Investigations of activation energy barriers for Al surface hopping on α-Al2O3 (0001) surfaces have been carried out by means of first-principles density functional theory calculations and the nudged elastic band method. Results show that surface diffusion on the (most stable) Al-terminated surface is relatively fast with an energy barrier of 0.75 eV, whereas Al hopping on the O-terminated surf...

Upon the isothermal oxidation of an ODS FeAl Grade 3 intermetallic alloy, a structured oxide scale is developed between 800 and 950o C. TEM studies have revealed a three-layered structure with a top nanoequiaxed alumina, a central alumina and a bottom Fe-Al spinel. At these temperatures, aluminium outward diffusion does not seem to be suppressed neither by the spinel sub-layer nor by the yttria...

The microstructures of chemical vapor deposited coatings on four tool inserts have been comprehensively characterized using electron backscatter diffraction mapping and these data have been used as input for finite element models used to calculate the residual thermal strains in the coatings. The results indicate that the thermal strains and stored elastic energy in the α-Al2O3 layer are larger...

High temperature/pressure in situ Attenuated Total Reflection Infrared (ATR-IR) spectroscopy was used to investigate the phase transformation of support γ-Al2O3 into boehmite (AlO(OH)) under the hydrothermal conditions of aqueous phase reforming (APR). Activation energy barriers of boehmite formation in hot compressed water at temperatures between 150 and 180 °C were calculated to be 15.9 ± 4.8...

Chlorodifluoromethane (R-22), the most abundant freon in atmosphere, was subjected to successful hydrodechlorination presence of palladium supported on ?-alumina, at a relatively low reaction temperature (180 °C). The combination catalytic actions alumina (performing dismutation) and Pd nanoparticles (catalyzing C–Cl bond splitting hydrogen) results transformation into valuable, chlorine-free p...

The possibilities offered by catalytic γ-Al2O3 substrates are explored, and the mechanism governing graphene formation thereon is elucidated using both numerical simulations and experiments. The growth scheme offers metal-free synthesis at low temperature, grain-size customization, large-area uniformity of electrical properties, single-step preparation of graphene/dielectric structures, and rea...

Objetivo: En este estudio se evaluó el efecto de la modificación con óxido zinc del soporte convencional en catalizadores hidrodesulfuración (HDS) a base polioxometalato Anderson-Evans NiMo5W. Metodología: Los fueron sintetizados por método co-precipitación NiMo5W sobre Al2O3. caracterizaron FRX, MEB/EDS, CHONS, propiedades texturales, FT-IR, Raman y titulación potenciométrica n-butilamina. Res...

Alumina (Al2O3) decorated anatase TiO2 nanotubes with ordered mesoporous pore walls (Al2O3/meso-TiO2 nanotubes) are successfully synthesized through vacuum pressure induction technology, and then combined with the thermal decomposition of a mesoporous TiO2 sol precursor, inside the cylindrical nanochannels of an anodic aluminium oxide (AAO) template. The decorated Al2O3 was formed by in situ de...

X-ray photoelectron spectroscopy (XPS) technique was employed to characterize Al2O3-TiO2 support and MoO3/Al2O3TiO2 catalyst calcined at different temperatures from 773 to 1073 K. The Al2O3-TiO2 (1:1.3 mole ratio) binary oxide support was obtained by a coprecipitation procedure with in situ generated ammonium hydroxide. A nominal 12 wt.% MoO3 was impregnated over the calcined (773 K) support by...