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An electrothermal analysis for barium-titanate-based ceramics is presented, combining the Heywang–Jonker model for the electric resistivity with a heat dissipation mechanism based on natural convection and radiation in a one-dimensional model on the device level with voltage as the control parameter. Both positive-temperature-coefficient (PTC) and negative temperature coefficient (NTC) effects are accounted for through the double Schottky barriers at the grain boundaries of the material. The problem formulated in this way admits uniform and non-uniform multiple-steady-state solutions that do not depend on the external circuit. The numerical bifurcation analysis reveals that the PTC effect gives rise to several multiplicites above the Curie point, whereas the NTC effect is responsible for the thermal runaway (temperature blowup). The thermal runaway phenomenon as a potential thermal shock could be among the possible reasons for the observed thermomechanical failures (delamination fracture). The theoretical results for the NTC regime and the thermal runaway are in agreement with the experimental flash sintering results obtained for barium titanate, and 3% and 8% yttria-stabilized zirconia.

Leucoxene-quartz concentrate is a large-tonnage by-product of development of the Timan oil-titanium field (oil-saturated sandstones) which is not commercially used at present. High content of titanium compounds (to 50 % by weight) and lack of industrial, cost-effective, and safe technologies for its processing determine a high relevance of the work. Conventional processing technologies allow increasing the concentration of TiO2, but they are only a preparation for complex and hazardous selective chlorination. The process of pyrometallurgical conversion of leucoxene-quartz concentrate into aluminium and magnesium titanates was investigated. It was ascertained that the temperature of solid-phase reaction in Al2O3-TiO2-SiO2 system necessary for the synthesis of aluminium titanate (Al2TiO5) is 1,558 °С, and for MgO-TiO2-SiO2 system – 1,372 °С. Scaling up the process made it possible to synthesize a significant number of samples of titanate-containing products, the phase composition of which was studied by X-ray phase analysis. Two main phases were identified in the products: 30 % aluminium/magnesium titanate and 40 % silicon dioxide. In products of pyrometallurgical processing in the presence of aluminium, phases of pseudobrookite (3.5 %) and titanite (0.5 %) were also found. It was ascertained that in magnesium-containing system the formation of three magnesium titanates is possible: MgTiO3 – 25, Mg2TiO4 – 35, MgTi2O5 – 40 %. Experiments on sulphuric acid leaching of samples demonstrated a higher degree of titanium compounds extraction during sulphuric acid processing. An integrated conceptual scheme for processing leucoxene-quartz concentrate to produce a wide range of potential products (coagulants, catalysts, materials for ceramic industry) was proposed.

Advanced ceramic breeder (ACB) pebbles consisting of the two phases Li4SiO4 and Li2TiO3 serve as the EU reference tritium breeding material. In the present study, the phase stability with regard to a lithium-burn-up is investigated. The loss of lithium due to its transmutation will lead to a compositional change of the breeder material. Li4SiO4 and Li2TiO3 will partly be transformed to the lithium-poorer phases Li2SiO3 and Li4Ti5O12, respectively. However, from the phase diagram it is anticipated that only Li2SiO3 will occur as a third phase after a lithium burn-up as the generated Li4Ti5O12 is expected to further react with Li4SiO4 to form again Li2TiO3 and more Li2SiO3. Therefore, the reaction between Li4SiO4 and Li4Ti5O12 and its temperature dependence were investigated in detail and its reaction kinetics were determined. It was found that this diffusion-controlled reaction with an activation energy of 75 kJ/mol (0.78 eV) will slow down at low irradiation temperatures and may not take place at very low temperatures.

Outstanding materials and novel device structures are key factors in satisfying the increasing demand for energy storage. Li‐ion capacitors, as one typical model of asymmetric supercapacitors, benefit from the battery's ultrahigh specific energy and supercapacitor's superlarge specific power to meet the balanced electrochemical energy storage requirements. The inherent and irreplaceable advantages make spinel lithium titanate an optimal candidate for power batteries and Li‐ion capacitors. However, upstream market volatility, including price spikes and supply shortages, tremendously threatens spinel lithium titanate's production, sale, and application. Lithium hydroxide hydrate is an alternative raw material to synthesize spinel lithium titanate synthesis, which can help address these concerns. The indirect production path generates high‐quality lithium carbonate as an intermediate product. Spinel lithium titanate is synthesized preferably via another economically and technically more efficient method that skips the isolation step after carboxylation. The electrochemical performance of the resulting spinel lithium titanate is evaluated to be better than that of commercial competitors. The spinel lithium titanate negative electrode‐based lithium‐ion capacitor achieves a specific energy of 89.5 Wh kg−1. These results demonstrate the success of efforts to find a feasible and affordable synthesis route to mitigate market risks.

In the present study, a numerical bifurcation analysis of a PTC thermistor problem is carried out, considering a realistic heat dissipation mechanism due to conduction, nonlinear temperature-dependent natural convection, and radiation. The electric conductivity is modeled as a strongly nonlinear and smooth function of the temperature between two limiting values, based on measurements. The temperature field has been resolved for both cases were either the current or the voltage (nonlocal problem) is the controlling parameter. With the aid of an efficient continuation algorithm, multiple steady-state solutions that do not depend on the external circuit have been identified as a result of the inherent nonlinearities. The analysis reveals that the conduction–convection parameter and the type of the imposed boundary conditions have a profound effect on the solution structure and the temperature profiles. For the case of current control, depending on the boundary conditions, a complex and interesting multiplicity pattern appears either as a series of nested cusp points or as enclosed branches emanating from pitchfork bifurcation points. The stability analysis reveals that when the device edges are insulated, only the uniform solutions are stable, namely, one “cold” and one “hot”. A key feature of the “hot” state is that the corresponding temperature is proportional to the input power and its magnitude could be one or even two orders of magnitude higher than the “cold” one. Therefore, the change over from the “cold” to the “hot” state induces a thermal shock and could perhaps be the reason for the mechanical failure (delamination fracture) of PTC thermistors.

