Space Group Fd3m Research Articles

Magnetic properties of a multicomponent intermetallic compound Tb$_{0.25}$Dy$_{0.25}$Ho$_{0.25}$Er$_{0.25}$Al$_2$

Polycrystalline multicomponent Laves phase rare earth intermetallic compound Tb_{0.25}0.25 Dy_{0.25}0.25Ho_{0.25}0.25Er_{0.25}0.25Al_{2}2 has been synthesized by arc-melting and characterized by powder X-ray diffraction, magnetization and heat capacity measurements. The sample has MgCu_22-type cubic structure (space group Fd-3m) at 300 K. The compound Tb_{0.25}0.25Dy_{0.25}0.25Ho_{0.25}0.25Er_{0.25}0.25 Al_{2}2 orders ferromagnetically at 50 K (T_CC). This value is almost equal to the average of the ferromagnetic ordering temperatures of the individual RAl_22 (R = Tb, Dy, Ho and Er) compounds. Field dependence of magnetization below T_CC indicates soft-ferromagnetic nature. From the magnetization vs field data obtained near T_CC and the temperature dependence of heat capacity, low field magnetocaloric effect has been estimated.

Influence of (Zn0.5Ti0.5)3+ substitution on structural evolution, bond characteristics, and microwave dielectric properties of spinel Li(Zn0.5Ti0.5)xGa5-xO8 solid solutions

In this study, the evolution of phase and bond characteristics, as well as the consequent effects on the microwave dielectric properties of Li(Zn0.5Ti0.5)xGa5-xO8 ceramics were investigated. XRD and Rietveld refinement patterns revealed that the sample underwent a transformation from a low-symmetry inverse cubic spinel phase, characterized by the P4332 space group, to a high-symmetry cubic spinel phase associated with the Fd-3m space group. All samples displayed compact grain structures in their surface micro-morphologies, and they achieved high relative densities exceeding 97% when sintered at their respective optimal temperatures. With increasing x value, the dielectric constant increases due to the growth in ionicity and αtheo/Vm. Concurrently, the τf value shifts from −69.29 ppm/°C to −48.73 ppm/°C, a trend that aligns with the bond valence changes at the octahedral position as a function of x. In the range of 0 ≤ x ≤ 3, the Q × f value initially increased due to the change in symmetry, growth in lattice energy, and reduction of Ti3+ content. However, it subsequently decreased as a result of further disruption in ordering and diminishing lattice energy. The optimal microwave dielectric properties were obtained for the x = 3 sample (LiZn1.5Ti1.5Ga2O8) sintered at 1220 °C, displaying characteristics of εr = 16.46, Q × f = 79,268 GHz and τf = −53.36 ppm/°C.

Structural and electrochemical properties of Cu doped NiCo2O4 prepared by microwave hydrothermal method

A series of NiCuxCo2-xO4 with x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10 samples were synthesized using microwave hydrothermal method (MH). The structural, microstructural, and spectroscopic characterizations were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). All the samples are in Cubic phase with space group Fd3m. The samples x ≥ 0.08 shows some impurity phases. The average grain size for all the samples is in the range of 30–55 nm. The specific capacitance (Csp) 250.66 Fg−1, energy density (E) 22.22 Whkg−1 and power density (P) 757.80 Wkg−1 was observed for x = 0.06 with a mass loading of 7 mgcm−2 and in 2 M aqueous KOH electrolyte solution at a current density of 1 Ag−1. Therefore, the Cu doping with x = 0.06 shows good redox activities and hence can be used in electric batteries and supercapacitors.

Small polaron hopping transport mechanism, dielectric relaxation and electrical conduction in NiAl2O4 electro-ceramic spinel oxide

