Novel electrospun SnO2@carbon nanofibers as high performance anodes for lithium‐ion batteries

SnO₂@carbon (SnO₂@C) nanofibers (NFs) have been prepared by electrospinning method and evaluated as anodes in lithium‐ion battery half cells. XRD were carried out to provide further information about the structure of the as‐prepared NFs, and all the peaks can be readily indexed to the rutile phase SnO₂ (JCPDS No. 41–1445). Electrochemical characterization by galvanostatic charge‐discharge tests shows that the NF anodes have first discharge capacities of 1375.5 mA h g⁻¹ at 80 mA g⁻¹current density. This excellent Li‐ion storage capability of SnO₂ NFs is probably resulting from protection of amorphous carbon and the synergy arising from that the ultrafine SnO₂ particles embedded in the carbon nanofiber (CNF) matrix: the nanometer‐sized SnO₂@C NFs can provide not only negligible diffusion times of ions thus faster phase transitions but also enough space to buffer the volume changes during the lithium insertion and extraction reactions. The highly dispersed NFs are expected to be applied as attractive anodes for lithium‐ion batteries.     

Comparison of tin‐doped indium oxide films fabricated by spray pyrolysis and magnetron sputtering

A comparison of the properties between Tin‐doped Indium Oxide (ITO) films fabricated by sputtering and spray pyrolysis is presented. This analysis shows that the ITO films fabricated by DC magnetron sputtering in pure argon gas requires of a subsequent annealing for the improvement of their structural, electrical and optical properties, when they are compared to films fabricated by single‐stage spray pyrolysis process that includes a new approach. The optimum annealing temperature for ITO films sputtered at room temperature lies in the 300‐350 °C range. Under such conditions, the ITO sputtered films are slightly more resistive than the resistivity (2 × 10^‐4 Ω‐cm) shown by films sprayed at 480 °C using a solution with a 5 % of tin to indium ratio, and almost four times the worst value of the combination of transparency and conductivity determined by the value of the figure of merit (FOM). The sprayed films have a high value of the FOM, 2.9×10^‐2 Ω^‐1, which is comparable with the best published results.     

Structure and morphological stability of (Lu1–xEux)2O3 thin films

(Lu_1–xEu_x)₂O₃ smooth, crack‐free, transparent films were prepared by the Pechini sol–gel method and a spin‐coating technique. Thermogravimetric analysis, differential thermal analysis and FITR spectroscopy were used to study the chemical processes during annealing of the films. Film structure, morphology and optical properties were investigated. X‐ray diffraction (XRD) analysis reveals the cubic phase of (Lu_1–xEu_x)₂O₃ films annealed in the 600–1000 °C temperature range. Smooth and crack‐free films with thicknesses of 250–1000 nm were obtained in the 600–800 °C temperature range. The thickness upper limit (1000 nm) of morphological stability of films (Lu_1–xEu_x)₂O₃ on sapphire substrates has been studied.     

Accurate measurement of deposition rates for growth of Bi‐based oxide thin films

Bi‐based oxide thin films are important superconducting materials because of its wide applicability, high transition temperatures, and low toxicity. To achieve high quality Bi‐based oxide thin films by molecular beam epitaxy (MBE), the composition is a key parameter. Here, Bi, Cu, Cu/Sr and Cu/Ca thin films on glass substrates prepared by MBE have been examined by using both X‐ray reflectivity and surface profiler. The thickness and surface roughness were obtained through calculation and simulation. In comparison with the film thicknesses measured by these two methods, they are in good agreement. The lines of thickness deposition rate (R) versus source temperature (T) are according with LogR=a+b/T based on Clausius‐Clapeyron equation. Moreover, the Bi_2.1Ca_ySr_1.9‐yCuO_6+δ thin films with different composition and thickness were successfully prepared by MBE by applying the thickness deposition rate lines. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of highly c‐axis textured SrTiO3 thin films directly grown on Si(001) substrates by ion beam sputter deposition

Highly c‐axis textured SrTiO₃ (STO) thin films have been directly grown on Si(001) substrates using ion beam sputter deposition technique without any buffer layer. The substrate temperature was varied, while other parameters were fixed in order to study effect of substrate temperature on morphology and texture evolution of STO films. X‐ray diffraction, pole figure analysis, atomic force microscope, and high‐resolution electron microscopy were used to characterize and confirm quality and texture of the STO films. The experimental results show that optimum substrate temperature to achieve highly c‐axis textured films is at 700 °C. The full width at half maximum (FWHM) of 002_STO was found to be 2° and fraction of (011) orientation was as low as 1%. The surface morphology was Volmer‐Weber growth mode with a small roughness ∼1 nm. The lowest leakage current density (5.8 μA/cm² at 2 V) and the highest dielectric constant (ε_STO ∼ 98) were found for highly c‐axis textured films grown at 700 °C. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)