Citrate Auto-combustion Method Research Articles

Mechanical and durability properties of cementitious brick containing Nano Ferrite

This research investigates the influence of addition of Nano materials (Nano ferrite) on the physical and mechanical properties of the cementitious brick, by adding 1, 2, 3% of Nano ferrite by weight of cement. Bearing strength tests at RT and exposure to 100, 200, 300°C temperature after 4 hour, Bulk density and water absorption of resulting bricks were tested. Ni-Zn-Mg-ferrite nanoparticles were prepared using citrate auto combustion method using the X-Ray Diffraction (XRD) to characterize the prepared sample where found the particle size is (49.6 nm) with good crystalline structure. The results show that possibility to synthesize nanoparticles, the optimum content of the Nano ferrite was 2% that produces the ultimate increase in the bearing strength and improvement in physical properties. The mechanical test results showed a tendency to lose strength at high temperature. It was found that a decrease in the water absorption from 4.913 to 3.273 wt % occurred at 3% of Nano ferrite.

Synthesis, characterization of NdCoO3 perovskite and its uses as humidity sensor

The perovskite NdCoO3 nanoparticles were prepared by the citrate auto combustion method. The synthesized powders were characterized by XRD, HRTEM, EDAX, and AFM analyses. The XRD pattern of NdCoO3 confirms the orthorhombic perovskite structure with an average crystallite size of 14.46 nm. The EDAX data indicate that the precursors have fully undergone the chemical reaction to form the predictable composition of the investigated sample. The magnetic hysteresis properties were carried out at room temperature and 100 K. At low temperature, the coericivity of the investigated samples is approximately equal to 22.644 G which is approximately 2.5 greater than its value at room temperature. The investigated sample shows paramagnetic behavior at both temperatures. This behavior can be attributed to the change of electron configurations and ligand field states. The ferroelectric nature was identified by taking the P–E loops at various applied voltages. The spin state of cobalt ions plays an important role in the magnetic properties and humidity-sensing behavior. The humidity-sensing behavior of the prepared sample was studied in a wide range of working humidity (11–97% RH) and testing frequency (100 Hz–100 kHz). The proposed humidity sensor was evaluated in terms of hysteresis, repeatability, and recovery time. Based on the obtained data the optimum testing frequency was chosen to be 100 Hz. The proposed sensor shows a very fast response of 3 s for low humidity. The humidity sensor exhibits good sensitivity over a middle RH range (11–43%).

Optimizing the physical properties of cobalt/graphene nanocomposites for technological applications

Cobalt nanoferrites with formula CoFe2O4, and CoFe2O4/GR were synthesized using a citrate auto-combustion method. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy (SEM) and the Fourier-transform infrared (FTIR) spectroscopy. The dependence of structure, magnetic and optical properties of cobalt/graphene nanocomposites on the graphene content was studied. The obtained data show that the CoFe2O4 nanoparticles are homogenously decorated on the graphene layers, which act as magnetically inactive layers in turn affecting the magnetization. The high coercivity Hc values reflect that CoFe2O4/GR nanocomposites are hard magnets at room temperature. The energy band gap of the cobalt/graphene is estimated using Kubelka–Munk equation. The energy gap of the investigated nanocomposites was found about 1.4 eV for direct transition. The samples with high saturation magnetization values can affect by the external magnetic field, which is favorable to their application in high adsorption capacity.

Hexaferrite materials displaying ultra-high coercivity and sub-terahertz ferromagnetic resonance frequencies

Single-domain Sr 1− x /12 Ca x /12 Fe 12− x Al x O 19 ( x = 4–6) particles are synthesized by a simple citrate auto-combustion method. The room temperature coercivity of the materials rises with aluminum content from 21.3 kOe ( x = 4) to a maximum of 36 kOe ( x = 5.5). This value is the highest among ferrite materials to date. Moreover, the magnetic alignment of the particles leads to further coercivity improvement up to 40 kOe. Due to large magnetic anisotropy the samples demonstrate sub-terahertz electromagnetic wave absorption by natural (zero-field) ferromagnetic resonance (NFMR). The absorption lines shift with aluminum substitution from 160 GHz ( x = 4) to 250 GHz ( x = 5.5), which is the record NFMR frequency known for a magnetic material. This research paves the way for development low-cost materials with extremely high coercivity and sub-terahertz NFMR.

