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Иваненко, В. И.; Udalova, I. A.; Локшин, Э. П.; Калинников, В. Т.

doi:10.1023/a:1012753629674

Cited by 2 publications

(1 citation statement)

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“…Conversion into other niobium oxide-related materials was also examined. Among niobium oxide-related materials, alkaline niobates are promising materials for piezoelectric materials, optical devices, and photocatalysts, − and many kinds of crystal phases that have varying alkali metal/niobium ratios have been reported. − Many of the preparation methods of alkaline niobates, however, contain a solid-phase reaction, a liquid-phase reaction via a hydroxide solution, and a solvothermal process, which progress under harsh conditions and lead to the destruction of the morphologies of the starting materials. Modifying niobium oxide monoliths into other materials while maintaining the starting structures can enlarge the application fields of niobium oxide monoliths.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Hierarchically Porous Niobium(V) Oxide and Alkaline Niobate Monoliths via Sol–Gel Accompanied by Phase Separation

2023

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Hierarchically porous niobium(V) oxide monoliths were prepared through the sol−gel process accompanied by phase separation and subsequent heat treatment. Macroporous and mesoporous characteristics as well as crystal structures were investigated in detail. Macroporous structures were controlled by the starting composition to manipulate phase separation, whereas mesoporous structures were modified by heat treatment in air to crystallize niobium(V) oxide. The results showed that by heat treating the as-dried gel at 550 °C in air, a hierarchically ordered macro/ mesoporous material with BET surface area of 54 m 2 g −1 was obtained. With an increase of the heat treatment temperature, an increase in the mesopore size accompanied by a decrease in the specific surface area was observed as a result of crystallite growth. Heat treatment under a N 2 atmosphere resulted in the formation of phases with lower-valence niobium such as NbO 2 and Nb 12 O 29 , which were derived from the reduction by the carbothermal reaction due to the presence of carbonized organic compounds. The conversion of niobium(V) oxide into niobium-containing complex oxides was also examined. Alkaline metals, namely, Li, Na, and K, were incorporated by postgelation treatments. Niobium-rich alkaline niobate phases were obtained when alkaline chloride was incorporated, whereas the majority of lithium niobate (LiNbO 3 ) phases were obtained when samples were treated with lithium hydroxide.

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Section: Introductionmentioning

confidence: 99%

Preparation of Hierarchically Porous Niobium(V) Oxide and Alkaline Niobate Monoliths via Sol–Gel Accompanied by Phase Separation

2023

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Thermodynamics of Ion-Exchange of Alkali Metal Ions on Crystalline Niobium(V) Phosphate

Ahmad¹,

Rafatullah²,

Danish³

2006

Bulletin of the Chemical Society of Japan

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Exchange isotherms for hydrogen ion/alkali metal ions (H+/Li+, H+/Na+, H+/K+, H+/Rb+, and H+/Cs+) have been studied at 20, 40, and 60 °C at a constant ionic strength of 0.1 on the crystalline phase of niobium(V) phosphate. The isotherms show an irregular (S-shaped) behavior without a phase transition. A selectivity reversal has been observed over the entire system of solid compositions. Plots of the selectivity coefficient (loge scale) versus equivalent ionic fraction of metal ion in the exchanger phase are linear for all of the systems and at all temperatures studied. The ion-exchange capacities and the maximum uptake at equilibrium is on the order of Li+ < Cs+ < Rb+ < Na+ < K+. The higher selectivity of potassium ion compared to other alkali ions has been explained in terms of steric hindrance and the stiff three-dimensional structure of the exchanger having a fixed pore size. The thermodynamic parameters for the overall and for zero loading have been worked out using the Gaines–Thomas equation.

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Cited by 2 publications

References 5 publications

Preparation of Hierarchically Porous Niobium(V) Oxide and Alkaline Niobate Monoliths via Sol–Gel Accompanied by Phase Separation

Preparation of Hierarchically Porous Niobium(V) Oxide and Alkaline Niobate Monoliths via Sol–Gel Accompanied by Phase Separation

Thermodynamics of Ion-Exchange of Alkali Metal Ions on Crystalline Niobium(V) Phosphate

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