O. S. Polezhaeva

ZnO formation under hydrothermal conditions from zinc hydroxide compounds with various chemical histories

The sequence of phase transformations of zinc hydroxide compounds with various chemical histories during hydrothermal (HT) treatment is studied by X-ray powder diffraction and thermal analysis (TG/DTA). ɛ-Zn(OH)2 (wulfingite) is the major intermediate in ZnO production by the HT process. The micromorphology and photocatalytic activity of ZnO powders are studied.

Formation mechanism of nanocrystalline ceria in aqueous solutions of cerium(III) nitrate and hexamethylenetetramine

The formation mechanism of ceria nanoparticles in solutions of cerium(III) nitrate and hexamethylenetetramine has been studied for the first time, using UV/visible spectroscopy and x-ray diffraction. The process has been shown to involve, as an intermediate step, the formation of cerium(III) hydroxycarbonate. The effects of synthesis temperature and solution composition on the micromorphology of the powders have been investigated.

Synthesis and thermal stability of nanocrystalline ceria sols stabilized by citric and polyacrylic acids

New methods are proposed for preparing aqueous sols of nanocrystalline ceria stabilized by citric or polyacrylic acid. Transmission electron microscopy and UV-Vis spectroscopy were used to study the stability of sols in hydrothermal treatment at temperatures in the range of 120–210°C.

Oxygen Nonstoichiometry of Nanocrystalline Ceria

Correlation relations between oxygen nonstoichiometry and particle size in nanocrystalline CeO2 − x are revised. The ceria unit cell parameter is shown to increase from 0.5410 to 0.5453 nm as the particle size decreases from 23 to 2.3 nm. The CeO2 − x critical particle size where cerium(IV) is completely reduced to cerium(III) is calculated as 1.1–1.3 nm.

Nanocrystalline ceria: Synthesis, structure-sensitive properties, and promising applications

Directed search for further manifestations of size-dependent effects in the functional properties of nanomaterials constitutes a key line of nanotechnologies research. The major size-dependent effects were analyzed for nanocrystalline ceria. The practically significant techniques for preparation of ceria nanopowders with controllable micromorphology were analyzed. Selected promising applications of this material were described.

Fractal structure of ceria nanopowders

The formation of ceria nanoparticles from water-alcohol solutions of cerium(III) nitrate has been studied by UV/VIS spectroscopy, low-temperature nitrogen adsorption measurements, x-ray diffraction, transmission electron microscopy, and thermal analysis, and the effect of high-temperature annealing on the fractal structure of the CeO2 nanopowders has been examined.

Synthesis of nanosized ceria with controlled particle sizes and bandgap widths

The formation dynamics of nanosized ceria in cerium nitrate(III) and hexamethylenetetramine (HMTA) solutions has been studied for the first time using UV-visible spectroscopy. The bandgap width and particle size of CeO2 are controlled by the synthesis duration, reaction temperature, and the concentrations and molar ratio of the reagents.

Microwave-hydrothermal synthesis of stable nanocrystalline ceria sols for biomedical uses

A new microwave-hydrothermal process has been developed for preparing stable aqueous sols of nanocrystalline ceria. Transmission electron microscopy, UV-Vis spectroscopy, and dynamic light scattering shows that CeO2 nanoparticle size remains unchanged during hydrothermal treatments. Sodium adenosine triphosphate and sodium citrate are proposed for additional stabilization of the sols.

Thermal stability of nanocrystalline CeO2 prepared through freeze drying

The growth of ceria nanoparticles during annealing at high temperatures (up to 700°C) has been studied by X-ray diffraction, transmission electron microscopy, and low-temperature nitrogen adsorption measurements. The results indicate that CeO2 nanopowders prepared using freeze drying offer enhanced thermal stability.

Synthesis of ultrathin ceria nanoplates

A new method was developed for manufacturing ceria plates of subnanometer thicknesses. Growth of CeO2 nanoparticles in the presence of hexamethylenetetramine preferably occurs via oriented attachment.