Tetragonal CuFe2O4 Research Articles

Cubic CuFe2O4 Spinel with Octahedral Fe Active Sites for Electrochemical Dechlorination of 1,2-Dichloroethane.

CuFe2O4 spinel has been considered as a promising catalyst for the electrochemical reaction, while the nature of the crystal phase on its intrinsic activity and the kind of active site need to be further explored. Herein, the crystal phase-dependent catalytic behavior and the main active sites of CuFe2O4 spinel for electrochemical dechlorination of 1,2-dichloroethane are carefully studied based on the combination of experiments and theoretical calculations. Cubic and tetragonal CuFe2O4 are successfully prepared by a facile sol-gel method combined with high temperature calcination. Impressively, CuFe2O4 with the cubic phase shows a higher activity and ethylene selectivity compared to CuFe2O4 with the tetragonal phase, suggesting a significant facilitation of electrocatalytic performance by the cubic crystal structure. Moreover, the octahedral Fe atom on the surface of cubic CuFe2O4(311) is the active site responsible to produce ethylene with the energy barrier of 0.40 eV. This work demonstrates the significance of crystal phase engineering for the optimization of electrocatalytic performance and offers an efficient strategy for the development of advanced electrocatalysts.

A 3D oxalate‐bridged [CuIIFeII] coordination polymer as molecular precursor for CuFe2O4 spinel—photocatalytic features

AbstractA 3D heterometallic oxalate‐bridged coordination polymer [CuIIFeII2(H2O)(terpy)(C2O4)3]n (terpy = 2,2′:6′,2″‐terpyridine) (1) was investigated both as photocatalyst for the organic dye removal and as a single‐source precursor for the preparation of the copper ferrite (CuFe2O4) nanocrystals by thermal processing. The dual functionality of 1 was supported by the degradation of aqueous solutions of rhodamine B (RhB) and methylene blue (MB) solutions under visible (Vis) and ultraviolet (UV) light irradiation, powder X‐ray diffraction data collection at room temperature, and the optical and scanning electron microscopy analyses. A close inspection of the X‐ray diffraction patterns unveiled qualitative and quantitative information on the phase composition obtained after the single‐source molecular precursor route to spinel oxide. By optimizing the temperature levels and setting the controlled heating rate at 6 h of holding time, the phase composition of thermal processing of 1 was evaluated—thermal treatment of 1 at 950°C for 6 h and a heating/cooling rate of 10°C min−1 resulted in the formation of solely tetragonal spinel phase of CuFe2O4, whereas the formation of both tetragonal and cubic CuFe2O4 phases was observed at 950°C by the heating rate of 30°C min−1. To obtain the high‐temperature cubic CuFe2O4 oxide, compound 1 was heated and then quenched at 925°C, which led to the formation of the cubic spinel ferrite as the main crystalline oxide phase. Moreover, the photocatalytic properties of the t‐CuFe2O4 spinel were investigated under the same conditions as for 1. The optical bandgap energies were estimated from UV–Vis absorption spectra for both metal oxide and precursor powder.

Synthesis of glycine-mediated CuO–Fe2O3–MgO nanocomposites: Structural, optical, and antibacterial properties

Multi-phase metal oxides nanocomposites (NCs) have attracted considerable attention due to their extraordinary properties and novel applications over monometallic ones. Hence, trimetallic oxides nanoparticles (NPs) are preferred because of their immensely improved optical, catalytic, and biological properties, but few materials have been reported. Besides, glycine is an excellent structure-directing agent for NPs production with tailored physicochemical properties. Thus, in this work, a novel tri-phase CuO–Fe2O3–MgO (1:1:1) NCs was prepared via a sol-gel method in the presence of glycine as a fuel. The obtained NCs were characterized by Fourier transmission infrared, X-ray diffraction (XRD), Scanning electron micrographs, and UV-Vis. The XRD analysis emphasized the formation of NCs with monoclinic CuO, cubic MgO, hexagonal Fe2O3, and tetragonal CuFe2O4 crystals. The average crystallite size (D) was in the order of 10th of nm as computed by Scherrer method, with ternary phase seemingly affect the straightforward influence of glycine fuel concentration on the final crystallite sizes. UV-Vis analysis indicates two optical energy bandgaps which increased as glycine concentration increase. The antibacterial test against Staphylococcus aureus and Escherichia coli bacteria revealed comparable activity to that of Azithromycin standard drug, which increased with glycine concentration increase. The glycine-based tailored structural, optical, and biological properties of such trimetallic NCs making them of considerable candidate for certain applications development, possibly electronics and antibiotics; a case that encourage further investigations.

