Combustion Synthesis of Nanocrystalline Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Powders Using Urea as Fuel: Influence of Different Combustion Aids

Meng, Fan Cheng; Tian, Zhong Qing; Zhang, Fan; Tian, Chang Cheng; Huang, Wenxin

doi:10.4028/www.scientific.net/kem.434-435.868

Cited by 2 publications

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“…SC-reaction initiation is achieved through external heating of the reaction mixture up to its ignition temperature. Different electrical heating devices, such as muffle oven, hot plate, aluminum open cylindrical reactor, and pressure reactor [31][32][33][34][35][36] have been used for supplying the required energy for heating the solution mixture. However, most of these traditional heating processes lead to a thermal gradient between the interior and exterior of the heated solution, resulting in a local inhomogeneity of the prepared material.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Fuel/Oxidant Ratio on the Elaboration of Binary Oxide Catalyst by a Microwave-Assisted Solution Combustion Method

et al. 2020

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Three series of binary metal oxide catalysts containing Ni, Cu, or Co oxides were prepared, fully characterized and tested in CO oxidation. The catalysts, with a constant transition metal loading of 10 wt%, were prepared from metal nitrates and urea mixtures by a microwave-assisted solution combustion method. The RV/OV ratio, corresponding to the stoichiometry of the reactants, calculated from their elemental oxidizing and reducing valences, was varied. In order to modify the redox character of the synthesis medium from the quantity of urea; an excess of urea was used for attaining reducing conditions, while a deficit of urea shifted the medium to oxidizing conditions. Three RV/OV ratios (0.9, 1.0, and 1.1) were selected to elaborate the different binary metal oxide catalysts, nine oxide catalysts were synthesized. Then, the influence of the stoichiometry (RV/OV ratio) on the bulk and surface properties of the binary metal oxide catalysts was investigated. Similarly, the influence of the RV/OV ratio on the CO oxidation activity was discussed and the optimal value of RV/OV ratio was identified. The results show that the increasing of the RV/OV ratio from 0.9 to 1.1, particularly in Ni- and Co-containing catalysts, induces stronger metal-aluminum interactions, in the form of aluminates phases, and that are correlated to the dramatic reduction of the CO oxidation activity. The best physicochemical properties and highest catalytic activities were achieved with the catalysts prepared in redox systems stoichiometrically balanced (RV/OV = 1). The Cu-containing catalysts presented the best catalytic activities in CO oxidation.

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