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Mixed oxide
About: Mixed oxide is a research topic. Over the lifetime, 5224 publications have been published within this topic receiving 115567 citations.
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TL;DR: In this article, the technical TiAl-alloy γ-MET (Ti 46.5Al-4(Cr, Nb, Ta, B)) was oxidised thermocyclically (24-h-cycle-test) at 900°C in wet and dry air.
42 citations
TL;DR: In this article, it was shown that the encapsulated Pd exists in the form of metallic particles on the order of 10 nm in diameter held under a large (as much as 3.6 GPa) compressive stress by the mixed oxide.
Abstract: Redox aging above 1000°C of initially high-surface-area (of order 100 m2/g) cerium-rich ceria-zirconia mixed oxides containing a few wt% Pd results in the loss of most of the surface area and concomitant encapsulation of a substantial fraction of the Pd. The encapsulated Pd exists in the form of metallic particles on the order of 10 nm in diameter held under a large (as much as 3.6 GPa) compressive stress by the mixed oxide. This stress, evidently arising from changes in lattice parameter of the mixed oxide, induced by aging, produces a volume contraction of Pd, which appears as a shift of Pd-peak positions in XRD measurements. Subsequent reduction and reoxidation of the mixed oxide in turn relieves and restores the stress on the Pd particles, which remain metallic throughout, demonstrating that this portion of the Pd is effectively lost for catalytic purposes.
41 citations
TL;DR: In this paper, a remarkably improved catalytic activity of Mn/γ-Al 2 O 3 catalyst promoted with potassium doping in the selective oxidation of benzyl alcohol with molecular oxygen was reported.
Abstract: In this study, we reported a remarkably improved catalytic activity of Mn/γ-Al 2 O 3 catalyst promoted with potassium doping in the selective oxidation of benzyl alcohol with molecular oxygen. Characterizations of powder X-ray diffraction (XRD), Raman spectroscopy, X-ray absorption fine structure (XAFS), and hydrogen temperature-programmed reduction (H 2 -TPR) revealed that the co-impregnation of potassium to the Mn/γ-Al 2 O 3 gave rise to the presence of α-MnO 2 rather than β-MnO 2 , resulting in a stable catalyst with enhanced catalytic performance. We also demonstrated this alumina-supported K–Mn mixed oxide catalyst can effectively catalyze aerobic oxidation of various aromatic alcohols.
41 citations
TL;DR: In this article, a high surface area titania-zirconia mixed oxide support was prepared by the technique of precipitation from homogeneous solutions, which was then subjected to thermal treatments from 500 to 800 °C.
Abstract: A high surface area titania-zirconia mixed oxide support was prepared by the technique of precipitation from homogeneous solutions. Vanadia (12 wt %) was impregnated on TiO2−ZrO2 support by using an oxalic acid solution of NH4VO3. The TiO2−ZrO2 binary oxide support and the V2O5/TiO2−ZrO2 catalyst were then subjected to thermal treatments from 500 to 800 °C. The influence of thermal treatments on the dispersion and stability of the catalyst was investigated by X-ray diffraction (XRD), FT infrared (FTIR), UV−vis absorption, and X-ray photoelectron spectroscopy (XPS) techniques. The characterization results suggest that the TiO2−ZrO2 binary oxide support is thermally quite stable up to 800 °C. Calcination of the coprecipitated titanium−zirconium hydroxides at 500 °C result in the formation of an amorphous phase, and further heating at 600 °C converts this amorphous phase into a crystalline ZrTiO4 compound. Impregnation of V2O5 and heating of the V2O5/TiO2−ZrO2 catalyst beyond 600 °C results in the formation ...
41 citations
TL;DR: The present study was centered on the determination of possible adherence zone compounds in four composite ceramic-metal couples examined by x-ray energy analysis and revealed the presence of a predominant Al-Cr interaction resulting from the formation of an Al- Cr-O compound or mixed complex.
Abstract: Bonding between porcelain and dental ceramic alloys is thought to be dependent upon the establishment of a continous electron structure across the ceramicmetal interface (Pask, Proc. Procelain Enamel Inst., 33, 1, 1971). Such a structure most likely results from the compatibility of metal ions at the metal surface saturated in an oxide form with the complex oxide structure of the ceramic matrix. Reaction zone compounds are expected to play a prominent role in the strength of the ceramic–metal bonds but thus far none have been detected or identified.
The present study was centered on the determination of possible adherence zone compounds in four composite ceramic–metal couples examined by x-ray energy analysis. Elemental analysis of four couples revealed the presence of a predominant AlCr interaction resulting from the formation of an AlCrO compound or mixed oxide complex. The Cr ions were supplied by the Cr2O3 oxide layer at the metal surface and the Al was provided by the initial bonding-agent coating.
41 citations