Spinel Cobalt Ferrite Research Articles

Changing the Magnetic Properties of Cobalt Ferrite Nanoparticles with Different Fabrication Conditions

In this study, crystalline nanoparticles CoFe2O4 with a spinel structure were prepared by hydrothermal methods. The magnetic properties of non-calcined cobalt ferrite formed from nanocrystalline powders. The dependence of the particle size and crystalline structure of obtained nanoparticles in the synthesis conditions was examined and characterized using field emission scanning electron microscope (FESEM), and X-ray diffraction analysis (XRD). The XRD analysis revealed a high degree of crystallinity and confirmed the spinel structure of crystalline nanoparticles CoFe2O4. The FESEM image shows the presence of spherical ferrite particles with an average diameter of about 13-18 nm. The results also show that the formation of cobalt ferrite spinel structures was affected by fabrication conditions. Magnetic hysteresis loop data confirm that the magnetic properties of nanoparticles depend on the synthesis conditions. The material prepared by the hydrothermal route and calcination at 150ºC with molar ration Co2+: Fe3+ = 1:2.2 for 2 hours has higher magnetic saturation than that of the surveyed samples.

Oxidation Behavior of Maraging 300 Alloy Exposed to Nitrogen/Water Vapor Atmosphere at 500 °C

Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical properties required in several industries, i.e., nuclear, automotive, etc. In this research, samples of maraging 300 alloy were aged using a novel procedure that combines different steps with two atmospheres (nitrogen and water vapor) for several hours. The oxidized surface layer was chemical, microstructural and micromechanically characterized. Due to the thermodynamic and kinetic conditions, these gases reacted and change the surface chemistry of this steel producing a thin iron-based oxide layer of a homogeneous thickness of around 500 nm. Within the aforementioned information, porosity and other microstructural defects showed a non-homogeneous oxide, mainly constituted by magnetite, nickel ferrite, cobalt ferrite, and a small amount of hematite in the more external parts of the oxide layer. In this sense, from a chemical point of view, the heat treatment under specific atmosphere allows to induce a thin magnetic layer in a mixture of iron, nickel, and cobalt spinel ferrites. On the other hand, the oxide layer presents an adhesive force 99 mN value that shows the capability for being used for tribological applications under sliding contact tests.

Development of magnetic, ferrite supported palladium catalysts for 2,4-dinitrotoluene hydrogenation

Cobalt, copper, and nickel ferrite spinel nanoparticles have been synthesized by using a combination of sonochemical treatment and combustion. The magnetic nanoparticles have been used as supports to prepare ~4 wt% palladium catalysts. The ferrites were dispersed in an ethanolic solution of Pd(II) nitrate by ultrasonication. The palladium ions were reduced to metallic Pd nanoparticles, which were then attached to the surface of the different metal oxide supports. Thus, three different catalysts (Pd/CoFe2O4, Pd/CuFe2O4, Pd/NiFe2O4) were made and tested in the hydrogenation of 2,4-dinitrotoluene (DNT). A possible reaction mechanism, including the detected species, has been envisaged based on the results. The highest 2,4-diaminotoluene (TDA) yield (99 n/n%) has been achieved by using the Pd/NiFe2O4 catalyst. Furthermore, the TDA yield was also reasonable (84.2 n/n%) when the Pd/CoFe2O4 catalyst was used. In this case, complete and easy recovery of the catalyst from the reaction medium is ensured, as the ferrite support is fully magnetic. Thus, the catalyst is very well suited for applicationy in the hydrogenation of DNT or other aromatic nitro compounds.

