O3 System Research Articles

Ca(Mo,W)O4 Solid Solutions Formation in CaMoO4‐CaWO4 System

AbstractThe formation of solid solutions in the CaMoO4‐CaWO4 binary system is investigated by X‐ray diffraction, Raman spectroscopy, and scanning electron microscopy methods. The intermixtures of CaMoO4 and CaWO4 components are sintered in 600—1200 °C temperature range (in 100 °C increments). The solidus of the CaMoxW(1‐x)O4 system is studied by the differential scanning calorimetry method in the x = 0.3 … 1.0 range. CaMoO4‐CaWO4 phase diagram is constructed up to 1550 °C. The minimal sintering temperature in order to get CaMoxW(1‐x)O4 solid solution is shown to be 800 °C. Cathodoluminescence study of CaMoxW(1‐x)O4 compounds showed higher intensity of molybdate luminescence type.

Optical, Magnetic, and Electrical Properties of New Binary CoTiO3-Modified Ba(Zr0.2Ti0.8)O3 System as Solid Solution

Optical, Magnetic, and Electrical Properties of New Binary CoTiO3-Modified Ba(Zr0.2Ti0.8)O3 System as Solid Solution

First principles study of the electronic structure and Li-ion diffusion properties of co-doped LIFex-1MxPyNy-1O4 (M=Co/Mn, N[dbnd]S/Si) Li-ion battery cathode materials

In this work, a first-principles method based on density functional theory was systematically employed to investigate the stability, electronic properties, lithium-ion migration rates, and capacity-voltage curves of the LiFex-1MxPyNy-1O4 (M = Co/Mn, NS/Si) system. The results indicate that the lattice constants of the LiFex-1MxPyNy-1O4 (M = Co/Mn, NS/Si) system show little variation, and the system exhibits low formation and binding energies. Among the investigated systems, LFP-Mn/S demonstrates the best structural and thermodynamic stability. The bandgap of the doped systems decreases, leading to enhanced electronic conductivity. The LiFe0.875Co0.125P0.875Si0.125O4 and LiFe0.875Mn0.125P0.875Si0.125O4 systems remain semiconductors, while the LiFe0.875Co0.125P0.875S0.125O4 and LiFe0.875Mn0.125P0.875S0.125O4 systems exhibit semi-metallic properties due to the introduction of sulfur. Differential charge density calculations reveal changes in the covalent bond strength of the doped systems, with the introduction of Si and S respectively increasing and decreasing the covalency of their bonds with surrounding oxygen atoms. Additionally, doping reduces the Li-ion diffusion energy barriers, with the LiFe0.875Co0.125P0.875Si0.125O4 system exhibiting the lowest migration energy barrier. The Li-ion diffusion rate is four orders of magnitude faster than that of the intrinsic system. This is attributed to changes in the average lengths of Li–O, Co–O, and Fe–O bonds. Finally, doping also alters the de-lithiation voltage, with values ranging from 2.69 V to 3.65 V for the doped systems, and the LiFe0.875Co0.125P0.875Si0.125O4 system shows the highest complete de-lithiation voltage of 3.65 V. The overall performance improvements of the doped system have significant implications for enhancing the performance of Li-ion batteries.

Sonoelectrochemical degradation of aspirin in aquatic medium using ozone and peroxymonosulfate activated with FeS2 nanoparticles

The catalytic performance of nano-FeS2 in the sonoelectrochemical activation of peroxymonosulfate (PMS) and ozone to remove aspirin (ASP) was studied for the first time. The crystal structure and Fe bonds in the catalyst were confirmed through XRD and FTIR analysis. Within 30 min, ASP (TOC) was removed by 99.2 % (81.6 %) and 98.6 % (77.4 %) in nano-FeS2/PMS and nano-FeS2/O3 sonoelectrochemical systems, respectively. Water anions, especiallyHCO3− (almost 50 %), had an inhibitory effect on ASP removal. The probes confirmed that SO4•−and HO• were the key to ASP degradation in nano-FeS2/PMS and nano-FeS2/O3 systems, respectively. The effective activation of oxidants due to the ideal distribution of Fe2+ by catalyst was the main mechanism of ASP removal, in which electric current (EC) and ultrasound (US) played a crucial role through the recycling of Fe ions, dissolution and cleaning of the catalyst. LC-MS analysis identified thirteen byproducts in the ASP degradation pathways. The energy consumption of the proposed sonoelectrochemical systems was lower than previous similar systems. This study presented economic and sustainable hybrid systems for pharmaceutical wastewater remediation.

