The effect of Al3+ concentration on the properties of alumina powders obtained by reaction between aluminium sulphate and urea in boiling aqueous solution

Synthesis of quantum-size cerium oxide nanocrystallites by a novel homogeneous precipitation method

“…In consequence of the easy peptization of the Ce(OH) 4 -containing precipitate and HRTEM results, one may assume that the adjacent cerianite-Ln(OH) 3 structure of the grains and the acid-solubility difference between cerianite and Ln(OH) 3 were favorable for the peptization. With non-cerium hydroxide being selectively leached out from the grains by dilute hydrochloric acid, the multi-component coexistence structure of the grains was gradually disintegrated, which enabled the cerianite subunits to be freed and dispersed in LnCl 3 solution.…”

“…The direct formation of nanocrystalline ceria strongly suggests that the species being aggregated and deposited was cerianite hydrosol particulates. Should cerium exist in the form of free cerous-aquo species, the precipitate would have been cerous carbonates due to the chelation of CO 3 2− anion ligand [5][6][7][8]. Based on above, a solaggregation mechanism can be proposed for the formation of the quantum-size ceria powder.…”

“…In homogeneous precipitation, thermal decomposition of urea (or hexamethylenetetramine) into carbon dioxide and ammonia induces a gradual, highly uniform increase of the pH of metallic salt solution, which leads to the nucleation and growth of insoluble metal hydroxycarbonates [1,2] or hydroxides [3,4]. Previous studies on ultrafine ceria preparation showed that the direct product obtained by homogeneous precipitation of cerous salt was crystalline Ce 2 O(CO 3 ) 2 ·H 2 O [5,6] or CeOHCO 3 phase [7,8], indicating carbonate ions as an effective cerous cation chelator in aqueous solution.…”

Synthesis of Nano‐γ‐Ferric Oxide by Thermolysis of the 2‐Mercapto‐5‐Methylpyridine‐N‐Oxide‐Iron(III) Complex via Factorial Design

“…In Pechini's method, the formation of a metal complex takes place with organic chelating agents such as EDTA, oxalic acid, urea, or citric acid in the presence of a polyol to establish a linkage with the metal chelate resulting in gelation of the reaction mixture followed by thermolysis at higher temperatures (∼500-600°C) [27,28]. The present method is faster and more convenient than Pechini's method as it needs only one reagent for precipitation of the metal complex.…”

Applications of the zero-order reaction rate model and transition state theory on the intra-particle sintering of an alumina powder by using surface area measurements

“…Preparation and same physicochemical properties of the alumina powder selected for material in this study were investigated in our previous works [40,41]. An alumina precursor was precipitated in boiling aqueous solution contained 0.20 M Al 3+ and excess urea.…”