Removal of ultralow concentration arsenic by high-temperature synthesized tetragonal CuFe2O4 with surficial grafting hydroxyl

Copper ferrite (CFO) as an excellent spinel adsorption material can significantly reduce the concentration of As in water. This work explores a method to synthesize hydroxyl-rich copper ferrite (h-CFO) at a low cost and on a large scale via combining sintering method and hydrothermal treatment using CuO and Fe2O3 as raw materials. This work has optimized the performance of h-CFO via adjusting atmosphere, temperature, holding time, and used it to removal As(V) in water. The results show that tetragonal CFO prepared at 800 °C for ten hours (h-CFO800-10 h-Air) has the best As(V) removal performance, h-CFO800-10 h-Air can reduced the concentration of As(V) from 10 mg L−1 to 4.77 μg L−1 in the acidic aqueous solution. Through XPS, BET, FTIR and Raman spectroscopy characterization, it can be known that the ability of h-CFO is related to its crystal form and the number of hydroxyls on its surface. The result of XPS and Raman spectroscopy also show that the As ion-containing in water will be interacted with the hydroxyls of the As ion-containing which has been adsorbed on h-CFO to form secondary adsorption.

Construction of single-crystal nanoparticles assembled CuFe2O4 spinel microspheres towards high infrared emissivity

Recently, spinel-based materials have attracted tremendous interest in high infrared radiation regimes owing to their unique crystal structure. Nevertheless, to date, it still remains a formidable challenge to efficiently design and synthesize spinel materials with excellent infrared radiation properties at lower temperatures, especially for the tetragonal CuFe2O4 spinel. Herein, a simple two-step strategy (i.e., solvent-thermal treatment and subsequent calcination) was developed to fabricate single-crystalline nanoparticles assembled tetragonal CuFe2O4 microspheres (MSs) at a low sintering temperature of 800 °C (denoted as CFO-800). Thanks to the synergy of intrinsic factors including the single crystal properties and moderate CuO impurity as well as the unique spherical structure, the resultant CFO-800 specimen is endowed with enhanced infrared absorption. Consequently, the emissivity values are achieved as high as 0.514 at room temperature and even 0.972 at a test temperature of 800 °C in the wavelength range of 3 – 5 µm. More importantly, this research provides valuable insights into the rational design and construction of single-crystalline spinel materials with enhanced infrared radiation performance.

Facile solid-state synthesis of tetragonal CuFe2O4 spinels with improved infrared radiation performance

Spinel materials are gradually becoming promising materials for high infrared emissivity owing to their unique crystal structure. However, the facile low-temperature solid-state synthesis of infrared radiation materials with superior emissivity remains a tremendous challenge. Herein, a general and simple approach for scalable synthesis of CuFe2O4 samples with spinel structure at low temperatures is smartly developed. The optimal experimental conditions for the infrared emissivity of CuFe2O4 are obtained by the detailed investigation into experimental parameters including calcination temperatures, heating rates, and the mass of polyvinyl pyrrolidone. Under the optimal experimental conditions, the infrared emission values of CuFe2O4 in the wavelength range of 3–5 μm can be as high as 0.986. More significantly, the work here will provide significant guidance for the efficient preparation of spinel materials with excellent infrared emissivity, especially at low temperatures.