In this work the band gap for a set of titanium oxide photocatalysts: TiO2 (rutile, brookite, anatase), SrTiO3, BaTiO3, CaTiO3, MgTiO3, KLaTiO4, K2La2Ti3O10, was theoretically investigated within density functional theory. For the PBE-based hybrid functional the band gap as a function of the fraction of the Hartree-Fock exchange energy (α) was calculated. A correlation between the Goldschmidt tolerance factor and the value of α parameter, that provides an agreement with the experimental band gap, was determined. A wide range of standard hybrid functionals was tested. It was found that the B1WC and WC1LYP hybrid functionals (with α = 0.16) provide the best agreement with experimental data for the set of studied compounds. However, for a more accurate description of the band structure of titanium oxide photocatalysts the α parameter should be chosen accounting for the structural distortion of TiO6 octahedra and their mutual arrangement. The results obtained can be used in predicting the properties of modified structures based on titanium oxides.

This work presents the synthesis by the new ‘firing salts method’ (FSM) of orthorhombic Gd _2 TiO _5 which requires only two hours at 1200 °C. X Ray Diffraction, High Resolution Transmission Electron Microscopy, Fourier Transform Infrared Spectroscopy and Raman spectroscopy characterized it. Electron microscopy shows particle size distribution between 50–500 nm with orthorhombic structure according to Rietveld analysis. Raman—infrared spectroscopies and first principles calculations indicate that the second order contribution to the spectra comes from the Ti-O5 interactions. First principles calculations (Density Functional Theory) were used as an aid for the interpretation of the experimental results to assign the normal modes to the bands on the Raman and IR spectra; it also provided an insight of the chemical reactivity of the synthesis.

This paper investigated the synthesis of inorganic polymer composites for electromagnetic radiation absorption using potassium titanates. The selected polyamide 6 and potassium polytitanate materials contain TiО2, K2СО3, and KCl obtained by charge sintering. Results showed that modification of polyamide 6 with sintering products in the form of a fine powder of potassium polytitanate that contains different phases K2O × 2TiO2, K2O × 4TiO2, and K2O × 6TiO2 which increased their strength properties. With increased potassium titanates (PTT) synthesis, a gradual transition from di to potassium hexatitanates occurs K2O × 2TiO2 – K2O × 4TiO2 – K2O × 6TiO2. The optimal content of potassium polytitanate was over 20 % by mass. To fully ensure the reinforcing effect due to the filling of potassium polytitanate polyamide 6, it is necessary to use whiskers K2O × 6TiO2, which can be collected by the additional crystallization of the amorphous charge sintering product. By designing experimental-statistical mathematical models in equal regressions, mathematical optimization of inorganic polymer composites for electromagnetic radiation absorption using PTT was carried out.

Porous CoxNi1-xTiO3 nanorods were successfully synthesized through a solution-based method following an ethylene glycol route at room temperature. The effect of calcination temperature from 300 °C to 900 °C for NiTiO3 and CoTiO3 nanorods was studied using X-ray diffractometry and scanning electron microscopy in order to investigate their structural and morphological properties. The optimum calcination temperature to prepare pure ilmenite type structure rods with high crystallinity and hexagonal shape was 600 °C. Co0.5Ni0.5TiO3 exhibited the highest photocatalytic activity for the degradation of ethyl paraben, an endocrine disrupting compound, under simulated solar or visible light irradiation. Nearly complete (i.e. 92%) paraben degradation occurred after 5 h of solar irradiation and this decreased to 48% when only the visible part of the radiation was employed. The solar photocatalytic activity of CoTiO3 and NiTiO3 was found to be 42% and 67%, respectively.

The aim of this study was to explore the influence of various n-propylamines (mono, di, and tri) and tert-butylamine on the properties of prepared peroxo-titanates and annealed TiO2. Detailed structural characterization (SEM, TEM with EDX, XRD) confirmed the 2D-foil morphology of TiO2 nanocrystals and the CHNS analysis together with XPS showed presence of carbon (under 1 wt%). The annealed TiO2 showed excellent photocatalytic activity and up to four times higher decomposition rate constant upon UV irradiation than the P25. Favourable growth of TiO2 crystals was observed especially when propylamine and tert-butylamine were used (as precursors for the peroxo-titanates). Increased photocatalytic efficiency of the highly crystalline nano-TiO2 was confirmed due to high-reactive anatase facets and the morphology composed of microsheets formed by interconnected nanocrystals. The photoinduced electron transfer was confirmed via EPR spectroscopy. This synthesis’ procedure offers a novel preparation method of highly photoactive C-doped TiO2 achieved relatively easily after annealing of lyophilized amino-peroxo-titanate.

