No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Superparamagnetic and ferromagnetic behavior of ZnFe2O4 nanoparticles synthesized by microwave-assisted hydrothermal method
Abstract
Zinc ferrite (ZnFe2O4) nanoparticles were successfully synthesized from Zn(NO3)2 · 6H2O and Fe(NO3)3 · 9H2O by microwave hydrothermal method at 150°C for 1 h. Cubic ZnFe2O4 with particle size below 7 nm was formed in the solution at pH ≥ 6. The crystallinity and particle size of ZnFe2O4 nanoparticles were increased after calcination. The effects of pH of the precursor solution and calcination on the particle size and crystallinity of the particles were studied. At room temperature the products show superparamagnetic and ferromagnetic properties, determined by their size. The formation mechanism of ZnFe2O4 was also discussed according to the experimental results.
... The dependence of particle size on the magnetic behavior, i.e., ferromagnetic to super paramagnetic behavior by microwave-assisted hydrothermal synthesized ZnFe 2 O 4 is reported by Anukorn Phuruangrat et al. [13]. The micro-to nanometric scale ferromagnetism in ZnFe 2 O 4 is also reported to have mixed spinel state (Zn 1-x Fe x ) A [Fe 2-x Zn x ] B , where Zn 2? and Fe 3? cations are distributed both in the tetrahedral (A) and octahedral (B) sites [14]. ...
... It is found that the lattice parameter slightly increases linearly as the doping concentration increases. The minimum and maximum crystallite size is found to be nearly, 13 The distribution of the cations in the cubic spinel structure was carried out with the following assumption: ...
The phase pure Ca²⁺-doped ZnFe2O4, spinel ferrite, synthesized by solvothermal method were analyzed using X-ray diffraction data. The structure factor corresponding to miller lattice planes and parameters like cell constants, anion positional parameter (O²⁻), etc., are calculated using Rietveld refinement strategy, considering cubic spinel structure. The cation distribution study reveals mixed spinel structure with both Ca²⁺ and Fe³⁺ ions occupying both tetrahedral A site and octahedral B site and Zn²⁺ occupying only at tetrahedral A site. The quantitative and visual electron bonding study reveals covalent bonding between A site ions and O²⁻ ions and ionic bonding between B site ions and O²⁻ ions for all the compositions and both are dominating for the composition Ca0.2Zn0.8Fe2O4. Also, the maximum entropy method-based electron density studies reveals that A–B interaction is maximum compared to A–A and B–B interactions and A–A interaction is the weakest one. The surface morphology using SEM shows spherical particle nature and energy dispersive X-ray analysis shows its stoichiometric compositions without any impurity elements. The magnetic properties are analyzed using vibrating sample magnetometer, which reveals the prepared sample with composition Ca0.2Zn0.8Fe2O4 show good ferromagnetic properties at room temperature. The observed saturation magnetization, remanent magnetization, coercivity and squareness ratio (Mr/Ms) for the composition Ca0.2Zn0.8Fe2O4 are 32.588 emu/g, 9.4265 emu/g, 407.98 gauss, and 28.95%, respectively. The present work reveals that Ca0.2Zn0.8Fe2O4 may be one of the best alternative low-cost and environment friendly semi-hard ferrite, useful in high-frequency device applications.
... The linear magnetization curves of ZnFe 2 O 4 , ZnFe 2 O 4 /rGO and 'S' like curve of Ag@ZnFe 2 O 4 /rGO at 15 kOe with zero coercivity and remanence indicates the superparamagnetic nature of all the samples. The saturation magnetization of ZnFe 2 O 4 slightly larger than ZnFe 2 O 4 /rGO due smaller particle and crystallite size[108]. However, the saturation magnetization of ...
