Sol Gel Self-combustion Method Research Articles

Structure-activity relationship between pore morphology and thermochemical energy storage properties based on MgCO3/MgO

Thermochemical energy storage (TCES) is a pivotal technology for addressing the space-time mismatches in energy supply and demand. MgCO3/MgO carrier offers the advantages of high energy density, seasonal storage capability, and abundant nontoxic reserves. However, it is encumbered by poor exothermic activity and kinetic irreversibility. In this study, innovative preparation approaches for MgCO3/MgO have been developed, involving the regulation of physical morphology, so as to reveal the structure-activity relationship between pore morphology and TCES properties. The results indicate that SD-cotton-MgO (MgO prepared by structure-directing agent, cotton) could carbonate up to 76.98 %, facilitated by its mesopores that aid in the transport of reactants. SGSC-MgO (MgO prepared by sol-gel self-combustion method) exhibits the fastest reaction rate at the initial stage, with a rate of 593.1 μmol/min/g adsorbent because distributed macropores expose the other nanopores. As for SD-CPM-MgO (MgO prepared by structure-directing agent, carboniferous polysaccharide microsphere), owning to long pore distance of micropores hindering CO2 diffusion, its kinetics gradually decreases as the CPM size decreases. Porous media with mixed aperture could exhibit strong kinetic performance. Furthermore, the heat storage density and maximum power of SD-cotton-MgO increase as the endothermic temperature rises, achieving a peak energy density of 1385.7 kJ/kg MgCO3 at 400 °C. Still, its heat release density increases and then decreases with exothermic temperature, reaching 1964.3 kJ/kg MgO at 320 °C. Finally, the cycle stability is contingent on the activation of the chemical modification for the first heat release and antidegradation of the physical structure for subsequent cycles. SD-cotton-MgO doped with Na0.5K0.5NO3 maintains at 50 % after 30 cycles, exhibiting no collapse or agglomeration due to its robust porous structure with strong thermal stability and permeability.

Analysis of the Structural, Morphological, and Elastic Properties of Nanosized CuFe2O4 Spinel Synthesized via Sol-Gel Self-Combustion Method

Nanosized CuFe2O4 ferrite was synthesized through the sol-gel self-combustion technique, using iron and copper nitrates with citric acid as fuel. The synthesized ferrite was subsequently analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). X-ray diffraction studies validated the crystalline nature of the CuFe2O4, identifying it as having a mixed spinel structure within the Fd3m space group. Particle sizes were quantified using several methods including Debye-Scherrer, Williamson-Hall, Halder-Wagner, modified Debye-Scherrer, and size-strain plot (SSP), with all methods indicating a consistent average particle size of 28 nm. The elastic properties of the nanoparticles were extensively characterized, utilizing both diffraction line broadening (via the Williamson-Hall method) and Fourier-transform infrared spectroscopy (FTIR) to evaluate the materials' structural dynamics. Additionally, microstrain within the crystal lattice and various elastic constants, such as Young's modulus, Shear modulus, Debye temperature, and the velocities of longitudinal and transverse wave propagation were calculated. An electron density distribution was also constructed from the X-ray diffraction data, providing insight into the electronic environment and bonding characteristics of the material.

The role of Cu doped Ba0.5Sr0.5Fe0.95Zr0.05O3-δ: Local structure distortion, conductivity, and magnetization

