the first time, are utilized as the anticorrosive fillers in the epoxy coating to reduce the porosity, consequently promoting the gas and water barrier properties of the composite coating. The polymer coating containing 1.0 wt% ZrO2 nanosheets shows a high initial impedance (89.1 GΩ·cm2) that can protect the metal substrate from being corroded during long-term immersion (60 days), which is better than that of the reduced graphene oxide (rGO)-incorporated coating and the ZrO2 nanoparticles-incorporated coating. This work offers valuable insights into the design and preparation of novel and efficient 2D electric-inert nanofillers for anticorrosion coatings.
PubDate: 2021-12-01
DOI: 10.1007/s42864-021-00108-3

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