[en] Highlights: • WO₃ is a promising candidate of photocatalyst. • The hollow spherical structure is synthesized by hydrothermal synthesis. • This hollow structure consists of WO₃ nano-plates. • WO₃ nano-plates are obtained by addition of high concentration HNO₃. • Porous WO₃ structure exhibits wonderful photocatalytic activity. - Abstract: A new kind of 3D hollow aggregate spherical structure WO₃ nano-plates was prepared via a simple hydrothermal synthesis without any template. In this paper, the effects of HNO₃ addition on the preparation of WO₃ powder were systematically investigated. With HNO₃ concentration increasing, the product was converted from WO₃(H₂O)_0.33 to monoclinic WO₃·H₂O until the reaction to complete. Meanwhile, the morphology and size of particles changed from mocro-scale spheres to nano-plates. In the WO₃·H₂O structure, H₂O integrates the H₂O molecules via hydrogen bond, while WO₃ bonds with other WO₃ molecules and finally form a hollow spherical structure. During subsequent drying, WO₃·H₂O is deprived of crystal water to become monoclinic WO₃, remaining this porous spherical structure. Compared with the industry-use catalyst of Degussa P25 TiO₂, the as-prepared WO₃ exhibits the wonderful photocatalytic activity due to the plate-like morphology and porous structure.

[en] Highlights: • W-Al₂O₃ ultrafine powder was prepared by hydrothermal synthesis. • Al₂(WO₄)₃ was a key process for forming nano-Al₂O₃ coated W structure. • This coated structure inhibited the further growth of W particles. • Dispersed Al₂O₃ particles improved obviously mechanical properties of W alloy. • Fracture mode changed into intergranular from transcrystalline with Al₂O₃ addition. - Abstract: W-Al₂O₃ composite powder was prepared via hydrothermal synthesis containing doping, annealing and reduction. The precursors WO₃ and AlOOH were synthesized by the two sets of the hydrothermal reactions, respectively. The formation of Al₂(WO₄)₃ from these two precursors in an aqueous solution is a key process, which is beneficial to improve the mixing uniformity of final powder to a molecular level. During subsequent reduction, nano-Al₂O₃ coated W particles were obtained, and inhibited the further deposition of reduced W atoms on the adjacent W particles, obtaining ultra-fine Al₂O₃/W composite powder. After sintering, the dense and fine-grained W-Al₂O₃ alloy was obtained due to the high sintering activity of ultra-fine powder. Compared with the pure tungsten, the W-Al₂O₃ alloy displays obvious higher values of both strength and plasticity especially when the Al₂O₃ content is 2 wt%.

[en] Spherical porous Al₂O₃ nanoparticles were synthesized by hydrothermal method using C₆H₅(NH₄)₃O₇·2H₂O and Al(NO₃)₃·9H₂O as raw materials. The morphology and size of the Al₂O₃ particles were significantly influenced by hydrothermal temperature, time, and the molar ratio of Al³⁺ to (C₆H₅O₇)³⁻. The interphase Al(OH)₃ is a key factor on the preparation of γ-Al₂O₃. Under the hydrothermal conditions of high temperatures, Al(OH)₃ decomposes into the precursor γ-AlOOH instead of the exothermic reaction between Al(OH)₃ and H⁺. In the form of hydrogen bonds, (C₆H₅O₇)³⁻ adsorbs on the surface of γ-AlOOH nanoparticles to form some nano-chains, which interweave and tangle each other to become spheres. During calcination, the precursor γ-AlOOH converts to γ-Al₂O₃ nanoparticles while the spherical morphology is retained. Gas outrush during calcination should be the formative cause of the porous structure. The as-prepared spherical porous Al₂O₃ nanoparticles can be used as a catalyst or carrier due to the favorable adsorption property. (paper)

