Synthesis and Structural Properties of Niobium Pentoxide Powders: A Comparative Study of the Growth Process

Raba, Angela; Bautista-Ruiz, J.; Joya, M. R.

doi:10.1590/1980-5373-mr-2015-0733

Cited by 121 publications

(55 citation statements)

References 27 publications

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“…XRD diffractograms of mechanochemically synthesized Nb nanocomposites are shown in Figure 2. As observed, S4-Nb2O5 catalyst was the most crystalline sample, with a clear pseudohexagonal structure [39] due to the existence of dominant diffractions peaks at 22.5° (001), 28.3° (180), 36.5° (181), 46.1° (002), 50.5° (380) and 54.8° (212). However, the other prepared catalysts presented polymorphism due to the mixture with other crystalline phases.…”

Section: Morphology Of Nb2o5-polysaccharides Based Nanoparticlessupporting

confidence: 56%

Mechanochemical Preparation of Novel Polysaccharide-Supported Nb2O5 Catalysts

et al. 2019

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Polysaccharides extracted from natural sources can be used as starting material for the preparation of nanoparticle supported composites. A novel family of bio-nanocomposites was mechanochemically synthesized by using niobium oxide and enzymatically produced polysaccharides. The structural, textural and surface properties of nanomaterials, were determined by X-Ray diffraction (XRD), nitrogen adsorption-desorption (N_2 porosimetry), pulse chromatography, infrared spectroscopy (ATR-IR) and dynamic light scattering (DLS). Selective oxidation of isoeugenol to vanillin was carried out to demonstrate the catalytic activity of the Nb-polysaccharides nanocomposites. Interestingly, most of our material showed high conversion of isoeugenol (60-70%) with selectivity to vanillin over 40%. The optimum conversion and selectivity were achieved with a reaction time between 8 and 24 h.Catalysts 2019, 9, 38 2 of 12 activity and selectivity of the catalysts [3,[6][7][8]. Heterogeneous catalysis can therefore be considered a key and priority activity for a Sustainable Chemistry [9].On the other hand, nanotechnology has generated a great scientific interest since allows discovering a multitude of new materials. But also evaluating already known materials from a new point of view. This is the case of metallic nanoparticles. They have been known since antiquity and from which, as early as 1857, Faraday [10] performed a first systematic study, based on the synthesis and properties of colloidal suspensions in catalysis [11]. However, it has been in recent years that most progress has been made in this regard.Nanoparticles (NP) have been studied in recent years due to their high activity, interaction specificity and interesting properties compared to metals (high surface/volume ratio combined with their small sizes) [12][13][14]. The specific properties of NP are directly related to their morphology and size, the dispersion of the metal or metal oxide on the support, the metal loading and the electronic properties of the NP in the material. In addition, NP have the additional advantage of their recyclability and reuse. These are essential and desired properties in many applications of these nanomaterials in catalysis [12,15], sensors [15,16] and even in the field of medicine [12]. There are several methods for the preparation of NP. Some of them include conventional physic-chemical methodologies of impregnation/reduction and coprecipitation [13,15,17], precipitation/deposition [13,15,17,18]. Nowadays more innovating methods have appeared such as photochemical deposition [13,15,17], ultrasonic deposition [13,15,17,18], use of laser treatment [13,15,17], supercritical fluids [13,15,17,19], plasma [13,15,17] or microwave irradiation [13,15,17,20,21].The mechanochemistry is a novel procedure for the production of NP. It consists on the melting, deformation and fracture of a mixture of reactants, normally solid, in a repetitive way during grinding. This reaction takes place at the interface of nanosized particles, those which are being continu...