It is shown that the potassium polytitanate powder (PPT) synthesized at 500 °C via the treatment of powdered TiO2 (rutile) in molten mixtures of KOH and KNO3 is a cheap and effective catalyst of H2O2 chemical decomposition in aqueous solutions. At the same time, the PPT catalytic activity strongly depends on the [TiO2]:[KOH]:[KNO3] weight ratio in the mixture used for the synthesis, increasing with [KNO3] in the order of PPT (30:30:40) < PPT (30:50:20) < PPT (30:70:0). The obtained results are explained by increased [Ti3+] in the PPT structure (XPS data), which is grown in this order from 0 to 4.0 and 21.9 at.%, respectively, due to the reduced oxidation activity of the melt used for PPT synthesis. The mechanism of the autocatalytic process taking place in the PPT-H2O2-H2O system is analyzed. Taking into account the data of FT-IR spectroscopy, it is assumed that the increased catalytic activity of the investigated materials is related to the increased surface concentration of the Ti4+-O(H)-Ti4+ groups, formed from the Ti3+-O(H3O+)-Ti4+ clusters and further transformed into Ti-O-O-H catalytic centers. Some possible applications of the PPT-H2O2-H2O catalytic system, including the oxidation processes of green chemistry and photo-catalysis, are discussed.

The bottleneck in the implementation of hybrid lithium-sodium-ion batteries is the lack of anode materials with a desired rate capability. Herein, we provide an in-depth examination of the Li-storage performance of sodium titanate nanowires as negative electrodes in hybrid Li,Na-ion batteries. Titanate nanowires were prepared by a simple and reproducible hydrothermal method. At a low reaction pressure, the well-isolated nanowires are formed, while by increasing the reaction pressure from 2 to 30 bar, the isolated nanowires tend to bundle. In nanowires, the local coordinations of Na and Ti atoms deviate from those in Na2Ti3O7 and Na2Ti6O13 and slightly depend on the reaction pressure. During the annealing at 350 °C, both Na and Ti coordinations undergo further changes. The nanowires are highly defective, and they easily crystallize into Na2Ti6O13 and Na2Ti3O7 phases. The lithium storage properties are evaluated in lithium-ion cells vs. lithium metal anode and titanate electrodes fabricated with PVDF and carboxymethyl cellulose (CMC) binders. The Li-storage by nanowires proceeds by a hybrid capacitive-diffusive mechanism between 0.1 and 2.5 V, which enables to achieve a high specific capacity. Sodium titanates accommodate Li+ by formation of mixed lithium-sodium-phase Na2−xLixTi6O13, which is decomposed to the distinct lithium phases Li0.54Ti2.86O6 and Li0.5TiO2. Contrary to lithium, the sodium storage is accomplished mainly by the capacitive reactions, and thus the phase composition is preserved during cycling in sodium ion cells. The isolated nanowires outperform bundled nanowires with respect to rate capability.

3D ordered superstructures of mesocrystalline NH4TiOF3 and (NH4)2TiOF4 are synthesized via in-situ evolution from anodic TiO2 nanotube arrays grown on the Ti metal substrate under high current density. As revealed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy characterizations, the obtained NH4TiOF3 and (NH4)2TiOF4 mesocrystals consist of well aligned nanoparticle subunits at atomic level and can be converted to TiO2 (anatase) mesocrystals with their original exterior shapes retained upon thermal annealing. Close examination suggests that NH4TiOF3 and (NH4)2TiOF4 mesocrystals form via a nonclassical crystal growth process involving fast oriented aggregation of particles assisted by electric field-dipole interaction.

The barrier properties of a capacitor heterostructure based on a ferroelectric lead zirconate-titanate were investigated by using the methods of current-voltage and voltage-capacitance characteristics. The variable values of the potential barrier on the PZT-Pt interface were determined by the C-V method (from 0.5 to 1.6 eV) and the I-V method (from 0.5 to 0.7 eV). The spontaneous polarization influence on the potential barrier at the PZT-Pt interface was estimated.

Abstract The quantum of research in the area of supercapacitors is typically focused on the electrode materials. As such, there are many opportunities for the optimization of the other components, such as the separators, to further increase the power, efficiency, and longevity of supercapacitors. To contribute to this field of research, we present an innovative alternative for the fabrication of separators; using polymer/ceramic composites (PCC) based on polyvinylidene fluoride (PVDF) and polypropylene (PPG) mixed with different alkaline earth metal‐based titanates (eg barium, calcium, and strontium). The PCC separators were prepared via phase inversion precipitation technique, a feasible and scalable method for the fabrication of these composites. Different additives were used to modulate the porosity and thus, improve the charge transfer rates. Then, a heating process ensured a uniform organization of the composites. Furthermore, we tested the effect of thermally annealing the ceramics on the separators’ performance. The precursor materials and the PCC's were extensively characterized by means of X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical, mechanical, and dielectric properties of the PCC's were measured and compared to common commercial separators used today. Results suggest that thermal treatment improves tensile strength of the separators by at least ca. 60% without compromising the similar electrochemical profile to the commercial separators (44.52 ± 2.82 Ω vs 67.65 ± 29.01 Ω). Lastly, all of the fabricated PCC's showed higher dielectric constants (4.52 in average for the as prepared separators and 2.99 for the heated PCC's) than the polymer based commercial separators (2.2).