The composition Ba0.5Sr0.5Fe1-xCuxZr0.05O3-δ (BSFCZ-x, x = 0–0.20) was successfully synthesized by the sol-gel self-combustion method using citric acid as fuel combustion. Structure, local structure, electrical, and magnetic properties are investigated. The X-ray diffraction revealed the oxides exhibit a cubic structure (Pm3 m), and the lattice parameter increases with x. The X-ray absorption data are analyzed to determine the oxidation state of B site metal transition Fe and Cu through edge-energy E0 evaluation. Fe performs the oxidation states Fe3+ and Fe4+, similarly to Cu2+ and Cu3+. Furthermore, the pre-edge was analyzed to determine the spin state configuration of the 3d subshell. The local lattice distortion was evaluated through EXAFS, resulting in a distorted FeO6 octahedron elongated to the z-axis, inducing the Jahn-Teller effect. The nonstoichiometric δ-value (3-δ) measurement leads to oxygen vacancy VO⦁⦁ defect. The electrical conductivity of semiconducting behavior increases significantly after Cu is dissolved in BSFZ up to 60 S/cm at 500 °C, from initially 5 S/cm. Furthermore, the magnetic properties show a slight magnetic saturation Ms for BSFZ related to the low spin state configuration of Fe 3d subshell, then significantly increased on BSFCZ samples due to Cu provoking spin state dragged partly to high spin state configuration.

Interfacial Metal-Support Interaction and Catalytic Performance of Perovskite LaCrO3-Supported Ru Catalyst.

Interfacial metal-support interaction (MSI) significantly affects the dispersion of active metals on the surface of the catalyst support and impacts catalyst performance. Understanding MSI is crucial for developing highly active and stable catalysts with a low metal loading, particularly for noble metal catalysts. In this work, we synthesized LaRuxCr1-xO3 catalysts with low Ru loading (x = 0.005, 0.01, and 0.02) using the sol-gel self-combustion method. We found that all of the Ru atoms immediately above or below the metal-support interface are closely bonded to the perovskite LaCrO3 surface lattice through Ru-O bonds, enhancing the MSI via interfacial reaction and charge transfer mechanisms. We identified a variety of Ru species, including small 3D Ru nanoparticles, 2D dispersed Ru surface atoms, and even 0D Ru single atoms. These highly dispersed Ru species exhibit high activity and stability under dry reforming of methane (DRM) conditions. The LaRu0.01Cr0.99O3 catalyst with very low Ru loading (0.42 wt %) was stable over a 50 h DRM test and the carbon deposition was negligible. The CH4 and CO2 conversions at 750 °C reached 83 and 86%, respectively, approaching the theoretical thermodynamic equilibrium values.

The Influence of Reaction Medium pH on the Structure, Optical, and Mechanical Properties of Nanosized Cu-Fe Ferrite Synthesized by the Sol-Gel Autocombustion Method

Nanoscale mixed ferrites with a spinel structure are highly versatile materials widely employed across diverse fields, including engineering, biomedicine, and ecology. This study explores the influence of pH on the structure, morphology, electrophysical, and mechanical properties of CuFe2O4 spinel, synthesized using the sol-gel self-combustion method. The investigation reveals that the pH level significantly impacts the structure formation, even at the gel formation stage, thereby shaping the subsequent structure and properties of the synthesized ferrite. X-ray diffraction (XRD) analysis demonstrates that the dominant phase (>90%) corresponds to the cubic spinel phase with the chemical formula CuFe2O4, belonging to the Fd3m space group. Notably, the pH of the reaction medium exerts a profound influence on the distribution of iron and copper ions within the octahedral and tetrahedral sublattices of the spinel structure. This variation in cationic distribution manifests in notable changes in the synthesized ferrite's magnetic, mechanical, and degradation properties. Furthermore, the study delves into the impact of the synthesized CuFe2O4 spinel as a photocatalyst for degrading organic dyes through the photo-Fenton process. It demonstrates that degradation efficiency is closely related to the ferrite's band gap width and particle size. This study aimed to determine how the pH of the reaction medium impacts the structure, morphology, optical, mechanical, and magnetic characteristics of the nanosized ferrites being synthesized. Furthermore, the synthesized materials were evaluated for their photocatalytic abilities in degrading organic dyes in water. The ferrite powders showcased remarkable dye degradation capabilities via the photo-Fenton process. Degradation efficiency largely hinged on the band gap width and the size of the particles. The most notable outcome was achieved with sample P1, which had particle sizes averaging 12.14 nm. By unraveling the complex relationship between pH, structure, and properties, this research enhances our understanding of the design and optimization of nanoscale mixed ferrites.

