Stable Core Shell Co₃Fe₇–CoFe₂O₄ Nanoparticles Synthesized via Flame Spray Pyrolysis Approach

Air stable Co₃Fe₇–CoFe₂O₄ nanoparticles have been synthesized via one-step flame spray pyrolysis of a mixture of Fe/Co precursor solution under stronger reducing atmosphere. The as-synthesized nanoparticles with diameters of 20–80 nm showed a typical core shell structure and high stability for being one month in air, whose metallic Co₃Fe₇ cores were protected against oxidation by a surface shell of about 2–4 nm cobalt iron oxide (CoFe₂O₄). The ratio of metallic Fe/Co alloy nanoparticles was 7:3. The alloy nanoparticles exhibited enhanced saturation magnetization (126.1 emu/g), compared with flame sprayed iron nanoparticles with the same conditions. The formation process of metallic alloy nanoparticles with core–shell structure was investigated, which included three stages: flame combustion, reducing, and surface oxidation during the flame process. It is reckoned that such a continuous production approach is an effective way to produce the stable Co₃Fe₇ alloy nanoparticles with high saturation magnetization

In Situ Deposition of Hierarchical Architecture Assembly from Sn-Filled CNTs for Lithium-Ion Batteries

In this paper, we have demonstrated a hierarchical architecture assembly from Sn-filled CNTs, which was in situ deposited on Cu foils to form binder-free electrode by incorporating flame aerosol deposition (FAD) with chemical vapor deposition (CVD) processes. The reversible capacity of Sn-filled CNTs hierarchical architecture anode exhibited above 1000 mA h g^–1 before 30th cycle and stabilized at 437 mA h g^–1 after 100 cycles at a current density of 100 mA g^–1. Even at as high as 2 A g^–1, the capacity still maintained 429 mA h g^–1. The desirable cycling life and rate capacities performance were attributed to great confinement of tin in the interior of CNTs and the superior conducting network constructed by the 3D hierarchical architecture. The novel, rapid and scalable synthetic route was designed to prepare binder-free electrode with high electrochemical performance and avoid long-time mixing of active materials, binder, and carbon black, which is expected to be one of promising preparation of Sn/C anodes in lithium-ion batteries

Mixed Solvents Assisted Flame Spray Pyrolysis Synthesis of TiO₂ Hierarchically Porous Hollow Spheres for Dye-Sensitized Solar Cells

A novel one-step and template-free preparation process had been developed to synthesize TiO₂ hierarchically porous hollow spheres (HPHSs) by mixed solvents assisted flame spray pyrolysis (FSP). The as-obtained TiO₂ HPHSs had hierarchically porous hollow structure such as central cavities, macropores on shells, and mesopores accumulated by TiO₂ nanocrystallites. The unique hierarchically porous structure endowed the TiO₂ spheres with high specific surface area and excellent light scattering property. A mechanism of the formation of TiO₂ HPHSs depending on the competition between chemical reaction rate and diffusion rate of the components of the precursor was proposed, in which mixed solvents and short flame residence time were of importance. Furthermore, the dye-sensitized solar cells (DSSCs) performance of TiO₂ HPHSs as light scattering layer was investigated. The photoelectric conversion efficiency (η) was improved by 38.2% (from 5.00% to 6.91%), comparing to that of single layer P25 films