In this study, the frequency and temperature dependent dielectric relaxation and electrical conduction mechanisms in NiAl2O4 spinel oxide ceramic have been explored in a frequency range of over a measured temperature from 163–283 K. The polycrystalline NiAl2O4 was synthesized via solid state reaction route and sintered at 1000 °C. The room temperature x-ray powder diffraction pattern confirmed the formation of NiAl2O4 spinel phase with Fd3m space group. The surface morphology of the sample was investigated by scanning electron microscopy and chemical properties by Fourier transform infrared spectroscopic analysis. Complex impedance studies revealed the presence of relaxation time distribution and charge carriers were found to be thermally activated. The Nyquist plots exhibited depressed semicircles and their fitting by an equivalent circuit model with configuration (RGCG)(RGBCGB) resolved the contributions of grains and grain-boundaries to the electrical transport properties of the material. Electrical conductivity analysis followed the Jonscher’s power law behavior and the frequency exponent suggested small polaron hopping as the governing transport mechanism in NiAl2O4 spinel oxide. Non-Debye type nature of dielectric relaxation was confirmed by the complex modulus analysis whereas dielectric constant and tangent loss analysis verified that the hopping mechanism was thermally activated.

Structural, morphological and frequency dependent dielectric properties of [formula omitted][formula omitted]) nanoparticles prepared by sol-gel method

In this work, the spinel ferrite NixZn0.6−xMn0.4Fe2O4(x=0.0,0.1,0.2,0.3,0.4) nanoparticles (NPs) have been synthesized via the sol-gel method. It is observed that the presence of Ni2+ ions cause an appreciable change in the different properties of the Ni substituted Zn0.6−xMn0.4Fe2O4 NPs. The Fourier transform infrared (FTIR) spectroscopy analysis confirms the formation of the NixZn0.6−xMn0.4Fe2O4 spinel structure. Rietveld's refinement of X-Ray Diffraction (XRD) patterns confirms the single-phase cubic spinel structure belonging to the Fd3m space group. The estimated lattice constant is found to decrease with increasing Ni contents except for x=0.1 and the average crystallite size varies from 6.7nmto100nm due to the reduction of grain growth upon Ni2+ occupation in the octahedral site. Frequency-dependent dielectric constant, dielectric loss, AC resistivity, and conductivity of the compositions have also been examined at room temperature. The ac resistivity exponentially decreases with the increase of frequency due to the effect of multilayer capacitance. Conversely, the ac conductivity is observed to increase exponentially with the frequency due to increased hopping between metallic cations Fe2+ and Fe3+. The electrical charge conduction behavior and contribution of grain and grain boundary resistance have been explained using Nyquist/Cole-Cole plot. Hence, the Ni doped Zn0.6−xMn0.4Fe2O4 NPs excellent dielectric behavior can be used for various potential applications including the fabrication of the nano-electronic device and multi-layers chip inductors applications.

Single-Crystal Growth of a Cubic Laves-Phase Ferromagnet HoAl2 by a Laser Floating-Zone Method

The successful growth of single crystals of a cubic Laves-phase material HoAl2 with the space group Fd-3m is reported in this study. The crystals were grown by a floating-zone method with five laser diodes as a heat source. Al-rich feed rods were prepared as compensation for heavy evaporation during the growth. The nominal ratio for the feed rods was optimized as Ho:Al = 1:2.5. Single crystals of HoAl2 with a length of 50 mm were first grown in this technique. Obtaining the large-sized crystal by the floating-zone method enabled us to systematically explore the physical properties using the same batch crystal. The crystal possessed a second-ordered ferromagnetic transition at 29 K and a first-ordered spin-reorientation transition at 20 K. The bulk physical properties, such as specific heat, magnetic susceptibility, isothermal magnetization, and thermal expansion measurements, were measured. Additionally, a magnetocaloric effect was evaluated by the magnetic entropy change. We demonstrate that anisotropic physical properties along the principal axes ([100], [110], and [111]) emerged below the magnetically ordered states, in contrast to the isotropic behavior in the paramagnetic state.

Micro-structural and magnetic analysis of spinel high entropy oxides synthesized by two-step pressureless sintering provides insight into high entropy ceramics

High-entropy oxides are novel materials consisting of many metallic elements of equal proportions. Hence, the complex structure of high-entropy oxides leads to interesting properties. In this work, seven single-phase high entropy oxides were synthesized by two-step pressureless sintering. According to the experimental XRD data, all samples are found in the cubic crystal structure with the Fd-3m space group. This result shows that high entropy oxides have a high possibility of phase formation. For all samples, the EDS results show that all expected elements have similar elements content. The magnetization curves show that the magnetic properties change systematically with the changes in the high-entropy stable oxide composition. The seven different samples are divided into three groups for comparison. In group 1, with the substitution of iron for zinc, Hc increased from 19 Oe to 221 Oe, while Ms changed slightly. In group 2, the substitution of zinc for nickel leads to the rapid weakening of magnetism. In group 3, with nickel replacing cobalt, Ms increased from 15.060 emu/g to 19.801 emu/g, and Hc decreased from 28 Oe to 11 Oe. The complex element composition makes high entropy materials have great development space in the field of magnetic materials. Thus, the magnetic properties of the high-entropy spinel oxides can be adjusted according to this concept.