Hydrothermal Synthesis of a Valence State Constant High-Entropy Perovskite Sr(TiZrHfVNb)O3 with Improved Photoresponsiveness.

A vanadium ion valence state constant high-entropy perovskite system was synthesized using the hydrothermal method with a trivalent vanadium ion as the vanadium source. The B-site of the perovskite crystal lattice was loaded with five atoms in equal proportions. We tried to synthesize the Sr(TiZrHfVNb)O3 high-entropy system using different methods. However, the valence state of the vanadium ion could only be kept constant using the hydrothermal process in the valence balanced high-entropy composition system. There was significant vanadium element segregation and second phase in the Sr(TiZrHfVNb)O3 system prepared using the solid-state reaction process. Also, obvious vanadium ion valence state ascending from V3+ to V5+ appeared in this high-entropy system with an increase in calcination temperature. Inconspicuous vanadium element segregation appeared at 900 °C, the significant segregation phenomenon and second phase appeared at 1200 °C, and the particle size increased with the temperature. This meant that the high-entropy value could not only stabilize the crystal phase, but also stabilize the ionic valence state. Moreover, the constant trivalent vanadium ion valence state could provide coordinated performance with a wide optical response range and a low band gap for the high-entropy system. This suggests that the system might grow a potential ceramic material for optical applications.

Engineering Multiphase Phase Transitions for Exceptional Electrocaloric Performance and Ultraweak Electrostrictive Response in Ferroelectrics.

In the pursuit of eco-friendly alternatives for refrigeration technology, electrocaloric materials have emerged as promising candidates for efficient solid-state refrigeration due to their high efficiency and integrability. However, current advancements in electrocaloric effects (ECEs) are often constrained by high temperatures and elevated electric fields (E-field), limiting practical applicability. Informed by phase-field simulation, this study introduces a (1-x)Pb(Yb1/2Nb1/2)O3-xPb(Mg1/3Nb2/3)O3 system, strategically engineered to incorporate highly ordered YN and disordered MN mixtures. The synergistic interplay between E-field/temperature-induced polarization reorientation and cation shift initiates multiple ferroelectric-antiferroelectric-paraelectric phase transitions. Our results demonstrate that under a moderate E-field of 50 kV cm-1, the x = 0.22 composition achieves remarkable performance with a giant temperature change (ΔT) of 3.48 K, a robust ECE strength (ΔT/ΔE) of 0.095 K cm kV-1, and a wide temperature span (Tspan) of 38 °C. Notably, the disrupted lattice structure contributes to ultralow electrostrains below 0.008%, with an average electrostrictive coefficient Q33 of 0.007 m4 C-2. The significantly weakened electrostrictive activity favors enhancing the performance stability of subsequent devices. This work introduces an innovative strategy for developing robust electrocaloric materials, offering substantial ΔT and low electrostrains, presenting promising advancements in ECE applications with an extended lifetime.

Surface Mn-O3* complex-mediated nonradical electron transfer for boosting catalytic ozonation of organic pollutants

As initial and important reactive species, surface O3 complexes are rarely investigated in catalytic ozonation, which might be one cause of dispute in mechanistic understanding. Herein, In-situ DRIFTS and premixing-standing experiments confirmed the generation of long-lived Mn-O3* complexes upon O3 adsorption on surface Lewis acid sites of α-MnO2. In α-MnO2/O3 system, the oxidation rate of various pollutants showed a good linear correlation with their redox potentials, as well as the energy gap between the pollutants and Mn-O3* complexes. Joint catalytic mechanism experiments and density functional theory calculations revealed that the oxidation of pollutants was boosted mainly because there was fast nonradical intermolecular electron transfer from the HOMO of pollutants to the LUMO of Mn-O3* complexes. This study illustrates the significance of surface Mn-O3* complex in catalytic ozonation and discloses an efficient nonradical catalytic ozonation process that is resistant to pH fluctuation and matrix interference.