The effect of an external magnetic field on the photocatalytic activity of CoFe2O4 particles anchored in carbon cloth

Reducing the recombination capacity of electron-hole pairs is essential to optimize the photocatalytic process guided by semiconductors. This research aims to use an external magnetic field to study the influence that the external potential generated by the field can cause in degradation systems by heterogeneous photocatalysis.The catalytic process is improved by Lorentz force, using Helmholtz Coils to generate a 200 mT field of flow, in a heterogeneous photocatalysis system that makes use of CoFe2O4 particles as a catalyst for the degradation of Methylene Blue (MB) and Ibuprofen (IB) solutions, both at 20 mg L−1of concentration. The characterization showed that the inverted spinel cobalt ferrites were successfully synthesized by the protein sol-gel method. In addition, the obtained material has an electronic structure similar to cobalt ferrites described in the literature and it has good degradation capacity of both solutions. Photocatalytic efficiency could be improved by 80 % in the best of conditions just by positioning a permanent photocatalytic field. This study suggests that the Lorentz force acts in a way that is contrary to the photogenerated electrons in the process, reducing the recombination of these charges.Experimentally and quantitatively it is possible to see the increased degradation capacity of the catalysts in the presence of the magnetic field, from spectroscopic analysis of the solution being degraded.

Electrospinning of multiferroic CoFe2O4@ Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 nano-structured fibers via two different routes

Multiferroic composite materials have attracted a lot of attention for their excellent ferroelectric and ferromagnetic properties. For the first time one-dimensional core-shell structure of CoFe2O4/Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (CFO@BZCT) multiferroic composite was synthesized by electrospinning. The effect of electrospinning routes on the composite fibers properties was investigated. To do so, two different routes were utilized: the electrospinning of core and shell solutions using coaxial nozzle and the electrospinning of BZCT solution containing CFO fibers (with three different concentrations of 2, 4 and 8 g/100 ml solution). The fiber morphology was maintained for all samples in calcination temperatures up to 900 °C. Spinel cobalt ferrite and perovskite BZT-0.5BCT phases were crystallized for calcined composites. The nano and core-shell structure of composites were confirmed by the TEM analysis. Magnetoelectric coupling of CFO and BZCT phases was investigated by the temperature-dependent SQUID measurement, where a ferroelectric phase transformation at 100 °C induced magnetization changes. Low saturation magnetization and dielectric constant of 6.7 emu/g and 300 ± 10 were obtained for the sample synthesized by the first method while these values rose to 36.8 emu/g and 400 ± 30 respectively for the second method. A comparison of the two methods exhibited a larger fiber diameter, porous fibers and lower ferroic properties for the sample synthesized by the first method.

Cobalt ferrite microspheres as a biocompatible anode for higher power generation in microbial fuel cells

In the present study, spinel cobalt ferrite hierarchical flower-like microspheres (CoFe2O4-MS) are fabricated using a hydrothermal method and utilized as a biocompatible anode in microbial fuel cells (MFCs) for power generation. A maximum power density of 1964 mW m−2 is achieved with CoFe2O4-MS in a mediator-less MFC using Escherichia coli as a biocatalyst and glucose as a fuel. The unprecedented power generation by CoFe2O4-MS can be attributed to (i) the morphology of the flower-like CoFe2O4-MS, with a rough surface and large surface area suitable for biofilm formation, (ii) the rapid immobilization of negatively charged E. coli cells on the positively charged CoFe2O4-MS, facilitating stronger bacterial adhesion between the bacterial cells and CoFe2O4-MS, which leads to lower contact resistance and advantageous interfacial properties with rapid electron transfer, and, more importantly, (iii) enhanced interfacial charge transfer due to the presence of multi-valent cations and multiple valence states in the highly electrocapacitive CoFe2O4-MS. Thus, the enrichment of electroactive E. coli on CoFe2O4-MS produces a large number of electron-shuttling endogenous redox mediators, which promotes efficient extracellular electron transfer between E. coli and the electrocapacitive CoFe2O4-MS during the oxidation of the substrate, thus generating higher power output.