One pot molten salt synthesis and photocatalytic studies of magnetically separable copper ferrite microcrystals

The preparation of tetragonal and cubic structured CuFe2O4 microcrystals by the one-pot molten salt synthesis in a eutectic mixture of NaCl - KCl molten salts at 800–900 °C is reported. Phase evolution and single-phase formation of CuFe2O4 on temperature and soaking period effect were studied. The structure and morphology of the synthesized compounds were investigated using techniques such as powder X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Microscopy studies revealed microcrystals of CuFe2O4 in an octahedron morphology. Photoluminescence and X-ray photoelectron spectroscopy analysis revealed the existence of surface oxygen defects on both prepared compounds. The photocatalytic studies of tetragonal and cubic structured CuFe2O4 catalysts shown 89% and 93% degradation of the Rhodamine-B (RhB) dye, respectively, under UV-A (366 nm) irradiation in 90 min. Photocatalytic and magnetic studies indicate that these CuFe2O4 samples are suitable magnetic separable photocatalysts for efficient dye degradation, and can be reasonably reused.

IMPACT OF CHROMIUM DOPING ON STRUCTURAL, OPTICAL, MAGNETIC AND ELECTRICAL PROPERTIES OF NANO-COPPER FERRITE

Nanoparticles copper ferrites doped with chromium CuCrxFe2- xO4 (0≤x≤ 0.25) were prepared using sol-gel auto combustion. Analysis of XRD revealed that the samples crystallized in single phase tetragonal CuFe2O4 structure. Results of Rietveld refinement using Full proff program showed that the lattice parameter a increased, lattice parameter c, the unit cell volume and tetragonal distortion decreased with increasing Cr3+ concentration. A cation distribution ensured that a system (CuCrFeO4) is completely inverse and distorted. In addition, crystallite size increased with the increase of Cr3+content.Furthermore, optical energy band gap of the obtained spinel ferrite decreased from 2.441eV to 2.228 eV with the increase of Cr. Results of magnetic properties indicated that the saturation magnetization decreased from 24.1 to18.3 emu/g with Cr increment, due to a lower magnetic moment of Cr3+ ion (3mB) than that of Fe3+ ion (5mB).Coercivity decreases with increasing Cr-concentration can be attributed to the reduction in magnetocrystalline anisotropy (K) where, chromium ferrite has negative magnetocrystalline anisotropy. Squareness ratio decreased continuously with Cr content, which it displayed that the materials exhibited to soft magnetic properties. Dielectric properties were analyzed in frequency range (0.1-7MHz) at different temperatures (50- 150ºC).From electrical measurements, it was found that έ decreased at lower frequency, become nearly constant at higher frequencies for all samples and increased with increasing temperature. έ was found to increase with increasing Cr because the Cr is reducing the hopping probabilities across the grain boundaries. . Also, it was found that activation energy ΔE decreased with increasing Cr concentration.

Effect of pre-oxidation on surface scale microstructure and electrical property of Cu-Fe coated steel interconnect

Pre-oxidation is introduced to optimize the performance of the Cu-Fe coated steel as interconnect for solid oxide fuel cell. Oxidation kinetics, microstructure and area specific resistance (ASR) are investigated. Pre-oxidation effectively improves the oxidation resistance of Cu-Fe coated steel, and its influence of surface scale microstructure is significant. Pre-oxidation not only inhibits the growth of the Cr2O3 layer and decreases the contents of Cr and Mn in Cu-Fe conversion oxide layer, but also stabilizes the tetragonal CuFe2O4 and CuO on scale surface. Moreover, the scale ASRs of the Cu-Fe coated steels are clearly reduced by pre-oxidation.

