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•Fabrication of Fe2TiO5 ceramic on the TiO2 particles.•Investigation of the optimum pH and calcination temperature of the synthesis.•Evaluation of the phase composition and DRS ...properties.•SAED pattern determination of pseudobrookite structure and TiO2 rutile.•Achieving to the indirect band gap of 1.96 and 2.45 eV for Fe2TiO5 and Fe doped TiO2, respectively.
In the present paper, TiO2/Fe2TiO5 ceramic has been prepared through the reaction between iron (III) hydroxide and dispersed suspension of TiO2 particles. The experiments were done using addition of the ammonia solution into a suspension including dispersed titania particles in FeCl3 solution. Suspensions at different values of pH (2, 3, 5, and 7) were prepared. Consequent calcination of the washed product leads to crystallization of the Fe2TiO5 phase on the surface of titania particles. X-ray diffraction (XRD) results approve the formation of pseudobrookite Fe2TiO5 at 1000 °C. The rising of the suspension pH value from 5 to 7 cause to formation of Fe2O3 due to increasing the hydrated iron. Transmission electron microscopy (TEM) results approve the existence of pseudobrookite structure Fe2TiO5 beside the TiO2 with the rutile structure. According to the UV–Vis diffuse reflectance spectra (UV-DRS) and Kubelka-Munk method, the synthesized sample at pH = 5 and consequent calcination at 1000 °C has two direct band gap energies of 2.28 and 2.93 eV that are related to the Fe2TiO5 coating and TiO2 support, respectively.
A novel compositionally-complex flexible (Mg0.2Al0.2Fe0.2Ni0.2Co0.2)2Ti2.8O8 (abbreviated as CCC) ceramic with pseudobrookite structure was synthesized by solid-state reaction method. As compared to ...the fabrication process of flexible aluminum titanate ceramic (C. Babelot, 2011), the sintering temperature was significantly reduced from 1600 °C to 1200 °C by co-doping. And, the combinations of displacement (0.11–0.25 mm) and bending strength (10–40 MPa) were achieved by controlling the sintering condition. Among these, the specimen sintered at 1200 °C for 2 h (abbreviated as CCC-1200-2) presents a single-phase crystal structure and uniform elemental distribution. After that, its near-zero thermal expansion coefficient of 0.47 × 10−6 K−1 at low temperature was obtained and the nonlinear thermal expansion behavior was observed. Lastly, the thermal stability of sample CCC-1200-2 was checked out by annealing the samples between 900 °C and 1600 °C for various times up to 100 h. As a result, this study successfully fabricated the flexible CCC ceramics with improved mechanical properties, high thermal stability, and low sintering requirements, providing a new technology strategy for pseudobrookite-type ceramics and compositionally-complex ceramics fabrication.
•Flexible (Mg0.2Al0.2Fe0.2Ni0.2Co0.2)2Ti2.8O8 was successfully synthesized by compositionally complex ceramics method.•The sintering temperature was significantly reduced from 1600 °C to 1200 °C by co-doping.•The as-synthesized samples exhibit excellent thermal stability and mechanical properties.•Near-zero thermal expansion coefficient of 0.47 × 10−6 K−1 was obtained and nonlinear thermal expansion behavior was observed.
We propose the pseudobrookite Fe2TiO5 nanofiber with abundant oxygen vacancies as a new electrocatalyst to ambiently reduce nitrate to ammonia. Such catalyst achieves a large NH3 yield of 0.73 mmol ...h−1 mg−1cat. and a high Faradaic Efficiency (FE) of 87.6 % in phosphate buffer saline solution with 0.1 M NaNO3, which is lifted to 1.36 mmol h−1 mg−1cat. and 96.06 % at −0.9 V vs. RHE for nitrite conversion to ammonia in 0.1 M NaNO2. It also shows excellent electrochemical durability and structural stability. Theoretical calculation reveals the enhanced conductivity of this catalyst and an extremely low free energy of −0.28 eV for nitrate adsorption at the presence of vacant oxygen.
Pseudobrookite Fe2TiO5 nanofiber with oxygen vacancies is proposed as an efficient electrocatalyst for reducing nitrate to ammonia, which achieves a large NH3 yield of 0.73 mmol h−1 mg−1cat. and a high Faradaic efficiency of 87.6 %. It also shows excellent electrochemical durability and structural stability. Theoretical calculations reveal its high electrical conductivity and extremely low free energy for nitrate adsorption.
