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This paper presents the obtaining and characterization of recycled polypropylene/strontium ferrite (PP/SrFe12O19) polymer composite materials with applications in the electromagnetic shielding of vehicle interiors (mainly automotive electronics-carcasses) from the electromagnetic radiation emitted mainly by exterior sources-electrical lines and supply sources-in terms of the development of the new electrical vehicles. With this aim, suitable polymer composite materials were developed using SrFe12O19 filler in two forms (powder and concentrate). The recycled PP polymer and composite materials with a PP/SrFe12O19 weight ratio of 75/25 and 70/30 were obtained in two stages, i.e., pellets by extrusion and samples for testing through a melt injection process. The characterization of the obtained materials took into account the requirements imposed by the desired applications. It consisted of determining the mechanical and dielectric properties, and microstructure analyses, along with the determination of the resistance to the action of a temperature of 70 °C, which is higher than the temperatures created during the summer inside vehicles. The performance of these materials as electromagnetic shields was assessed through functional tests consisting of the determination of magnetic permeability and the estimation of the electromagnetic shielding efficiency (SE). The obtained results confirmed the improvement of the mechanical, dielectric, and magnetic properties of the PP/SrFe12O19 composites compared to the selected PP polymers. It is also found that all the composite materials exhibited reflective shielding properties (SER from -71.5 dB to -56.7 dB), with very little absorption shielding. The most performant material was the composite made of PP/SrFe12O19 powder with a weight ratio of 70/30. The promising results recommend this composite material for potential use in automotive shielding applications against electromagnetic pollution.

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The current research presents the evaluation of supramolecular proficiency of the designed platform for electrocatalytic determination of pernicious food colorants, amaranth and fast green. The approach involving surface modification of glassy carbon electrode with beta cyclodextrin decorated strontium ferrite reduced graphene oxide nanocomposite (SFrGO-ßCD) to ensure fast and reversible electro-oxidation of hydroxyl groups of the colorant molecules. The synergy between SF and rGO facilitated the sensor with enhanced surface area and conductivity through faradic redox reaction. Tremendous decrease in the obtained values of peak separation potential and impedance as manifested in CV and EIS analysis, enabled by electrostatic interactions between surface functionalities of rGO and ßCD has resulted in the significant augmentation of sensitivity. The value of charge transfer coefficient, number of electrons involved, nature of electron transport process at electrode electrolyte interface during the analysis of electrochemical detection were explored through CV experiments. Food samples analysis (without spiking) utilizing screen printed electrode manifested the sensor as portable device for real time monitoring. Outstanding detection limit (0.022 nM for amaranth and 0.051 nM for fast green), excellent regenerability (Relative standard deviation less than 3%) and apparent recovery rate (above 90%) of the modified electrode presented a colossal potential for the development of sustainable and commercially competitive electrochemical sensor in food sector.

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Novel radar-wave absorption nanocomposites are developed by filling the nanoscaled ferrites of strontium ferroxide (SrFe12O19) and carbonyl iron (CIP) individually into the highly flexible liquid silicone rubber (LSR) considered as dielectric matrix. Nanofiller dispersivities in SrFe12O19/LSR and CIP/LSR nanocomposites are characterized by scanning electronic microscopy, and the mechanical properties, electric conductivity, and DC dielectric-breakdown strength are tested to evaluate electrical insulation performances. Radar-wave absorption performances of SrFe12O19/LSR and CIP/LSR nanocomposites are investigated by measuring electromagnetic response characteristics and radar-wave reflectivity, indicating the high radar-wave absorption is dominantly derived from magnetic losses. Compared with pure LSR, the SrFe12O19/LSR and CIP/LSR nanocomposites represent acceptable reductions in mechanical tensile and dielectric-breakdown strengths, while rendering a substantial nonlinearity of electric conductivity under high electric fields. SrFe12O19/LSR nanocomposites provide high radar-wave absorption in the frequency band of 11~18 GHz, achieving a minimum reflection loss of -33 dB at 11 GHz with an effective absorption bandwidth of 10 GHz. In comparison, CIP/LSR nanocomposites realize a minimum reflection loss of -22 dB at 7 GHz and a remarkably larger effective absorption bandwidth of 3.9 GHz in the lower frequency range of 2~8 GHz. Radar-wave transmissions through SrFe12O19/LSR and CIP/LSR nanocomposites in single- and double-layered structures are analyzed with CST electromagnetic-field simulation software to calculate radar reflectivity for various absorbing-layer thicknesses. Dual-layer absorbing structures are modeled by specifying SrFe12O19/LSR and CIP/LSR nanocomposites, respectively, as match and loss layers, which are predicted to acquire a significant improvement in radar-wave absorption when the thicknesses of match and loss layers approach 1.75 mm and 0.25 mm, respectively.