Synergistic catalytic enhancement of chemical oxygen demand removal using Mn-Bi doped submicron fly ash carrier: Mechanistic insights and environmental adaptability

This study presents a novel approach to enhancing the removal efficiency of Chemical Oxygen Demand (COD) from water using a submicron fly ash carrier (MFA) doped with manganese (Mn) and bismuth (Bi). The synthesis process involved mechanical ball milling and alkali activation of original fly ash (FA) to obtain MFA, followed by impregnation calcination to prepare the Mn-Bi@MFA composite. The synergistic effect of Mn and Bi facilitated the formation of abundant oxygen vacancies on the catalyst surface, significantly reducing the band gap width. The Mn-Bi@MFA composite exhibited remarkable properties with a specific surface area and pore structure reaching 15.17 m2/g and 0.062 cm3/g, respectively, surpassing FA by 7.16 and 20.67 times, respectively. Utilizing the Mn-Bi@MFA/O3 system, the COD removal amount reached 562.73 mg/g under specific conditions (reaction time = 60 min, pH=7.0, catalyst dosage = 1.0 g/L, ozone dosage = 2.0 g/h), exceeding that of the ozone-alone system by 51.62 %. Moreover, Mn-Bi@MFA demonstrated excellent environmental adaptability and repeatability. An investigation into the contribution order of different free radicals revealed •OH>O2•- >1O2 in COD removal, elucidating the mechanisms of ozone oxidation, catalytic ozonation, and photocatalysis. This research provides valuable insights into the development of efficient and sustainable water treatment strategies employing advanced nano-material-based catalysts.

Cu2S/Ni3S2 nanosheets combined with nickel foam substrate for efficient catalytic ozonation of p-nitrophenol in wastewater

Cu2S/Ni3S2@NF catalyst was prepared by hydrothermal method, and the catalytic ozonation of PNP solution (100 mg/L) was carried out. The removal rate of PNP under optimal experimental conditions was 99.9 % in 40 minutes, which was a significant increase over other systems. ESR revealed that singlet oxygen and superoxide radicals were the primary active ingredients. After the catalyst was used for five times, the catalytic activity remained basically unchanged. The possible degradation pathway and mechanism of Cu2S/Ni3S2@NF catalytic ozonation of PNP were proposed by gas chromatography-mass spectrometry. In real wastewater samples with complex compositions, the Cu2S/Ni3S2@NF/O3 system also achieved efficient degradation. The mechanism and possible pathway of Cu2S/Ni3S2@NF catalytic ozonation of PNP were proposed. This study provides an efficient, durable, and easy-to-recycle ozone catalyst, which provides a feasible pathway for the treatment of phenolic pollutants.

Doublet doped titanate ferroelectric system for capacitors and NTC thermistor applications

A simple negative temperature coefficient (NTC) thermistor Ba0.85Sr0.15Ti0.85Zr0.15O3 system is elaborated using a conventional solid-state reaction route. The structural analysis confirms that the elaborated pseudo-cubic system, which is indexed in the P4mm space group, exhibits one single phase. The dielectric properties and the electrical resistivity data are investigated over a large temperature range from 413 K to 673 K. In this temperature interval, the Steinhart–Hart equations are employed to confirm that Ba0.85Sr0.15Ti0.85Zr0.15O3 is a promising system for sensor application. Accordingly, the thermistor constant (β=10154 K), the sensitivity factor (-5.5 %/K≤α≤-2 %/K), the activation energy (Ea=0.875 eV), and the stability factor (SF=2.27) parameters are calculated to approve that Ba0.85Sr0.15Ti0.85Zr0.15O3 exhibits an NTC-thermistor behavior. The temperature dependence of the electrical resistivity confirms that Ba0.85Sr0.15Ti0.85Zr0.15O3 reveals a semiconductor behavior. The dielectric investigation shows that Ba0.85Sr0.15Ti0.85Zr0.15O3 exhibits a motivating dielectric properties (elevated dielectric constant value (105<ε’<106) and low dielectric losses (mostly < 0.007) with almost frequency independence between 20 Hz to 500 kHz). The colossal dielectric response of Ba0.85Sr0.15Ti0.85Zr0.15O3 is attributed to the internal barrier layer capacitor (IBLC) and the surface barrier layer capacitor (SBLC) effects. Such response suggests the suitability of Ba0.85Sr0.15Ti0.85Zr0.15O3 ceramic for high temperature capacitor applications.