Structural, magnetic, and impedance properties of Co1-xZrxFe2O4 nanocrystallites by PEG-assisted sol-gel route

This work presents the Zr4+-substituted CoFe2O4 nanocrystallites at lower concentrations prepared via sol-gel method in order to investigate their structural and magnetic properties along with their impedance properties. XRD patterns confirm the inverse spinel phase of CoFe2O4 and the presence of zirconium (Zr) nanoparticles in the spinel network. The crystallite size was found to decrease after Zr substitution. CoFe2O4 nanocrystallites of 34-nm size and lattice parameter slightly increase with Zr4+ substitution into cobalt ferrite as observed from the XRD pattern. The presence of all functional groups involved in the present synthesis was determined from FTIR spectroscopy. Characteristic peaks of cubic spinel structured cobalt ferrites are observed in the Raman spectrum of each ferrite composition. The HRSEM images revealed the spherical morphology and nanosize of the Zr4+-doped CoFe2O4 nanocrystallites. EDX analysis confirmed that the applied process for the fabrication of Co1-xZrxFe2O4 nanoparticles is a proper process for the synthesis of spinel cobalt ferrites with homogeneity in composition. The TEM images evidently exposed formation of well-shaped nanoparticles and the fringes are uniform with 0.44-nm width and the selected area electron diffraction pattern exposed periodic arrangements. The results of magnetic hysteresis revealed that the zirconium-substituted cobalt ferrite nanoparticles increase the saturation magnetization and coercivity with increasing zirconium content. Impedance increased when Zr4+ was substituted, but for higher concentration it was reduced.

CoFe2O4 decorated g-C3N4 nanosheets: New insights into superoxide anion mediated photomineralization of methylene blue

Graphitic carbon nitride (g-C3N4) based photocatalysts have recently gained much attention for environmental remediation. However, the correlation between constituent counterparts in g-C3N4 based nanocomposites as well as mechanistic understanding related to the reactive oxygen species (ROS) have not been discussed much. Herein, ascribing to the significant thermodynamic potential of surface charge transfer between their conduction bands, we present spinel cobalt ferrite (CoFe2O4) decorated g-C3N4 nanosheets for photocatalytic mineralization of methylene blue (MB). The ROS are investigated using electron spin resonance (ESR) spectroscopy and the results confirm the formation of superoxide anion radical (O2-) as primary oxidant. Furthermore, UV–vis-NIR diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) analysis are utilized to plot alignment of energy levels against standard hydrogen electrode (SHE). The band diagram does not only support the O2- formation but also provides interesting insights to explain the degradation dynamics based on the respective band positions in the nanocomposite.

Synthesis, Characterization and Magnetic Hyperthermia of Monodispersed Cobalt Ferrite Nanoparticles for Cancer Therapeutics.

Magnetic nanoparticles such as cobalt ferrite are investigated under clinical hyperthermia conditions for the treatment of cancer. Cobalt ferrite nanoparticles (CFNPs) synthesized by the thermal decomposition method, using nonionic surfactant Triton-X100, possess hydrophilic polyethylene oxide chains acting as reducing agents for the cobalt and iron precursors. The monodispersed nanoparticles were of 10 nm size, as confirmed by high-resolution transmission electron microscopy (HR-TEM). The X-ray diffraction patterns of CFNPs prove the existence of cubic spinel cobalt ferrites. Cs-corrected scanning transmission electron microscopy–high-angle annular dark-field imaging (STEM–HAADF) of CFNPs confirmed their multi-twinned crystallinity due to the presence of atomic columns and defects in the nanostructure. Magnetic measurements proved that the CFNPs possess reduced remnant magnetization (MR/MS) (0.86), which justifies cubic anisotropy in the system. Microwave-based hyperthermia studies performed at 2.45 GHz under clinical conditions in physiological saline increased the temperature of the CFNP samples due to the transformation of radiation energy to heat. The specific absorption rate of CFNPs in physiological saline was 68.28 W/g. Furthermore, when triple-negative breast cancer cells (TNBC) in the presence of increasing CFNP concentration (5 mg/mL to 40 mg/mL) were exposed to microwaves, the cell cytotoxicity was enhanced compared to CFNPs alone.