Green Synthesis of Nanomagnetic Copper and Cobalt Ferrites Using Corchorus Olitorius

This study aims to develop a self-combustion method for use in the preparation of copper and cobalt ferrites. This development was based on the full use of dry leaves of Corchorus olitorius plant in order to stimulate the preparation of the studied ferrites by making full use of the small amount of carbon produced from the combustion process. The fabrication of CuFe2O4 and CoFe2O4 with spinel-type structures and the Fd3m space group is confirmed by XRD and FTIR investigations. Two major vibration bands occur laterally at 400 cm−1 and 600 cm−1. We were able to understand the existence of two stages through the thermal behavior based on TG-DTG analysis for the materials under investigation. The first is from room temperature to 600 °C, which indicates the formation of reacting oxides with Co or Cu ferrites, while the second is from 600–1000 °C, which indicates the growth in the ferrite fabrication. The surface morphological analyses (SEM/EDS and TEM) display formation of homogeneous and nanosized particles. The surface properties of the samples containing CoFe2O4 are superior compared to those of the samples not containing CuFe2O4. Every sample under investigation displays type-IV-based isotherms with a type-H3 hysteresis loop. The VSM approach was used to evaluate the magnetic characteristics of Cu and Co ferrites. Copper ferrites have a magnetization of 15.77 emu/g, and cobalt ferrites have a magnetization of 19.14 emu/g. Moreover, the squareness (0.263) and coercivity (716.15 G) of cobalt ferrite are higher than those of copper ferrite.

Cr and Mg codoped bismuth tantalate pyrochlores: Thermal expansion and stability, crystal structure, electrical and optical properties, NEXAFS and XPS study

A series of Bi2Cr1-xMgxTa2O9+Δ solid solutions with the pyrochlore structure was synthesized by the method of solid-phase synthesis. Structural parameters of the disordered pyrochlore were determined by the Rietveld method (space group Fd-3m:2 (No. 227), Z = 8). As the magnesium content increases, the unit cell parameter rises continuously from 10.4596 ± 0.0001 Å (x = 0.3) to 10.5463 ± 0.0001 (x = 1.0) according to the Vegard rule. The grain size varies in the range of 0.5–2 μm, regardless of the magnesium/chromium(III) ratio. Chromium ions increase the range of thermal stability of ceramics up to 1110 °C.The thermal expansion coefficient in the range of 30–1110 °C increases continuously from 4.1 to 8.6 × 10−6 °C−1 (for x = 0.5). The oxidation states of ions were determined by X-ray spectroscopy (XPS and NEXAFS). It was shown that bismuth and magnesium ions in the pyrochlore are in the Bi(+3), Mg(+2) charge states, and for chromium the states Cr(+3), Cr(+6) are most probable. Based on the presence of an energy shift in the region of Ta4f, Ta5p and Ta5d absorption edges by ΔЕ∼0.7 eV and ∼1 eV, respectively, it was concluded that the oxidation degree of the Ta(+5-δ) ion decreased. The band gap for the samples in the case of direct allowed electronic transitions is in the range of 2.14–2.29 eV. At RT and in the frequency range (102–106 Hz), the dielectric permittivity of the samples is practically constant and it decreases with increasing amount of chromium from 20 (x = 0.7) to 16 (x = 0.3) at 1 MHz.In the high-frequency region (≥105 Hz), the dielectric loss tangent for all samples is independent on frequency and takes low values of ∼0.004 (1 MHz). The activation energy of conductivity for the samples varies in the range of 1.39–1.48 eV. The ability to adsorb water was found for chromium pyrochlores.