57Fe Mössbauer study of high-yield CuFe2O4 nanoparticles produced by the levitation-jet aerosol technique with post-synthesis annealing

Pseudo-spherical cubic-shaped nanoparticles of spinel ferrite CuFe2O4 have been prepared using a two-stage process. At first, an evaporation of levitating copper–iron drop into mix of helium–air gas flow took place, which resulting in copper ferrite-based powders. Then, such powders were additionally oxidized trough the heterogeneous auto-wave combustion in open air. We studied the effect of performing the synthesis in either an air or a helium environment on the phase composition of nanoparticles, and how the use of a post-synthesis annealing step modifies this, using room temperature 57Fe Mossbauer spectroscopy. By applying this technique, we are able to distinguish between the normal (non-magnetic) and inverse cubic (magnetic) phases of CuFe2O4, which is usually inaccessible using X-ray diffraction, as well as quantifying their relative amounts within each sample. Furthermore, we have been able to quantify trace amounts of the tetragonal CuFe2O4, phases that are typically obscured by line-broadening effects within our X-ray diffraction data, which indicates that annealing using a propane flame can also cause a cubic to tetragonal distortion in the crystal structure of the spinel lattice. Finally, by combining our Mossbauer parameters, which are sensitive to the Fe-containing phases only, with X-ray diffraction data, which are sensitive to all phases, we report on the full phase composition for the first time for nanoparticles produced via this synthesis route.

A kinetic study on the mechanisms of metal leaching from the top surface layer of copper aluminates and copper ferrites.

Recent studies have reported the potential copper immobilization in aluminates (CuAl2O4 and CuAlO2) and ferrites (tetragonal CuFe2O4 and cubic CuFe2O4) and suggested a reliable method to stabilize metals in reusable ceramic products. In this study, copper immobilization effect was further analyzed in the leaching solutions with pH close to environmental conditions. The results from the chemical equilibrium model Visual MINTEQ illustrated that almost all copper, aluminum, and iron formed complexes with CH3COO- ions in the leachates. The dissolution behavior on sample surface was further explicated by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The weight percentage of leached copper was lower than 0.1% even after 22-day leaching, indicating the successful copper stabilization in aluminates and ferrites. The results showed the highest copper concentrations in CuAlO2 leachates and the smallest leached copper amount from tetragonal CuFe2O4, respectively. The incongruent dissolution with Al-O or Fe-O bonds still remaining on the solid surface may be beneficial for preventing further leaching of copper. Furthermore, the modeling of reaction kinetics found that copper leaching from the CuAl2O4 and CuAlO2 obeyed the second-order reaction with correlation coefficients higher than 0.99. Moreover, the shrinking core model was chosen to analyze the leaching mechanisms of both CuFe2O4 ferrites, and the diffusion through product layer model acted as the rate-controlling step in their leaching process.

Influence of Cu dope on the structural behavior of MgFe2O4 at various temperatures

The influence of Cu doping on the MgFe2O4 crystal and magnetic structure has been studied at various temperatures. A series of Mg1-xCuxFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) spinels have been prepared by a chemical solid-state reaction method. The diffraction patterns confirmed that the formation of the single cubic spinel phase obtained for samples with a Cu content of up to 0.6. The second phase of a small amount of tetragonal CuFe2O4 phase was observed in the sample with x = 0.8. Cu doping increased and stabilized the magnetization of MgFe2O4 at a high temperature. The crystal phase of Cu doped MgFe2O4 was not changed up to 753 K.

Preparation and study of (1 − x)CuFe2O4–xBaTiO3 (x = 0, 0.1 and 1) composite multiferroics

The parent and mixed spinel–perovskite composite of (1 − x)CuFe2O4–xBaTiO3 (x = 0, 0.1 and 1) has been prepared by solid-state reaction method and studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Mossbauer spectroscopy, magnetometry and P-E lope tracer. The XRD results showed the formation of single phase tetragonal spinel CuFe2O4 and tetragonal perovskite BaTiO3 at room temperature, further XRD of composite 0.1CuFe2O4–0.9BaTiO3 reflects the two crystallographic phases with 1:9 ratio. The SEM micrographs show the homogeneous and uniform formation of the samples. Through EDAX analysis, the chemical composition of the sample is found to be same as the nominal composition. The high field Mossbauer data of CuFe2O4 sample shows the ferrimagnetic ordering in the sample. The observed M-H and P-E loops of the composite 0.1CuFe2O4–0.9BaTiO3 sample show the presence of spontaneous magnetization and spontaneous electric polarization indicating the multiferroic nature of the sample.