Heterogeneous activation of peroxymonosulfate for bisphenol A degradation using CoFe2O4 derived by hybrid cobalt-ion hexacyanoferrate nanoparticles

A facile coprecipitation-thermal method is reported to prepare spinel cobalt ferrites CoFe2O4 nanoparticles (NPs) with a well-defined mesoporous dominated structure using hybrid cobalt-ion hexacyanoferrate (CoFeHCF) NPs as a template. The properties of the synthesized catalysts are evidenced by various characterization methods. And the effects of time, pH, catalyst/oxidant/BPA dosage, coexisting ions and natural organic matter (NOM) on catalytic degradation of bisphenol A (BPA) are investigated. The as-prepared CoFe2O4 shows a high catalytic performance of 97% elimination for 45 μM BPA in 40 min. The excellent catalytic performance could be attributed to the large specific surface area (66.18 m2/g) and high content of cobalt (the atomic ratio of Fe/Co is 1.86) of CoFe2O4 NPs. Slightly alkaline pH, higher catalyst dosage and anions including Cl− and CO32−/HCO3− are favorable for BPA degradation. Especially, 81.57% mineralization of BPA could be achieved in 60 min under the optimization system. The catalytic capacity of CoFe2O4 could be regenerated by simple washing and drying at 200℃, which is much lower than the crystal temperature. SO4∙− and HO∙ are the primary reactive species responsible for BPA oxidation while SO4∙− might play a dominant role. This work provides a novel method to produce CoFe2O4 nanocatalysts for contaminant degradation and encourage the extended application of CoFeHCF in the environment.

Induced symmetric 2D Mesoporous Graphitic Carbon Spinel Cobalt Ferrite (CoFe2O4/2D-C) with high porosity fabricated via a facile and swift sucrose templated microwave combustion route for an improved supercapacitive performance

Symmetric 2D Mesoporous Graphitic Carbon spinel cobalt ferrite (CoFe2O4/2D-C) with high porosity has been fabricated via a facile and swift sucrose template microwave combustion process followed by an additional annealing treatment. The CoFe2O4/2D-C composite comprises carbon coated spinel cobalt ferrite with densely connected porous layered structure facilitating fast electron and ion transport. Benefiting from such an inimitable structure, CoFe2O4/2D-C is employed as supercapacitors electrode material and exhibited a high specific capacitance (1318.1 Fg−1 at 2.5 A g−1 current density) and energy density (77.3 W h kg−1) with an excellent electrochemical capacity retention of 97.2 % after 4000 cycles. Power law which expresses the dependence of peak CV current on scan rate at fixed potential confirmed that, the charge storage mechanism for the electrode material (CoFe2O4/2D-C) is influenced congruently by both the capacitive and diffusive controlled process which promoted an efficient energy storage for CoFe2O4/2D-C. Accordingly, this outstanding performance put forward its application as an effective material for electrochemical capacitors.

Effect of decorating cobalt ferrite spinel structures on pistachio vera shell –derived activated carbon on energy storage applications

In this work, a simple insitu chemical co-precipitation technique was adopted for the synthesis of CoFe2O4 (Cf) decorated Pistachio shell derived activated carbon (Cf@Pv-AC) composite to fabricate electrodes for supercapacitor (SC) application. Doping of Cf particles on the surface of the Pv-AC effectively enhanced the diffusion of electrolyte ions by facilitating a porous structural morphology which act as the reservoir of electrolyte ions during the electrochemical redox reactions. FT-IR spectrum of Cf@Pv-AC composite exhibited the strong absorption band at 608 cm−1, which was associated to M-O bonds (Where M=Co and Fe) in Cf structure. FE-SEM images of Cf@Pv-AC suggested that Co-ferrite particles have evenly covered the surface of porous Pv-AC rods. Further, Cyclic voltammetric analysis (CV) of Cf@Pv-AC coated Ni foil electrode proved the battery type behavior of Cf in Cf@Pv-AC sample and delivered the specific capacity of 1233 C/g in the potential range of 0–0.69 V at the scan rate of 5 mV/s. These results revealed that the specific capacity value increased two fold than that of pure Cf (434 C/g) at the same scan rate. Moreover, the obtained results were also substantiated by Galvanostatic charge-discharge (GCD) measurements. About 93% of specific capacity retention was achieved by Cf@Pv-AC electrode, even after 5000 GCD cycles at the current density of 4 A/g, which were evident for the better capacitive performance of Cf@Pv-AC electrode material.