[en] Highlights: • The effects of deformation and annealing on the properties of tungsten alloy were investigated. • The strength and toughness of tungsten alloy can be improved by large rotary swaging ratio. • The doping of zirconia prolonged the recovery and recrystallization process of tungsten alloy. • W-1.5ZrO₂ alloy has the best properties after annealing at 1100–1200 °C for 1 h. -- Abstract: W-1.5ZrO₂ alloy bars with two diameters, named as D9 and D5, were prepared by liquid phase method and rotary swaging method. The effects of swaging and annealing on the microstructure and mechanical properties of tungsten alloys were investigated. Under the same swaging ratio, the compressive strength of D5 tungsten alloy and D9 tungsten alloy is 23.27% and 22.37% higty her than that of pure W, respectively. After multi-pass swaging, the diameter of tungsten alloy decreased from 9 mm to 5 mm, and the hardness and compressive strength increased by 14.6% and 21.93%, respectively. After multi-pass rotary swaging, the diameter of tungsten alloy is reduced from 9 mm to 5 mm, and the hardness and compressive strength are increased by 14.6% and 21.93% respectively. The fracture mode has gradually changed from intergranular fracture to trans-granular fracture. Therefore, the strength of tungsten alloy can be improved by adding zirconia and proper swaging process. With the increase of annealing temperature or time, recrystallization and grain growth will be caused. The addition of ZrO₂ can delay the recrystallization of tungsten alloy during annealing, and inhibit grain growth. When the annealing temperature is lower than 1200 °C, the compressive strength of tungsten alloy remains unchanged, while the failure strain increases. After annealing at 1500 °C, the strength and failure strain of tungsten alloy decreased by 18.9% and 35.7% respectively. In order to obtain excellent strength and toughness, annealing at 1100–1200 °C for 1 h can be chosen for W-1.5ZrO₂ alloy.

[en] Highlights: • Fine-grained Cu(70-90)-W composites were successfully fabricated by sintering nano-scale CuW powders at different temperatures. • The CuW composite sintering process is ascribed to the sintering interactions that occur both within each powder and between the powders. • The spherical and nano-sized tungsten particles were evenly embedded in the copper matrix and CuW interface had a semi-coherent relation. • The effect of the sintering temperature on the properties of CuW composites had been analyzed. -- Abstract: Fine-grained Cu(70–90%)-W composites were successfully produced using nano-scale CuW powders in vacuum condition. The sintering process of CuW composites is ascribed to the sintering interactions that occur both within the powders and between the powders. Microstructure analysis of the CuW composites showed that the big spherical and nano-sized tungsten particles were evenly embedded in the copper matrix. The CuW interface had a semi-coherent relation and displayed good contact. The relative density, hardness, electrical conductivity and W crystal size in the CuW composites increased when the sintering temperature rose from 1000 °C to 1090 °C. With elevating copper content, the hardness and the tungsten grain size of CuW composites were found to decrease, but the relative density and electrical conductivity improved. The relation of the electro-conductivity, sintering temperature, and W crystal size of the CuW composites was described with a regression formula.

[en] Highlights: • The application of graphene-based interlayer materials in Lithium–sulfur batteries is summarized. • The various modification strategies of graphene-based interlayer materials are reviewed. • Challenges and future prospects of application of graphene-based interlayers in lithium-sulfur batteries are proposed. Lithium–sulfur (LiS) batteries have been widely studied, and considered as one of the most promising energy storage systems, because of their superior theoretical energy density, non-toxicity, high abundance, and environmental friendliness. However, LiS batteries suffer from problems such as the electrical insulating characteristic of sulfur and unsatisfactorily long cycling life. As a superior type of carbon material, graphene have been intensively investigated as intermediate layers to overcome these problems because of its large surface area, good chemical stability, and excellent electrical conductivity. In this review, we summarize the recent application of graphene-based materials, including simple graphene and graphene-based nanocomposites, as modifying interlayers in LiS batteries. Furthermore, the strategies to enhance their electrochemical performance are summarized and discussed, for example, physical and chemical confinement. Finally, the limitation and challenges of graphene-based materials as interlayers for LiS batteries, as well as their prospects for future research, are proposed. We hope that this review will be helpful for scientists to design and fabricate high-performance LiS batteries based on graphene-based interlayers and boost their practical applications.