High‐entropy ceramics exhibit various excellent properties owing to their high configurational entropy, which is caused by multi‐principal elements sharing one lattice site. The configurational ...entropy will further increase significantly if multi‐principal elements randomly share two different lattice sites. For this purpose, pseudobrookite phase containing two cationic lattice sites (A and B sites) is selected, and corresponding high‐entropy pseudobrookite (M2+0.4M3+1.2)Ti1.4O5 is synthesized. Herein, the distribution of the 2‐valent and 3‐valent cations in the A and B sites are analysed in depth. The distance between the A and B sites in the crystal structure models which are constructed by the Rietveld analysis is calculated and defined as distance d. Meanwhile, the atomic column positions in the STEM images are quantified by a model‐based mathematical algorithm, and the corresponding distance d are calculated. By comparing the distance d, it is determine that the 2‐valent and 3‐valent cations are jointly and disorderly distributed in the A and B sites in high‐entropy (M2+0.4M3+1.2)Ti1.4O5. The density functional theory (DFT) simulations also demonstrate that this type of crystal structure is more thermodynamically stable. The higher degree of cationic disorder leads to a higher configurational entropy in high‐entropy (M2+0.4M3+1.2)Ti1.4O5, and endows high‐entropy (M2+0.4M3+1.2)Ti1.4O5 with very low thermal conductivity (1.187−1.249 W m−1 K−1).
New high‐entropy ceramics (M2+0.4M3+1.2)Ti1.4O5 with multi‐principal cations sharing two different cationic lattice sites together are synthesized. The degree of cationic disorder and the configurational entropy are analyzed and compared by constructing the crystal structure models, quantifying the atomic column positions in the STEM images, and the density functional theory simulations.
Fe2(Ti1-xNbx)O5 (x=0, 0.005, 0.01, 0.02, 0.05) pseudobrookite with high relative densities have been prepared by solid state reaction and conventional sintering. The solubility of Nb in Fe2TiO5 is ...low, in between x=0.01 and 0.02. Introducing Nb into Fe2TiO5 within the solubility limit improves the electrical conductivity and decreases the absolute value of the Seebeck coefficient. Small polaron hopping model is applied to explain the electrical conduction of Fe2(Ti1-xNbx)O5, as verified by the linear fit of the electrical conductivity and the temperature independent Seebeck coefficient above approximately 600K. All compositions show low thermal conductivity, about 1–1.5Wm−1K−1 from 673K to 1000K. It is found that similar ZT value (∼0.006) is obtained for Fe2(Ti1−xNbx)O5 with x=0.01 and 0.02 at 1000K.
Pseudobrookite, Fe2TiO5, precursor films were obtained by spray pyrolysis (SP) at 550 °C on fused silica and FTO (F-doped tin oxide on borosilicate glass) using iron (III) acetylacetonate (FeAcAc) ...and titanium diisopropoxide bis(acetylacetonate) (DIPTiAcAc) in methanol. SP was followed by annealing in air from 600 °C to 1000 °C for various durations, and for T ≥ 750 °C, phase pure pseudobrookite was obtained. (Photo)electrochemical experiments of Fe2TiO5 electrodes in junctions with aqueous electrolytes showed n-type behaviour of the material with a maximum photocurrent of 0.35 mA/cm2 under simulated AM1.5 sunlight. A valence band energy between 6.6 and 6.8 eV was estimated using the electrochemical results. The position of the Fe2TiO5 valence band enables the passage of (photogenerated) holes in hematite into a pseudobrookite layer and further on towards an electrolyte, if a hematite/pseudobrookite stratified film would be applied in a solid / liquid junction. The valence band potential is not positive enough for producing OH· radicals, only solvent oxidation and reactions which do not require OH· radicals can proceed.
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•Fe2TiO5 precursor films were synthetized by spray pyrolysis on fused silica and FTO.•For obtaining phase pure material, annealing in air for 60 h at temperature ≥ 750 °C was necessary.•Fe2TiO5 showed n-type behaviour with a photocurrent of 0.35 mA/cm2 (1 sun).•The position of the valence band enables the passage of holes from hematite into Fe2TiO5.