Effects of Zinc Substitution on the Microstructural and Magnetic Characteristics of Cubic Symmetry Nickel Ferrite System

The preparation of ZnxNi1−xFe2O4 (x = 0 and 0.3) nanoparticles using glycine-mediated combustion route was successfully completed depending on the zwitterion and combustion characteristics of glycine. Using a variety of methods, including XRD, FTIR, SEM/EDX, and TEM, the investigated ferrites were characterized. XRD and FTIR analyses confirm that Zn0.3Ni0.7Fe2O4 and NiFe2O4 nanoparticles crystallize in the cubic symmetry in the space group Fd3m. An increase in the lattice parameters and a subsequent decrease in crystallite size were caused by the process of replacing Ni ions with Zn ions. In accordance with Waldron’s hypothesis, FTIR spectra demonstrate that the ferrites have a spinel-type structure as they are produced. The substitution process by Zn led to different changes in the half band widths with subsequent in splitting in the absorption band around 400 cm−1. The examined ferrites’ cation distribution showed that Zn2+ and Ni2+ ions favored the tetrahedral (A) and octahedral (B) sites, respectively, while Fe3+ ions occupied both A- and B-sites, providing mixed spinel ferrite. TEM analysis indicates the formation of spinel nanocrystalline particles with low agglomerations. The particle size of the as-synthesized ferrites did not exceed 16 nm. By applying the VSM approach at room temperature, the magnetic characteristics of the ferrites under investigation were established. The magnetization of Zn0.3Ni0.7Fe2O4 nanoparticles was found to be higher than that of NiFe2O4 nanoparticles according to the magnetic data. Increasing the magnetization and the experimental magnetic moment of Zn0.3Ni0.7Fe2O4 were accompanied by a decreasing of its coercivity. The net magnetization is oriented along different high symmetry directions. On the other hand, the anisotropy of the nickel ferrite increases by substituting Ni with a Zn ion.

Preparation of Ni–Zn dual-doped polyhedral LiMn2O4 for endurable cycling lithium ion batteries at high rate

Jahn-Teller distortion and manganese dissolution are always the dominant problem of attenuating long cyclic performance and rate capacity of spinel LiMn2O4 cathode materials. Herein, a Ni–Zn dual-doping strategy is proposed to synthesize various LiNi0.05ZnxMn1.95-xO4 (x = 0–0.05) materials via a solid phase combustion method. All the as-prepared Ni–Zn co-doping materials have a good spinel structure with Fd3m space group and present unique polyhedron morphology with exposed (111) facets, which is conductive to relieving the manganese dissolution and Jahn-Teller effect. Moreover, the Ni–Zn co-doping gives rise to the extended Li–O bond and increased cell volume, hence boosting the favorable intercalation and deintercalation kinetics of Li+ ions. Consequently, the optimized LiNi0·05Zn0·02Mn1·93O4 cathode exhibits good electrochemical performance with the initial discharge capacity of 127.30 mAh g−1 and capacity retention of 70% after 1000 cycles at 1 C. At 5 C, an ultra-long cycle stability with a capacity retention of 61% is obtained up to 1800 cycles. Even at the high current rates of 10 C and 20 C, the relatively high first discharge capacities of 106.50 mAh g−1 and 99.40 mAh g−1 are also delivered, respectively. The Ni–Zn co-doping polyhedral LiMn2O4 will provide a solution for developing high-performance cathode materials in lithium ion battery.

Nanoparticle−preparation−procedure tune of physical, antibacterial, and photocatalyst properties on silver substituted cobalt ferrite