Efficient Ni/Y2O3 catalyst prepared by sol-gel self-combustion method for ammonia decomposition to hydrogen

Ammonia has sparked a lot of interest as a promising hydrogen carrier for the development of renewable energy and as a workable method to produce COx-free hydrogen for fuel cells through its on-site decomposition. The catalysts, composed of nickel as an active metal supported on the Y2O3, were synthesized by the sol-gel self-combustion method conveniently, in which the active metals are uniformly dispersed. 700–1.25Ni1Y1Oα exhibits the best catalytic activity and has the most active metal dispersion (6.15 %). The ammonia conversion can reach 96 % at 550 °C and 12000 ml·gcat−1·h−1 gas hourly space velocities (GHSVs) as well as 100 % at 600 °C and the same GHSVs. Temperature-programmed reduction, temperature-programmed desorption, and X-ray photoelectron spectroscopy were used to characterize the catalysts. It was found that 700–1.25Ni1Y1Oα has the best capacity for hydrogen desorption resulting in weakening the inhibitory effect of hydrogen to the reaction and enhancing the reactivity of the catalyst. The electron transfer from Y in Y–O–Ni structure increases gradually as the Ni to Y ratio becomes appropriate, enhancing the alkalinity of the catalyst and electron density around the Ni, which is beneficial to NH3 decomposition.

Structural analysis and polarization study of CoCr2O4 nanoparticles

We present the room temperature polarization study of the multiferroic compound CoCr2O4. The co-existence of two elements (Co and Cr) in partially filled d-blocks makes these compounds exhibit a wide range of physical properties. The Cr3+ions almost invariably cover the octahedral (Oh) sites as the crystal field stabilization energy (CFSE) is more than 224 kJ mol −1. The chemical based Sol-gel self-combustion method has been used to successfully synthesize CoCr2O4 chromite. Laboratory X-ray diffraction (LXRD) and synchrotron X-ray diffraction (SXRD) investigations approve the single-phase face centered crystalline structure. The obtained space group is Fd3m. The average crystallite size has been determined by Debye Scherrer’s method and the Williamson Hall [W-H] method. The obtained size is found to be ~ 27 and 17 nm respectively, for both methods when the data is measured by SXRD. The scanning electron micrograph (SEM) shows the agglomeration of particles, which is confirmed by surface topography. Room temperature polarization study exposes the weaker strength of ferroelectricity, which is principally due to charge reversal in the CoCr2O4 compound. The experimental value for retaining polarization is found to be ~ 65% at room temperature (300K).

Ascorbic acid enhanced CuFe2O4-catalyzed heterogeneous photo-Fenton-like degradation of phenol

CuFe2O4 particles were synthesized using the sol-gel self-combustion method and characterized for their compositional surface morphology and crystal structure. When compared to the photo-Fenton system without ascorbic acid (AA), the presence of AA significantly enhanced the catalytic degradation of phenol using CuFe2O4. The highest catalytic degradation efficiency was achieved at an AA concentration of 1 mmol/L, resulting in up to 98.6 % elimination of phenol in just 40 min. The reaction rate was found to be 31.7 times higher than that of the system without AA. The mechanism of AA enhancement in the CuFe2O4 photo-Fenton system was further investigated. Two key factors were found to contribute to the enhancing mechanism of AA introduction in the CuFe2O4 photo-Fenton system. Firstly, AA promoted the Cu/Fe redox cycle on the catalyst surface, leading to a more efficient generation of reactive species that are responsible for phenol degradation. Secondly, AA accelerated the leaching of metal ions from the catalyst surface, facilitating the homogenous Fenton effect. The Cu/Fe bimetallic cycle system offers new perspectives on effective Fenton catalyst design and provides crucial insights for reductant-enhanced photo-Fenton activation.