Bimetallic oxides are demonstrated to show better electrochemical performance than single transition metal oxides. Recently, ilmenite-type transition metal titanate (MTiO3, M = Fe, Co, Ni, etc.) is emerging as a promising anode for lithium-ion batteries (LIBs) due to its comparable theoretical capacity and small volumetric change during cycling. However, the practical electrochemical performance is still harmed by its poor electronic conductivity. Herein, for the first time, a Nb-doping strategy is adopted to modify CoTiO3 hexagonal microprisms by a facile solvothermal method combined with an annealing treatment. Benefiting from the unique 1D morphology and the ameliorated conductivities induced by Nb-doping, the optimized Nb-doped CoTiO3 anode exhibits an improved lithium-storage capacity of 233 mA h g−1 at 100 mA g−1 after 100 cycles and excellent rate capability, which are superior to that of pure CoTiO3. This work sheds light on the potential application of titanium containing bimetallic oxide in the next-generation advanced rechargeable LIBs.

Zinc titanates are compounds that have shown great application versatility, including in the field of semiconductors. Solid state reactions, the polymeric precursor method and the hydrothermal method are the most mentioned synthesis of these compounds in the literature. In the present work, we use microwave assisted hydrothermal method (MAH) to synthesize zinc titanate and evaluate its potential for solar cell applications through structural and optical characterization techniques. The synthesized samples were also subjected to a variable temperature heat treatment in the range of 500 °C–800 °C. The analysis showed that the crystallization of the material starts at 500 °C and that samples submitted to temperatures of 600 °C–800 °C showed the formation of two phases of zinc titanates, being a cubic phase of ZnTiO3, considered rare in the literature, predominant up to a temperature of 800 °C. The optical characterization, based on the techniques of photoluminescence spectroscopy and UV-Visible spectroscopy, showed that the photoluminescent activity and the energy of the band gap increased with the increase of the temperature of the heat treatment, having the highest response in 700 °C, facts that can be linked to the predominant formation of the cubic phase of ZnTiO3 and simultaneous of the cubic and rhombohedral phases of ZnTiO3 at 700 and 800 °C. Finally, we highlight as the most important results, the fact that it was possible to obtain these titanates at a temperature lower than that reported in the literature, and that the heat-treated sample at 500 °C is the one with the lowest energy expenditure to be synthesized and the one with the greatest potential for application in dye-sensitized solar cells (DSSC's).

Abstract By combining the hydrothermal and pulsed laser deposition methods, several three‐dimensional Pt catalysts on TiO2 structures are prepared and used for the electro‐oxidation of ethanol in acidic medium. SEM reveals that TiO2 prepared with 0.6 M of HCl consist of a mixture of nanowires and nanorods. For higher HCl concentrations, the TiO2 are either in the form of vertically aligned bars or large branched crystals in the form of flowers‐like. Despite having the same loading of Pt, among the 3D Pt/TiO2/Ti structures, only those with TiO2 prepared with 0.6 M of HCl shows a higher area specific activity and current mass activities exceptionally superior of about >50 times than those of unsupported Pt/Ti catalyst toward ethanol oxidation reaction, which suggests a promising application in ethanol fuel cells.

Dielectric permittivity (ε′), magnetic permeability (µ′) and dielectric and magnetic loss (tan δε and tan δµ, respectively) of magneto-dielectric cobalt ferrite-titania (CFO-TO) ceramic composites are determined from 200 to 300 MHz. The four different combinations of phases - that can be produced in the sintered composite, according to the starting CFO/TO molar ratio - allow to tune the macroscopic permittivity and permeability. For the first time impedance, miniaturization and magneto-dielectric loss of the four classes of composites are calculated and discussed. The displayed miniaturization factors between 4.4 and 8.2 in the very-high frequency (VHF) range corroborate their potential application as magneto-dielectric substrate materials for antennas. Remarkably, the ceramic composites characterized by 2 vol.% and 3 vol.% of CFO and TO, respectively, dispersed in Fe2CoTi3O10 (FCTO) matrix display a magneto-dielectric loss lower than 0.07 and a miniaturization factor of 4.8.

Zinc titanates nanopowders viz.; Zn _2 TiO _4 , ZnTi _3 O _8 and ZnTiO _3 were synthesized through the thermal decomposition course of ZnC _2 O _4 .2H _2 O-TiO _2 precursors mixture (1:1 mole ratio), prepared via a new co-precipitation method up to 900 °C. Thermogravimetric measurement (TG) was utilized to characterize the precursors mixture decomposition while x-ray diffraction (XRD), Fourier transform infra-red (FT-IR) were used to characterize the decomposition products as well as the phase transitions at different temperatures. XRD revealed the starting of titanates formation at 700 °C via detecting Zn _2 TiO _4 along with ZnO and TiO _2 (anatase) diffraction peaks. By increasing the calcination temperature to 800 °C, the ZnO content vanished with the appearing of Zn _2 Ti _3 O _8 besides ZnTi _2 O _4 and impurities of TiO _2 (anatase). Finally at 900 °C, the Zn _2 Ti _3 O _8 content was decomposed into ZnTiO _3 . Nitrogen adsorption-desorption isotherm of the calcined precursors mixture at 900 °C indicated low specific surface area of 7.1 m ^2 g ^−1 in accordance with the agglomeration nature estimated via transmission electron microscopy (TEM) study. The conductivity measurements showed semiconducting behavior of the prepared titanates with ferroelectric transition in the range 200 °C–308 °C. The obtained low dielectric value suggests the uses of present titanates as a co-fired ceramic or resonator ceramics.

