Papers by Keyword: Chemical State

Abstract: To develop novel cathode materials with high electrical performances for intermediate temperature solid oxide fuel cells (IT-SOFCs) and optimize the preparation process, perovskite-type oxides Pr_1-x-ySr_xCa_yCo_1-zFe_zO_3-δ (x=0.1, 0.2; y=0.1, 0.2; z=0.2, 0.3, 0.4; denoted as PSCCF-81182, PSCCF-72173 and PSCCF-62264) were prepared by solid state reaction. The formation process, phase structure and microstructure of the prepared samples were measured using TG-DTA, FT/IR, XRD and SEM techniques. The mixed conductivity of the samples was measured using DC four-terminal method in the range of 150-950 °C. Chemical state of the elements was measured by XPS experiments. The results show that the prepared samples PSCCF-81182, PSCCF-72173 and PSCCF-62264 exhibit a single phase with cubic perovskite structure after sintered at 1200 °C for 6 h. The mixed conductivity of the samples increases with temperature up to a maximum value, and then decreases. At lower temperature, the conductivity follows small polaron hopping mechanism. The negative temperature dependence occurring at higher temperature is due to the creation of oxygen vacancies for charge balance. At intermediate temperature (600-800 °C), the mixed conductivity values of the prepared samples are all much higher than 100 S•cm^-1，and can meet the demand of cathode materials for IT-SOFC. XPS tests show that Co and Fe elements in PSCCF-72173 are all of + 3 and + 4 valence. Absorbed oxygen can also be found from the XPS patterns, which is related to the concentration of oxygen vacancies in the perovskite-type oxides.

Abstract: In the present work, the surface properties of various Al oxide films were investigated. The oxide films were produced on a stainless steel by spray pyrolysis and cathodic deposition methods. The films obtained represent typical layers that can be used as a support in model systems to investigate alumina-based catalysts. Information about the chemical environment of the Al and O ions in the oxide films depending on the preparation conditions has been deduced from the binding energies of the Al 2p and O 1s electron core levels and corresponding Auger parameters.

Abstract: BCN films were prepared with unbalanced magnetron sputtering boron carbide film followed by nitrogen plasma-based ion implantation at different voltages on Si substrate. The implantation voltages vary from 10 kV to 50 kV. The chemical states of B, C and N of the films were studied with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The nano-hardness and elastic modulus of films were measured by Nano-Indenter. The results showed that amorphous BCN films formed in the nitrogen implanted layer. The amorphous peak becomes obvious with increasing of the implanted voltage when the voltage is under of 40 kV. The Nano-Indenter measurement showed that the B-C bond content and the disorder degree affect the hardness and modulus.