Sol-Gel synthesis of Ni-doped Zn-based spinel nanoferrites with structural and dielectric characterizations along with magnetic analysis

Ni-doped zinc ferrites (NixZn1−xFe2O4, 0.00 ≤ x ≤ 0.20 in steps of 0.05) were successfully synthesized using a sol-gel self-combustion method. The addition of nickel was aimed at modifying the high-frequency dielectric and magnetic properties of zinc ferrites. Various characterizations, including XRD, FTIR, LCR, and VSM analyses, were conducted to examine the crystal structure, absorption bands, dielectric properties, and magnetic properties of the compounds. XRD patterns revealed a monophasic cubic spinel structure with a preferred (311) plane orientation. The incorporation of Ni resulted in an increased crystallite size as determined by the Scherrer equation and Williamson-Hall method. The lattice parameters and unit cell volume decreased, while X-ray density increased. FTIR transmittance spectra confirmed absorption bands associated with tetrahedral and octahedral bonding. Dielectric parameters were studied across a frequency range of 1 MHz to 3 GHz, with the Maxwell-Wagner model used to explain the observations. Both components of the complex dielectric constant decreased with increasing frequency, indicating normal dispersion behavior of spinel ferrites. The electric modulus revealed relaxation mechanisms, while AC conductivity demonstrated conduction mechanisms. Magnetic properties were characterized using M-H loops measured via VSM. Increasing the Ni concentration led to higher saturation magnetization (Ms), magnetic remanence (Mr), and coercivity (Hc). Magnetic moments and anisotropy constants were calculated based on observed values of Ms and Hc. In summary, the nickel-doped zinc ferrites exhibited notable structural, magnetic, and dielectric properties, suggesting their potential utility in microwave and high-storage magnetic devices.

Influence of Exposure Cd1-xMgx Fe₂O4 Compound by RF Plasma

Background:
 The work focuses on enhancing the structural properties, where the Cd1-x Mgx Fe2O4 products prepared by sol-gel solution were characterized. Auto ignition approach using several automated equipment, as FESEM, XRD, for concentrations (x=0.0,0.8 and 1), post-synthesis plasmas were exposed in a low-pressure chamber using the RF Magnetron Sputtering System and the results compared. by X-ray diffraction analysis, confirms the configuration to the FCC cubic structure of the studied samples. Plasma treatment did not affect the crystallization but the crystal size (D) of the particle size decreases after exposure to plasma from (32.33- 27.083)nm . Morphological studies confirmed surface shape changes and particle size reduction upon exposure to plasma.
 Materials and Methods:
 The sol-gel method common and old a chemical process for the production of a variety of nanostructures, most notably nanoparticles of metal oxide. In which The molecular feedstock is combined with water or alcohol and then subjected to moderate heating while being agitated. The basic principle pertaining to the sol-gel technology is to manufacture a homogenous solution created from raw materials also then gelatinized . The powders are ground and sintered in a refractory oven at 1100 ° C for 6 hours. The powder was then pressed by a hydraulic press at a pressure of 150 kN into molds to form a disc with a diameter of 20 mm. The work will take place in two phases: before exposing it to the plasma, and then when the samples are placed into the RF Magnetron Sputtering.
 Results:
 The X-ray measurements showed that the un-exposure and plasma- exposure samples have a cubic spinel structure, and that the variation of the structural parameters with the exposure is irregular, Consequently enhancing the atoms' ability to diffuse after being put onto the substrate and grain size of the sample. The morphological analysis of the as-prepared ferrite Cd1-xMgxFe2O4 samples was performed using FE-SEM, which gives details on the size and structure of the particles that make up the nanocrystals. The surface exposed to the plasma shows a change in the positions of the crystals and their cohesion with each other , which may result from a decrease in supermagnetic effect and lattice defects in Ferrite nanocrystalline films.
 Conclusion:
 The aim of this work is to synthesize Cd1-xMgx Fe₂O4 ferrite nanoparticles in spinel cube structure by sol-gel self-combustion method. Then, the synthesis of thermal plasma using Radio frequency (RF) plasma, where the structural properties, surface shape, and interpretation were studied properties of ferrite nanoparticles produced before and after plasma exposure. According to the conducted XRD investigations the validity of the cubic spinel structure of ferrite and that the irregular difference in the size of the crystals before and after the exposure, the particle size decreases after exposure to plasma from (32.33- 27.083)nm, and the capillary parameter they were reduced from (8.892 to 8.743)nm for plasma-treated samples. the results obtained from shaping cubic spinel phase in both iron nanoparticles before and after plasma exposure supported by the XRD results. The morphological study revealed irregularity grain distribution and dominant agglomeration in ferrite before and after exposure.