SnO2 QDs@CoFe2O4 NPs as an efficient electrocatalyst for methanol oxidation and oxygen evolution reactions in alkaline media

We successfully decorated SnO2 quantum dots (SQDs) on the surface of spinel cobalt ferrite (CFO) at room temperature by cost-effective method. Pristine CFO and CFO nanocomposites (CFO-Sn1 and CFO-Sn2) were used as an electrocatalyst for methanol oxidation reaction (MOR) and oxygen evolution reaction (OER). CFO-Sn2 led to superior MOR and OER in alkaline media owing to the improved conductivity and higher electrochemically active surface area compared to the pristine CFO and CFO-Sn1. CFO-Sn2 exhibited the highest anodic peak intensity (Ipc) for MOR and significant peak separation upto 4.0 M concentration of MeOH. CFO-Sn2 exhibited the lowest overpotential value of 290 mV at 10 mA cm−2 vs RHE for OER, which was the highest among the electrocatalyst, and a Tafel slope of 85 mV/dec.

Re-collectable and recyclable epichlorohydrin-crosslinked humic acid with spinel cobalt ferrite core for simple magnetic removal of cationic triarylmethane dyes in polluted water

Abstract Spinel cobalt ferrite (CoFe2O4) was successfully functionalized with humic acid (CoFe2O4-HA) via hydrothermal method. In order to prevent detachment, the humic acid layer on the CoFe2O4-HA surface was crosslinked with epichlorohydrin to obtain CoFe2O4-HA-ECH. Synthesized adsorbents were then tested for their ability to remove of basic fuchsin (BF), methyl violet 2B (MV), and malachite green (MG) from aqueous solutions. Particle size analysis, vibrating sample magnetometry, scanning electron microscopy, X-ray diffractometry, Fourier transform infrared spectrophotometry, thermogravimetric analysis, and ζ-potential analysis were conducted to characterize the as-synthesized adsorbents. The effects of adsorption parameters including pH, contact time, initial dye concentration, temperature, and ionic strength were explored. The kinetics data fitted well with a pseudo-second order model with Coefficient of Determination (R2) ≥ 0.998, Chi-squared (χ2) ≤ 0.171, and Average Relative Error (ARE) ≤ 3.443, suggesting that adsorption is the rate-limiting step. The Langmuir isotherm model provided R2 ≥ 0.999, χ2 ≤ 0.025, and ARE ≤ 0.891, indicating that adsorption occurs on a single layer on a homogenous surface. The maximum adsorption capacities of CoFe2O4-HA-ECH were 96.494, 62.627, and 48.74 μmol ⋅ g−1 for BF, MV, and MG, respectively, which were 10 times higher than those of CoFe2O4. Thermodynamic studies suggested that the adsorption processes are spontaneous-endothermic. Furthermore, CoFe2O4-HA-ECH can be re-collected and recycled for up to 10 cycles.

A combined experimental and theoretical study of the magnetic properties of bulk CoFe2O4

This work is devoted to studying experimentally and theoretically the structural and magnetic properties of bulk cobalt spinel ferrite. Solid-state reaction with optimized synthesis conditions is used to prepare CoFe2O4. The crystallization of CoFe2O4 in the FCC structure was confirmed with the X-ray diffraction. The microstructural properties are performed using the scanning electron microscopy. The magnetic properties of the bulk cobalt ferrite were performed experimentally using the superconducting quantum interference device magnetometer (SQUID). Monte Carlo simulation with periodic boundary conditions was used to simulate bulk CoFe2O4 with a large enough size of the system. The obtained magnetization and susceptibility as a function of temperature show that CoFe2O4 exhibits a second-order transition to paramagnetic phase around 725 K. To carry out the maximum energy product, experimental and theoretical magnetic hysteresis loops at room temperature were performed. It is found that the synthesized CoFe2O4 has a high saturation magnetization of about 87.89 emu/g, which is close to the theoretical value of 97.13 emu/g. Lower coercivity–sugariness ratio was found which indicates that bulk cobalt spinel ferrite is a magnetic multi-domain in nature. To evaluate the efficiency of bulk CoFe2O4, the maximum energy product was calculated at room temperature. Our results demonstrate from a microscopic to the macroscopic scale the performance of CoFe2O4 as a promising magnetic material in the new energy technology generation.