Phase equilibria of Al2O3–TiOx system were experimentally determined in a wide range of T and PO2: 1300 °C ≤T≤ 1600 °C and −16.6≤logPO2≤−8.0 (in atm). X-Ray diffraction and electron probe ...micro-analysis were employed to obtain equilibrium phases and compositions. Corundum (Al2O3 with limited Ti2O3), rutile (TiO2 with limited Al2O3), and pseudobrookite (Al2TiO5–Ti3O5) solid solutions were found. The liquid oxide phase was not found up to 1650 °C. At each temperature, the cationic ratio of the pseudobrookite solid solution (RTi = nTi/(nAl + Ti)) increased as PO2, thereby forming a wide range of solid solution from Al2TiO5 (RTi = 1/3) to Ti3O5 (RTi = 1.0). The pseudobrookite solid solution was a complete miscible solution at 1600 °C, while it exhibited a small miscibility gap at 1500 °C. Based on the results obtained in the present study, the behavior of Al2TiO5 was discussed in two aspects: (1) changes in physical properties and (2) evolution of Al–Ti complex oxide inclusions in liquid steel.
CrxFe2-xTiO5 compositions of the solid solutions series from pseudobrookite Fe2TiO5 to monoclinic Cr2TiO5 have been prepared by the ceramic route and gel methods. At 1400 °C, pseudobrookite ...crystallizes in the x = 0–0.4 range, both pseudobrookite and monoclinic Fe-Cr2TiO5 coexist at x = 0.5, while in the range x = 0.7–1.5 monoclinic Fe-Cr2TiO5 crystallizes. Powders were 5 wt% glazed within a double-firing frit and the composition with x = 0.1 fired at 1000 °C exhibits the best red color (L*a*b* = 43.2/18.8/12.5), showing an intense band at 520 nm in the UV–Vis–NIR absorption spectrum associated with Cr4+ in octahedral coordination. The unit cell volume of the pseudobrookite decreases smoothly with the chromium amount, associated with the entrance of Cr4+ replacing Ti4+, while the volume of the Fe-Cr2TiO5 unit cell increases with the entrance of Fe3+ replacing Cr3+. The use of flux agents, the compaction pressure and the gel methods increase the crystallization of pseudobrookite but do not improve the reddish color, which is associated with the concentration of Cr4+ in the pigment. The optimized pigment composition Cr0.1Fe1.9TiO5 also shows a high NIR reflectance (55% in powder, 54% in glazed sample).
Heterogeneous photocatalysis is an attractive alternative route to enhance the degradation of environmental pollutants. In this work, we have fabricated Fe2TiO5/TiO2 binary nanocomposites using ...natural ilmenite via bottom up approach. Synthesized nanocomposites were characterized by X-ray diffractometry, X-ray fluorescence, transmission electron microscopy, Raman spectroscopy, diffuse reflectance UV–Visible spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. These nanoparticles are in the range of 40–70 nm and are of type I heterostructure with a band gap of 2.02 eV. They are sensitive to visible light and show higher photocatalytic activity under direct solar energy. Photocatalytic activity of Fe2TiO5/TiO2 was assessed using a model textile dye, methylene blue. Over a period of 2 h, 76% of methylene blue was photodegraded at a rate of 0.0084 min−1 in the presence of Fe2TiO5/TiO2.
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•Fe2TiO5/TiO2 binary nanocomposite is successfully synthesized by using natural ilmenite as the raw material.•Synthesized binary nanocomposite is of type I heterostructure.•The synthesized nanocomposite is efficient in photodegrading methylene blue under sunlight.
Renewable energy production from diverse sources (such as solar, wind) is essential for achieving a sustainable and CO2-free society within a short duration. Green hydrogen is regarded as the most ...feasible fuel for the next generation of fuel-cell electric vehicles and associated technologies. Solar water splitting is a promising strategy for green hydrogen production because it is based on renewable sources with the potential to minimize the power costs in the production of H2 via electrolysis, which presents significant barriers. Iron titanate (Fe2TiO5), a visible-light-active photocatalyst, has emerged as a possible material for designing the next generation of water splitting photoelectrodes, as it is a low-cost, plentiful, and non-toxic oxide with favorable electronic, optical, and chemical properties for this application. This review summarizes recent advances in the use of Fe2TiO5 as a semiconducting material for solar water splitting applications, covering single photocatalytic systems and heterostructures such as Fe2TiO5/TiO2, Fe2TiO5/BiVO4, and Fe2TiO5/Fe2O3. Furthermore, this perspective review discusses and highlights strategies for developing effective Fe2TiO5 based water-oxidation materials.
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