MORPHOLOGICAL DESIGN OF NANOCRYSTALLINE CERIUM DIOXIDE DURING THERMAL DECOMPOSITION OF CERIUM (III) OXALATE DECAHYDRATE
D. V. MASLENNIKOV1,2, A. A. MATVIENKO1,2, A. A. SIDELNIKOV1,2, S. A. CHIZHIK1,2
1Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Keywords: оксалат церия, нанокристаллический диоксид церия, псевдоморфоза, термическое разложение, cerium oxalate, nanocrystalline cerium oxide, pseudomorph, thermal decomposition
Pages: 289-297
Abstract
Materials based on cerium dioxide are used in various fields of high-tech industry: from precision polishing of optical glasses and the production of high-strength ceramics to using them as three-route catalysts in engines and medical applications as biomimetics. Due to a wide range of practical applications of such materials, there is an actual task to develop a method for producing cerium oxide with the ability to control its textural characteristics. To solve this problem in this work, the method of thermal decomposition of the precursor Ce2(C2O4)3·10H2O was chosen. The main advantage of this method is the possibility of obtaining products in the form of a pseudomorph consisting of nanoparticles of the product and preserving the shape and size of the crystals. In the course of the work, the conditions for obtaining pseudomorph were found, i.e. porous granules of cerium oxide nanoparticles, the size of which is set at the stage of synthesis of precursor crystals. Techniques have been developed for growing Ce2(C2O4)3·10H2O crystals of various sizes and habit. The work also revealed the factors that influence the textural characteristics of the resulting oxides during thermal decomposition of the selected precursor. It was shown that during thermal decomposition of thin (<20 µm) precursor plates with a basal face (010) in air, cerium dioxide pseudomorph transparent to visible light was formed. Thicker crystals were destroyed parallel to the (010) face with a fracture scale of about 10 μm. It was shown that an increase in water vapor pressure during dehydration led to structural changes other than those during dehydration in air. With such a rearrangement of the structure, the initial crystals are destroyed into particles less than 5 μm. In this work, we were able to obtain a pseudomorph consisting of 5-6 nm particles of cerium dioxide with a surface area of 140-150 m2/g and 40% porosity. Controlled annealing allowed the microstructure to be enlarged to the required size of crystallites that make up the pseudomorph.
DOI: 10.15372/CSD2019141
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