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In this study, strontium ferrite (SF)-incorporated zeolite imidazole framework (ZIF-8) (SFZIF-8) that can simultaneously uptake Pb(II) and tetracycline (TC) in solution was synthesized and characterized. The physicochemical properties of the as-prepared SFZIF-8 were characterized by various functional groups, higher average pore diameter (3.414 nm), and stronger negative charge (-30.5 mV). Adsorption kinetics, isotherms, effect of various water conditions including solution pH and temperature, and reusability were studied to evaluate its adsorption performance. The adsorption capacity of SFZIF-8 was compared with that of commonly used adsorbents (powder and granular activated carbon). SFZIF-8 showed much higher adsorption performance (429.6 mg/g and 433.4 mg/g for Pb(II) and TC, respectively) than powder activated carbon (129.9 mg/g and 142.0 mg/g for Pb(II) and TC, respectively) and granular activated carbon (249.3 mg/g and 263.0 mg/g for Pb(II) and TC, respectively) in Pb(II) and TC binary solutions. The SFZIF-8 adsorption behaviors for the removal of Pb(II) and TC were explained by the pseudo-first-order and Langmuir models from the adsorption kinetics and isotherm experiments, respectively. The regenerated SFZIF-8 exhibited a competitive performance even after the third cycle. These results indicate that Pb(II) and TC can be removed with SFZIF-8 via electrostatic attraction, surface complexation, hydrogen bonding, and π-π interactions. Therefore, by exhibiting effective and efficient adsorption performance, SFZIF-8 nanocomposites can be utilized as alternative and promising adsorbents for the simultaneous removal of both Pb(II) and TC.

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Perovskite solar cells attract significant interest due to their high-power conversion efficiencies. The replacement of charge-transporting layers using inorganic materials is an effective approach for improving stability and performance, as these materials are low-cost, highly durable, and environmentally friendly. This work focuses on the inorganic hole and electron transport layers (HTL and ETL), strontium ferrite (SrFe2O4), and zinc oxide (ZnO), respectively, to enhance the efficiency of perovskite solar cells. Favorable band alignment and high charge-collection capability make these materials promising. Experimental and computational studies revealed that the power conversion efficiency of the fabricated device is 7.80% and 8.83%, respectively. Investigating electronic properties and interface charge transfer through density functional theory calculations further corroborated that SrFe2O4 is a good HTL candidate. Our numerical device modeling reveals the importance of optimizing the thickness (100 nm and 300 nm) of the HTL and perovskite layers and defect density (1016 cm-3) of the absorber to achieve better solar cell performance.

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The paper is focused on the development and optimization of strontium ferrite nanomaterial and photosintered flexible thin films. These magnetic thin films are characterized with direct current (DC) and high frequency measurements. For photosintered strontium ferrite samples, we achieved relative complex permeability of about 29.5-j1.8 and relative complex permittivity of about 12.9-j0.3 at a frequency of 5.9 GHz.

