Nanostructured Yttria Powders Via Gel Combustion
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Nanostructured yttria powders via gel combustion Sukumar Roy,a) Wolfgang Sigmund, and Fritz Aldinger Max-Planck-Institut f¨ur Metallforschung, Universit¨at Stuttgart, Institut f¨ur Nichtmetallische Anorganische Materialien, Pulvermetallurgisches Laboratorium, 70569 Stuttgart, Germany (Received 2 September 1997; accepted 1 July 1998)
Nanostructured yttria powders were prepared by a gel combustion technique. The technique involves exothermic decomposition of an aqueous citrate-nitrate gel. The decomposition is based on a thermally induced anionic redox reaction. A variety of yttria powders with different agglomerate structures can be made by altering the citrate-nitrate ratio g. The gel with g 0.098 in situ yields nanostructured yttria powder at 258 ±C that is porous and agglomerated with an average of 25 nm primary particles. Its specific surface area is 55 m2yg. The decomposition of the gels was investigated by simultaneous thermogravimetry analysis (TGA) and differential thermal analysis (DTA) experiments. The produced ashes and calcined powders are characterized by x-ray diffraction (XRD), ir spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer, Emmett, and Teller (BET) analysis.
I. INTRODUCTION
Ceramic materials containing nanosized structures are of recent interest.1 One major application of nanoceramics is in the area of catalysis. This application of nanoparticles depends neither on the use of agglomeratefree powders nor upon the use of a fully dense solid. Rather, a carefully tailored nanostructured material is preferred while dealing with industrial processes concerning chemicals production, energy conversion systems, and separation or purification processes. The use of the rare earth and transition metal oxides is common in this regard. Y2 O3 is a material known with a wide range of applications from traditional refractories to advanced ceramics, including catalysts.2,3 Synthesis of yttria powders by different routes, e.g., sol-gel processes,4–6 colloidal processes,7–9 polymeric routes,10,11 and other solution routes12,13 is known. This paper describes a gel combustion technique for synthesizing nanostructured yttria powders suitable for catalytic applications. Combustion techniques14–17 for synthesizing fine powders are of significant interest, primarily due to the overall simplicity of the technique. These techniques deal with a different combination of combustible anions in the precursor. Such precursors upon combustion directly yield the required ceramic material as a combusted product. The choice of combustible anions plays a significant role in the synthesis conditions and subsequently influences the properties of the derived powder. The particular combination of combustible anions can make a low temperature combustion reaca)
On leave from Ceramic Technological Institute, Bharat Heavy Electricals Limited, Bangalore 560 012, India.
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http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 4, A
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