Cobalt catalysts supported on γ-alumina, ceria and γ-alumina-ceria, with 10 or 20%wt of cobalt load, prepared by the wet impregnation method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission transmission electron microscopy (FETEM), N2 adsorptiondesorption isotherms (BET/BJH methods), energy-dispersive X-ray spectroscopy (EDX), X-ray photoemission ...

Alumina-supported manganese catalysts with cryptomelane and/or birnessite structure have been prepared using a simple method based on the thermal decomposition of potassium permanganate. The samples have been characterized by XRD, FTIR, TGA, DSC, N2 adsorption at −196 °C, SEM, H2-TPR and XPS, and their catalytic activity for soot combustion has been tested and compared to that of a reference Pt...

We report the structure and stability of ceria units deposited on the surface of γ-Al2O3 or incorporated in its cavities, as determined by periodic density functional calculations. Ceria species are modeled as CeO2 or Ce2O4 moieties or as a small nanoparticle, Ce13O26, on the (100) and (001) surfaces of a γ-Al2O3 slab. Among the studied structures the incorporation of Ce(4+) ions in cavities of...

Cold Sintering Process has been applied to hydroxide precursors Al(OH)3, xH2O promote in situ reactive sintering. The application of sintering temperatures < 400°C led the release OH groups and partial crystallization into boehmite γ-AlOOH. This latter step is accompanied by a densification stage leading production dense translucent pellet. From skeletal density measurements, it appears that no...

Alumina is the most widely used oxide ceramic material. It exists in many metastable forms which lead upon severe thermal treatment towards the thermodynamically stable phase alpha. Sintering of alumina generally takes part in a minimum of two stages: i) phase transition(s) towards the stable phase alpha and ii) densification of this phase alpha. The former step(s), linked to transition phase(s...

The present work reports the effects of γ-, θ-phase alumina on hydrothermal stability and properties non- strongly-interacting Rh species Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce amount occluded but also better stabilize during aging treatment. When time was prolonged 70 h, all non-interacting transformed into Rh. XPS results indicated that might exist in form Rh/Rh...

alumina-supported cs3[re(c2o4)3] precursor has been synthesized  for preparation of re-cs/g-al2o3 catalyst. cs3[re(c2o4)3]  has been prepared from the reaction of recl3 with  h2c2o4.2h2o and cscl in water. the complex has been characterized by elemental analysis and various spectroscopy techniques such as ft-ir, uv-vis and 13c-nmr. the complex was supported on γ-al2o3 by column chromatography. ...

Ferritic alumina-forming alloys showed high corrosion resistance to molten carbonates by forming a protective α-LiAlO2 scale at their surface. In this work, four ferritic were pre-oxidised before exposure (Li,Na,K)2CO3-melt 800 °C for 1000 h. Only outer transient alumina, such as γ-alumina, reacts with the melt, LiAlO2. At same time, innermost α-Al2O3 remains intact. α-Al2O3, well α-LiAlO2, are...

Alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) are currently the materials of choice to meet the need for tough, strong, and bioinert ceramics for medical devices. However, the mechanical properties of ZrO2/Al2O3 dispersion ceramics could be considerably increased by reducing the corresponding grain sizes and by improving the homogeneity of the phase dispersion. Here, we ...

This paper demonstrates that seeding nanocrystalline transition alumina powders is a viable option for producing high quality, alumina-based ceramics. By using a-Al2O3 concentrations of 51.25 wt.% a-Al2O3 seed particles (equivalent to 5 10 seeds/cm of g-Al2O3) the sintering temperature is reduced from 1600 C for unseeded g-Al2O3 to 1300–1400 C in dry pressed powders. The scale of the sinteredmi...