Zude Zhang

Synthesis of β-FeOOH and α-Fe2O3 nanorods and electrochemical properties of β-FeOOH

β-FeOOH nanorods with a tunnel-type structure were synthesized via a hydrothermal method at low temperature and characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and galvanostatic tests. From TEM bright-field images, a rodlike morphology with an average diameter of 30 ± 5 nm and an average length of 400 nm (aspect ratio ≈ 13) is observed. Electrochemical tests show that thesew nanorods deliver a large discharge capacity of 275 mA h g−1vs. Li metal at 0.1 mA cm−2 n (voltage window 1.5–4.2 V). α-Fe2O3 nanorods with a regular pore structure were obtained by calcining the as-synthesized FeOOH at 520 °C.

Citric acid-assisted sol-gel synthesis of nanocrystalline LiMn2O4 spinel as cathode material

Nanocrystalline LiMn2O4 spinel was synthesized by a sol–gel method using citric acid as a chelating agent at the calcination temperature of 600 � C for 10 h. The as-prepared LiMn2O4 was investigated by a variety of techniques, including X-ray powder diffraction, transmission electron microscopy (TEM), and X-ray photoelectron spectra. TEM images indicated that the average crystallite size is about 40 nm with a fairly narrow size-distribution. Results showed that the calcination temperature and the calcination time played significant roles in the formation of nanocrystalline LiMn2O4. A possible mechanism on the formation of the nanocrystallites was also discussed. r 2003 Elsevier Science B.V. All rights reserved.

Photoluminescence and Raman spectroscopy studies of Eu3+-doped rutile TiO2 nanocrystals at high pressures

Nanocrystal samples (particle size about 90 nm) of Eu3+-doped rutile titanium dioxide (TiO2) nanocrystals (rutile Eu3+/TiO2 nanocrystals) were synthesized by the sol–gel method with hydrothermal treatment. The pressure effect on photoluminescence (PL) and Raman spectra of the rutile Eu3+/TiO2 nanocrystals was investigated with a diamond anvil cell under hydrostatic pressure condition. Raman spectra of the samples at high pressures indicated that the critical pressure for the transition from the rutile phase to a new baddeleyite-type phase was between 10 and 14.2 GPa. The position of Raman bands shifted to high wavenumbers and the PL intensity of 5D 0→7F 2 transition of Eu3+ decreased down to zero with the increase of pressure before the phase transition occurred. After releasing the pressure, the rutile phase was not recovered and a α-PbO2-type phase was observed at ambient pressure.