Effect of magnetic particle size in semi-conductive layer on charge accumulation within insulation layer of HVDC cable

The key problem limiting the development of high-voltage direct current (HVDC) cable is the space charge accumulation within the insulation layer. A method is proposed to reduce the accumulation of space charge of cable insulation by a semi-conductive layer modified by magnetic particles. The physical essence is to change the charge migration path by the action of the Lorentz force in the semi-conductive layer. SrFe12O19 particles with different particle sizes from 80 nm to 1000 nm are prepared by the sol-gel self-combustion method. The magnetic properties and resistivity of the semi-conductive layer composites with various particle sizes are investigated. In addition, the effect of the semi-conductive layer electrode for charge accumulation in the insulation layer is studied. Finally, the relationship among SrFe12O19 particle size, magnetization intensity of the semi-conductive layer, and charge inhibition effect of the insulation layer is analyzed. The results of the experiments demonstrate that residual magnetization of magnetic particles has a significant impact on the space charge suppression. When SrFe12O19 particle size is 200 nm, the charge inhibition effect is the best. This work can provide a new view for the charge suppression of insulation layer.

Crystal structure and magnetic properties of Ga-Mn cosubstituted M-type strontium ferrite synthesized by sol-gel method

The M-type hexagonal strontium ferrites substituted by Gd-Mn ions were synthesized by the sol-gel self-combustion method. The synthesized samples were researched by X-ray diffraction (XRD), Fourier transform infrared spectroscopy analysis (FT-IR), scanning electric microscopy (SEM), and vibrating sample magnetometer (VSM). The XRD and the FT-IR results show that the pure M-type hexagonal ferrites phase is successfully obtained in the samples with the substitution amount (x) from 0.00 to 0.09 of Gd-Mn. The VSM results show that, as the substitution amount (x) of Gd-Mn increases, the remanent magnetization (Mr) and saturation magnetization (Ms) of the Sr1-xGdxFe12-xMnxO19 gradually increase, and the maximum values of 39.53 emu/g and 23.73 emu/g were obtained when x = 0.09. When x continues to increase, Mr and Ms decrease slightly, but they are still higher compared with those of the unsubstituted one. The coercivity (Hc) of the samples after doping is much higher than the coercivity of the pure sample, but as the substitution amount x increases, the coercivity first increases and then decreases, while the maximum value of Hc is 6738 Oe at x = 0.06.

Influences of Ni Content on the Microstructural and Catalytic Properties of Perovskite LaNixCr1−xO3 for Dry Reforming of Methane

Perovskite oxides were widely used as precursors for developing metal-support type catalysts. It is attractive to explore the catalytic properties of the oxides themselves for dry reforming of methane (DRM). We synthesized LaNixCr1−xO3 (x = 0.05–0.5) samples in powder form using the sol-gel self-combustion method. Ni atoms are successfully doped into the LaCrO3 perovskite lattice. The perovskite grains are polycrystalline, and the crystallite size decreases with increasing Ni content. We demonstrated that the LaNixCr1−xO3 perovskites show intrinsically catalytic activity for DRM reactions. Reducing the Ni content is helpful to reduce carbon deposition resulting from the metal Ni nanoparticles that usually coexist with the highly active perovskite oxides. The CH4 conversion over the LaNi0.1Cr0.9O3 sample reaches approximately 84% at 750 °C, and the carbon deposition is negligible.