Ag@ZnFe2O4/reduced graphene oxide (Ag@ZnFe2O4/rGO) ternary nanocomposites were successfully synthesized (NCs) via hydrothermal method and explored the LED assisted photocatalytic performance for the degradation of organic dyes as well as humidity sensing properties of the material. For comparison, bare ZnFe2O4, and ZnFe2O4/rGO also synthesized. The freshly prepared samples were investigated using XRD, TEM, UV–vis–NIR spectroscopy, VSM, Impedance analyzer, and particle size analyzer. The detailed structural parameters were calculated through X-ray peak profiling using Classical Scherrer, Modified Scherrer, Williumson-Hall, Halder-Wagner, Size Strain Plot methods along with Rietveld refinement. From UV–vis–DRS analysis, optical energy gaps were obtained in the range of 1.58–1.92 eV. Ag@ZnFe2O4/rGO NCs showed significant photocatalytic activity and exceptional adsorption capacities for the breakdown of methylene blue (MB) 95.7% and rhodamine B (RhB) 77.7% after 100 min. The synergistic interactions of Ag, ZnFe2O4, and rGO minimized NCs agglomeration and small particle size with higher surface area, resulting in a higher absorption in both UV and visible light. The photocatalysis mechanism was explored by scavenger test using ascorbic Acid, NaHCO3, and isopropyl alcohol. The magnetic studies revealed the paramagnetic nature of NCs. Frequency dependent dielectric data obey the modified Debye model with relaxation time of ∼10−4 s and spreading factor of 0.534 (±0.08). Complex impedance measurements support the grain-interior process that contributes to dielectric properties. The impedance-type humidity sensing characteristics of the fabricated sensor were investigated by exposing in a wide humidity range of 11–98% RH at ambient temperature. The Ag@ZnFe2O4/rGO sensor displayed an ultrahigh sensitivity when compared to traditional humidity sensors. On the basis of, Ag@ZnFe2O4/rGO NCs are exciting nanomaterials for outstanding photocatalytic activity for the degradation of organic dyes along with potent humidity sensor.
... All the investigated systems intend to display ferrimagnetic features that are mainly complemented from the substantial presence of ZnFe 2 O 4 component in the composite mixtures. The strong ferrimagnetic features of ZnFe 2 O 4 is well established from the previous investigations [69]. ...
NiFe2O4/ZrO2 composite with varied compositional ratios was formed through solution‐based sol‐gel synthetic route. The ability to retain NiFe2O4/ZrO2 composite structures was dependent on the concomitant effect of temperature gradient and precursor concentration. The crystallization of t‐ZrO2 alongside the incidence of NiFe2O4 and NiO was evident at 900°C. However, the gradual elimination of NiO and simultaneous enhancement in NiFe2O4 content is inevitable at 1300°C. Morphological analysis of the composite revealed discrete distribution of ZrO2 and NiFe2O4 grains and also portrays the dense and pore‐free microstructures. Despite the presence of varied amount of NiFe2O4 in the composites, the resultant mechanical properties displayed relatively better values and exhibited good similarities with the hard tissue. As expected, a gradual increment in the ferrimagnetic properties as a function of enhanced NiFe2O4 content was induced. Further, in vitro analysis delivered good biocompatibility features of the investigated NiFe2O4/ZrO2 composite.
... The saturation magnetization was 10 emu/g when the particle size was 32 nm. Phuruangrat et al. [15] synthesized zinc ferrite nanoparticles by using microwave assisted hydrothermal method and obtained a saturation magnetization of 19.5 emu/g and coercivity of 9 Oe for 3.5 nm zinc ferrite nanoparticles. As seen, in recent years, many techniques have been developed to prepare magnetic zinc ferrite nanoparticles such as; ball milling, co-precipitation, sol-gel, thermal decomposition and hydrothermal method [16,17]. ...
Superparamagnetic zinc ferrite nanoparticles with high magnetization were successfully synthesized by hydrothermal method at 110 ° C under different reaction times from 2 to 24 h. Elemental analysis of the nanoparticles determined by inductively coupled plasma atomic emission spectroscopy and energy dispersive X-ray spectrometer results proved that the samples are zinc ferrite. X-ray diffraction (XRD) and Fourier transmission infrared spectroscopy analysis displayed that zinc ferrite nanoparticles were single phase of cubic ferrite. The particles size, dXRD of the nanoparticles calculated from XRD patterns increased as the reaction time increased. From the images of transmission electron microscopy (TEM), the particle sizes, dTEM were also calculated and increased from 6.8 ± 2.5 to 10.6 ± 5.1 nm as the reaction time increased, which were consistent with the dXRD. Magnetic measurements revealed that the magnetization curves of the synthesized nanoparticles show superparamagnetic behavior with zero coercivity and remanence. And, the magnetization values also increased to a maximum value of 30.8 emu/g (measured at 20 kOe) as the particle size increased to ∼10 nm with the increase of reaction time. At this particle size limit, this is a considerable high value compared to the superparamagnetic zinc ferrite nanoparticles studies. Magnetization values were also extrapolated. It is seen that to a certain degree, the average particle sizes of the products and hence high maximum magnetization can be tuned by simply adjusting the parameter, reaction time by hydrothermal process.
... One of the most important ferrimagnetic materials is certain double oxides of iron and other metals, named ferrites. However, all oxide ferrites do not have ferrimagnetic properties (Phuruangrat, Maisang, Phonkhokkong, Thongtem, & Thongtem, 2017). The magnetic ferrites with different crystal structures are divided into two groups: 1) cubic and 2) hexagonal structures. ...