Silver-substituted cobalt ferrite nanoparticles (Ag0·1Co0·9Fe2O4) were successfully synthesized by two simple methods i.e., sol-gel and coprecipitation. The structure, size, morphology, distribution of cations, and magnetic properties were studied by modifying the synthesis temperature to 70 °C, 80 °C, and 90 °C. Subsequently, the photocatalytic and antibacterial properties of Ag0·1Co0·9Fe2O4 were evaluated. All samples, SG70, SG80, SG90, CP70, CP80, and CP90, have a face-centered cubic (fcc) structure with a space group of Fd-3m according to the original crystalline structure of cobalt ferrite CoFe2O4. At 10% doping, a second phase is formed in the form of Ag, Ag3O4, and Fe2O3. In general, the crystallite size is 20–21 nm and correspondence to the grain size of 40–50 nm. For the whole nanoparticles sample, the grain size synthesized by the coprecipitation procedure is smaller than that of the sol-gel method one. The vibrating sample magnetometer result shows that the saturated magnetization increases with the increase of the synthesis temperature for both the sol-gel and the coprecipitation procedure. A superior photocatalytic performance of the samples is obtained as well as antibacterial properties. The best performance for the methylene blue (MB) degradation of around 90% is obtained for the Ag0·1Co0·9Fe2O4 nanoparticles sample with a synthesis temperature of 70 °C by coprecipitation route. The performance antibacterial (on Staphylococcus aureus and Escherichia coli) of the obtained nanoparticle magnetic show that the zone of inhibition increases and is confirmed by the mortality calculation of the total plate count increase within the increase of the synthesis temperature. Here, the surface-specific area as well as saturated magnetization should contribute to the effectivity of antibacterial performance.

Magnetic and electrical investigations of low dimensional Co0.5Zn0.5−xCuxFe2O4 nano ferrites

In this present work, low dimensional Co0.5Zn0.5−xCuxFe2O4 (x = 0.01, 0.02, 0.03, 0.04 and 0.05) (CZCFO) ferrite nanoparticles are engineered by modified sol-gel method, with citric acid (C6H8O7) as a fuel. Here we investigate the room temperature structure, magnetic, X-ray photoelectron spectroscopy, and electrical properties of CZCFO nanoparticles. The X-ray diffraction patterns of CZCFO samples, confirm the formation of pure a cubic structure, Fd-3m space group, and Rietveld refinement technique used to extract the atomic level structural information for all the compositions. Debye Scherer’s equation is used to estimate the crystallite size and micro strain, the obtained values are around 8–13 nm and 0.6246 × 10−3 respectively. The particle surface morphology was examined by Field emission scanning electron microscopy (FE-SEM), showing aggregated grains with a sponge-like structure. The Fourier transform infrared spectroscopy (FTIR) technique confirms the presence of functional groups and the formation of the spinel structure for all the samples. Room temperature M-H loops indicate the ferrimagnetic nature for all the samples and it is noticed that increasing saturation magnetization (Ms) and coercivity (Hc) for increasing dopant. X-ray photoelectron spectroscopy (XPS) technique is used to estimate the elements with an electron state of atoms within the material and determine the valance states at respected octahedral and tetrahedral sites. The frequency-dependent dielectric constant and loss tangent imply that, significantly decreases as increasing frequency and later, becomes almost linear. This typical nature reflects the Maxwell–Wagner type of polarization by Koop's theory. Additionally, room temperature complex impedance spectroscopy reveals the non-Debye type of relaxation and the Cole-Cole plot shows the semi-arc nature. Relative permeability studies at room temperature remark the decay in all samples.

Synthesis of Zinc Substituted Cobalt Ferrite Nanoparticles by Using Sol-Gel Method as Antibacterial Material

The synthesis of zinc-substituted cobalt ferrite (Co0.9Zn0.1Fe2O4) using the sol gel method has been successfully carried out. The thermogravimetric analysis and differential thermal analyzer curve shows that at 400°C the Co0.9Zn0,1Fe2O4 sample has formed the final phase of nanoparticles. Therefore, the modification of physical properties was carried out by annealing treatment at temperature of 450°C, 550°C, 650°C, and 750°C. The X-rays diffraction show that all samples are in a single phase with a face center cubic space group Fd-3m structure according to the ICDD 221086. The crystal size increased with the annealing temperature 33.69 nm to 45.88 nm. The Co0.9Zn0.1Fe2O4 showed as excellent antibacterial properties on Staphylococcus aureus and Escherichia coli. The most superior antibacterial activity to Staphylococcus aureus was Co0.9Zn0,1Fe2O4 sample which was annealed at 650°C with a clear zone diameter of 39.81 mm. Meanwhile, the Escherichia coli bacteria which had the most superior antibacterial activity were Co0.9Zn0,1Fe2O4 samples which were annealed at 450°C with a clear zone measuring 21.04 mm.