The increasing air pollution taking place in virtue of human activity has a novel impact in our health. Heterogeneous photocatalysis is a promising way of degrading volatile organic compounds (VOCs) that makes the quest of new and improved photocatalysts of great importance. Herein, perovskite-related materials ATiO3 with A = Mg, Ni, Co, Zn were synthesized through an ethylene glycol-mediated root, with ethylene glycol being used as a solvent and ligand. Characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy, and energy dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), UV-vis spectroscopy, Raman spectroscopy, Fourier transform infrared (FT-IR), and photoluminescence spectroscopy (PL) were used in order to confirm the structure, the nanorod morphology, their absorption in UV-vis, and the separation efficiency of photogenerated charge carriers. The highest photoactivity was observed for ZnTiO3 in which 62% of toluene was decomposed after 60 min under LED illumination (54 mW/cm2).

In the present work, we report the results on exfoliation and coating formation of inorganic–organic hybrids based on the layered perovskite-like bismuth titanate H2K0.5Bi2.5Ti4O13·H2O that could be prepared by a simple ion exchange reaction from a Ruddlesden–Popper phase K2.5Bi2.5Ti4O13. The inorganic–organic hybrids were synthesized by intercalation reactions. Exfoliation into nanosheets was performed for the starting hydrated protonated titanate and for the derivatives intercalated by n-alkylamines to study the influence of preliminary intercalation on exfoliation efficiency. The selected precursors were exfoliated in aqueous solutions of tetrabutylammonium hydroxide using facile stirring and ultrasonication. The suspensions of nanosheets obtained were characterized using UV–vis spectrophotometry, dynamic light scattering, inductively coupled plasma spectroscopy, and gravimetry. Nanosheets were coated on preliminarily polyethyleneimine-covered Si substrates using a self-assembly procedure and studied using atomic force and scanning electron microscopy.

The Bi4–xPrxTi3O12 (BPT) solid solutions (x = 0.05, 0.10, 0.15) with small praseodymium content were prepared by solid-state method. Thermal, electric, and dielectric properties of BPT were studied. It was revealed that BPT titanates crystalize in аn orthorhombic structure and exhibit p-type semiconductivity. Dielectric constant of BPT increased, Curie temperature (TC), electrical conductivity and dielectric losses decreased, but lattice parameters and thermo-EMF coefficient remained practically unchanged with the increase of praseodymium content in layered Bi4–xPrxTi3O12. It was determined that activation energy of direct current (DC) electrical conductivity and linear thermal expansion coefficient (LTEC) of BPT changes at ferroelectric (FE) → paraelectric (PE) phase transition. The activation energy and LTEC changed below and above TC from 1.08–1.56 eV to 0.45–0.86 eV and from (9.10–10.80)×10–6 K–1 to (13.12-14.61)×10–6 K–1, respectively. The AC electrical conductivity studies of BPT illustrated short-range order with ionic translations assisted by small-polaron hopping.

Novel glycolate precursors to metal titanates MTiO3 (M = Ni2+, Co2+, Zn2+) were synthesized by heating metal acetate and titanium isopropoxide in ethylene glycol up to 190 °C during distilling the water to avoid hydrolysis of precursors. These glycolate precursors were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), thermal analysis (TG-DTA), and scanning electron microscopy (SEM). The obtained three isostructural glycolate precursors were containing metal (Ni, Co, Zn), titanium, and ethylene glycol with a ratio of 1:1:4. The crystal growth processes of three precursors were different from each other. These precursors revealed homogeneous and well-defined rod-like structure with 0.5–3.0 μm in thickness and 4–20 μm in length. The obtained metal titanates were consisted of microrods with 0.4–1.5 μm in thickness and 2–15 μm in length.

This work reports the synthesis of a variety of materials with an ilmenite-type structure MTiO3 formula, where M= Fe, Co, and Ni, these materials were synthesized by the method of solvo-combustion, a simple and rapid method. These materials were characterized by X-ray Diffraction (XRD), scanning electron microscopy (SEM), FT-IR spectroscopy, thermogravimetric analysis (TGA/DTA), surface area determination by the BET method and analysis of particle size. The photocatalytic activity was measured in the degradation reactions of Rhodamine B (rhB) and tetracycline (TC). The results show that the crystallinity and surface area are factors that influence significantly on the photocatalytic activity of the synthesized titanates.

The aim of this work is focused on the study of a series of non-traditional catalytic nanomaterials to transform greenhouse CO2 gas into added-value products. We found encouraging results of CO2 hydrogenation activity over sodium titanates with different morphologies. The yield to methanol increases with the increase in the Na incorporated in the nanostructures confirming the proposed mechanism. Samples were prepared at different times of hydrothermal treatment (HTT) with NaOH solutions, and these materials were labeled as Ti-nR-x with x as the hours on the HTT. HRTEM initially showed sphere-shaped nanoparticles in the TiO2 commercial nanopowder, increasing the HTT resulted in morphological changes in which the structures passed from nanosheets and finally to nanorods after 30 h. The X-ray diffraction and Raman spectroscopy results indicated the formation of sodium titanates such as Na2Ti3O7 with short Ti-O bonds and that Na begins to be incorporated into the distorted TiO6 crystalline structure after 5 h of HTT (until 12 wt%). The crystalline and shape transformation resulted in a significant modification on the textural properties passing from 51 m2.g−1 to 150 m2.g−1 and from a pore volume of 0.12 cm3.g−1 to 1.03 cm3.g−1 for Ti-ref and Ti-nR-30 respectively. We also observed differences in the electronic properties as the bandgap presented a blue shift from 3.16 eV on the TiO2 reference nano-powder to 3.44 eV for the Ti-nR-30 calcined sample. This fact coincides with the presence of a more electron-rich state of the Ti4+ and the formation of negative charge layer induced by the presence of Na+ interlayer cations detected by XPS analysis, at the same this helped us to explain the catalytic activity results.

