Monodisperse Fe3O4 hollow spheres with average diameter of 400 nm and shell thickness of 60 nm were prepared through a one-pot solvothermal process with the presence of NH4Ac as the structure-directing agent, and a novel gas-bubble-assisted Ostwald ripening process was proposed to explain the formation of hollow structures. According to this mechanism, hollow Fe3O4 and MnFe2O4 ferrite microspheres with controlled particle size were obtained using urea and ammonia as the structure-directing agents, and porous Fe3O4 spheres with particle size of 100 nm and pore size of 10 nm were obtained by the assistance of bicarbonate of ammonia. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy were used to characterize the structure of synthesized products, and the magnetic property investigation shows that the hollow microspheres exhibit a ferromagnetic behavior and possess a higher saturation magnetization (M s) than that of the solid microspheres.

Hybrid lamellar porous electrodes with excellent electrochemical performance were successfully fabricated by homogeneously intercalating single-walled carbon nanotubes into the lamellar assembled WS2 nanosheets through vacuum filtration.

No abstract

In this paper, single-crystalline Co 3 O 4 hollow octahedral hollow cages with tunable surface aperture were synthesized by the carbon-assisted carbothermal method. On the basis of electron microscopic observation and structural analysis, all the following factors, including the precursor concentration, species of precursor, intrinsic crystal structure of products and carbon-assisted carbothermal reaction, play key roles in the formation of Co 3 O 4 octahedral hollow structures. When the as-prepared Co 3 O 4 samples were used as the anode materials in lithium ion batteries (LIBs), it was found that the octahedral hollow cages with large surface aperture performed better than both those with small surface aperture and Co 3 O 4 nanoparticles, indicating that not only the single-crystalline robust structure but also the tunable surface aperture in the shell could affect the electrochemical property in LIBs.

In this work, we report a simple one-pot approach to prepare hollow Co microspheres via self-assembly of octahedron-like nanocrystals. Uniform hollow Co spherical assemblies, prepared via a facile solvothermal reduction approach in the presence of NaCl, were composed of ordered nanooctahedra with a thickness of about 80–120 nm. The formation mechanism (NaCl-assisted Ostwald ripening) has been investigated with TEM/HRTEM/SEM/XRD methods. Surface morphologies of Co hollow spheres have been finely modulated from rough to smooth surface through altering reaction conditions (such as time, temperature, and amount of NaCl). The interior-cavity size of the Co hollow sphere has been well tunable by controlling reaction time or temperature. These materials exhibit good ferromagnetic characteristics, showing their potential applications for catalysts and other related devices. The influence of surface morphology, the interior cavity size, and surface modification upon the magnetic properties of hollow Co spheres have been systematically studied. The possible reasons for diverse magnetic properties of products obtained under different conditions are also discussed.