Heterogeneous catalytic ozonation of ciprofloxacin in wastewater with red mud: Characterization and performance

As a kind of solid waste, red mud (RM) contains various metal oxides, which have been proven to be effective as catalysts in different reactions. This study investigates the impact of RM on the catalytic ozonation for degrading ciprofloxacin (CIP). Compared to the single O3 system, the RM/O3 system improved CIP and Total Organic Carbon (TOC) removal rates by 44.8 % and 21.6 %, respectively, under identical conditions, and exceeded catalytic ozonation by most oxides. The influence factors, CIP degradation products, and reaction mechanisms were discussed in detail. The redox pairs of Fe2+/Fe3+ promoted the formation of oxygen vacancies (Ovac), and the hydroxyl groups and Ovac on the surface of RM were the active sites, facilitating ozone decomposition to reactive oxygen species (ROS). The scavenging experiments confirmed the presence of hydroxyl radical (·OH), peroxyl radical(·O2−), and singlet oxygen (1O2) in the RM/O3 system. Furthermore, toxicity assessment indicated reduced toxicity of intermediate products compared to the parent compound CIP. The catalytic performance of RM remained relatively stable after 5 cycles of experiments, with CIP removal remaining at 100 % and TOC removal decreasing by 5.3 %. This study offers a novel perspective on utilizing RM as an efficient catalyst in CIP ozonation, beneficial for both RM treatment and antibiotic pollution mitigation.

Effect of B2O3 content on the structural and optical properties of (Ba0.85Ca0.15) (Ti0.9Zr0.1)O3 glass

This study explores the structural and optical properties of (Ba0.85Ca0.15) (Ti0.9Zr0.1)O3 system mixed with B2O3. The samples with the composition xB2O3 + (100-x) (Ba0.85Ca0.15) (Ti0.9Zr0.1)O3 (where x = 5, 10, 20, 30 and 40 mol. %) were prepared using the melting quenching technique to form borate-based glass containing BaO, CaO, ZrO2 and TiO2 (BBCZT). X-ray diffraction analysis confirmed the amorphous nature of the prepared samples. The macroscopic structure of the glasses was assessed from the density measurements determined through Archimedes' principle, while information regarding the atomic structural units and vibrational modes were obtained from Infrared measurements. Increasing the B2O3 content led to variation of the relative intensity of these modes together with a decrease (increase) in density (molar volume), indicating a less dense and open-structure for the glass network. The absorption spectra showed absorption bands associated with the optical transitions B22g→B21g and B22g→A21g of Ti3+ ions occupying distortion octahedral sites (TiOh3+) in the glass matrix. The ligand field strength (10Dq), optical energy gap (Eopt), Urbach's energy (ΔE), and nonlinear optical properties (NLO) were calculated in the study.

Contribution of strong electron-phonon interaction in the transport properties of La0.8Ca0.2Mn0.5Ni0.5O3 system

