Q.P. Ding

Chelating agents role on phase formation and surface morphology of single orthorhombic YMn 2 O 5 nanorods via modified polyacrylamide gel route

YMn2O5 nanorods were synthesized through a modified polyacrylamide gel route. The synthesis strategy in this work is based on a sol-gel process using a polyacrylamide gel method in which oxalic acid, citric acid or tartaric acid is employed as the chelating agent. In the gel routes, oxalic acid was used as a carboxyl chelating agent, while citric acid or tartaric acid was a carboxyl and hydroxyl chelating agent. The as-prepared samples were characterized by means of techniques such as X-ray powder diffraction (XRD) measurement, thermogravimetric analysis (TG), differential scanning calorimetry analysis (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermal expansion measurement and field-emission scanning electron microscopy (SEM) investigations. It was found that oxalic acid is the best chelating agent with Y(NO3)3·6H2O and Mn(CH3COO)2·4H2O as precursors to prepare a single orthorhombic YMn2O5 nanorods at 1000°C. Scanning electron microscope observation shows that the morphology of YMn2O5 powders is significantly dependent on the chelating agent. The peaks (single orthorhombic YMn2O5 nanorods) at 642, 600, 573, 546, 521, 493, 486, 468, 448 and 400 cm−1 were observed from FTIR spectra. The phase, surface morphology and chelation mechanisms of YMn2O5 samples have been discussed on the basis of the experimental results.

Synthesis and Photoluminescence of γ-Al2O3 and C-doped γ-Al2O3 Powders

The γ-Al2O3 and C-doped γ-Al2O3 powders have been synthesized by a modified polyacrylamide gel method. XRD, SEM and luminescence characterization have been used to study the prepared samples. The results indicate that the particle size and morphology of the samples depend on the choice of chelating agent. In comparison with pure γ-Al2O3 sample, the intensity of emission peak at 420 nm of C-doped γ-Al2O3 powders has been obviously enhanced, which is expected to widen the potential applications of C-doped γ-Al2O3 composite powders. The photoluminescence spectrum detected at λex= 386 nm shows a new peak located at 440 nm due to oxygen vancancies distributed on the surface of the composite. Interestingly, the intensity of the emission peak located at 440 nm (C-doped γ-Al2O3) increases with the decrease of crystallite size.

Influence of Fe2O3 on Structural and Magnetic Properties of LaFeO3/Fe2O3 and Mn2O3/Fe2O3 Magnetic Nano-Composites

LaFeO3/Fe2O3 and Mn2O3/Fe2O3 magnetic nanocomposites have been prepared by a modified polyacrylamide gel route. The XRD result indicates the formation of LaFeO3/Fe2O3 and Mn2O3/Fe2O3 nanocomposites. Scanning electron microscope (SEM) observation shows that the LaFeO3/Fe2O3 particles appear to be regularly spherical in shape and highly uniform in size with a diameter of ~ 80 nm, while the Mn2O3/Fe2O3 sample exhibits a relatively broad particle size distribution with an average particle size centered around 20-60 nm. Result of vibrating sample magnetometer (VSM) of LaFeO3/Fe2O3 magnetic nanocomposites revealed that coercivity values decreased with the increase sintering temperature. However, the coercivity values of Mn2O3/Fe2O3 magnetic nanocomposites appear to an anomaly phenomenon.