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Abstract
One of the greatest challenges in the application of organic phase change materials (PCMs) is to increase their thermal conductivity while maintaining high phase change enthalpy. 1-Tetradecanol/Ag nanowires composite PCM containing 62.73 wt% (about 11.8 vol%) of Ag nanowires showed remarkably high thermal conductivity (1.46 W m−1 K−1) and reasonably high phase change enthalpy (76.5 J g−1). This behavior was attributed to the high aspect ratio of Ag nanowires, few thermal conduct interfaces, and high interface thermal conductivity of Ag nanowires in the composite PCM. These results indicated that Ag nanowires might be strong candidates for thermal conductivity enhancement of organic PCMs.
Abstract
Highly oriented single crystal antimony nanowire arrays have been synthesized within anodic aluminum oxide (AAO) template by pulsed electrodeposition. Thermal behavior and oxidation analysis of the antimony nanowires have been investigated by means of thermogravimetry and differential scanning calorimetry in Ar and air atmosphere, respectively. Compared to bulk antimony, the antimony nanowires exhibit a lower sublimation temperature at 496.4°C. Evident oxidation of the Sb nanowires occurs at 429.8°C in air atmosphere and α-Sb2O4 nanowires have been obtained as the oxidation product. The results indicate that the sublimation and the oxidation of the antimony nanowires in the AAO template is a slow multi-step process. The present results are of relevance when processing antimony nanowries for thermoelectric applications at high temperatures.
Abstract
Ruthenium catalysts have been prepared by incipient wetness impregnation of ruthenium(III) nitrosylnitrate, Ru(NO)(NO3)3 onto high surface area titanate supports obtained by hydrothermal treatment of TiO2 P25 in concentrated alkaline solutions. These Ru-containing catalysts were evaluated in the catalytic wet air oxidation of p-hydroxybenzoic acid (p-HBZ), a model compound representative of phenolic pollutants present in olive mills wastewaters, at 413 K and 50 bars of air. Two different titanates morphologies were tested as supports for this reaction: hydrogenotitanate nanotubes (HNT) obtained with concentrated NaOH and hydrogenotitanate nanowires (HNW) formed in the presence of highly concentrated KOH solution. The HNT and HNW supports and their corresponding supported Ru catalysts were characterized by means of N2 adsorption–desorption, XRD, UV and TEM analyses. Results showed that the use of high surface area titanate supports led to catalysts much more active than similar Ru catalysts supported on conventional TiO2 supports.
The deposition of nanowires for interconnects in nanoelectronic devices werestudied morphologically by scanning electron microscopy (SEM), atomic force microscopy (AFM) and by in-situ resistance measurements. The deposition and basic characterization of nanometer size tungsten wires by gas injection (GIS) and focused ion beams (FIB) was carried out in-situ in a LEO 1540 XB workstation. The I(V) measurement showed that the deposited W wires have ohmic characteristic. The variation of the resistance during an ex-situ heating was linear with a low thermal coefficient (4% of the pure metallic W).
We present a simple method of nanocrystal growth during the heating of Au-covered GaAs single crystals in a closed quartz ampoule, previously evacuated to 10-1 Pa. The process is the final stage of surface transformations in such crystals which include the disruption of initially continuous, 50 nm thick Au layer and formation of Au-particle fractals in the relatively low 300-500 °C temperature range and a next step, when a variety of crystalline nanowires and even nanotubes grows on the crystal surface during the further short-period heating up to 550-650 °C. These nanostructures were identified by SEM and TEM measurements as b-Ga2O3 and a non-stoichiometric arsenic oxide. It is supposed that the growth of few nanometer thick arsenic oxide tubes follows the vapour-solid mechanism, whereas the catalytic Au-metal growth of thicker b-Ga2O3 nanowires was dominated by the vapour-liquid-solid mechanism.
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Figure 2 shows the experimental setup schematic along with a scanning electron micrograph of a focused-ion-beam deposited platinum nanowire across lithographically patterned gold electrodes. The substrate is a commercially available silicon wafer with
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