La0.8Ca0.2Mn0.5Ni0.5O3 NTC (negative thermal coefficient) thermo-sensitive material was prepared using a conventional solid-state reaction method. From the structural results, we found that the material is pure and crystallizes in the orthorhombic structure with a Pnma space group. It is found that the La0.8Ca0.2Mn0.5Ni0.5O3 ceramic can be used as an NTC thermistor compound in specific temperature sensors and attenuators. Based on Holsten's theory, detailed electrical investigations concerning the nature of the activated small polaron hopping mechanism were reported. The temperature dependence of the DC conductance was used to determine the electrical conduction processes that govern the transport properties of La0.8Ca0.2Mn0.5Ni0.5O3. Hence, the DC mechanisms exhibit changes from the variable range hopping at very low temperatures to the non-adiabatic small polaronic hopping at T = 210 K. In the intermediate temperature range, the semiconductor behavior of La0.8Ca0.2Mn0.5Ni0.5O3 was attributed to the contribution of the tunneling transport process. At various temperatures, the conductance spectra were discussed based on Jonscher and Bruce's laws. Contributions of the overlapping-large-polaron-tunneling, the correlated barrier hopping, the quantum mechanical tunneling, and the non-overlapping small polaron tunneling mechanisms to the transport properties were observed in the dispersive region of the conductance spectra. In addition, Summerfield scaling and corrected Summerfield scaling approaches prove that the charge mobility is temperature-dependent. The positive value of the correction parameter α = 1.2 confirms the presence of interactions in the studied sample.

Efficient catalytic ozonation for hexazinone degradation by Fe/Ce-doped MOF derivatives

High catalytic efficiency and strong anti-interference catalyst for refractory pollutants removal remains a challenge for the catalytic ozonation. Metal-organic framework (MOF) have shown excellent performance in catalysis filed, but there is a risk of metal ion leaching. Designing MOF derivatives by high temperature modulation is considered to be an effective way to enhance the performance and reduce leaching risk of MOFs. In this paper, Fe/Ce bimetallic metal–organic framework (FeCe-MOF) was synthesized and three MOF derivatives were prepared by calcination at different temperatures. The performance of MOF derivatives in the degradation of hexazinone via catalytic ozonation and the effects were investigated. The mechanism of catalytic ozonation by FeCe@C-600 was also elucidated by the analysis of structural characterization of the fresh and used FeCe@C-600, electron paramagnetic resonance (EPR) and quenching experiment. FeCe@C-600/O3 system achieved 78.78 % removal of hexazinone and 42.37 % degradation of TOC within 20 min. During the catalytic ozonation, FeCe@C-600 has high structural stability and avoiding the release of metal ions. FeCe@C-600 showed excellent performance to degrade and mineralize of hexazinone, and it is more stable and has wider pH applicability. The electron transfer and redox cycling of Mn+/Mn+1 were promoted along with the conversion of lattice oxygen to oxygen vacancies. The degradation of hexazinone was mainly attributed to the generation of reactive oxygen species (•OH, •O2–, 1O2) during catalytic ozonation. MOF derivatives exhibited good adsorption capacity during the degradation of hexazinone. FeCe@C-600 effectively reduces metal leaching while retaining high catalytic activity, providing new ideas for the development of new efficient and environmentally friendly ozone catalysts.

Novel cow dung-doped sludge biochar as an efficient ozone catalyst: Synergy between graphitic structure and defects induces free radical pathways

A composite material, cow dung-doped sludge biochar (Zn@SBC-CD), was synthesized by one-step pyrolysis using ZnCl2 as an activating agent and applied to a catalytic ozonation process (COP) for methylene blue (MB) removal. SEM, XRD, FTIR, XPS and BET analyses were performed to characterize the biochar (BC) catalysts. Zn@SBC-CD had high graphitization degree, abundant active sites and uniform distribution of Zn on its surface. Complete removal of MB was achieved within 10 min, with a removal rate much higher than that of ozone alone (32.4%), implying the excellent ozone activation performance of Zn@SBC-CD. The influence of experimental parameters on MB removal efficiency was examined. Under the optimum conditions in terms of ozone dose 0.04 mg/mL, catalyst dose 400 mg/L and pH 6.0, COD was completely removed after 20 min. Electron paramagnetic resonance (EPR) analysis revealed radical and non-radical pathways were involved in MB degradation. The Zn@SBC-CD/O3 system generated superoxide anion radicals (•O2−), which were the main active species for MB removal, through adsorption, transformation, and transfer, Furthermore, Zn@SBC-CD exhibited good reusability and stability in cycling experiments. This study provides a novel approach for the utilization of cow dung and sludge in synthesis of functional biocatalysts and application in organic wastewater treatment.