The conditions for the formation of nanocomposites based on the basis of lattice packings SiO2 nanospheres (opal matrices) with included clusters of crystalline phase of titanium oxide (TiO2 and TiO) and rare-earth titanates of the general formula R2TiO5 or R2Ti2O7, where R - Er, Dy, Gd, Pr, Tb and Yb in interspherical nanospacing are considered. The composition and structure of the nanocomposites studied electron microscopy, X-ray diffraction and Raman spectroscopy. Results of measuring of the frequency dependences of real and imaginary components of the permittivity and microwave conductivity (ranging 10-2-1012 Hz) obtained nanostructures are viewed.

The Sabatier reaction could be a key tool for the future of the renewable energy field due to the potential of this reaction to produce either fuels or to stabilize H2 in the form of stable chemicals. For this purpose, a new composite made of ruthenium oxide nanoparticles (NPs) deposited on titanate nanotubes (TiNTs) was tested. Titanate nanotubes are a robust semiconductor with a one-dimensional (1D) morphology that results in a high contact area making this material suitable for photocatalysis. Small ruthenium nanoparticles (1.5 nm) were deposited on TiNTs at different ratios by Na+-to-Ru3+ ion exchanges followed by calcination. These samples were tested varying light power and temperature conditions to study the reaction mechanism during catalysis. Methanation of CO2 catalyzed by Ru/TiNT composite exhibit photonic and thermic contributions, and their ratios vary with temperature and light intensity. The synthesized composite achieved a production rate of 12.4 mmol CH4·gcat−1·h−1 equivalent to 110.7 mmol of CH4·gRu−1·h−1 under 150 mW/cm2 simulated sunlight irradiation at 210 °C. It was found that photo-response derives either from Ru nanoparticle excitation in the visible (VIS) and near-infrared (NIR) region (photothermal and plasmon excitation mechanism) or from TiNT excitation in the ultraviolet (UV) region leading to electron–hole separation and photoinduced electron transfer.

Grain boundary effect on BaTiO3 has been widely investigated for several decades. However, all of them tailored the grain boundary by grain size of BaTiO3. In this case, a direct way was introduced to modify the grain boundary by coating technique to investigate the role of grain boundary in ferroelectric materials. Nonferroelectric phase TiO2 was employed to investigate grain boundary effects on the electrical properties of BaTiO3 piezoelectric ceramics. TiO2 coating can result in the reduction of piezoelectric and ferroelectric properties and the annealing process in oxygen can increase piezoelectric behavior of pure BaTiO3 due to valence state of Ti ions while that remains for Ti-modified composition possibly due to the increased grain boundary effect by impedance analysis. Compared with ferroelectric grain, grain boundary plays a critical role to impact the electrical properties of perovskite-type ferroelectric materials.

Potassium polytitanates are new promising type of ferroelectric ceramic materials with high ionic conductivity, highly polarizable structure and extremely high permittivity. Its structure is formed by [TiO6] octahedral units to layers with mobile potassium and hydroxonium ions in-between. The treatment in solutions containing nickel ions allows forming heterostructured materials which consist of potassium polytitanate particles intercalated by Ni2+ ions and/or decorated by nickel oxides NiOx. This modification route is fully dependant on solution pH, i.e. in acidic solutions the intercalation process prevails, in alkaline solutions potassium polytitanate is mostly decorated by the oxides. Therefore, electronic structure and electrical properties can be regulated depending on modification conditions, pH and ions concentration. Here we report the data on electric properties of potassium titanate modified in nickel sulfate solutions at different pH.

Metal−semiconductor nanocomposites have become interesting materials for the development of new photocatalytic hybrids. Along these lines, plasmonic nanoparticles have proven to be particularly efficient photosensitizers due to their ability to transfer plasmonic hot electrons onto large bandgap semiconductors such as TiO2, thus extending the activity of the latter into a broader range of the electromagnetic spectrum. The extent of this photosensitization process can be substantially enhanced in those geometries in which high electromagnetic fields are created at the metal−semiconductor interface. In this manner, the formation of plasmonic hot spots can be used as a versatile tool to engineer the photosensitization process in this family of hybrid materials. Herein, we introduce the use of titanate nanowires as ideal substrates for the assembly of Au nanorods and TiO2 nanoparticles, leading to the formation of robust hybrids with improved photocatalytic properties. Our approach shows that the correct choice of the individual units together with their rational assembly are of paramount importance in the development of complex nanostructures with advanced functionalities.

The aim of this paper was mechanochemical preparation of magnesium titanates. Powder mixtures of starting oxides MgO and TiO2 were mechanically activated in a planetary ball mill for the time interval from 0 to 160 minutes. Structural, stereological, thermal characterizations were performed on produced powders. The effects of activation on morphology were investigated by scanning electron microscopy and particle size analyses, while the changes in the phase composition were determined by X-ray diffraction. It is determined that the first traces of MgTiO3 became detectable after 40 minutes of milling, while after 160 minutes the pure magnesium titanates were noticed. The differential thermal analyses and thermo gravimetric analysis, in temperatures range from 25 oC to 1100 oC, has been performed in order to investigate thermal behavior of the mixtures.

