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Abstract: Single crystal SiC has been synthesized by a novel liquid phase epitaxy using mixture of (Sm:Co) as unique solvent. The synthesized high quality crystals have been characterized by field emission gun scanning electron microscopy and field emission gun transmission electron microscopy. The above analysis shows the epitaxial growth of single crystal SiC along [111] direction parallel to the Si wafer, followed by polycrystalline 3C–SiC and 6H–SiC whiskers. The formation mechanisms of single crystal SiC and SiC whiskers have been proposed. [Copyright &y& Elsevier]

Abstract: In the present study, manganese oxide electrodes with promising pseudo-capacitive properties were prepared by electrophoretic deposition (EPD) using needle-like manganese dioxide powders. As-deposited coating exhibited a porous microstructure where the size and shape of the starting powders can be observed. The electrochemical performance of the as-deposited coating was then evaluated by cyclic voltammetry (CV) up to 300 times. The initial specific capacitance was 236F/g which dropped to 200F/g after 25 CV tests, and decreased gradually to 190F/g thereafter. The electrochemical behaviors during EPD and CV were examined by synchrotron X-ray absorption spectroscopy techniques from which it was deciphered that a reduction reaction from Mn4+ to Mn3+ occurred during EPD concomitant with re-oxidization during repetitive CV cycles. [Copyright &y& Elsevier]

The conventional techniques for 3D printing ceramic parts are the ceramic powder laser sintering and lithography process that are usually costly in equipment and materials. A low-cost technique for robocasting ceramic has been developed via polysilazane preceramic precursor incorporated with nano γ-alumina powders to form a gel-like preceramic precursor with the aim to be used as the raw material for robocasting ceramic parts. The gel-like preceramic precursor is simply extruded for shaping by CAD design with the self-incorporated robocasting machine, and then pyrolyzed the shaped gel-like preceramic precursor at 700, 850 and 950 °C, respectively to transform from a polymeric composite to core-shell silicon oxycarbide ceramic composite that has been characterized by XRD representing an amorphous silicon oxycarbonitride structure coating on the surface of nano γ-alumina. The Vickers hardness of the core-shell silicon oxycarbide ceramic is about HV 266–300 that is two times higher than that of 7000 series aluminum alloy. [ABSTRACT FROM AUTHOR]

Abstract: The Nb-doped WO3 films were deposited by e-beam co-evaporation method using ceramic WO3 targets and metal Nb slugs. The films were analyzed by glancing incident angle X-ray diffraction (GIAXRD), UV/visible spectrophotometer, electrochemical cyclic voltammetry, X-ray photoelectron spectroscopy (XPS). The as-prepared film is brown and amorphous in structure. The film has low transmission in optical visible region. The XPS results indicate that the as-deposited film is non-stoichiometric. By applying a negative potential, the as-deposited film does not show obvious electrochromic effect. However, the electrochromic properties of Nb-doped WO3 films are improved by post annealing treatment at 350, 400, and 450°C in oxygen atmosphere. The Nb-doped WO3 films transform into crystalline structure and become transparent after post annealing treatment. The energy band gap, optical modulation, and color efficiency increase with annealing temperature. [Copyright &y& Elsevier]

Abstract: Tungsten oxide (WO3) films prepared by annealing electrochemically anodized metallic tungsten (W) films deposited by radio-frequency sputtering were characterized. Tungsten oxide films of various morphology, crystallinity, and porosity can be prepared by carefully altering the anodization time (20–50min) and annealing temperature (450–550°C). The film obtained after 40min of anodization, and that annealed at 500°C shows the best electrochromic performance with optical modulation of 43.6% and coloration efficiency of 42.8cm2/C. The effects of anodization time and annealing temperature on microstructure and electrochromic properties were addressed. [Copyright &y& Elsevier]

Hydrogen has been considered as one of the most promising renewable energy for production and storage. Here, we report an efficient method to synthesize MoS 2 -MoO 2 composite by hot-injection method using MoO 3 and S powder as precursors with oleic acid (OA) and oleylamine (OLA) as solvent, respectively. The X-ray diffraction shows the presence of the peaks from both MoS 2 as well as MoO 2 . With increasing reaction temperature and time, oleic acid reorganizes the octahedral units of MoO 3 and gradually turn into low valence of Mo. After injecting S-precursor, OLA first reduces Mo-precursor to MoO 2 as core, and then S atoms replace O atoms to form MoS 2 as shell, eventually forming MoS 2 -MoO 2 core-shell structure. MoO 2 with few-layer MoS 2 can be observed by transmission electron microscope. A Tafel slope of 129 mV/dec is obtained for MoS 2 -MoO 2 composite, which is much better than MoS 2 and MoO 2 . The enhanced HER performance is attributed to the abundance active sites from MoS 2 and the improved charge transfer direction by MoO 2 . [ABSTRACT FROM AUTHOR]