Phase Homogeneity in Y₂O₃–MgO Nanocomposites Synthesized by Thermal Decomposition of Nitrate Precursors with Ammonium Acetate Additions

Abstract

Nanocomposite powders with equal volume fractions of Y 2 O 3 and MgO have been produced by the thermal decomposition of precursor mixtures of yttrium nitrate and magnesium nitrate. Solutions of the precursor salts were mixed with ammonium acetate fuel, dried to form a gel-like substance, and then calcined to give nanocrystalline ceramic powders. The amount of ammonium acetate added to the metal nitrate precursors was varied systematically, and the morphology and distribution of the component phases in consolidated compacts of the resultant ceramic powders were examined by a combination of focused ion beam sectioning, scanning, and transmission electron microscopy. The dispersion of the Y 2 O 3 and MgO phases within the synthesized powders improved, and the sizes of the phase domains reduced, with increasing ammonium acetate content up to the quantity required for a stoichiometric redox reaction with the metal nitrates. The addition of excess ammonium acetate gave no further improvement in phase domain dispersion or reduction in phase domain sizes. These phenomena are related to the thermal characteristics for the decomposition of the precursors and their effect on phase separation during oxide crystallization.M. Cinibulk-contributing editor Manuscript No. 29465.

Hot Pressing of Infrared‐Transparent Y2O3–MgO Nanocomposites Using Sol–Gel Combustion Synthesized Powders

“…The transmittance of sintered nanocomposite ceramics at 3.25 μm decrease slightly due to the stretching vibration of hydroxyl groups (O–H), because the synthesized composite nanopowder has a very high specific surface area (45.9 m 2 /g), large amount of the moisture in the air can be absorbed during handing especially for MgO component . The absorption peak at about 7 μm are ascribed to asymmetrical and symmetrical stretching vibrations of the carboxylate group (O‐C=O), which was formed during the combustion process and was not released after calcination process . In addition, the contamination from the graphite die also contribute to the existence of carboxylate group.…”

Physics and Chemistry of Sol-Gel Nanocomposites Formation

“…Variety of the method is gas-flame spray-pyrolysis, for example, for production of nanocomposites on the basis MgO-ZrO 2 ,Y 2 O 3 -MgO, CoO x -Al 2 O 3 [222][223][224][225].…”

“…%.) [245] Homogenous separation of domains of submicron phase is found in MgO-ZrO 2 [222] and in MgO-Y 2 O 3 [260]. A composite containing about 90 mol % of MgO is prepared from respective amounts of 0.5 M Y(NO 3 ) 3 (7 mmol) and 0.…”

High Reactive MgO‐Y2O3 Nanopowders via Microwave Combustion Method and Sintering Behavior

“…Many approaches such as sol‐gel, combustion, and flame pyrolysis techniques have been employed to synthesize MgO‐Y 2 O 3 nanopowders . Among these methods, the combustion method has become the most efficient choice in case of large‐scale economical production of nanopowders.…”

“…Acetate–nitrate mixtures are often used as starting chemicals of combustion synthesized MgO‐Y 2 O 3 nanopowders, in which metal nitrate acts as oxidizer and the mental acetate as reducer. However, the ratio of oxidizing to reducing valence in the yttrium acetate–magnesium nitrate mixture for the preparation of MgO‐50 vol% Y 2 O 3 is 0.83 while that for the yttrium nitrate–magnesium acetate mixture is 0.44 . Both mixtures are fuel rich as their respective ratios are <1.…”