Lead zirconate titanate (PZT) particles with pure tetragonal structure were synthesized by solid-state reaction method and used for preparation of slurries with different solid contents (34–80 wt.%). Then, PZT thick films were fabricated by the nonaqueous tape casting method. It was shown that the slurry prepared from ball-milled particles exhibited better rheology properties than slurry from particles which were not ball-milled. Measurement of sedimentation volumes and zeta potentials indicated particle aggregation, resulting in weak stability of the slurries with high solid contents. The microstructure, piezoelectric and ferroelectric properties of PZT sintered films were investigated in terms of solid contents. Ceramic films prepared from the slurry with solid contents of 73 wt.% had the optimal structure and properties. After poling at 200 °C with an applied field of 1.2 kV/cm, a d33 of 294 pC/N was achieved; typical ferroelectric properties were also observed with a Ps of 38 μC/cm2.

Recent advances in near-edge X-ray-absorption fine-structure spectroscopy coupled with transmission X-ray microscopy (NEXAFS–TXM) allow large-area mapping investigations of individual nano-objects with spectral resolution up to E/ΔE = 104 and spatial resolution approaching 10 nm. While the state-of-the-art spatial resolution of X-ray microscopy is limited by nanostructuring process constrains of the objective zone plate, we show here that it is possible to overcome this through close coupling with high-level theoretical modelling. Taking the example of isolated bundles of hydrothermally prepared sodium titanate nanotubes ((Na,H)TiNTs) we are able to unravel the complex nanoscale structure from the NEXAFS–TXM data using multichannel multiple-scattering calculations, to the extent of being able to associate specific spectral features in the O K-edge and Ti L-edge with oxygen atoms in distinct sites within the lattice. These can even be distinguished from the contribution of different hydroxyl groups to the electronic structure of the (Na,H)TiNTs.

Hydrogen titanates (H-titanates) of different nanostructures (nanotubes, nanowires, nanosheets) have been synthesized by hydrothermal methods. The europium (III) sorption from aqueous solutions onto nano-sized H-titanates was studied as a function of contact time, pH values, and initial Eu (III) concentration in batch experiments. Reversibility of adsorption of europium has been investigated as well. Nano-sized H-titanates can be used for tri-valent f-elements removal in polluted water treatment due to fast and efficient sorption of Eu (III).

Titanate structures were synthesized in highly alkaline solution using hydrothermal procedure. As-preparedpowders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR)and transmission electron microscopy (TEM). A specific surface area of the powders was measured by BETmethod. Results confirmed formation of layered trititanates, already after one hour of hydrothermal synthesis.To examine the photocatalytic activity of the as-prepared layered titanates, methylene blue (MB) was employedas a target compound in response to visible light at ambient temperature. It was observed that the specificsurface area, size distribution and crystallinity are important factors to get high photocatalytic activity for thedecomposition of MB.

One-dimensional titania structures were synthesized trough a simple hydrothermal process in a highly alkaline conditions. The aim of this work was to elucidate the effect of time on the formation of 1D titanates as well on its structural characteristics (morphology, phase composition, surface area). Apart from that, the effect of heat treatment conditions on the stability of titanate based 1D samples has been investigated. The results have revealed that it is possible to form one-dimensional titanates already after 1 hour of hydrothermal synthesis. Although the composition of titanates is still under debate, the results probably correspond to the layered sodium titanates. The 1D prepared structures show a remarkable stability during heating, remaining the basic morphology and composition even up to 700°C.

Chromites, titanates and Pt-YSZ-CeO2 cermets have been investigated as potential electrode materials for an alternative concept of Solid Oxide Fuel Cell (SOFC), the symmetrical SOFCs (SFC). In this configuration, the same electrode material is used simultaneously as anode and cathode. Interconnector materials, such as chromites, could be considered as potential SFC electrodes, at least under pure hydrogen-fed at relatively high temperatures, as they do not exhibit significant catalytic activity towards hydrocarbon oxidation. This may be overcome by partially substituting Cr in the perovskite B-sites by other transition metal cations such as Mn. La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) is a good candidate for such SFCs, rendering fuel cell performances in excess of 500 and 300mW/cm2 using pure H2 and CH4 as fuel, at 950 oC. Similarly, typical n-type electronic conductors traditionally regarded as anode materials, such as strontium titanates, may also operate under oxidising conditions as cathodes by substituting some Ti content for Fe to introduce p-type conductivity. Preliminary electrochemical experiments on La4Sr8Ti12-xFexO38-δ-based SFCs show that they perform reasonably well under humidified H2, at high temperatures. A third group of materials is the support material of any typical cermet anode, i.e. YSZ, CeO2 plus a current collector. It has been found that this combination could be optimised to operate as SFC electrodes, rendering performances of 400mW/cm2 under humidified pure H2 at 950oC.Cromitas, titanatos y cermets de Pt-YSZ-CeO2 han sido investigados como potenciales materiales de electrodo para un concepto alternativo de Pilas de Combustible de Óxidos Sólidos (SOFC), las pilas SOFC simétricas (SFC). En esta configuración, el mismo material de electrodo se utiliza simultáneamente como ánodo y cátodo. Materiales utilizados de interconector, como las cromitas, podrían ser considerados como potenciales electrodos SFC, al menos con hidrógeno puro como combustible y a temperaturas relativamente elevadas, debido a que no presentan una actividad catalítica relevante hacia la oxidación de hidrocarburos. Esto puede ser superado mediante la sustitución parcial del Cr, en el sitio B de la perovskita, por otro metal de transición como Mn. La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) es un buen candidato para SFCs, generando rendimientos superiores a 500 y 300mW/cm2 empleando hidrógeno y metano puro como combustibles, respectivamente, a 950 oC. De igual manera, conductores electrónicos comunes, tipo-n, tradicionalmente considerados como materiales de ánodo, como los titanatos de estroncio, podrían también funcionar bajo condiciones oxidantes como cátodos, substituyendo parte del contenido en Ti por Fe para introducir conductividad tipo-p. Estudios electroquímicos preliminares en SFCs basadas en La4Sr8Ti12-xFexO38-δ muestran que pueden funcionar razonablemente bien bajo hidrógeno húmedo a alta temperatura. Un tercer grupo de materiales lo constituye la base típica de cualquier material cermet de ánodo, esto es YSZ, CeO2 más un colector de corriente. Se ha encontrado que esta combinación puede ser optimizada para funcionar como electrodo SFC, dando lugar a rendimientos del orden de 400mW/cm2 en hidrógeno puro húmedo a 950oC.