Enhanced Anisotropy in Tetragonalized (Cu,Co)Fe2O4 Particles via the Jahn–Teller Effect of Cu2+ Ions

We studied the Jahn–Teller (JT) effect of Cu2+ ions on the tetragonalization of CuFe2O4 and (Cu,Co)Fe2O4 particles. Sub-micrometer-sized CuFe2O4 and (Cu,Co)Fe2O4 particles were synthesized via coprecipitation and flux methods, followed by a heat-treatment process. From the X-ray diffraction patterns, all particles were found to be cubic spinel after flux treatment. The tetragonalization process was carried out by a heat-treatment process in air, where the temperature was varied between 700 °C and 900 °C, followed by furnace cooling. We confirmed that the ideal temperature for the tetragonalization of both CuFe2O4 and (Cu,Co)Fe2O4 is 900 °C. The obtained single-phase tetragonal spinel-structured CuFe2O4 and (Cu,Co)Fe2O4 particles indicate tetragonal distortion as a consequence of the JT effect of the Cu2+ ions. The results of saturation magnetization suggest that most of the divalent ions are in the B sites. The lengthening of the c-axis due to the JT effect increased the coercivity of the CuFe2O4 and (Cu,Co)Fe2O4 particles during the cubic–tetragonal phase transformation. The tetragonal (Cu,Co)Fe2O4 particles showed a saturation magnetization of 26 emu/g and a coercivity of 2200 Oe.

Structural analysis and magnetic properties of biphasic chromium-substituted copper ferrites

Nano CuFe2−xCrxO4 ferrite has been prepared by citrate autocombustion method. The impact of heat treatment and Cr contents on the structural phases and parameters were studied by tracing X-ray diffraction (XRD) patterns. As-prepared samples were found to contain a major cubic CuFe2O4 phase associated with minorities of CuO and tetragonal CuFe2O4 phases. Upon annealing at 600 °C, the content of tetragonal phase increased while CuO phase disappeared. On the other hand, replacing Fe by Cr in the CuFe2−xCrxO4 system reduces the formation of the tetragonal phase. Carrying out Rietveld analysis, the phase percentage and lattice parameters of both phases as well as the crystallite size were correlated with Cr content. Moreover, the change of the inversion occupancy parameter and the degree of tetragonality were studied in detail. Finally, magnetic properties including saturation magnetization and coercive field of the annealed samples, and their dependence on the degree of tetragonality and crystallite size, were elaborated using vibrating sample magnetometry (VSM).

Effect of fabrication method on the structural and the magnetic properties of copper ferrite

Copper ferrites (CuFe2O4) were fabricated by using the self-combustion urea and glycine process (UNP, and GNP), the polymerized complex (PC), the solid-state reaction (SSR), and the molten-salt (MS) methods. The synthesized powders were calcined in static air at different temperature from 773 to 1173 K. The effects of the fabrication method on the microstructural and the magnetic properties were investigated. X-ray diffraction (XRD) analysis results revealed the cubic CuFe2O4 spinel structure for the original powders. The tetragonal CuFe2O4 spinel structure was obtained after calcination. Vibrating sample magnetometry (VSM) showed significant changes in the magnetic properties of the CuFe2O4 system with fabrication method, phase composition, and heat treatment.

Redox chemistry of a binary transition metal oxide (AB2O4): a study of the Cu(2+)/Cu(0) and Fe(3+)/Fe(0) interconversions observed upon lithiation in a CuFe2O4 battery using X-ray absorption spectroscopy.

Copper ferrite, CuFe2O4, is a promising candidate for application as a high energy electrode material in lithium based batteries. Mechanistic insight on the electrochemical reduction and oxidation processes was gained through the first X-ray absorption spectroscopic study of lithiation and delithiation of CuFe2O4. A phase pure tetragonal CuFe2O4 material was prepared and characterized using laboratory and synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. Ex situ X-ray absorption spectroscopy (XAS) measurements were used to study the battery redox processes at the Fe and Cu K-edges, using X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and transmission X-ray microscopy (TXM) spectroscopies. EXAFS analysis showed upon discharge, an initial conversion of 50% of the copper(ii) to copper metal positioned outside of the spinel structure, followed by a migration of tetrahedral iron(iii) cations to octahedral positions previously occupied by copper(ii). Upon charging to 3.5 V, the copper metal remained in the metallic state, while iron metal oxidation to iron(iii) was achieved. The results provide new mechanistic insight regarding the evolution of the local coordination environments at the iron and copper centers upon discharging and charging.