Multiferroic properties of Gd/Er doped chromium ferrite nano sized particles synthesized by citrate auto combustion method

The non-stoichiometric Gd/Er doped Chromium nano ferrite with uniform and tunable size has been successfully synthesized by citrate auto combustion method. The prepared samples exhibit a combination of nonstoichiometry and non electroneutrality. The neutrality in the investigated samples is well maintained via the reduction of oxygen or removal of Cr ions. The ferromagnetic as well as the ferroelectric hysteresis loops of the investigated samples were studied. The obtained data shows that the antiferromagnetic nature in CrFe2O4 (CrFeO3) is turned into weak ferromagnetism in rare earth doped chromium. The substitution of rare earth ions for Fe can dramatically improve the saturation magnetization and remnant magnetization. The band gap energy was calculated from near infrared (NIR) and visible (VIS) reflectance spectra using the Kubelka-Munk function. Special attention should be given to chromium ferrite nanoparticles which are suitable candidates to be used in many applications like non-volatile data storage and camera flashes due to their ferroelectrics properties.

Synthesis of cobalt/calcium nanoferrites with controllable physical properties

In the present study, Co1−xCaxFe2O4 (0.0 ≤ x ≤ 1.0) were prepared by the citrate auto-combustion method. The evaluation of XRD patterns and HRTEM images indicated a fine particle nature. The average crystallite sizes are found to be in the range of 7.979–37.730 nm. The prepared calcium sample showed a orthorhombic phase structure, while the other investigated samples showed a cubic spinel structure. Elemental maps with the energy-dispersive X-ray spectroscopy (EDAX) analysis provide a visual representation of the elements present. The magnetic hysteresis measurements at different temperatures (77, 100, and 300 K) were achieved using a vibrating sample magnetometer. Magnetic constants such as magnetic moment, squareness ratio, saturation magnetization, coercivity, maximum energy density, and the switching field distribution were calculated and reported. The obtained data shows that, the shape of investigated nanoferrite particles can be used as a powerful tool for adapting magnetic properties. The appearance of double peaks in SFD reveals the competition between strong dipolar interactions and exchange coupling. The substitution of calcium instead of cobalt decreases the magnetic energy loss and the switching field distribution. However, for these reasons, the studied samples can be used in transformer cores and high density recording.

Photocatalytic Degradation of Humic Acids Using LaFeO3

TiO2 photocatalytic degradation of dissolved organic matter (DOM), namely humic substances composed of humic (HA) and fulvic acids, has been investigated for decades. However, the application of non-TiO2 photocatalysis for this purpose has only received recent attention. Aiming to fill this gap, this study was performed to elucidate the photocatalytic degradation of HAs using the novel photocatalyst LaFeO3 (LF) under simulated solar light irradiation. HA was selectively fractionated by ultrafiltration to two different molecular size fractions representing high molecular fraction as 100 kDa and lower molecular size fraction comprised of humic components expressing size fractions smaller than 30 kDa. Photocatalyst LF was prepared by the citrate auto-combustion method and characterized by using various techniques and Brunauer–Emmett–Teller (BET) surface area. Ultraviolet-visible (UV-vis) and excitation-emission matrix (EEM) fluorescence spectroscopic features were used to characterize the treated HA and photocatalytic mineralization extend was followed by dissolved organic carbon (DOC) contents. Photocatalytic performance of LF was compared to the metal modified version as Cu-doped LF. Highest mineralization was achieved upon the use of a photocatalyst dose of 0.25 mg/mL of LaFe0.90Cu0.10O3−δ (Cu-LF) for 30 kDaHA, whereas lowest mineralization was attained for 100 kDaHA upon the use of LF. Photocatalytic degradation kinetics indicated the possible use of LF and Cu-LF for the degradation of HA.

Influence of synthesis methods on structural and magnetic characteristics of Mg–Zn-ferrite nanopowders

Abstract Structural characteristics and magnetic properties of MgxZn1–xFe2O4 (x = 0.25; 0.5; 0.7) nanomaterials prepared by autocombustion, co-precipitation and spray pyrolysis methods were studied. Different characterization techniques are used to study the structural formation of the generated nanoparticles, namely X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopy (TEM), infrared spectroscopy (FT-IR) and vibrating sample magnetometery (VSM). In case of citrate autocombustion and co-precipitation methods, the magnetization goes through a maximum at Mg0.5Zn0.5Fe2O4 composition, while the dependence on the composition is subtle for spray pyrolysis. An increase in temperature and duration of heat treatment during the synthesis process leads to a particle size growth and to a cation redistribution between spinel sub-lattices. These resulted in a significant increase in the specific magnetization of the particles generated by citrate autocombustion method. The nanoparticles synthesized by co-precipitation method exhibit superparamagnetic behavior with no coercivity at room temperature. Nonetheless, the materials prepared by spray pyrolysis and citrate autocombustion methods are found to possess small coercivity of 30–80 Oe. The highest specific magnetization at room temperature is referring to Mg0.5Zn0.5Fe2O4 nanoparticles obtained by citrate autocombustion method (30 emu/g). The revealed correlations can be used to synthesize spinel ferrite nanoparticles with well-defined collective properties for a wide spectrum of applications.