Mesoporous Cobalt Ferrite Nanosystems Obtained by Surfactant-Assisted Hydrothermal Method: Tuning Morpho-structural and Magnetic Properties via pH-Variation.

A facile and cheap surfactant-assisted hydrothermal method was used to prepare mesoporous cobalt ferrite nanosystems with BET surface area up to 151 m2/g. These mesostructures with high BET surface areas and pore sizes are made from assemblies of nanoparticles (NPs) with average sizes between 7.8 and 9.6 nm depending on the initial pH conditions. The pH proved to be the key factor for controlling not only NP size, but also the phase purity and the porosity properties of the mesostructures. At pH values lower than 7, a parasite hematite phase begins to form. The sample obtained at pH = 7.3 has magnetization at saturation Ms = 38 emu/g at 300 K (54.3 emu/g at 10 K) and BET surface area SBET = 151 m2/g, whereas the one obtained at pH = 8.3 has Ms = 68 emu/g at 300 K (83.6 emu/g at 10 K) and SBET = 101 m2/g. The magnetic coercive field values at 10 K are high at up to 12,780 Oe, with a maximum coercive field reached for the sample obtained at pH = 8.3. Decreased magnetic performances are obtained at pH values higher than 9. The iron occupancies of the tetrahedral and octahedral sites belonging to the cobalt ferrite spinel structure were extracted through decomposition of the Mössbauer patterns in spectral components. The magnetic anisotropy constants of the investigated NPs were estimated from the temperature dependence of the hyperfine magnetic field. Taking into consideration the high values of BET surface area and the magnetic anisotropy constants as well as the significant magnetizations for saturation at ambient temperature, and the fact that all parameters can be adjusted through the initial pH conditions, these materials are very promising as recyclable anti-polluting agents, magnetically separable catalysts, and targeted drug delivery vehicles.

Co3O4/α-Fe2O3 nanocomposites (NCs): synthesis and characterization

Cobalt oxide, hematite, and Co3O4/α-Fe2O3 nanopowders (NPs) have been successfully synthesized by hydrothermal technique. Co3O4 is well crystallized in spinel cubic structure, while the hematite possesses the rhombohedral structure. The mixture of these two materials gave spinel cobalt ferrite. The average crystallite size calculated from Scherer’s equation was 49 and 34 nm for Fe2O3 and Co3O4, respectively, while it is decreased to 19 nm for the Co3O4/α-Fe2O3 NCs. This reduction is probably attributed to the high enthalpy of formation of the mixture in comparison with the two other materials. Scanning electron microscopy and transmission electron microscopy photographs indicate that the Co3O4/α-Fe2O3 NPs are composed of homogenous spherical grains and small agglomerated crystallites. All the prepared samples exhibited a superparamagnetic behavior with very low remanence and coercivity. The origin of the superparamagnetism may be related to the uncompensated surface spin and tiny size of the nanoparticles. The magnetization at saturation of the mixture is strongly enhanced to 45.7 emu/g after it was around 2 emu/g for both Co3O4 and hematite. BET analysis showed that the composite had a high surface area (around 60 m2/g) compared to Co3O4 and hematite. This makes Co3O4/α-Fe2O3 a good candidate for several applications such as drag delivery, supercapacitors, and magnetic resonance imaging.

Facile Synthesis of Spinel CoFe₂O₄ Nanoparticle and Its Application as Magnetic Recoverable Photocatalyst for Degradation of Metronidazole and Some Selected Organic Dyes.