Beneficial use of aluminium and iron components of sludge incineration residues in ceramic materials

A huge amount of sludge is generated from sewage treatment and waterworks. With the development of sludge incineration technology, most of the produced residues are buried in landfills, resulting in the loss of major constituents such as aluminium and iron that are present in the sludge residue. Moreover, toxic metals can leach out, causing further pollution. The need for “waste-to-resource” technology provides an incentive to develop economically viable reuse options. This study investigated the feasibility of beneficially incorporating aluminium and iron into marketable ceramic products. With CuO in the system, the CuAl2O4 spinel predominantly incorporated aluminium from waterworks sludge residues, while the CuFe2O4 spinel was a major iron-containing phase in the sewage sludge residue series. The maximum fraction of aluminium in the CuAl2O4 reached 98% and 83% for the α-Al2O3 + CuO and kaolinite + CuO systems, respectively. Using Fe2O3, iron was transformed into both tetragonal and cubic CuFe2O4, reachi...

Structural, dielectric and electromagnetic shielding properties of Ni–Cu nanoferrite/PVP composites

Abstract Nickel–copper (Ni–Cu) nanoferrites were synthesized using solution combustion method. The XRD pattern of the as prepared and calcinated samples at 600 °C revealed the presence of both cubic NiFe2O4 and tetragonal CuFe2O4 phases. Frequency and temperature dependence of dielectric constant (ɛ′), dielectric loss (tan δ) and a.c. conductivity (σac) studies have been undertaken on the Ni–Cu nanoferrites blended with polyvinylpyrrolidone (PVP) in the range 100 Hz–5 MHz. Studies have shown increasing trend of ɛ′, tan δ and σac with the increase of temperature for Ni–Cu ferrite nanoparticles in the PVP matrix. Further, frequency and temperature dependence of electromagnetic interference (EMI) shielding effectiveness (SE) is studied. The SE is found to increase with the temperature and decrease with an increase in the frequency. Ni–Cu nanoferrite/PVP composites were demonstrated a promising efficient material for the absorbing of electromagnetic waves because of a large amount of dipole polarizations in the polymer backbone and the interfaces of the ferrite nanoparticles and PVP matrix.

Photocatalytic Activities of CdO-Fe<sub>2</sub>O<sub>3</sub>, CdO-CuFe<sub>2</sub>O<sub>4</sub> and CdO-ZnFe<sub>2</sub>O<sub>4</sub> Nanocomposites

Magnetically separable CdO-Fe2O3, CdO-CuFe2O4 and CdO-ZnFe2O4 nanocomposites have been prepared by precipitation method. The X-ray diffractogram shows face centered cubic CdO, cubic CdO2, rhombohedral α-Fe2O3, orthorhombic β-Fe2O3, cubic γ-Fe2O3 and tetragonal FeOOH as the constituents of CdO-Fe2O3 composite. The components of CdO-CuFe2O4 composite are face centered cubic CdO, body centered tetragonal CuFe2O4 and cubic γ-Fe2O3. Face centered cubic CdO and ZnFe2O4, cubic γ-Fe2O3 and rhombohedral α-Fe2O3 are the constituents of CdO-ZnFe2O4 composite. The energy dispersive X-ray spectra confirm the presence of the corresponding elements and provide the composition. The scanning electron micrographs show that the composite particles are of spherical shape and of nanodimension. The composites absorb visible light. The charge transfer resistances of the composites are larger than their constituents. CdO-Fe2O3 and CdO-CuFe2O4 composites display ferromagnetic behavior. The visible light-photocatalytic activities and bactericidal activities of the composites are larger than their precursors.