• Energy Research
• materials engineering close
• Chinese Academy of Sciences close

AbstractIn this study, morphological, microstructural and phase changes of four types of tungsten materials after exposure to dense deuterium plasma were examined. The microstructures of the prepared materials mutually differ by the porosity, grain size and phase content. It was found that inherent porosity of sintered materials leads to a specific mechanism of erosion and might be a significant source of dust in the case of materials with higher porosity. Further, a preferential erosion of the dispersed particles by melting and evaporation and subsequent formation of thin film on the surface of W-Y2O3 was described as well.

La3Te4-based rare-earth telluride is a kind of n-type high-temperature thermoelectric (TE) material with an operational temperature of up to 1273 K, which is a promising candidate for thermoelectric generators. In this work, the Sm substitution in La3−xSmxTe4/Ni composites is reported. The electrical transport property of La3−xSmxTe4 is modified by reducing carrier concentration due to the substitution of Sm2+ for La3+. The electric thermal conductivity decreases by 90% due to carrier concentration reduction, which mainly contributes to a reduction in total thermal conductivity. Lattice thermal conductivity also decreases by point-defect scattering by Sm doping. Meanwhile, based on our previous study, compositing nickel improves the thermal stability of the La3 − xSmxTe4 matrix. Finally, combined with carrier concentration optimization and the decreased thermal conductivity, a maximum zT of 1.1 at 1273 K and an average zTave value of 0.8 over 600 K–1273 K were achieved in La2.315Sm0.685Te4/10 vol.% Ni composite, which is among the highest TE performance reported in La3Te4 compounds.

Pure W, and W–0.5wt%ZrC (WZC) and W–2.0wt%Zr–0.5wt%ZrC (WZZC) alloys are fabricated using vacuum hot pressure (VHP) method to investigate the effects of trace ZrC or Zr/ZrC on the mechanical properties and microstructure of tungsten. It was found that from W to WZC and to WZZC, the average grain size was refined from 6.2 µm of W to 5.8 μm of WZC and finally to 4.8 um for WZZC and relative density increase continually from 97.0% to 98.0% and to 98.5%. The tensile tests indicated that ZrC or ZrC/Zr significantly increases the strength and ductility/plasticity. The comparison of VHPed and spark plasma sintered (SPSed) specimen are made. The microstructure analysis indicate that the W–Zr–O and/or Zr–C–O particles resulting from the reaction of Zr or ZrC with free O pin grain boundaries (GBs) of tungsten and inhibits the migration of GBs, and then refining the grain size. The synergistic effects of the decrease of free O impurity and nano-sized ZrC dispersion strengthening strengthen GBs and improve the mechanical properties. Keywords: Tungsten, Trace Zr/ZrC, Mechanical property, Microstructure

Abstract Shear thickening fluid (STF) has been used in many areas due to its unique rheological property. In this study, the dynamic mechanical properties of STF-filled composite structures were investigated by in-house fabricated drop weight testing apparatuses. Results indicated that the strength and modulus increase with strain rate for all tube structures. Liquid-filled tubes possess similar strength and modulus, which are larger than air-filled tube at all strain rates. However, STF-filled tube absorbs 5 and 4 times more impact energy than air- and silicone oil-filled tubes, respectively. The energy absorption capacity of STF-filled tube increases with input impact energy. Meanwhile, the shear thickening effect of STF is more sensitive to the loading rate than the input energy, which is an important reference for the designing of STF integrated composite. The STF-filled silicone gel achieves repeatable test due to good protection of the encapsulation, which absorbs 4 times more energy than neat silicone gel during impact. Longitudinal symmetrical profile can be achieved for silicone gel encapsulated STF during impact due to the hardening of the STF which leads to a quick balance state. Moreover, the mechanical response of STF is found to correspond with the rheological performance of the STF.

High-alumina coal fly ash (HAFA) is an important aluminum and silicon resource. In the process of preparing aluminum-silicon materials from HAFA, the influence of impurity elements on its performance must be considered. In this work, the occurrence state of impurities in HAFA, micro morphology, and the bond energy of different impurity coordination were studied. Sulfuric acid leaching method and density functional theory were used to study the leaching behavior of impurities to verify the difficulty of removing different impurity elements. The results show that iron existed in the form of magnetic particles (34.78%), amorphous phase (49.24%), and crystalline phase (15.96%) in HAFA. Titanium mainly existed in amorphous phase (29.34%) and crystalline phase (69.4%). In sulfuric acid leaching, titanium was more difficult to leach, and the content of TiO2 decreased from 2.30% to 2.25%, whereas that of Fe2O3 decreased from 1.50% to 0.86%. The actual leaching behavior of impurity elements was consistent with the simulation results, with more energy required to remove Ti than Fe. These studies of impurity elements in HAFA will provide theoretical support for the preparation of aluminum-silicon materials.

The global market for wind energy has increased exponentially in the past few decades, and there is a continuous effort to develop cost-effective materials with higher strength to mass ratio for wind blades. With unique structural and transport properties, carbon nanotubes (CNTs) have attracted much interest as the reinforcement to develop polymer-based nanocomposites delivering exceptional mechanical properties and multi-functional characteristics. In light of previous and current status in carbon-based materials, herein the suitabilities of CNT/polymer nanocomposites for wind blade materials are analyzed. Special emphasis is placed on the mechanical, fatigue, electrical, thermal and barrier properties of CNT/polymer nanocomposites, which are important considerations when selecting suitable materials for wind blades with larger rotary radius. The application of CNT/polymer nanocomposites as sensory materials for the monitoring of defects in composite structures is also discussed. Finally, based on the progress made so far, some suggestions paving the way for the large commercialization of these nanocomposites for wind blades are presented.

The creep behavior of Ni–Cr–W alloy at 950 °C has been investigated by a novel creep testing system which is capable of in-situ measurement of strain. Tubular specimens were pressurized with argon gas for effective stresses up to 32 MPa. Experimental results show that the thermal fatigue reduces the creep life of the tubular specimens and with the introduction of thermal cycling fatigue the primary stage disappears and the creep rate higher than the pure thermal creep (without thermal fatigue). Also the creep behavior of Ni–Cr–W alloy doesn't consist in the secondary stage. A new creep equation has been derived and implemented into finite element method. The results from the finite element analyses are in good agreement with the creep experiment.

The low solubility of gadolinium (Gd) limits its application in iron-based neutron shielding alloys. In this study, a high content of Gd up to 7.87 wt.% was added into 316L stainless steel by mechanical alloying (MA) of Gd2O3 with 316L powder. Neutronics calculation results showed that the shielding efficiency of 0.2 mm thick 7.87 wt.% Gd-316L alloy was equivalent to that of 33 mm thick 316L for thermal neutrons. Microstructure analysis indicated that Gd-Si-O particles with an average size of 12.5 nm were uniformly dispersed in the matrix. It revealed that Gd2O3 dissolved into the 316L matrix during MA and re-precipitated at around 780 °C as Gd2SiO5 by XRD and TG-DSC. This study provides a novel Gd-containing alloy designed to achieve integration of structural alloys with good neutron shielding function for future application.