Synergies of Mn modified Fe-based MOF enhanced catalytic ozonation: charge transfer and multiple sites mechanism

The conjoint improvement of catalytic ozonation activity and stability for MOFs materials has always been an urgent challenge. Metal doping offers a viable approach to inspire the interaction between active components and O3 due to the optimization of electronic structure and introduction of surface-active sites. In this work, 88A-Mn catalyst derived from MIL-88A was prepared by loading Mn to MIL-88A with a simple pyrolysis method. The structure and physical characterizations confirmed the coexistence of Fe and Mn in the catalyst. The 88A1-Mn1-350 exhibited the efficient degradation of ibuprofen in catalytic ozonation system, with its degradation rate showing 3.6 times and 2.6 times higher than those of the O3 system and the 88A-T/O3 system, respectively. Mechanism analysis indicated the synergistic effect among Fe/Mn interaction, surface hydroxyl group, and O-C=O group promoted the continuous generation of ROS, including ·OH and ·O2-. Specifically, the regeneration of Fe2+ derived from the Mn doping contributed to the recovery of catalytic activity and played an indispensable role in maintaining high efficiency. In addition, 88A1-Mn1-350 possessed outstanding stability in a wide range of pH (3-11) and the coexistence of anions. It also exhibited the superiority compared with traditional catalysts. This finding provides a feasible modification approach to enhance the property of MOFs materials, and achieves the efficient remove of refractory organics in catalytic ozonation system.

The Degradation of Aqueous Oxytetracycline by an O3/CaO2 System in the Presence of HCO3-: Performance, Mechanism, Degradation Pathways, and Toxicity Evaluation.

This research constructed a novel O3/CaO2/HCO3- system to degrade antibiotic oxytetracycline (OTC) in water. The results indicated that CaO2 and HCO3- addition could promote OTC degradation in an O3 system. There is an optimal dosage of CaO2 (0.05 g/L) and HCO3- (2.25 mmol/L) that promotes OTC degradation. After 30 min of treatment, approximately 91.5% of the OTC molecules were eliminated in the O3/CaO2/HCO3- system. A higher O3 concentration, alkaline condition, and lower OTC concentration were conducive to OTC decomposition. Active substances including ·OH, 1O2, ·O2-, and ·HCO3- play certain roles in OTC degradation. The production of ·OH followed the order: O3/CaO2/HCO3- > O3/CaO2 > O3. Compared to the sole O3 system, TOC and COD were easier to remove in the O3/CaO2/HCO3- system. Based on DFT and LC-MS, active species dominant in the degradation pathways of OTC were proposed. Then, an evaluation of the toxic changes in intermediates during OTC degradation was carried out. The feasibility of O3/CaO2/HCO3- for the treatment of other substances, such as bisphenol A, tetracycline, and actual wastewater, was investigated. Finally, the energy efficiency of the O3/CaO2/HCO3- system was calculated and compared with other mainstream processes of OTC degradation. The O3/CaO2/HCO3- system may be considered as an efficient and economical approach for antibiotic destruction.

A Superparaelectric State in Relaxor Ferroelectric (Sr,Bi)TiO3-Bi(Mg,Ti)O3-Modified BaTiO3 Ceramics to Achieve High Energy Storage Performance.

