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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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Journal ArticleDOI
TL;DR: A series of ZnO/Al2O3 mixed oxide samples with varying Zn/Al ratio is prepared by coprecipitation, ageing, drying, and calcination as mentioned in this paper.

70 citations

Journal ArticleDOI
TL;DR: In this paper, the mesoporous-assembled 0.93TiO2-0.07ZrO2 mixed oxide was synthesized by a sol-gel process with the aid of a structure-directing surfactant prior to the metal loadings.

70 citations

Journal ArticleDOI
TL;DR: In this article, the effect of temperature, loading, Cu/Cr ratio, particle size and the pretreatment in reducing or oxidizing environment on the activity and selectivity of the CO oxidation and the NO reduction with CO, both individually and simultaneously, were considered.

70 citations

Journal ArticleDOI
TL;DR: In this paper, spc-Ni/MgAl catalysts were used for steam reforming of CH4 into synthesis gas, and they showed high CH4 conversion following thermodynamic equilibrium even at a high space velocity of 9×105 ml h−1 g-cat−1, while a commercial Ni/α-Al2O3 catalyst showed a clear decline in activity.
Abstract: spc-Ni/MgAl (spc: solid phase crystallization method) catalysts have been prepared from Mg–Al hydrotalcite-like compounds as the precursors and tested for steam reforming of CH4 into synthesis gas. The precursors based on [Mg(II)1−xAl(III)x(OH)2]x+(CO3−)x·mH2O, in which a part of Mg(II) ions were replaced by Ni(II) ions, were prepared by co-precipitation method, thermally decomposed and reduced to form spc-Ni/MgAl catalyst. Surface areas of spc-Ni/MgAl catalysts were always high at around 150 m2 g-cat−1. Ni(II) ions first substituted a part of the Mg(II) sites in the Mg–Al hydrotalcite-like compounds and then incorporated in the rock-salt type Mg–Ni–O solid solutions in the mixed oxide after the decomposition. The dispersion of Ni was thus repeatedly enhanced during the spc-preparation, resulting in the formation of highly dispersed Ni metal particles after the reduction. The activity of spc-Ni/MgAl catalyst was high when Ni/Mg was larger than 0.2, and the most suitable ratio of Mg/Al was 1/3. When the catalysts were tested in the steam reforming of CH4, spc-Ni0.5/Mg2.5Al showed high CH4 conversion following thermodynamic equilibrium even at a high space velocity of 9×105 ml h−1 g-cat−1, followed by imp-Ni/Mg3Al-aq prepared by impregnation of Mg–Al mixed oxide in aqueous solution. It is considered that, during the preparation of imp-Ni/Mg3Al-aq, surface reconstitution of the Mg–Al hydrotalcite layered structure took place by a “Memory Effect” of the hydrotalcite, resulting in the high dispersion of Ni metal particles. When spc-Ni0.5/Mg2.5Al was tested in the steam reforming of CH4, no deterioration in the catalytic activity was observed for 600 h of reaction time even under a low steam to carbon ratio of 1.6, while a commercial Ni/α-Al2O3 catalyst showed a clear decline in the activity. The CH4 conversion as well as the distribution of products followed thermodynamic equilibrium during the reaction for 600 h. It is concluded that spc-Ni0.5/Mg2.5Al is a hopeful candidate as a catalyst for the production of H2 for polymer electrolyte fuel cells.

70 citations

Journal ArticleDOI
TL;DR: In this article, it is found that the oxidation of polycrystalline SixGe1−x films with different compositions (i.e., different values of x) is carried out in pyrogenic steam at 800 °C for various lengths of time.
Abstract: The oxidation of polycrystalline SixGe1−x films with different compositions (i.e., different values of x) is carried out in pyrogenic steam at 800 °C for various lengths of time. It is found that the oxidation is enhanced by the presence of germanium and that the enhancement effect is more pronounced for the films richer in germanium. A mixed oxide in the form of either (Si,Ge)O2 or SiO2–GeO2 is found at the sample surface if the initial SixGe1−x contains more than 50% of germanium. However, a surface silicon cap layer of about 14 nm is found to have a significant impact on the oxidation of the Si0.5Ge0.5 films; it leads to the growth of about 115-nm-thick SiO2 which is about four times that of the SiO2 resulting from the oxidation of the cap layer itself. On the SixGe1−x films with only 30% of germanium, the SiO2 continues to grow after oxidation for 180 min resulting in 233-nm-thick SiO2 which is about 2.4 times greater than the SiO2 grown on 〈100〉 silicon substrates. Rejection of germanium results in p...

70 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202318
202265
2021184
2020198
2019175
2018178