Among the most challenging problems that human beings appear to face are depleting energy sources and increasing environmental pollutions. Heterogeneous photocatalytic processes are the most rewarding technology to generate renewable energy and degrade environmental pollutants. In these processes, semiconductors are used as photocatalysts. ZnO is a widely used photocatalyst, because of its strong oxidation ability, cost effectiveness, non-toxicity, versatility in synthesis, abundance in nature, and ease of crystallization. However, pure ZnO has some drawbacks, due to its wide band gap, poor solar-light utilization, and rapid recombination of the photoinduced charge carriers. Modification of ZnO using different strategies including coupling with narrow band gap semiconductors, noble metal deposition, surface sensitization by organic dyes, and elemental doping can easily address these shortcomings. In addition, separation of photocatalysts from the treated systems limits their broad applications. Incorporation of photocatalysts in magnetic materials will help their recycling using external magnetic field. This combination leads to a new generation of photocatalysts, known as magnetically separable photocatalysts. The present review provides helpful insights into preparation of magnetically separable photocatalysts based on ZnO and their applications for degradations of different pollutants.
The investigation underline the in situ formation of ZrO2/ZnFe2O4 composites and the resultant structural, morphological, mechanical and magnetic properties. The characterization results ensured the crystallization of tetragonal ZrO2 (t-ZrO2) and ZnFe2O4 phases at 900 °C. Depending on Zn2+/Fe3+ content, the composite system revealed a gradual increment in the phase yield of ZnFe2O4. The significance of monoclinic ZrO2 (m-ZrO2) is also evident in all the systems at 900 °C; however, the incremental heat treatment to 1300 °C indicated its corresponding loss, thus indicating the reverse m- → t-ZrO2 transition. The crystallization of ZnFe2O4 as a secondary phase in the t-ZrO2 matrix is also affirmed from the morphological analysis. Mechanical studies accomplished good uniformity in all the investigated compositions despite the variation in the phase content of ZnFe2O4 in composite system. All the t-ZrO2/ZnFe2O4 composites ensured strong ferrimagnetic features and moreover better biocompatibility and non-toxicity characteristics were displayed from in vitro tests.
Size-dependent properties of magnetite (Fe3O4) nanoparticles, obtained by convection heating and by the microwave method, are compared. Generally, the synthetic procedures involving microwave heating require less time and provide smaller particle sizes and narrower size distribution. Consequently, the specific area of the prepared samples increases. The results are based on the X-ray phase analysis, transmission electron microscopy (TEM), and nitrogen adsorption measurements (Brunauer–Emmett–Teller method).
Magnetization of the ZnFe2O4 sample of average size 4nm measured with SQUID in the temperature range 5–300K shows anomalous behaviour in field cooled (FC) and zero-field-cooled (ZFC) conditions. The FC and ZFC curves measured in 50Oe field cross each other a little before the peaks. No such anomaly is observed with samples of 6nm particle size made with the same procedure. The characteristics of the FC and ZFC curves are very different in ZnFe2O4 samples of the same size (6nm) made via two different chemical routes. The genesis of these differences are suggested to be in cationic configuration and spin disorder. Fe-extended X-ray absorption fine structure (EXAFS) studies show that there is around 80% inversion in case of zinc ferrite (ZnFe2O4) with the particle size 4nm, whereas ZnFe2O4 of size 6nm shows 40% inversion. The samples with an average particle size of 7nm and more show negligible inversion. Theoretical simulations suggest that the electrostatic energy of the system plays a crucial role in deciding the cationic configuration of spinel ferrites.
The results presented in this paper were focused on the easy development of cheap, sensitive and integrable spinel zinc ferrite (ZnFe2O4) thin film gas sensors for the detection of ethanol. ZnFe2O4 layers of about 450 nm thick were deposited by spray pyrolysis technique. The resulting films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Analysis confirmed the formation of monophasic spinel structured thin films with flat surface and dense microstructure consisting of nanosized grains. The sensor detects ethanol concentrations as low as 1 ppm and shows comparably fast behaviour of response and recovery.