Dielectric ceramic capacitors are highly regarded for their rapid charge-discharge, high power density, and cyclability in various advanced applications. However, their relatively low energy storage density has prompted intensive research aiming at developing materials with a higher energy density. To enhance energy storage properties, research has focused on modifying ferroelectric materials to induce relaxor ferroelectricity. The present study aims to induce a superparaelectric (SPE) state in relaxor ferroelectrics near room temperature by altering BaTiO3 ferroelectric ceramics using the (Sr,Bi)TiO3-Bi(Mg0.5Ti0.5)O3 system ((1-x)BT-x(SBT-BMT)). X-ray diffraction and Raman spectroscopy analysis demonstrated a shift in the crystal structure from tetragonal to cubic with an increasing x content. Notably, the compositions (except x = 0.1) satisfied the criteria for the SPE state manifestation near room temperature. The x = 0.2 specimen displayed characteristics at the boundary between the relaxor ferroelectric and SPE phases, while x ≥ 0.3 specimens exhibited increased SPE state fractions. Despite reduced maximum polarization, x ≥ 0.3 specimens showcased impressive energy storage capabilities, attributed to the enhanced SPE state, especially for x = 0.3, with impressive characteristics: a recoverable energy density (Wrec) of ~1.12 J/cm3 and efficiency (η) of ~94% at 170 kV/cm applied field. The good stability after the charge-discharge cycles reinforces the significance of the SPE phase in augmenting energy storage in relaxor ferroelectric materials, suggesting potential applications in high-energy density storage devices.

Polarization extension yielding ultrahigh piezoelectric response in xPb(Nb2/3Ni1/3)O3-(1-x)Pb(Zr0.3Ti0.7)O3 ferroelectrics ceramics

The heightened piezoelectric performance observed in most explored perovskite systems is typically attributed to the electric-field-induced phase transition near the morphotropic phase boundary (MPB) or polymorphic phase boundary (PPB). This study, however, unveils a distinct piezoelectric enhancement mechanism in the xPb(Nb2/3Ni1/3)O3-(1–x)Pb(Zr0.3Ti0.7)O3 (PNN-PZT) system, diverging from the MPB/PPB-centered piezoelectric systems. Notably, the composition with x = 0.55, positioned close to the tetragonal-pseudocubic (T-PC) phase boundary, achieves an unprecedented piezoelectric coefficient (d33) of 1264 pC/N, while retaining a tetragonal local structure. Importantly, on a local scale, electric fields do not incite phase transitions, suggesting that the exceptional piezoelectric performance in PNN-PZT stems from polarization extension near the T-PC boundary. Distinct from other mechanisms, the relative permittivity significantly increases post-poling due to this particular enhancement process. The dielectric behavior in poled specimens does not exhibit a conspicuous change at the ferroelectric-relaxor transition temperature. However, both the relative permittivity and planar electromechanical coupling coefficient experience a sharp rise in the temperature range of −25 °C to 25 °C. This investigation underscores the pivotal role of designing compositionally-driven T-PC phase boundaries, presenting a promising avenue for enhancing piezoelectric properties in ferroelectric ceramics.

Defluorination of perfluorooctanoic acid and perfluorooctane sulfonic acid by heterogeneous catalytic system of Fe-Al2O3/O3: Synergistic oxidation effects and defluorination mechanism

In this study, catalytic ozonation by Fe-Al2O3 was used to investigate the defluorination of PFOA and PFOS, assessing the effects of different experimental conditions on the defluorination efficiency of the system. The oxidation mechanism of the Fe-Al2O3/O3 system and the specific degradation and defluorination mechanisms for PFOA and PFOS were determined. Results showed that compared to the single O3 system, the defluorination rates of PFOA and PFOS increased by 2.32- and 5.92-fold using the Fe-Al2O3/O3 system under optimal experimental conditions. Mechanistic analysis indicated that in Fe-Al2O3, the variable valence iron (Fe) and functional groups containing C and O served as important reaction sites during the catalytic process. The co-existence of 1O2, OH, O2− and high-valence Fe(IV) constituted a synergistic oxidation system consisting of free radicals and non-radicals, promoting the degradation and defluorination of PFOA and PFOS. DFT theoretical calculations and the analysis of intermediate degradation products suggested that the degradation pathways of PFOA and PFOS involved Kolbe decarboxylation, desulfonation, alcoholization and intramolecular cyclization reactions. The degradation and defluorination pathways of PFOA and PFOS consisted of the stepwise removal of -CF2-, with PFOS exhibiting a higher defluorination rate than PFOA due to its susceptibility to electrophilic attack. This study provides a theoretical basis for the development of heterogeneous catalytic ozonation systems for PFOA and PFOS treatment.