Impact of Gd3+/graphene substitution on the physical properties of magnesium ferrite nanocomposites

Magnesium nano ferrite with composition MgFe2O4, MgGd0.05Fe1.95O4 and MgFe2O4 – 5 wt% GO was synthesized using a citrate auto-combustion method. The crystal structure, morphology, and magnetic properties of the investigated samples were studied. High Resolution Transmission Electron Microscopy (HRTEM) images show that the substitution of small amounts of Gd3+/GO causes a considerable reduction of the grain size. Studies on the magnetic properties demonstrate that the coercivity of GO-substituted magnesium nano ferrites is enhanced from 72 Oe to 203 Oe and the magnetocrystalline anisotropy constant increases from 1171 to 3425 emu Oe/gm at 300 K. The direct effects of graphene on morphology, crystal structure as well as the magnetic properties reveal that the studied sample are suitable for turbidity color and removal. The magnetic entropy change is estimated from magnetization data using Maxwell relation. The calculated Curie temperature from the Curie-Weiss law and the maximum entropy change are in good agreement with each other. Based on UV diffuse reflectance spectroscopy studies, the optical band gaps are in the range of 1.4–2.15 eV. In addition, the combination of small particle size and good magnetic properties makes the investigated samples act as a potential candidates for superior catalysts, adsorbents, and electromagnetic wave absorbers.

Physical and magnetic properties of (Ba/Sr) substituted magnesium nano ferrites

In the presented paper, strontium (Sr) and barium (Ba) nano ferrites were synthesized by citrate auto combustion method. The investigated samples are characterized by X-ray diffraction technique (XRD), field emission scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. The structural properties of the obtained samples were examined by XRD analysis showing that the synthesized nanoparticles are in cubic spinel structure. The average crystallite sizes are in the range of 22.66 and 21.95 nm for Mg0.7Ba0.3Fe2O4 and Mg0.7 Sr0.3Fe2O4 respectively. The VSM analysis confirms the existence of ferromagnetic nature of Sr2+/Ba2+ substituted magnesium nano particles. Exchange interaction between hard (Sr/Ba) and soft (Mg) magnetic phases improves the structural and magnetic properties of nano ferrite particles. Rigidity modulus, longitudinal and shear wave velocities are predicted theoretically from Raman spectroscopy and structural data of the investigated spinel ferrite. The magnetic and structural properties of magnesium are enhanced by doping with barium and strontium nano particles. The saturation magnetization, remanent magnetization and coercivity reported on vibrating sample magnetometer curve illustrate the promising industrial and magnetic recording applications of the prepared samples.

Modulation of microwave properties of La–Sr hexagonal ferrite with doping of Co–Zr and change in thickness

Cobalt–zirconium (Co2+–Zr4+) doped M-type lanthanum strontium hexaferrite with general formula, Sr0.85La0.15(CoZr)xFe12−2xO19 where x = 0, 0.25, 0.50, 0.75, 1.0, prepared by citrate auto-combustion method have been analyzed for the first time. These ferrites were characterized by X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscopy, vibrating sample magnetometer and vector network analyzer. The complex permittivity (ɛ′ − jɛ′′) and complex permeability (µ′ − jµ′′) were measured using vector network analyzer in 12.4–18.0 GHz (Ku-band) frequency range. Magnetic hysteresis data indicates 16.6% decrease in saturation magnetization Ms with substitution x (60.6 emu/g for x = 0.0 and 50.5 emu/g for x = 1.0). There is 53.79% decrease in coercivity Hc with substitution x (5692.55 Oe for x = 0.0 and 2630.38 Oe for x = 1.0). Microwave absorption of more than 99% has been obtained for all the synthesized ferrites at some frequency in Ku-band. So, microwave absorbers can be designed for different frequencies in Ku-band by varying the substitution x as well as thickness of the absorber.

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).

