The direct effect of nitrogen content and various nitrogen species on oxygen reduction reaction (ORR) activities in non-aqueous lithium-oxygen (Li-O 2 ) batteries are systematically investigated. Mesoporous carbon (MC) with various nitrogen species is prepared through heat treatment of N-containing precursor under different temperature. The effect of the heat treatment temperature on the performance of carbon materials in Li-O 2 battery is investigated. The bonding state of nitrogen atoms is found to have a significant effect on the ORR activity. The ORR activity in Li-O 2 battery is proved to be dependent on the quaternary N content while the total N content in the carbon material does not play a crucial role in the ORR process.
Niobium oxide (Nb 2 O 5 ) nanofibers have been synthesized by sol–gel based electrospinning technique. Pure hexagonal phase (H-Nb 2 O 5 ) and orthorhombic phase (O-Nb 2 O 5 ) nanofibers were obtained by thermally annealing the electrospun Nb 2 O 5 /polyvinylpyrrolidone composite fibers in air at 500 °C and 700 °C, respectively. The fibers were characterized using the X-ray diffraction, scanning electron microscopy, specific surface area analyzer and UV–vis diffuse reflectance spectroscopy. Photocatalytic activities of the obtained nanofibers were evaluated depending on the degradation of methyl orange. The results indicate that the heat-treatment temperature, the crystalline structure and the morphology affected the physical and chemical properties of the as-prepared Nb 2 O 5 nanofibers. The H-Nb 2 O 5 nanofibers obtained at lower temperature showed better potential for the application as a promising photocatalyst.
The effect of calcination temperature on the coating layer and the phase of the alloy matrix is the main problem to improve the heat treatment process of SMCs and obtain excellent magnetic properties . In this study, FeNiMo@Al 2 O 3 powders which were coated by sol-gel and calcined at 900–1300 °C were prepared and these powders were pressed into SMCs. The results showed that the surface of the powder was uniformly coated with Al 2 O 3 . As the heat treatment temperature increases, the phase of the coating changed from AlOOH to γ-Al 2 O 3 , δ-Al 2 O 3 , θ-Al 2 O 3 , and α-Al 2 O 3 . Meanwhile, the new phase γ-Fe, Ni appeared in the alloy matrix. The magnetic permeability of the sample is very stable in the frequency range of 10–500 kHz. The magnetic loss decreases first and then increases, with a minimum at 1100 °C. The permeability and magnetic loss of the sample pressed from the powder obtained by calcination at 1100 °C are 321.78 mw/cm 3 and 87.61 (50 kHz, 100 mT) at the typical industrial application conditions of Iron–Nickel SMCs. The microstructure and the magnetic properties show that the obtained α-Al 2 O 3 have excellent insulation and heat resistance. This resulted in a significant reduction in core losses of FeNiMo SMCs.