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Calcium-ion batteries (CIBs) are considered as promising alternatives in large-scale energy storage due to their divalent electron redox properties, low cost, and high volumetric/gravimetric capacity. However, the high charge density of Ca2+ contributes to strong electrostatic interaction between divalent Ca2+ and hosting lattice, leading to sluggish kinetics and poor rate performance. Here, in situ formed poly(anthraquinonyl sulfide) (PAQS)@CNT composite is reported as nonaqueous calcium-ion battery cathode. The enolization redox chemistry of organics has fast redox kinetics, and the introduction of carbon nanotube (CNT) accelerates electron transportation, which contributes to fast ionic diffusion. As the conductivity of the PAQS is enhanced by the increasing content of CNT, the voltage gap is significantly reduced. The PAQS@CNT electrode exhibits specific capacity (116 mAh g-1 at 0.05 A g-1), high rate capacity (60 mAh g-1 at 4 A g-1), and an initial capacity of 82 mAh g-1 at 1 A g-1 (83% capacity retention after 500 cycles). The electrochemical mechanism is proved to be that the PAQS undergoes reduction reaction of their carbonyl bond during discharge and becomes coordinated by Ca2+ and Ca(TFSI)+ species. Computational simulation also suggests that the construction of Ca2+ and Ca(TFSI)+ co-intercalation in the PAQS is the most reasonable pathway. [ABSTRACT FROM AUTHOR]

Herein, the Fe3C nanoparticles encapsulated in carbon nanotubes (Fe3C/CNTs) were successfully prepared through a simple method using g‐C3N4 from thermal polymerization of melamine. The structure, morphology and magnetic properties of the prepared samples were investigated by various technologies. The results show that the Fe3C nanoparticles encapsulated in carbon nanotubes exhibit good magnetic properties with high saturated magnetization (83.7 emu g−1). Importantly, this simple approach provides a way to synthesize metal carbides encapsulated in carbon nanotubes. [ABSTRACT FROM AUTHOR]

Carbon nanotubes with encapsulated Co nanospheres (Co@CNTs) were prepared via a simple approach that exhibits promising control over the morphology and size distribution. The individual CNTs interweave with each other and form a three-dimensional network structure. Test results indicate that the presence of polarized interfaces between the Co spheres and CNTs, as well as an excellent impedance match, leads to a superior performance in electromagnetic wave absorption. A maximum reflection loss of −70.8 dB at 6.24 GHz is obtained for a paraffin containing a 30 wt% Co@CNT inclusion. In addition, the effective absorption bandwidth (with a reflection loss below −10 dB) is 12.95–17.7 GHz at a thickness of 1.9 mm, covering most Ku bands. In particular, such Co@CNT structures demonstrate superior and sustainable electromagnetic wave-absorption properties even in contact with concentrated acid or base, owing to their specific encapsulated structure. These findings could provide new guidelines for the preparation and employment of promising microwave absorption materials that can work under harsh environments through a simple and feasible strategy. [ABSTRACT FROM AUTHOR]

Abstract: Uniform TiO2:Eu3+ nanotubes have been successfully synthesized through a simple solvothermal process with carbon nanotubes (CNTs) as templates, free of any surfactant or catalyst. X-ray diffraction (XRD) results demonstrate that the product is a pure anatase phase of TiO2. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images indicate that the as-obtained TiO2:Eu3+ nanotubes are uniform in size and distribution, and the thickness of the wall is about 8nm. The possible formation mechanism has also been proposed. The luminescent spectrum shows that TiO2:Eu3+ nanotubes exhibit a red emission at 612nm due to the 5D0→7F2 transition. Furthermore, this synthetic route is promising for the preparation of other one-dimensional inorganic nanomaterials because of its simplicity and the low cost of the starting reagents. [Copyright &y& Elsevier]