Structures, formation mechanisms, and ion-exchange properties of α-, β-, and γ-Na<sub>2</sub>TiO<sub>3</sub>

Meng, Fancheng; Liu, Yahui; Xue, Tianyan; Su, Qian; Wang, Weijing; Qi, Tao

doi:10.1039/c6ra16984h

Cited by 21 publications

(13 citation statements)

References 45 publications

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“…5) were in agreement with the XRD results. At 900°C, the peaks of rutile TiO 2 can be e fibers annealed at 900°C in air seen on the spectra (the peaks at around 243 cm -1 , 447 cm -1 , and 612 cm -1 can be, respectively, assigned to the second-order Raman scattering, E g and A 1g modes of rutile TiO 2 [28,30]), and also some small peaks of the anatase remained. However, at 550°C, only the anatase TiO 2 peaks were visible.…”

Section: Resultsmentioning

confidence: 97%

Thermal properties of electrospun polyvinylpyrrolidone/titanium tetraisopropoxide composite nanofibers

Kéri

Bárdos

Boyadjiev

et al. 2019

J Therm Anal Calorim

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In this work, polyvinylpyrrolidone/titanium tetraisopropoxide (PVP/TTIP) composite nanofibers were prepared by electrospinning from alcoholic solutions. The morphology and the properties of the fibers were investigated by SEM, Raman spectroscopy, and XRD. The thermal properties and the evolved gases were studied in detail by TG/DTA-MS. The as-spun 800-900-nm-thick PVP/TTIP fibers were then, respectively, annealed in different atmospheres (air and nitrogen) and at different temperatures (550°C, 900°C) in order to obtain anatase and rutile TiO 2 nanofibers. The investigation of the thermal properties was important before the preparation of the oxide nanofibers, because based on them the crystallinity and the composition of the TiO 2 nanofibers could be controlled. Metal oxide nanofibers with a slightly smaller diameter, made up mostly by anatase TiO 2 , were successfully prepared when the annealing was done at 550°C, while at 900°C, rutile TiO 2 fibers were obtained. If nitrogen atmosphere was applied, the nanofibers contained some carbon residue as well.

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Section: Resultsmentioning

confidence: 97%

Thermal properties of electrospun polyvinylpyrrolidone/titanium tetraisopropoxide composite nanofibers

Kéri

Bárdos

Boyadjiev

et al. 2019

J Therm Anal Calorim

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“…1) We found that NaOH could react with TiO 2 to form titanate, which is in amorphous state and dispersed at the surface of the catalyst (Figure d and S10). Through comparing crystal structure parameters, the bond length of Ti–O in Na 2 TiO 3 (a common titanate as example) is much longer than that in TiO 2 , i.e., 2.02–2.40 Å in Na 2 TiO 3 and 1.937–1.983 Å in TiO 2 , respectively. , Besides, titanate material can be used as oxygen transport membrane for its excellent chemical and redox stability at high temperature . Therefore, the weaker Ti–O bond along with the mobility of O in titanate may result in easier reduction of the support.…”

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confidence: 99%

Fabrication of More Oxygen Vacancies and Depression of Encapsulation for Superior Catalysis in the Water–Gas Shift Reaction

Pei

Qiu

et al. 2021

J. Phys. Chem. Lett.

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Fabrication of sufficient oxygen vacancies and exposure of active sites to reactants are two key factors to obtain high catalytic activity in the water–gas shift (WGS) reaction. However, these two factors are hard to satisfy spontaneously, since the formation of oxygen vacancies and encapsulation of metal nanoparticles are two inherent properties in reducible metal oxide supported catalysts due to the strong metal–support interaction (SMSI) effect. In this work, we find that addition of alkali to an anatase supported Ni catalyst (Ni/TiO2(A)) could well regulate the SMSI to achieve both more oxygen vacancies and depression of encapsulation; therefore, more than 20-fold enhancement in activity is obtained. It is found that the in situ formed titanate species on the catalyst surface is crucial to the formation of oxygen vacancies and depression of encapsulation. Furthermore, the methanation, a common side reaction of the WGS reaction, is successfully suppressed in the whole catalytic process.

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“…7,8 This suggests that the changes in the grain size are probably somehow related with presence of the Na-rich phase. Some sodium titanates have melting temperatures close to 1000 • C. 26 Another scenario is related to increased concentration of oxygen vacancies, according to assumptions described above.…”

Section: Resultsmentioning

confidence: 99%

Composition and microstructure of Na_0.5Bi_0.5TiO₃ ceramics with excess Bi

et al. 2022

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In the present work, Na0.5Bi0.5TiO3 (NBT) ceramics with the addition of excess Bi in two different ways – before calcination and before sintering – are considered, revealing how the excess Bi affects their microstructure and chemical content. Average grain size is seen to decrease, with the grain size distribution becoming less diffused at higher excess Bi concentrations. The reason for such a feature is the shift of the sintering temperature region where the abnormal grain growth starts to contribute towards higher temperatures. The influence of excess Bi is more pronounced in the case if it is added before calcination. It was discovered that a small amount of excess Bi helps to prevent the formation of Bi‐deficient inclusions. While, high concentrations of excess Bi induce the formation of Bi‐rich inclusions – most probably Na0.5Bi4.5Ti4O15. Possible mechanisms of formation of both types of inclusions are discussed in detail. Instead of Bi over‐stoichiometry, elevated Na content and slightly lower O content were detected in the matrix grains of the sintered NBT ceramics prepared with excess Bi. These deviations increase upon increasing the added excess Bi concentration. The presence of another, Na‐rich phase, is assumed, which could not be detected by X‐ray diffraction or by energy‐dispersive X‐ray analysis.

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Structures, formation mechanisms, and ion-exchange properties of α-, β-, and γ-Na₂TiO₃

Abstract: The structure of β-Na2TiO3 was refined. The formation/transformation mechanisms and ion-exchange properties of α-, β-, and γ-Na2TiO3 were investigated.

Cited by 21 publications

References 45 publications

Thermal properties of electrospun polyvinylpyrrolidone/titanium tetraisopropoxide composite nanofibers

Thermal properties of electrospun polyvinylpyrrolidone/titanium tetraisopropoxide composite nanofibers

Fabrication of More Oxygen Vacancies and Depression of Encapsulation for Superior Catalysis in the Water–Gas Shift Reaction

Composition and microstructure of Na_0.5Bi_0.5TiO₃ ceramics with excess Bi

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Structures, formation mechanisms, and ion-exchange properties of α-, β-, and γ-Na2TiO3

Abstract: The structure of β-Na2TiO3 was refined. The formation/transformation mechanisms and ion-exchange properties of α-, β-, and γ-Na2TiO3 were investigated.

Cited by 21 publications

References 45 publications

Thermal properties of electrospun polyvinylpyrrolidone/titanium tetraisopropoxide composite nanofibers

Thermal properties of electrospun polyvinylpyrrolidone/titanium tetraisopropoxide composite nanofibers

Fabrication of More Oxygen Vacancies and Depression of Encapsulation for Superior Catalysis in the Water–Gas Shift Reaction

Composition and microstructure of Na0.5Bi0.5TiO3 ceramics with excess Bi

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Structures, formation mechanisms, and ion-exchange properties of α-, β-, and γ-Na₂TiO₃

Composition and microstructure of Na_0.5Bi_0.5TiO₃ ceramics with excess Bi