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Section: Morphology Of Nb2o5-polysaccharides Based Nanoparticlessupporting

confidence: 56%

Mechanochemical Preparation of Novel Polysaccharide-Supported Nb2O5 Catalysts

et al. 2019

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“…For the 90°C sample, it is possible to verify a low‐intensity vibrational mode at 650 cm −1 , indicating lower distortion vibrations of the NbO polyhedra (NbO 6 , NbO 7 and NbO 8 ), which is characteristic in amorphous or low crystallinity samples . As the temperature increases to 500°C, the center of the vibrational mode shifts to 685 cm −1 , due to the increased order of binding of the polyhedra, indicating crystallization in the TT‐Nb 2 O 5 phase . At 550°C, the vibrational mode of 685 cm −1 is more intense, indicating a higher crystallization of TT‐Nb 2 O 5 .…”

Section: Resultsmentioning

confidence: 93%

Investigation of the properties of niobium pentoxide for use in dye‐sensitized solar cells

et al. 2018

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This work demonstrates the obtention of Nb2O5 nanoparticles by the microwave‐assisted hydrothermal synthesis method in a fast way and with the use of low temperatures. The heat treatment applied on the samples promotes the phase change in Nb2O5 from pseudohexagonal to orthorhombic as the temperature increases, with a particle size between 7.3 and 32.6 nm. The band gap of the samples decreases with increasing temperature, obtaining a minimum value of 3.04 eV at 800°C. Dye‐sensitized solar cells (DSSC) were assembled using the Doctor Blade coating technique. The photovoltaic parameters of open‐circuit voltage (Voc) and short‐circuit current density (Jsc) were evaluated. The cells showed a photovoltaic response, demonstrating that Nb2O5 has a semiconductive potential. The DSSC have different characteristics regarding Jsc and Voc, showing that according to the temperature increase in the semiconductor sample, there is a decrease in the photovoltaic parameters of the cells.

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“…The starting precursors were niobium (V) ethoxide, (Nb(OC 2 H 5 ) 5 99.999% Alfa Aesar) and niobium clorure (NbCl 5 99% Sigma-Aldrich). The niobium pentoxide nanostructure materials obtained were calcined at 500 • C, 650 • C and 750 • C for 2 h [19,20].…”

Section: Methodsmentioning

confidence: 99%

“…Structurally isolated NbO 6 octahedra are not efficient luminescent centers [18], whereas isolated distorted niobate groups, such as in LaNbO 4 , where the Nb(V) has a 4 + 2 coordination, provide very efficient centers. The closer the Nb-O-Nb angles are to 180 the more pronounced the effects of the NbO 6 condensation become [16,17,[19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Nano-Particles of Niobium Pentoxide with Orthorhombic Symmetry

Joya

Barba-Ortega

Raba-Páez

et al. 2017

Metals

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Abstract:In this work, a set of nanoparticles of Nb 2 O 5 nanoparticles were grown by both the Pechini and the sol-gel methods. The amorphous materials were calcined at 650 • C or at 750 • C. X-ray diffraction, scanning electron microscopy, luminescence and Raman spectroscopy were used in order to characterize the materials. From the study, it is possible to state that the method of production of nanoparticles, beyond the temperature of synthesis, has a great influence on whether the phase produced is hexagonal or orthorhombic. Additionally, compared to de Sol-gel method, the Pechini method produced samples with smaller particle sizes. The photoluminescence spectra of niobium pentoxide nanostructure materials show that the emission peaks are positioned between 334 to 809 nm and there is a change of intensity which varies depending on the synthesis route used. High pressure Raman spectra at room temperature were obtained from two samples grown by the sol-gel method. Up to 6 GPa, where it is possible to observe the Raman bands, no modification other than the increase of disorder was observed, and this can be associated with a change of phase.

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Synthesis and Structural Properties of Niobium Pentoxide Powders: A Comparative Study of the Growth Process

Cited by 121 publications

References 27 publications

Mechanochemical Preparation of Novel Polysaccharide-Supported Nb2O5 Catalysts

Mechanochemical Preparation of Novel Polysaccharide-Supported Nb2O5 Catalysts

Investigation of the properties of niobium pentoxide for use in dye‐sensitized solar cells

Synthesis and Characterization of Nano-Particles of Niobium Pentoxide with Orthorhombic Symmetry

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