Features of Phase Formation of Pyrochlore-type Ceramics Bi2Mg(Zn)1-x Ni x Ta2O9.

The phase formation of complex pyrochlores (space group Fd-3m) Bi2Mg(Zn)1-x Ni x Ta2O9 was investigated during solid-phase synthesis. It was found that the pyrochlore phase precursor in all cases was α-BiTaO4. The pyrochlore phase synthesis reaction proceeds mainly at temperatures above 850-900 °C and consists in the interaction of bismuth orthotantalate with a transition element oxide. The influence of magnesium and zinc on the course of pyrochlore synthesis was revealed. The reaction temperatures of magnesium and nickel (800 and 750 °C, respectively) were determined. The change in the pyrochlore unit cell parameter depending on the synthesis temperature was analyzed for both systems. Nickel-magnesium pyrochlores are characterized by a porous dendrite-like microstructure with a grain size of 0.5-1.0 microns, and the porosity of the samples reaches 20 percent. The calcination temperature does not significantly affect the microstructure of the samples. Prolonged calcination of the preparations leads to the coalescence of grains with the formation of larger particles. Nickel oxide has a sintering effect on ceramics. The studied nickel-zinc pyrochlores are characterized by a low-porous dense microstructure. The porosity of the samples does not exceed 10%. The optimal conditions for obtaining phase-pure pyrochlores (1050 °C and 15 h) were determined.

Effects of Al and Co doping on the structural stability and high temperature cycling performance of LiNi0.5Mn1.5O4 spinel cathode materials

The poor structural stability and capacity retention of the high-voltage spinel-type LiNi0.5Mn1.5O4 (LNMO) limits their further application. Herein, Al and Co were doped in LNMO materials for a more stable structure and capacity. The LNMO, LiNi0.45Al0.05Mn1.5O4 (LNAMO) and LiNi0.45Co0.05Mn1.5O4 (LNCMO) were synthesized by calcination at 900 °C for 8 h, which was called as solid-phase method and applied universally in industry. XRD, FT-IR and CV test results showed the synthesized samples have cation disordering Fd-3m space group structures. Moreover, the incorporation of Al and Co increased the cation disordering of LNMO, thereby increasing the transfer rate of Li+. The SEM results showed that the doped samples performed more regular and ortho-octahedral. The EDS elemental analysis confirmed the uniform distribution of each metal element in the samples. Moreover, the doped samples showed better electrochemical properties than undoped LNMO. The LNAMO and LNCMO samples were discharged with specific capacities of 116.3 mA·h·g−1 and 122.8 mA·h·g−1 at 1 C charge/discharge rate with good capacity retention of 95.8% and 94.8% after 200 cycles at room temperature, respectively. The capacity fading phenomenon of the doped samples at 50 °C and 1 C rate was significantly improved. Further, cations doping also enhanced the rate performance, especially for the LNCMO, the discharge specific capacity of 117.9 mA·h·g−1 can be obtained at a rate of 5 C.

Microwave-assisted synthesis of ternary transition metal ferrite: Structural, morphological, optical, magnetic and electrochemical properties

Transition metal oxides are promising materials in photocatalysts, sensors, photovoltaics, and especially as supercapacitor electrodes for their rapid, reversible faradaic redox reactions. Nanosized ternary transition metal ferrite (NiMnFe 2 O 4 ) has been synthesized using an easy and inexpensive microwave-assisted combustion method. The powder XRD confirms the nanoparticles as in spinal cubic structure with space group Fd-3m. FTIR has analyzed to understand the vibration of metal ions in the prepared NiMnFe 2 O 4 . The elemental composition and surface morphology of the nanoparticles have been studied by scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray (EDX) analysis. The UV–Visible diffuse reflectance spectra are used to examine the optical properties and to calculate the band gap energy of NiMnFe 2 O 4 , which is found to be 1.08 eV. The electrochemical properties of the prepared metal ferrite have been studied by electrochemical impedance spectroscopy (EIS), Galvanostatic charge-discharge (GCD) and cyclic voltammetry (CV). The specific capacitance of the modified electrode is found to exhibit the highest value of 476 F/g at 5 mV/s. • Nanostructured ternary transition metal ferrite has been prepared by a low-cost Microwave-assisted combustion method. • SEM analysis exhibit the irregular shape morphology. • The prepared NiMnFe 2 O 4 electrode revealed a higher energy density of 1.226 W h/Kg and superior power density of 1125 W/kg. • Cyclic stability of the NiMnFe 2 O 4 exhibits capacity retention of 83.67%.