Fascinating improvement in physical properties of Cd/Co nanoferrites using different rare earth ions

Cadmium-cobalt-rare-earth nanoferrite samples of composition Cd0.7Co0.3Fe2O4 and Cd0.7Co0.3R0.05Fe1.95O4 (R = Ce, Sm, Gd, Er) were prepared by citrate auto combustion method. All samples were characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Micrographs (HRTEM), Energy Dispersive X ray Spectroscopy (EDAX) and Atomic Force Microscope (AFM). XRD confirmed the formation of cubic spinel structure with the appearance of small peaks designated as secondary phases. The average crystallite sizes were found to be between 40.3 and 22.1 nm for pure and Gd doped samples respectively. The magnetic properties were studied by carrying out the hysteresis of the investigated samples at room temperature and at 100 K. The magnetic parameters, such as the saturation magnetization, coercivity Hc, squareness and loop area are markedly affected by increment of rare earth ions at the expense of Fe3+ ions in a spinel structure. The increase in magnetization of the nano ferrite samples at 100 K, may be clarified by annihilation of a nonmagnetic layers (surface dead layers) due to the rare earth doping. Greater than nearly nine-fold increase in coercivity was observed in pure and Ce, Sm doped compared to the Gd and Er samples. The data for Hc, Ms and Mr of lanthanide doped ferrites suggest their suitability in applications like magnetic targeting and separators.

Investigation of Electromagnetic Properties of La-Doped Strontium Ferrite in X and Ku Bands

In the present study, the lanthanumsubstituted strontium ferrite particles with general formula, Sr1−xLa x Fe12O19 (x = 0, 0.10, 0.15, 0.20, and 0.25) were prepared using citrate auto-combustion method. These ferrites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM), and vector network analyzer (VNA). X-ray diffraction patterns show the formation of M-type hexaferrite phase without any secondary phases for all the synthesized samples. The complex permittivity (e ′– j e ″) and complex permeability (μ ′–j μ ″) were measured using VNA in X-band (8.2–12.4 GHz) and Ku-band (12.4–18 GHz) frequency range at room temperature. More than 90 % absorption was obtained in the Ku band for all the La3+ substituted strontium ferrites. The composition x = 0.15 exhibits a minimum reflection loss of −20.66 dB at 16.5 GHz and an absorption bandwidth of 2.1 GHz (15.63 to 17.64 GHz) with an absorber layer thickness of 1.6 mm. These materials can be used as cost-effective and thinlayer microwave absorbers in higherfrequency range.

Should the mass of a nanoferrite sample prepared by autocombustion method be considered as a realistic preparation parameter?

Detectable variations in structural, elastic and magnetic properties have been reported depending on the mass of the cobalt nanoferrite sample prepared by citrate autocombustion method. Heat released during the autocombustion process and its duration are directly proportional to the mass to be prepared, and is thus expected to affect both the crystallite size and the cation distribution giving rise to the reported variations in microstrain, magnetization, and coercivity. Formation of a pure spinel phase has been validated using X-ray diffraction patterns (XRD) and Fourier-transform infrared (FTIR) spectra. Crystallite sizes obtained from Williamson-Hall (W-H) method range from 28–87nm, being further supported by images of high-resolution transmission electron microscope (HRTEM). Saturation magnetization and coercivity deduced from M-H hysteresis loops show a clear correlation with the cation distribution, which was proposed on the basis of experimentally obtained data of XRD, VSM, and IR. Elastic parameters have been estimated using the cation distribution and FTIR data, with a resulting trend quite opposite to that of the lattice parameter.

Physical and magnetic properties of Mn–Zr doped La–Sr ferrite prepared by the auto-combustion route

This is the first report ever on (Mn2+–Zr4+) doped M-type lanthanum strontium hexaferrite with general formula, Sr0.85La0.15(MnZr)xFe12−2xO19 where x=0.0, 0.25, 0.50, 0.75, and 1.0, prepared by citrate auto-combustion method. These ferrites were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDX) and Vibrating sample magnetometer (VSM). X-ray diffraction patterns show the formation of high purity hexaferrite phase without other secondary phases for all the synthesized samples. It was observed from magnetic hysteresis data that the coercive force is reduced from 5692.5Oe to 1669.2Oe with increase in doping contents but the net magnetization of the samples varies slightly from 60.6 to 55.2emu/gm. High saturation magnetization (Ms), low coercivity (Hc) and remanence magnetization (Mr) values of these materials make them particularly suitable for data recording.

