Synthesis of Zirconia Micro-Nanoflakes with Highly Exposed (001) Facets and Their Crystal Growth

Abstract

This study reports a novel preparation method of zirconia micro-nanoflakes with high (001) facets that is generated through a hydrolysis reaction of the fluozirconic acid (H2ZrF6). Zirconia micro-nanoflakes synthesized at varied conditions were analyzed by the SEM, EDS, μ-XRD, and Raman spectroscopy to characterize the morphology and probe into the crystal growth mechanism. The synthesized zirconia crystals in the form of elliptical micro-nanoflakes or irregular nanoflakes generally display the highly exposed (001) facets with a thickness of 1–100 nm and a length of 0.1–2.0 μm. As the temperature and initial solution concentration increased, the particle sizes of the synthesized zirconia micro-nanoflakes became more uniform and the thicknesses of the (001) facets became larger, suggesting that the synthesized zirconia crystals grow along the (001) facets and mostly along the c-axis direction. This is confirmed by the data from the μ-XRD patterns. The results also demonstrate that an oriented attachment-based growth occurring in a fluorine-rich solution environment was involved in the aggregation and coarsening of zirconia micro-nanoflakes. Meanwhile, synthesized zirconia micro-nanoflakes also evolved from a mixture of monoclinic and tetragonal systems to a pure monoclinic system (i.e., baddeleyite) with the temperature increasing, suggesting a key role of temperature regarding zirconia’s growth.

Improvement of ORR Activity of Monoclinic Zirconium Oxides by Fe and F Co-addition for PEFC Cathodes

“…This indicates that the addition of F promotes the monoclinic phase, which is consistent with previous reports. [26][27][28][29] As shown in Fig. 2c, aggregated oxide particles in the size range of a few hundred nanometers were observed in the monoclinic phase.…”

“…The addition of F promotes the growth of monoclinic ZrO 2 . [26][27][28][29] In the previous report, Nafion μ was regarded as a surfactant to refine the precursor powder. However, in this study, Nafion μ was considered as a fluorine additive and the objective was to investigate the effect of adding Nafion μ to the precursor (i.e., fluorine addition) in the ORR activity and physical properties of the catalysts, and to reveal the factors affecting the ORR activity.…”

Osmium Transport and Enrichment From the Lithosphere to the Hydrosphere: New Perspectives From Hydrothermal Experiments and Geochemical Modeling

“…In this study, the potassium chlorosmate (K 2 OsCl 6 , Os ≥ 38.7%, AR, Macklin) was utilized as the starting material for initial aqueous solutions with variable Os concentrations at temperatures ranging from 150 to 600°C and pressure of 100 MPa. The experiment procedures employed in this study are similar to those used in previous studies (He et al, 2015a;Wang & Chou, 1987;Yan, He, et al, 2020;Yan, Di, et al, 2021;Yan, Sun, et al, 2021). The initial aqueous solutions had Os concentrations ranging from 157.7 to 786.5 ppm by dissolving known amounts of K 2 OsCl 6 in deionized water (the calculated pH of initial solutions varied from 2.21 to 2.72).…”

Complexation of REE in Hydrothermal Fluids and Its Significance on REE Mineralization

“…Fluorine can decrease the solidus temperature and viscosity of silicate melts, as well as enhance ion diffusion rates [46,[158][159][160][161]. Additionally, it can increase the solubility of minerals such as zircon, monazite, ilmenite, and rutile in fluids or melts [162][163][164][165][166][167]. This prevents REEs from being incorporated into these minerals and promotes their enrichment in residual melts [168].…”