Magnetic reduced graphene oxide-ZnFe2O4 composites (RG/ZF) were successfully prepared through a simple chemical co-precipitation method, and their composition, structure, and morphology were characterized by XRD, Raman, SEM, TEM and STEM. These results indicated that the as-prepared RGO with some defects and few reactive groups containing oxygen possessed the few-layered crystal structure, and the ZnFe2O4 nanoparticles with spinel structure were homogeneously dispersed in the interlayer of graphene sheets. The interactions between two components had been investigated by TG and FT-IR. Importantly, kinetic researches indicated that the adsorption behavior of RG/ZF composite could be well described by the second-order kinetic model. Their adsorption effect on RhB conformed to the Langmuir model and belonged to the monolayer chemical adsorption, which were illustrated by thermodynamic experiment. In addition, RG/ZF composites with different mass ratio of RG to ZF (mRG/ZF) presented good photocatalytic activity, and their photocatalytic behavior could be described by the first-order kinetic model under different pH. Among all composites, the RG/ZF composite with mRG/ZF = 0.4 showed the best photocatalytic activity under pH = 1. However, the enhanced photocatalytic activity may arise from the effective separation of photogenerated e−-h+ pairs and the positive synergetic effect between two components. Moreover, the obtained optimum RG/ZF composite had the saturation magnetization (9.8747 emu/g) enough to make it easy to be separated from solution by means of an external magnetic field. On the other hand, the antibacterial testing implied that the antibacterial properties of composite were depended on the mRG/ZF, and the RG/ZF with mRG/ZF = 0.4 likewise presented the most excellent antibacterial activity, especially to the C. albicans (its IZD and MID was respectively up to 34.5 mm and 12.5 μg/mL). Finally, the possible mechanisms of photocatalysis and antibacterial have been discussed.
Crystallographic, microstructural and magnetic properties of ZnFe2O4 nanoparticles synthesized by precipitation from non-aqueous solutions have been studied in the work. The transmission electron microscopy studies reveal particle sizes ∼5 nm for the as-prepared particles which increase up to ∼25 nm upon annealing at 500 °C. Characteristic magnetic parameters of the particles including average magnetic moment of an individual nanoparticle and effective anisotropy constant have been determined by means of the quasistatic magnetic measurements. The specific loss power which is released on the exposure of an ensemble of synthesized particles to an electromagnetic field is calculated and measured experimentally. It is shown that the particles demonstrate high heating efficiency in AC magnetic fields, which is enough for their use in medical applications.
Transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) revealed that ZnFe2O4 particles treated with an Fe(NO3)3 solution had a three-shell structure, comprising a ZnFe2O4 core, an external γ-Fe2O3 shell, and an outer, mixed Fe(NO3)3·9H2O and ZnO layer. The concentration of the Fe(NO3)3 solution played an important role in the treatment; it determined the ratio of the chemical species and the size of the particles. The magnetization of the treated particle was related to the concentration in a non-monotonic fashion, because of the competition between the ferrimagnetic γ-Fe2O3 phase and the nonmagnetic Fe(NO3)3·9H2O/ZnO mixture. The experiments showed that only below a concentration of 0.5 M was the magnetization of the treated particle enhanced with increasing concentration of the Fe(NO3)3 solution.
ZnFe2O4 nanoparticles with average grain size ranging from 40 to 60nm behaving superparamagnetic at room temperature have been produced using a low-temperature solid-state reaction (LTSSR) method without ball-milling process. Abnormal magnetic properties such as S-shape hysteresis loops and non-zero magnetic moments were observed. ZnFe2O4 nanoparticles were also synthesized using a NaOH coprecipitation method and a PVA sol-gel method to study the relationship between the preparation processes and the magnetic properties. Spin-glass behavior was observed in the low temperature solid-state reaction produced Zn ferrite in the zero-field cooled (ZFC) measurement. Our work proves that the various preparation methods will to some extent determine the properties of magnetic nanoparticles.
ZnFe2O4 sensors were fabricated from nano-ZnFe2O4 powders prepared by hydrothermal method and their gas-sensing properties were investigated. It was found that the phase composition of the product and the gas-sensing properties greatly depend on the reaction pH value and the reaction temperature. Nano-ZnFe2O4 powders could be obtained at a pH of 8–10 and the sensor based on the nano-ZnFe2O4 powder prepared at 220°C exhibited the best performance, characterized by high sensitivity to low concentrations of C2H5OH at 180°C, especially, the sensitivity to 100ppm C2H5OH was as high as 76.
Nanosized zinc ferrite (ZnFe2O4) has been prepared directly from metallic iron (Fe) and zinc (Zn) powders by using wet-milling technique. Structural and magnetic properties of the samples were investigated by X-ray diffraction (XRD), thermo gravimetric analysis (TGA) and vibrating sample magnetometer (VSM). It is found that the particle size varied from 38.2 to 19.4nm as the milling time was increased from 2 to 20h. Magnetic measurements at room temperature revealed that the magnetization of the samples increased as the particle size decreased.