A novel and facile approach for one-pot synthesis of spinel cobalt ferrites (CoFe₂O₄) nanoparticle (NPs) and is photocatalytic activity for degradation of pharmaceuticals waste and organic dye. The synthesis involves homogeneous chemical precipitation followed by hydrothermal heating, using of hexamine as a hydroxylating agent. As-synthesized CoFe₂O₄ photocatalyst was characterised by XRD, SEM, SEM Mapping, TEM, XPS, and BET-surface area analysis. The TEM image reveals cubic shapes with an average size of 10-20 nm. The surface area of the CoFe₂O₄ NPs was found to be 16.42 m² g-1. The photocatalytic activity of CoFe₂O₄ has proved to be an excellent photocatalyt for degradation of metronidazole and organic dyes such as methylene blue (MB) and rhodamine B (RhB). The rate of the reaction was found to be 0.102, 0.198 and 0.213 min-1 for metronidazole, MB and RhB respectively. The catalyst also proved to be noteworthy as it does not loss in its catalytic activity even after five cycles of reuse.

A Low-Cost Iron-Based Current Collector for Alkaline Battery Electrodes

The use of three-dimensional porous nickel foam as the current collector of the nickel hydroxide electrode adds significantly to the cost of the nickel-based alkaline rechargeable batteries. Although iron is considerably less expensive than nickel, iron corrodes at the operating potential of the nickel hydroxide electrode. We have found that a 70–100 nm thick thermal coating of cobalt ferrite spinel protects the iron from corrosion. Such a coated iron substrate was found to be stable against corrosion even when polarized anodically at 10 mA cm−2 in 30% potassium hydroxide electrolyte for 1000 h. While the thermal coating of cobalt ferrite protected iron against corrosion, incorporation of lithium ions into the coating was found to enhance the electrical conductivity of the coating. XPS and EXAFS studies confirmed that the enhanced conductivity resulted from an increase in the population of Co3+ in the ferrite spinel lattice. An inexpensive iron (steel) substrate protected by such a coating when used as a nickel hydroxide battery electrode exhibited a specific capacity of 0.25 Ah g−1 at C/5 discharge rate, comparable to a nickel hydroxide electrode based on a relatively expensive nickel foam substrate. The steel-based electrode also exhibited no noticeable degradation over 150 cycles at C/2 rate. This demonstration of a robust and economical steel substrate presents a unique opportunity for reducing the cost of the nickel hydroxide battery electrode in alkaline batteries.

Fabrication of Spinel Cobalt Ferrite (CoFe2O4) Nanoparticles with Unique Earth Element Cerium and Neodymium for Anticandidal Activities

AbstractThe present study, demonstrates the synthesis of spinel cobalt ferrite (CoFe2O4) nanoparticles (NPs), substituted with various concentrations of unique earth element neodymium (Nd3+) and Cerium (Ce3+), by sonochemical technique. Further examination for the influence of Nd3+ and Ce3+ on structure, surface morphology and anticandidal activities, using different techniques X‐ray diffraction pattern (XRD), scanning electron microscopy (SEM) coupled with Energy‐dispersive X‐ray (EDX) and transmission electron microscopy (TEM) were studied. The nanocrystalline size ranging from 11 to 16 nm with spherical shaped particles were obtained. The anticandidal effect of Nd3+ and Ce3+ doped cobalt ferrite NPs were studied against Candida albicans by evaluating the CFU (colony forming unit) and morphogenesis by SEM. The treatment with Nd3+ and Ce3+ doped cobalt ferrite nanoparticles, showed profound activity with the increasing ratio of Nd3+ and Ce3+ and in an incubation duration manner. The lowest survivability i. e. 40 and 30%, and maximum morphogenesis was obtained with x=0.15 and x=0.2, respectively. The findings lead to the conclusion, that the synthesized NPs have potential as therapeutic strategy targeting Candida infection, and other biomedical applications.