Synthesis of NixMg1-xO nano particles solid solution by sol-gel self combustion method and investigation of its structural and optical properties

In this paper, the NixMg1-x O (0.1 ≤ x ≤ 0.4) solid solution nano-powder was synthesized by new and soft non-alkoxide sol-gel self-combustion method. In this method, Ni(NO3)3·6H2O, Mg(CH3COO)2·4H2O and Citric acid (CA), were used as Ni2+, Mg2+ ion and gelling and combusting source, respectively. Then, by thermal gravimetric analysis (TGA) the chemical reaction and the appropriate temperature to form a stable compound were determined. The influences of molar ratio of component (x) on structural and optical properties of samples have been investigated by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and Fourier transform infrared (FTIR) analysis. By increasing in x, all the samples are shown decreasing ecreasing in lattice parameter (a) and crystallite size (D), which indicates the contamination of magnesium oxide with nickel and the formation of NixMg1-xO solid solution. The Band gap was decreased by increasing in x which shows that Ni2+ ions in MgO structure causes some modifications in the energy levels and the optical absorbance characteristics associated with F centers due to oxygen defect centers.

Enhanced Heterogeneous Fenton Degradation of Organic Pollutants by CRC/Fe3O4 Catalyst at Neutral pH.

Fe3O4-based heterogeneous Fenton catalysts have been widely employed for degrading organic pollutants, however it is challenging to use them in highly efficient and recyclable application in wastewater treatment. In this work, carboxylate-rich carbon (CRC)-modified Fe3O4 magnetic particles are prepared by the sol-gel self-combustion method, where CRC is obtained from the carbonization of sodium gluconate. The CRC/Fe3O4 catalyst exhibits high heterogeneous Fenton degradation performance. The complete 10 mg L−1 methylene blue (MB) removal is achieved in 180 min under conditions of 10 mM H2O2 and 1.00 g of L−1 CRC/Fe3O4 at neutral pH. After five cycles, the structure and morphology of CRC/Fe3O4 composites remained unchanged and the catalytic activity also remained unaltered. Moreover, phenol, benzoic acid (BA), sulfamethazine (SMT), and tetracycline (TC) were also degraded in the heterogeneous Fenton reaction using CRC/Fe3O4 as a catalyst. The strong coordinating ability of –COOH/ –COO– functionalities of CRC formed strong bonds with Fe(II/III) ions on the surfaces of Fe3O4 particles, which was conducive to adsorption of organic matter on the surface of the catalyst and promoted the occurrence of heterogeneous Fenton reactions. It was found that CRC/Fe3O4 had higher removal rates for the adsorptive exclusions of pollutants, such as TC and MB, whereas there were lower removal rates for phenol, BA, and SMT. This work brings potential insights for development of a novel adsorption-enhanced heterogeneous Fenton reaction for wastewater treatment.

Characterization and use for the degradation of phenol, of new core-shell mesoporous Si–Sn–Zr oxides synthesized by a surfactant-assisted sol–gel self-combustion method

Characterization and use for the degradation of phenol, of new core-shell mesoporous Si–Sn–Zr oxides synthesized by a surfactant-assisted sol–gel self-combustion method

Porous Nanostructured Gadolinium Aluminate for High-Sensitivity Humidity Sensors.

This paper presents the synthesis of gadolinium aluminate (GdAlO3), an oxide compound with a perovskite structure, for applications as a capacitive and/or resistive humidity sensor. Gadolinium aluminate was synthesized by the sol-gel self-combustion method. This method allowed us to obtain a highly porous structure in which open pores prevail, a structure favorable to humidity sensors. Most of the materials studied as capacitive/resistive humidity sensors have significant sensitivities only with respect to one of these types of sensors. In the case of the studied gadolinium aluminate with p-type electric conductivity, the relative humidity of the air has a significant influence on both capacitive and resistive types of electric humidity sensors. The capacity increases about 10,000 times, and the resistance decreases about 8000 times as the relative humidity increases from 0 to 98%. The investigated gadolinium aluminate can be used successfully to obtain high-sensitivity capacitive and/or resistive humidity sensors.