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In this work, Fe-doped strontium titanate SrTi1-xFexO3-x/2-δ, for x = 0-1 (STFx), has been fabricated and studied. The structure and microstructure analysis showed that the Fe amount in SrTi1-xFexO3-x/2-δ has a great influence on the lattice parameter and microstructure, including the porosity and grain size. Oxygen nonstoichiometry studies performed by thermogravimetry at different atmospheres showed that the Fe-rich compositions (x > 0.3) exhibit higher oxygen vacancies concentration of the order of magnitude 1022-1023 cm-3. The proton uptake investigations have been done using thermogravimetry in wet conditions, and the results showed that the compositions with x < 0.5 exhibit hydrogenation redox reactions. Proton concentration at 400 °C depends on the Fe content and was estimated to be 1.0 × 10-2 mol/mol for SrTi0.9Fe0.1O2.95 and 1.8 × 10-5 mol/mol for SrTi0.5Fe0.5O2.75. Above 20 mol% of iron content, a significant drop of proton molar concentrations at 400 °C was observed. This is related to the stronger overlapping of Fe and O orbitals after reaching the percolation level of approximately 30 mol% of the iron in SrTi1-xFexO3-x/2-δ. The relation between the proton concentration and Fe dopant content has been discussed in relation to the B-site average electronegativity, oxygen nonstoichiometry, and electronic structure.

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In the present study two sets of nanocomposites consisting of an epoxy resin and BaFe12O19 or SrFe12O19 nanoparticles were successfully developed and characterized morphologically and structurally via scanning electron microscopy and X-ray diffraction spectra. The dielectric response of the nanocomposites was investigated by means of broadband dielectric spectroscopy and their magnetic properties were derived from magnetization tests. Experimental data imply that the incorporation of the ceramic nanoparticles enhances significantly the dielectric properties of the examined systems and their ability to store electrical energy. Dielectric spectra of all systems revealed the presence of three distinct relaxation mechanisms, which are attributed both to the polymer matrix and the nanoinclusions: Interfacial polarization, glass to rubber transition of the polymer matrix and the re-orientation of small polar side groups of the polymer chain. The magnetic measurements confirmed the ferromagnetic nature of the nanocomposites. The induced magnetic properties increase with the inclusion of hexaferrite nanoparticles. The nanocomposites with SrFe12O19 nanoparticles exhibit higher values of coercive field, magnetization, magnetic saturation and remanence magnetization. A magnetic transition was detected in the ZFC/FC curves in the case of the BaFe12O19/epoxy nanocomposites.

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Strontium ferrite was compounded with acrylonitrile butadiene rubber to prepare rubber magnetic composites. For cross-linking of the prepared materials, peroxide curing systems consisting of dicumyl peroxide as curing agent and zinc salts of acrylic and methacrylic acids as co-agents were used. The amount of strontium ferrite was kept constant in all experiments, while the main objective of the work was to investigate the composition of curing system and both types of co-agents on the cross-linking, physical-mechanical, dynamic and magnetic properties of the rubber magnets. The results showed that the change in composition of curing system has significant influence on cross-link density and properties of the tested composite materials. With an increasing amount of zinc based co-agents, significant improvement of tensile strength was achieved. The application of zinc based co-agents in peroxide vulcanization of rubber magnetic composites leads to the preparation of rubber magnets with not only good magnetic properties, but also with improved physical-mechanical characteristics.

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A new heterostructured (La,Sr)2FeO4-δ (LSF214)-La0.8Sr0.2FeO3-δ (LSF113) electrode has been synthesized to improve the oxygen reduction reaction (ORR). This new materials system was fabricated by the deposition of Sr(NO3)2 into the LSF113 framework followed by subsequent heat treatment, resulting in a new three-dimensional (3D) LSF214-LSF113 heterostructured electrode. This material system consists of a with Ruddlesden-Popper (R-P) LSF214 phase formed on the surface of the LSF113 framework. The ORR activity has been enhanced by 1 order of magnitude using the LSF214-LSF113 heterostructured electrode. The ORR enhancement was the result of higher catalytic activity of the LSF214 phase and a mismatch in the lattice parameter between LSF214 and LSF113 regions which results in oxygen molecule adsorption and oxygen vacancy formation become more favered. Impedance spectroscopy measurements revealed that the presence of LSF214 reduced the polarization resistance of the LSF113 electrode on a ceria-based electrolyte. The high frequency resistance (RH) and low frequency resistance (RL) decreased substantially due to the enhanced oxygen transport process and accelerated oxygen incorporation rate in the LSF214-LSF113 heterostructured electrode. The heterostructured LSF214-LSF113 electrode provides a promising new approach to improve the oxygen reduction reaction activity through multiphase materials systems with tailored microstructures.