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Abstract Aluminum nitride (AlN) features an extremely interesting combination of very high thermal conductivity and excellent electrical insulation; therefore, it has been widely used in the high power electronic devices. The hydrolytic reaction of aluminum nitride powder decays the shelf-life and lowers the high power operating performance of the electronic devices. A protecting film of the polymer derived silicon oxycarbonitride ceramic is coated and fully wrapped on the surface of aluminum nitride powder against facilitating hydrolysis. Poly (organosilazane) precursor is incorporated with the commercial aluminum nitride powder pyrolyzed at 700 °C under argon environment for few hours to form a core-shell structure with a film thickness, 10–20 nm of silicon oxycarbonitride (SiCNO) ceramic shell and the aluminum nitride core. Measuring the pH value of SiCNO/AlN core-shell powder in deionized water at room temperature is to observe the hydrolytic behavior that its pH value is stable to maintain about 10 at ambient environment over ten days, whereas for the characterization of the reaction products, XRD, SEM and TEM analyses are employed. The hydrolytic behavior measured at 90 °C also shows that the SiCNO/AlN core-shell powder is still able to keep the protection from high temperature hydrolysis. XRD spectra proves that the characteristic crystalline peaks of SiCNO/AlN core-shell powder after hydrolysis over ten days are still the same as those of the commercial aluminum nitride powder before hydrolysis. These results directly indicate that the polymer derived silicon oxycarbonitride ceramic film fully protects the aluminum nitride powder from hydrolysis. When the content of silicon oxycarbonitride shell reduces to reach certain value, the hydrolytic protection gradually vanishes for long time. Highlights • SiCNO-AlN core-shell structure is developed by a fast and mass producible process. • The thin SiCNO shell can protect AlN core from hydrolysis over weeks. • The incubation period of the SiCNO-AlN core-shell structure approaches to zero. • The thickness of SiCNO shell is tunable for different industrial use. [ABSTRACT FROM AUTHOR]

Abstract: Cu nanowire arrays were synthesized via a porous alumina membrane (PAM) template with a high aspect ratio, uniform pore size (120–140nm), and ordered pore arrangement. The Cu2O nanowire arrays were prepared from the oxidization of Cu metal nanowire arrays. The electrochemical deposition potential of Cu metal nanowires (−180mV vs. SCE) was determined from X-ray diffraction (XRD) patterns. The microstructure and chemical composition of Cu nanowire arrays were characterized using field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). Results indicate that the Cu/Cu2O nanowire arrays assembled into the nanochannel of the porous alumina template with diameters of 120–140nm. The valence of copper was controlled by the porous alumina template during the annealing process. Copper nanowires transformed to the Cu2O phase with the space limitation of the PAM template. Single-crystal Cu2O nanowire arrays were also obtained under the template embedded. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous TiO2/SBA-15 matrix was prepared by the sol–gel synthesis of TiO2 in previously prepared SBA-15 particles. Nonionic surfactant was used as liquid template and Na2SiO4 as SiO2 precursor for the synthesis of mesoporous silica SBA-15 with high specific surface area. Different calcination temperature was used for the synthesis and analysis of TiO2/SBA-15 matrix. The synthesized titania/silica composites were characterized by X-ray diffraction, FTIR, TEM, UV–vis spectroscopy, etc. TEM micrographs showed titania is successfully embedded in SBA-15 channel. Different calcination temperature indicates different size of particle formation and different photocatalytic properties. The activity test indicated that TiO2/SBA-15 composite prepared by this method had better photocatalytic performance than pure TiO2. The preparation method and the textural characteristics of mesoporous materials have great influence for the photocatalytic activity. [Copyright &y& Elsevier]

Abstract: A c-axis orientated aluminium nitride (AlN) film on a 128°Y–X lithium niobate (LiNbO3) surface acoustic wave (SAW) device which exhibit a large electromechanical coupling coefficient (k 2) and a high SAW velocity property, is needed for future communication applications. In this study, a c-axis orientated (B, Al)N film (with 2.6at.% boron) was deposited on a 128°Y–X LiNbO3 substrate by a co-sputtering system to further boost SAW device properties. The XRD and TEM results show that the (B, Al)N films show highly aligned columns with the c-axis perpendicular to the substrate. The hardness and Young''s modulus of (B, Al)N film on 128°Y–X LiNbO3 substrates are at least 17% and 7% larger than AlN films, respectively. From the SAW device measurement, the operation frequency characteristic of (B, Al)N film on 128°Y–X LiNbO3 is higher than pure AlN on it. The SAW velocity also increases as (B, Al)N film thickness increases (at fixed IDT wavelength). Furthermore, the k 2 of (B, Al)N on the IDT/128°Y–X LiNbO3 SAW device shows a higher value than AlN on it. [Copyright &y& Elsevier]

Abstract: Nanocrystalline manganese oxide powder prepared by spray pyrolysis (SP) was mixed with multi-walled carbon nanotubes (MWCNTs) in a suspension and subsequently co-coated onto graphite substrates via an electrophoretic deposition technique (EPD). The deposited coatings with or without CNTs mix were examined by X-ray diffractometry (XRD); the coatings were examined by cycling voltammetry (CV) and charge/discharge tests. Structural investigation by XRD revealed that the as-deposited Mn-oxide powder exhibited Mn3O4 phase with nanocrystalline structure. The CNTs/Mn-oxide coatings exhibited a porous structure with some hollow or fractured Mn-oxide particles inserted and possessed a high surface area for the electrochemical redox reactions. CV examination showed that the porous CNTs/Mn-oxide coatings exhibited the high specific capacitance of 260 F/g which was higher than the value (234 F/g) of Mn-oxide coatings without CNTs mix at a scan rate of 25 mV/s. After 500 cycles of CV tests, the specific capacitance decreased to 228 F/g, showing a comparatively good efficiency of 88%. The high CV cycling stability of CNTs/Mn-oxide mixture is due to the fact that the CNTs network existent in between the Mn-oxide particles inhibits the structural breakdown of Mn-oxide particles during the repetitive insertion–expulsion of cations from aqueous electrolyte. [Copyright &y& Elsevier]

Abstract: Lead zirconate titanate (PZT) (53/47) powders were prepared by a cheating acetate sol–gel process. The drying temperature effect on crystallization behavior was conducted to determine the best conditions for preparing high content of perovskite PZT powders in the morphotropic region. DSC/TG analysis, FT-IR spectrum and X-ray diffraction were carried out to identify the reaction sequences and calculated the activation energy of every transition temperature during the drying procedures. In the present work, well-crystallized, single-phase perovskite PZT powders were obtained after drying PZT stock solution at 300°C for 1h, then heat treatment at 600°C for 30min. The dependence of this crystallization temperature on the drying conditions was discussed. [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]