Influence of synthesis parameters on sol–gel transition and physical properties of Nb2O5 mesoporous ambigels

Granados, Laura; Souza, Luciana V. de; Falk, Gilberto S.; Hotza, Dachamir; Escobar, Jairo Arturo; Neto, João Batista Rodrigues; Rambo, Carlos R.

doi:10.1007/s10971-017-4435-7

Cited by 10 publications

(7 citation statements)

References 38 publications

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“…The formation of a peak at 33° was also observed, which can be attributed to the formation of NbO 4 phase (JCPDS n° 22‐1125), indicating that possibly different niobium oxides were formed during the synthesis. [ 3,20,25 ]…”

Section: Resultsmentioning

confidence: 99%

“…The formation of a peak at 33 was also observed, which can be attributed to the formation of NbO 4 phase (JCPDS n 22-1125), indicating that possibly different niobium oxides were formed during the synthesis. [3,20,25] The HT-Nb 2 O 5 sample showed a T-phase with orthorhombic structure (JCPDS No. 00-027-1313) and welldefined peaks.…”

Section: Crystal Structure Analysismentioning

confidence: 99%

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Characterization of niobium pentoxide synthesized by spray pyrolysis technique and comparison with hydrothermal method

de Andrade Schaffner,

Oliveira,

Domingues

et al. 2023

Can J Chem Eng

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Niobium pentoxide (Nb2O5) is a polymorphic ceramic with semiconductor characteristics applied in various fields of study. In this work, the Nb2O5 synthesis by the spray pyrolysis route was compared to the hydrothermal technique. The obtained materials were characterized by N2 physisorption (BET‐N2), average particle size distribution by dynamic light scattering (DLS), X‐ray diffractometry (XRD), transmission electron microscopy (TEM), and X‐ray fluorescence (XRF) spectroscopy. The material synthesized by the spray pyrolysis technique presented high specific area and pore volume, high crystallinity, homogeneity, and nanometric particles, thus representing a potential technique for the Nb2O5 synthesis.

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Section: Resultsmentioning

confidence: 99%

Section: Crystal Structure Analysismentioning

confidence: 99%

Characterization of niobium pentoxide synthesized by spray pyrolysis technique and comparison with hydrothermal method

de Andrade Schaffner,

Oliveira,

Domingues

et al. 2023

Can J Chem Eng

View full text Add to dashboard Cite

show abstract

“…The alkoxide metal used, formed by the reaction of niobium chloride with ethanol, is highly reactive with nucleophilic reagents when compared with the other precursors [49]. This reactivity determines the structure of the gel and the shape resulting from the oxide, assuming complete hydrolysis and condensation, is typical of the sol-gel synthesis [50]. Figure 1c shows particles with irregular sizes and shapes, large particle aggregates, and few pores, representing the typical morphology of samples obtained by the polymeric precursor (PP) synthesis.…”

Section: Resultsmentioning

confidence: 99%

Multi-Photonic behavior of Nb2O5 and its correlation with synthetic methods

et al. 2021

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The performance of niobium pentoxide (Nb 2 O 5 ) as photoanodes in dye-sensitized solar cells (DSSCs) and as catalysts in the photocatalytic degradation of Rhodamine B (RhB) was investigated. Four samples of Nb 2 O 5 (Nb 2 O 5 _SG, Nb 2 O 5 _CR, Nb 2 O 5 _PP, and Nb 2 O 5 _MA) were synthesized by four different methods, respectively, entailing the sol-gel, combustion, polymeric precursors, and a microwave-assisted hydrothermal reaction. In all these samples, the orthorhombic phase of Nb 2 O 5 was obtained, which resulted in different shapes and assemblies, which is very relevant because the surface area, shape, and size distribution of the nanoparticles significantly contribute to the optical process. The bandgap remained constant at 3.0 eV for all the samples, even for the sample prepared by the combustion method. An additional phase, which is related to local distortions, was revealed by Raman spectroscopy within the vibration range of 688-260 cm -1 . DSSCs using photoanodes with smaller and more dispersed Nb 2 O 5 particles showed better results than those with inhomogeneities. For comparison, DSSCs were assembled using two different counter electrodes, platinum and graphite. The DSSC with platinum showed better photovoltaic results, mainly with photocurrents from 1.17 mA.cm -2 for Nb 2 O 5 _CR to 1.64 mA.cm -2 for Nb 2 O 5 _SG. The same trend was observed for the photocatalytic degradation of RhB, where the smaller and dispersed particles of Nb 2 O 5 _CR and Nb 2 O 5 _SG exhibited the best performance and, respectively, degraded approximately 75% and 61% of the RhB dye over 180 min. Therefore, the results of this study established a correlation between the synthesis methods and photonic behavior.

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“…Porous niobium oxide materials have also been reported, many of which concern the preparation of nanoparticles or films. There are a few reports on the preparation of monolithic niobium oxide materials, ,, whereas there are no reports on the preparation of niobium oxide monolith with ordered macropores to the best of our knowledge. In this Article, the preparation of macroporous niobium oxide monoliths has been demonstrated using a sol–gel process accompanied by phase separation, and effects of heat treatment process on the microstructure and crystalline structure were examined.…”

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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Influence of synthesis parameters on sol–gel transition and physical properties of Nb2O5 mesoporous ambigels

Cited by 10 publications

References 38 publications

Characterization of niobium pentoxide synthesized by spray pyrolysis technique and comparison with hydrothermal method

Characterization of niobium pentoxide synthesized by spray pyrolysis technique and comparison with hydrothermal method

Multi-Photonic behavior of Nb2O5 and its correlation with synthetic methods

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

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