Study on the Preparation of Magnetic Mn–Co–Fe Spinel and Its Mercury Removal Performance

In this study, the manganese-doped manganese–cobalt–iron spinel was prepared by the sol–gel self-combustion method, and its physical and chemical properties were analyzed by XRD (X-ray diffraction analysis), SEM (scanning electron microscope), and VSM (vibrating sample magnetometer). The mercury removal performance of simulated flue gas was tested on a fixed bed experimental device, and the effects of Mn doping amount, fuel addition amount, reaction temperature, and flue gas composition on its mercury removal capacity were studied. The results showed that the best synthesized product was when the doping amount of Mn was the molar ratio of 0.5, and the average mercury removal efficiency was 87.5% within 120 min. Among the fuel rich, stoichiometric ratio, and fuel lean systems, the stoichiometric ratio system is most conductive to product synthesis, and the mercury removal performance of the obtained product was the best. Moreover, the removal ability of Hg0 was enhanced with the increase in temperature in the test temperature range, and both physical and chemical adsorption play key roles in the spinel adsorption of Hg0 in the medium temperature range. The addition of O2 can promote the removal of Hg0 by adsorbent, but the continuous increase after the volume fraction reached 10% had little effect on the removal efficiency of Hg0. While SO2 inhibited the removal of mercury by adsorbent, the higher the volume fraction, the more obvious the inhibition. In addition, in an oxygen-free environment, the addition of a small amount of HCl can promote the removal of mercury by adsorbent, but the addition of more HCl does not have a better promotion effect. Compared with other reported adsorbents, the adsorbent has better mercury removal performance and magnetic properties, and has a strong recycling performance. The removal efficiency of mercury can always be maintained above 85% in five cycles.

Effects of sintering temperature on the microstructure, electrical and magnetic characteristics of copper-zinc spinel ferrite with possibility use as humidity sensors

In this paper was investigated the effect of sintering temperature on a copper-zinc spinel ferrite, Cu0.5Zn0.5Fe2O4, synthesised by using a sol-gel self-combustion method, as material with possible to application in the field of humidity sensors. In order to highlight the influence of temperature treatment on the structure, electrical and magnetic properties, the powders of ferrite were annealed at various temperatures: 850 °C, 900 °C, 950 °C, 1000 °C and 1050 °C. For the analyzed samples, the X-ray diffraction investigations have revealed the phase composition and the average crystallite size. By using techniques scanning electron microscopy (SEM) and atomic force microscopy (AFM) were find the influence of the sintering temperature on some parameters like the porosity, homogeneity, shape and size of the crystallites. We have also investigated the temperature variation of the electrical conductivity, relative magnetic permeability and relative permittivity variation with frequency at room temperature. Finally, we analyzed the time response, variations of electrical conductivity and relative permittivity for various humidity levels and the perspectives of applicability copper-zinc spinel ferrite as humidity sensor.

Crystal structure and Cu/Fe K-edge analysis of Ba0.5Sr0.5Fe1-xCuxO3-δ (x = 0–0.2) and the influence on conductivity

Ba0.5Sr0.5Fe(1-x) CuxO3-δ (BSFC-x; x = 0–0.2) was synthesized and characterized. A sol-gel self-combustion method with mixed cation nitrate solutions and citric acid was used to synthesize BSFC-x precursors. Calcination was conducted in air at 850 °C for 6 h, followed by sintering in air at 1100 °C for 6 h. The phase, structure, and lattice parameters of the sintered BSFC-x were determined by X-ray diffraction (XRD). X-ray absorption near-edge spectroscopy (XANES) was used to analyze the oxidation state of the cation in the octahedron site (Cu/Fe). It showed that copper's oxidation state was predominantly 3+ due to oxygen octahedron neighbors in the crystalline symmetry and shifted to a lower oxidation state at 800 °C. The oxidation state was thought to be the predominant factor contributing to the overall conductivity through hole creation. The electrical analysis demonstrated semiconductor behavior at up to 500 °C that was influenced by the hole concentration, oxygen vacancies, and hopping distance. Above the maximum conductivity values, oxygen losses dominated the electrical response and disrupted the conductivity. Considering the doping quantity, the optimum doping was x = 0.1 with an electrical conductivity of ≈60 S/cm.