Correlating structural, magnetic, and luminescence properties with the cation distribution of Co0.5Zn0.5+xFe2–xO4 nanoferrite

Structural, magnetic, and luminescence properties have been investigated for Co0.5Zn0.5+xFe2−xO4 nanoferrite (0.0≤x≤0.4, with a step increment of 0.1) prepared by citrate autocombustion method. X-ray diffraction (XRD) patterns and Fourier-transform infrared (FTIR) spectra proved the formation of a pure cubic spinel phase for all AP samples. Although the ionic radius of Zn2+ is larger than that of either Fe3+ or Co2+, Rietveld analysis showed that the lattice parameter mostly decreases with increasing Zn substitution. The crystallite size of AP samples decreases gradually with increasing Zn substitution from 16 to 10nm, which is confirmed with high-resolution (HRTEM) micrographs. Magnetic parameters such as saturation magnetization, coercivity, and remanent field obtained from vibrating sample magnetometry (VSM) revealed a strong dependence on the cation distribution being proposed according to the experimental data of XRD, FTIR, and VSM. The cation distribution indicated that introduced nonstoichiometry is compensated by oxidizing Co2+ into Co3+, which explains the trend of the lattice parameter with increasing x. The distribution of Fe3+ ions between octahedral and tetrahedral sites was further confirmed by photoluminescence (PL) emission spectra.

Influence of Ce-Substitution on Structural, Magnetic and Electrical Properties of Cobalt Ferrite Nanoparticles

Nano-crystalline samples of cerium substituted cobalt ferrites with chemical formula CoCe x Fe2−x O4 (0.0 ≤ x ≤ 0.1) were prepared using the citrate auto-combustion method. The prepared ferrites were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy spectra (FTIR), transmission electron microscopy (TEM), and a vibrating sample magnetometer (VSM). The XRD patterns and FTIR spectra confirm that the prepared samples reveal the formation of a single-phase spinel structure. TEM micrographs showed that the particles are made up of spherical and elongated nano-metric shapes. A limitation of the size of nanoparticles is observed as the Ce3+ concentration increases. VSM measurements showed that the coercivity H c and magnetization values M s are strongly dependent on Ce3+ content and particle size. The values of H c lie in the range of (411–1600 G), which suggest that these samples are convenient for different applications. The alternating current electrical conductivity (σ), dielectric permittivities (ɛ′, ɛ″), and dielectric loss tangent (tan δ) were studied at different ranges of frequency and temperature. The relation of conductivity with temperature revealed a semiconductor to semi-metallic behavior as cerium concentration increases. The variation in (tan δ) with frequency at different temperature shows abnormal behavior with more than one relaxation peak. The conduction mechanism used in the present study has been discussed in the light of cation–anion–cation interactions over the octahedral B-site.

Characterization and Transport Properties of Mixed Ferrite System Mn1-xCuxFe2O4; 0.0 ≤ x ≤ 0.7

A series of Cu-doped Mn ferrites with the formula Mn1-xCuxFe2O4 (0.0 ≤ x ≤ 0.7) were synthesized by citrate auto combustion method. The structural characterization and morphology of the samples were examined by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), and scanning electron microscopy (SEM). XRD and EDX confirmed the formation of single-phase cubic spinel structure. The electrical conductivity (σ), dielectric constant (ϵ′), and dielectric loss factor (ϵ′′) were studied as a function of temperature at different frequencies ranged from 100 kHz to 5 MHz. Increasing is observed in the values of σ, ϵ′, and ϵ′′ with substitution of copper up to x = 0.3. Above this value, a decrease in σ, ϵ′, and ϵ′′ was detected.

Structural, magnetic and electrical properties of Bi doped LaFeO3 nano-crystals, synthesized by auto-combustion method

La1−xBixFeO3; 0 ≤ x ≤ 0.2 have been prepared by citrate auto-combustion method. The results of X-ray diffraction showed that LaFeO3 has single phase with orthorhombic structure. With increasing Bi content, traces of secondary phase of rhombohedral structure are observed. The transmission electron microscope showed that the prepared compositions have nanocrystalline structure with an increase of the particle size increases with increasing Bi content. The magnetic properties of the samples were investigated by vibrating sample magnetometer, in which saturation magnetization (Ms) and coercivity (Hc) were determined. The value of Ms increases with increasing Bi content up to x = 0.10, while Hc decreases with increasing Bi content. The temperature dependence of dielectric constant, dielectric loss and ac conductivity at different frequencies (100 kHz–5 MHz) were studied.