Mesostructure, fractal properties and thermal decomposition of hydrous zirconia and hafnia

Ivanov, V. K.; Kopitsa, G. P.; Baranchikov, А. Е.; Sharp, Melissa; Pranzas, P. Klaus; Grigoriev, S. V.

doi:10.1134/s0036023609140022

Cited by 21 publications

(11 citation statements)

References 42 publications

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“…First of all, this manifests itself in an increase in the surface fractal dimension D S1 and characteristic size (upper self similarity boundary) R g1 of the particles of the first structural level. We note that in the precipita tion of hydrated zirconium and hafnium oxides an analogous increase in the surface fractal dimension was observed in [44][45][46]. In addition, the degree of aggregation grows for mass fractal clusters D m2 and aggregates D m3 of the second and third structural lev els, respectively.…”

Section: Mesostructure Of Yttrium and Aluminum Hydroxocompounds Precisupporting

confidence: 59%

Mesostructure of yttrium and aluminum basic salts coprecipitated from aqueous solutions under ultrasonic treatment

Yapryntsev

Gubanova

Kopitsa

et al. 2016

J. Synch. Investig.

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The influence of ultrasonic treatment on the micro and mesostructures and fractal characteristics of amorphous powders of yttrium and aluminum basic salts (precursors for the synthesis of neodymium acti vated yttrium-aluminum garnet, Nd:YAG, which were coprecipitated from aqueous solutions by different precipitants, namely, aqueous solutions of ammonia and ammonium bicarbonate) is studied. It is established that ultrasonication applied during the precipitation of the aforementioned powders does not significantly change the structure of the obtained materials but always leads to the formation of structures with a less homogeneous nuclear density, i.e., a more developed surface area. Moreover, the ultrasound assisted precip itation of the hydroxocompounds by ammonium hydrocarbonate results in a certain increase in the surface fractal dimension and the degree of aggregation for mass fractal aggregates of particles.

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Section: Mesostructure Of Yttrium and Aluminum Hydroxocompounds Precisupporting

confidence: 59%

Mesostructure of yttrium and aluminum basic salts coprecipitated from aqueous solutions under ultrasonic treatment

Yapryntsev

Gubanova

Kopitsa

et al. 2016

J. Synch. Investig.

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“…The excess of alkali in the reaction media results in rapid hydrolysis and condensation, forming a branched metal oxy-hydroxide network. In particular, hydrous zirconia precipitated above the point of zero charge possesses a higher specific surface area and surface fractal dimension than when it is synthesized at low pH [39].…”

Section: Introductionmentioning

confidence: 97%

“…[35][36][37]. The most convenient approach to synthesize these materials is based on the precipitation of amorphous hydrous zirconia gels in aqueous media using zirconium-containing precursors (e.g., zirconyl nitrate, zirconium alkoxides) and subsequent thermal or hydrothermal treatment of the resulting ZrO 2 xH 2 O gel [38,39]. The morphology and phase composition of such synthesized zirconia is, to a large extent, governed by the structure of the precursor gel, which in turn depends on the conditions of precipitation (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Combined SANS and SAXS study of the action of ultrasound on the structure of amorphous zirconia gels

Gubanova

Baranchikov

Kopitsa

et al. 2015

Ultrasonics Sonochemistry

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In the present work, we have studied for the first time the combined effect of both sonication and precipitation pH on the structure of amorphous zirconia gels synthesized from zirconium(IV) propoxide. The techniques of small-angle neutron and X-ray scattering (SANS and SAXS) and low temperature nitrogen adsorption provided the integral data on the changes in the microstructure and mesostructure of these materials caused by ultrasonic treatment.Amorphous ZrO 2 ·xH 2 O synthesized under ultrasonic treatment was found to possess a very structured surface, characterized by the surface fractal dimension 2.9-3.0, compared to 2.3-2.5 for the non US-assisted synthesis, and it was also found to possess a higher specific surface area, while the sizes of the primary particles remain unchanged.

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“…K. Ivanov et al 13,14 studied the mesostructure evolution of hydrous zirconia xerogels by Small and Ultra-Small Angle Neutron Scattering (SANS/USANS) techniques. By increasing the pH, products exhibit a slight increase of the monomer unit radius from about 14 to about 17 A, passing from a minimum of 13 A at pH ¼ 6. Above pH ¼ 6, the synthesized xerogels show a surface fractal behavior with a characteristic dimension of 2.35 that reaches a value of 2.6 at pH ¼ 9.…”

Section: Introductionmentioning

confidence: 99%

Bottom-up/top-down synthesis of stable zirconium hydroxide nanophases

Ambrosi

Fratini

Canton³

et al. 2012

J. Mater. Chem.

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It is well known that the structure of ZrO 2 powder synthesized by low temperature calcination of hydrous zirconia is strongly affected by the nature and properties of precursors. In the present paper, we combined a precipitation/restructuring approach (bottom-up/top-down methodology) to produce zirconium hydroxide nanoparticles that transform into stable nanophasic tetragonal zirconia by low temperature calcination. The dimension and structure of precursors could be modulated by adjusting pH. The synthetic route was investigated by Raman spectroscopy, X-Ray Diffraction, Small-Angle XRay Scattering and High-Resolution Transmission Electron Microscopy. The zirconium hydroxide nanoparticles represent the final product of the overall process, which starts as a bottom-up synthesis of the hydroxide gel, followed by a top-down reorganization stage. During this rearrangement, the evolving structure passes through a mass fractal that arises from the clustering of the primary zirconium hydroxide nano-units.

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Mesostructure, fractal properties and thermal decomposition of hydrous zirconia and hafnia

Cited by 21 publications

References 42 publications

Mesostructure of yttrium and aluminum basic salts coprecipitated from aqueous solutions under ultrasonic treatment

Mesostructure of yttrium and aluminum basic salts coprecipitated from aqueous solutions under ultrasonic treatment

Combined SANS and SAXS study of the action of ultrasound on the structure of amorphous zirconia gels

Bottom-up/top-down synthesis of stable zirconium hydroxide nanophases

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