The performance and potential application of the cubic members of the La4Srn-4TinO3n+2 series of compounds, i.e. n≥12, prepared by solid state reaction are discussed. Although these phases can be indexed as cubic perovskites by X-ray diffraction (XRD), there exists some oxygen beyond the ABO3 stoichiometry accommodated in linear defects reminiscent to the oxygen rich layers in La2Ti2O7. In the present work, we report preliminary fuel cell tests of the n=12,14 and 16 of the La4Srn-4TinO3n+2 series, which reveal moderate responses under hydrogen, but also some promising results implying activation favouring methane oxidation.En este trabajo se presentan las prestaciones y el potencial uso de las fases cúbicas de la serie homóloga con fórmula La4Srn-4TinO3n+2 (n≥12) preparadas por reacción en el estado sólido. A pesar de que estas fases pueden describirse como perovskitas cúbicas mediante difracción de rayos-X (DRX), existe una cantidad de oxígeno superestequiométrico respecto a la composición ideal de la perovskita ABO3 localizado en defectos lineales análogos a las capas ricas en oxígeno en La2Ti2O7. En el presente trabajo, se muestran ensayos en pilas de combustible realizados en las composiciones n=12,14 and 16 de la serie La4Srn-4TinO3n+2 , donde se muestran respuestas moderadas en hidrógeno, así como una cierta activación que favorece la oxidación del metano.

Bi5FeTi3O15 (BiFT) compound has been prepared by solid state reaction between the corresponding oxides. Its crystalline structure has been established by X ray Diffraction, (XRD). Ceramic samples with apparent density > 95% Dth have been sintered. On these samples, electrical conductivity and Curie temperature have been measured. Solid solutions of Bi5FeTi3O15 (BiFT) and CaBi4Ti4O15 (CBiT) have been prepared. On poled samples of these solid solutions, piezoelectric parameters have been established. The BiFT compound shows electrical conductivity values very similar to those of the Bi4Ti3O12 (BiT) compound. The electrical conductivity of solid solutions is a function of CBiT amount. A possible electrical conductivity mechanism which is different of that accepted for the BiT compound is discussed.Se ha preparado Bi5FeTi3O15 (BiFT) por reacción en estado sólido de los óxidos correspondientes. Se ha determinado su estructura cristalina por Difracción de Rayos X (DRX). Se han preparado compactos sinterizados con densidades superiores al 95%. Se ha determinado su temperatura de Curie, y la conductividad eléctrica entre 150 y 850ºC. Se han preparado soluciones sólidas de Bi5FeTi3O15 con CaBi4Ti4O15, (CBiT) y se han determinado los mismos parámetros de temperatura de Curie y de conductividad para ellas. En las soluciones sólidas se han determinado los parámetros Piezoeléctricos de muestras polarizadas Debe destacarse que el compuesto Bi5FeTi3O15 presenta unos valores de conducción eléctrica más próximos a los correspondientes al Bi4Ti3O12 (BiT) que a los de los compuestos MeBi4Ti4O15. La conductividad eléctrica de las soluciones sólidas varía con el contenido de CBiT. Se discute la posible existencia de un modelo de conducción eléctrica que difiere del aceptado hasta el momento para el BiT, basado en los defectos localizados en las capas Bi2O2 2-.

In this work barium titanate (BT) and strontium titanate (ST) were prepared by Microwave-Assisted Hydrothermal (MAH) method, using a Ti precursor different from those shown in the literature and various concentrations (1, 3 e 6 mol L-1) of KOH mineralizer. As a titanium precursor, an anatase complex with hydrogen peroxide were used. For the precursors of barium and strontium, chlorides were used. The materials resulting from the synthesis processes were characterized in room temperature by different techniques as like: X-Ray Diffraction (XRD), micro-Raman Spectroscopy, UV-Vis, Scanning Electron Microscopy (SEM) and Photoluminescence (PL). The results show that there were differences in crystallinity, morphology, number of phases and photoluminescence depending on the concentration of the mineralizer.