In this paper, porous nanocrystalline ZnFe2O4 “timber-like” superstructures were synthesized through the thermal decomposition of zinc ferrioxalate precursor prepared from metal sulfates and sodium oxalate without adding any additives. The resulting ZnFe2O4 superstructures were systematically characterized by X-ray powder diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG-DSC), scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). We found that the porous nanocrystalline ZnFe2O4 superstructures exhibited superparamagnetic properties at room temperature. These porous nanocrystalline ZnFe2O4 superstructures may be applied in magnetic devices. Meanwhile, this general approach could be extended to synthesize porous nanocrystalline CoFe2O4 and NiFe2O4 “timber-like” superstructures.
ZnFe2O4 nanoparticles have been successfully prepared through a polyethylene glycol (PEG)-assisted route. XRD, FTIR, TEM and VSM were used for the structural, morphological and magnetic investigation of the product. Transmission electron microscopy analysis revealed spherical Zn-ferrite particles with a narrow size distribution. Average particle size was obtained as 12 ± 3 nm from TEM, which agrees well with the XRD-based size estimate of 14 nm. ‘S’-shaped hysteresis loops and non-zero magnetic moments were observed indicating super-paramagnetism of the nanoparticles. Peaks observed on the temperature dependent-magnetization curves at 23 and 16 K indicates magnetostatic interactions between the particles and inclusion of antiferromagnetic phase.
A general method has been developed for the synthesis of homogeneous hollow core-shell microspheres of spinel ferrites (MFe 2 O 4 , M) Zn, Co, Ni, Cd) by using carbonaceous saccharide microspheres as template. The products were characterized by X-ray powder diffraction, inductively coupled plasma-atomic emission spectroscopy, scanning electronic microscopy, transmission electron microscopy, and nitrogen sorption measurement. The effects of the concentration of metal salts have been studied using ZnFe 2 O 4 as an example. Increasing the concentration of metal salts could avoid the generation of impurity phase. The core size and shell thickness of hollow spheres obtained can be manipulated by changing the concentration of metal salts. Gas-sensor investigations revealed the ZnFe 2 O 4 hollow spheres used as gas-sensor materials possess high sensitivity and quick responses to organic gases such as ethanol.
Well crystallized ZnFe2O4 ultrafine particles with octahedral shape and a size of 300nm were prepared by a hydrothermal reaction using metal Zn sheet and FeCl2 as reactants in ammonia solutions at 180degreesC. As-prepared ferrite particles display high magnetization with maximum saturation magnetization (sigma(max)) 61.2emg g(-1) at 80K and 54.6emg g(-1) at 300K, respectively. The results demonstrated that hydrothermal process is an effective pathway for producing high quality ferrite ultrafine particles.
ZnFe2O4 tubes with mesoscale dimensions were synthesized by pyrolysis of polyvinyl alcohol (PVA)-mediated xerogel using porous alumina as a template. The product formation was analyzed by X-ray powder diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), thermogravimetry and differential thermal analysis (TG–DTA), scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). This synthetic method yielded open-ended ZnFe2O4 tubes with a typical length of several micrometers, an outer diameter of about 200 nm, and an average thin wall of 20 nm composed of small nanocrystals. Application of the ZnFe2O4 tubes as gas sensor materials displayed low-energy consumption and high sensitivity to organics such as ethanol and acetone, due to the unique interconnected channel structure and small crystal size of the tubes, showing their potential application in sensor areas.
We report the microwave-hydrothermal ionic liquid (MHIL) synthesis and photocatalytic property over phenol of ZnFe(2)O(4) nanoparticles. Zn(CH(3)COO)(2).2H(2)O and Fe(NO(3))(3).9H(2)O were used as the zinc and iron sources, respectively, in the presence of CO(NH(2))(2) and the ionic liquid 1-n-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF(4)]). Deionized water was used as a solvent. The ionic liquid [BMIM][BF(4)] and microwave heating temperature have significant influences on the crystal phase of the product. Different dosages of [BMIM][BF(4)] or microwave heating temperature could lead to the formation of different products such as ZnFe(2)O(4) and beta-FeOOH. The MHIL method has the advantages such as simplicity, rapidness and energy saving. The ZnFe(2)O(4) nanoparticles prepared by the MHIL method exhibit high photocatalytic activity for the degradation of phenol, which was up to 73% within 360 min. The TOC measurement confirmed the good photocatalytic efficiency of ZnFe(2)O(4) nanoparticles.