Photocatalytic dye degradation efficiency and reusability of aluminium substituted nickel ferrite nanostructures for wastewater remediation

In this study, nickel ferrite and aluminum-doped nickel ferrite were synthesized using the hydrothermal method. The cubic ferrite structure with space group Fd3m was confirmed by powder X-ray diffraction (XRD) analysis. The functional groups of the nanoparticles were analyzed using FTIR and FT-Raman spectroscopy. The morphology and elemental composition of the products were examined using FESEM and EDX mapping analyses. The presence of O, Fe, and Ni, as well as the presence of Al in the doped sample, was confirmed by EDX in all the prepared nanoferrites, and TEM analaysis confirmed the shape and purity of the prepared samples. BET surface areas were found to be 46.39, 70.43, and 111.68 m2/g for samples NF, NFA3, and NFA6, respectively. The saturation magnetization was calculated to be 58.08, 38.41, and 28.15 emu/g, for the samples NF, NFA3, and NFA6 respectively. Finally, the prepared nanoparticles were used to determine their photocatalytic activity against methyl blue (MB) and methyl orange (MO) under visible-light irradiation. The photocatalytic activity of the NiAl0.6Fe1.4O4 NPs was found to be MB (97.48 %) and MO (93.04 %). The results showed that the aluminum-doped nickel ferrite (NiAl0.6Fe1.4O4) exhibited good photocatalytic activity.

Influence of Co doping on phase, structure and electrochemical properties of hydrothermally obtained CoxZn1−xFe2O4 (x = 0.0–0.4) nanoparticles

In this work, CoxZn1−xFe2O4 (x = 0.0–0.4) nanoparticles (NPs) were successfully synthesized by a hydrothermal method at 200 °C for 12 h. X-ray diffraction revealed a pure cubic spinel phase of all samples with space group Fd-3m. Fourier transform infrared spectrometry disclosed the vibrational modes of metal oxides in the spinel structure. Scanning electron microscopy and transmission electron microscopy disclosed a uniform distribution of cuboidal shape NPs with a decreased average NPs size from 22.72 ± 0.62 to 20.85 ± 0.47 nm as the Co content increased. X-ray absorption near edge spectroscopy results confirmed the presence of Zn2+, Co2+ and Fe2+/Fe3+ in Co-doped samples. The pore volume, pore size and specific surface area were determined using N2 gas adsorption/desorption isotherms by the Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) techniques. Electrochemical properties of supercapacitors, having active CoxZn1−xFe2O4 (x = 0.0–0.4) NPs as working electrodes, indicated pseudo-capacitor performance related to the Faradaic redox reaction. Interestingly, the highest specific capacitance (Csc), 855.33 F/g at 1 A/g, with a capacity retention of 90.41% after 1000 GCD cycle testing was achieved in the Co0.3Zn0.7Fe2O4 electrode.

Thermally Induced Phase Transition of Cubic Structure II Hydrate: Crystal Structures of Tetrahydropyran–CO2 Binary Hydrate

We report a thermally induced phase transition of cubic structure II hydrates of tetrahydropyran (THP) and CO2 below about 140 K. The phase transition was characterized by powder X-ray diffraction measurements at variable temperatures. A dynamical ordering of the CO2 guests in small pentagonal dodecahedral 512 host water cages, not previously observed in the simple CO2 hydrate, occurs simultaneously with the symmetry lowering transition from a cubic structure II (space group Fd-3m with cell dimensions a = 17.3202(7) Å at 153 K) to a tetragonal (space group I41/amd with cell dimensions a = 17.484(4) Å and c = 12.145(1) Å at 138 K) unit cell. The effect of guest molecules on the phase transition at low temperatures is discussed, which demonstrates that the clathrate hydrate structures and thermodynamic properties can be modified by adjusting the size and chemical structure of larger and smaller guest molecules.