Synthesis and characterization of chitosan coating of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles for biomedical applications

Nickel ferrite nanoparticle is a soft magnetic material whose appealing properties as well as various technical applications have rendered it as one of the most attractive class of materials; its technical applications range from its utility as a sensor and catalyst to its utility in biomedical processes. The present paper focuses first on the synthesis of NiFe₂O₄ nanoparticles through co-precipitation method resulting in calcined nanoparticles that were achieved at different times and at a constant temperature (773 k). Afterward, they were dispersed in water that was mixed by chitosan. Chitosan was bonded on the surface of nanoparticles by controlling the pH of media. In order to assess the structural and magnetic properties of nanoparticles, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) analyses were conducted at room temperature. As per the results of XRD analysis, the pure NiFe₂O₄ was synthesized. Additionally, nanoparticles grew in size by extending the calcination process duration. TEM micrographs were used to determine the size and shape of particle; the obtained results indicate that the particle size was in a range of 17–30 nm and of a circular shape. The proper chitosan covering was also indicated by FTIR results. The VSM analysis also revealed that the saturated magnetization of NiFe₂O₄ nanoparticles stood in a range of 29 emu/g and 45 Q_e. A stable maximum temperature ranging from 30 to 42 was successfully achieved within 10 min. Also, a specific absorption rate of up to 8.4 W/g was achieved. The study results revealed that the SAR parameter of the coated nickel ferrite nanoparticle is more than that of pure nickel ferrite or cobalt ferrite nanoparticles.     

UV excited green luminescence of SrAl<Subscript>2</Subscript>O<Subscript>4</Subscript>:Eu<Superscript>2+</Superscript>, Dy<Superscript>3+</Superscript> nanophosphor

Eu, Dy co-doped strontium aluminate nanophosphors were prepared by the combustion synthesis method. Their structure and morphology were investigated by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy. According to the XRD and the TEM analysis, the average crystallite size was found to be in the nanometer range. The phase structure of the prepared nanophosphor is consistent with a standard monoclinic phase with a space group P2₁. The prepared SrAl₂O₄:Eu²⁺, Dy³⁺ nanophosphor emitted green light with a peak at 510 nm showing blue shift, which is due to the reduction in the particle size. Two distinct peaks were observed in the ML intensity versus time curve. The two peaks in ML indicate the presence of charge transfer in an ML process.     

Magnetic NiFe2O4 nanoparticles: efficient,heterogeneous and reusable catalyst for synthesis of acetylferrocene chalcones and their anti‐tumour activity

A robust synthesis of magnetic NiFe₂O₄ nanoparticles via a hydrothermal technique was investigated. The prepared magnetic NiFe₂O₄ nanoparticles were characterized using powder X‐ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), high‐resolution TEM, energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, infrared spectroscopy and vibrating sample magnetometry. XRD and TEM analyses confirmed the formation of single‐phase ultrafine nickel ferrite nanoparticles with highly homogeneous cubic shape and elemental composition. Moreover, the prepared magnetic NiFe₂O₄ nanoparticles were used as an efficient, cheap and eco‐friendly catalyst for the Claisen–Schmidt condensation reaction between acetylferrocene and various aldehydes (aromatic and/or heterocyclic) yielding acetylferrocene chalcones in excellent yields, with easy work‐up and reduced reaction time. The products were purified via crystallization. The structures of the produced compounds were elucidated using various spectroscopic analyses (¹H NMR, ¹³C NMR, GC–MS). The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no discernible loss of catalytic activity. Furthermore, the prepared chalcone derivatives were evaluated for their anti‐tumour activity against three human tumour cell lines, namely HCT116 (colon cancer), MCF7 (breast cancer) and HEPG2 (liver cancer), and showed a good activity against colon cancer. Copyright © 2016 John Wiley & Sons, Ltd.     

Comparative study of the synthesis of CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> and NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> in silica through the polymerized complex route of the sol–gel method

In this work the synthesis of CoFe₂O₄-SiO₂ and NiFe₂O₄-SiO₂ nanocomposites was studied via the sol–gel method, using the polymerized complex route. The polymerized precursors obtained by the reaction of citric acid, ethylene glycol, tetraethylorthosilicate, ferric nitrate, and cobalt nitrate or nickel chloride were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. NMR and IR spectra of the precursors, without and with metallic ions, show the formation of polymeric chains with ester and ether groups and complexes of metal-polymeric precursor. The nanocomposites were obtained by the thermal decomposition of the organic fraction and characterized by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). XRD patterns show the formation of CoFe₂O₄ and NiFe₂O₄ in an amorphous silica matrix above 400 °C in both cases. When the calcination temperature was 800 °C the particle size of the crystalline phases, calculated using the Scherrer equation, reached ∼35 nm for the two oxides. VSM plots show the ferrimagnetic behavior that is expected for this type of magnetic material; the magnetization at 12.5 KOe of the CoFe₂O₄-SiO₂ and NiFe₂O₄-SiO₂ compounds was 29.5 and 17.4 emu/g, respectively, for samples treated at 800 °C.     

Preparation and Application of Magnetically Recoverable Cationic Exchanger Support on Monodisperse Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles

A magnetically recoverable cationic exchanger has been effectively prepared through immobilized chloroacetic acid (CA) onto the Fe₃O₄ nanoparticles. The magnetic nanoparticles (MNPs) were synthesized by a coprecipitation method in an aqueous system. The MNPs were modified with sodium silicate and chloroacetic acid (CA), thus endowed these nanoparticles with strong magnetism and good dispersion. The physicochemical properties of the cationic exchange materials were characterized with Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). The magnetic properties of the cationic exchange materials were analyzed by a vibrating sample magnetometer (VSM). The content of ions was measured by atomic absorption spectrophotometric method. The prepared cationic exchange nanoparticles display an excellent magnetic property with a saturation magnetization value of 26.58 emu/g and the prepared exchanger possess considerable thermal stability, which indicating a great potential application in heavy metal ion wastewater treatment. In this experiment, the exchange capacity of lead ion was 3.4 mmol g^–1, And the maximum lead removal rate is up to 73.85%.     

Coordination mechanism,characterization, and photoluminescence properties of spinel ZnAl<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles prepared by a modified polyacrylamide gel route

Single-phase ZnAl₂O₄ nanoparticles with the spinel structure were successfully synthesized using a modified polyacrylamide gel method according to the atomic ratio of Zn to Al = 1: 1.8. The as-prepared samples were characterized by means of X-ray powder diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetry analysis (DSC), field-emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL) spectra. XRD patterns show that the pure phase of ZnAl₂O₄ is obtained after heating the xerogel at 900°C for 5 h in air. The SEM images reveal that the ZnAl₂O₄ nanoparticles have a narrow particle size distribution and the average particle size is around 45 nm. Photoluminescence (PL) spectra demonstrate the single phase ZnAl₂O₄ nanoparticles have an emission peak located at 469 nm when excited by 350 nm light. The phase structure, coordination mechanism, and luminescence properties have been discussed on the basis of the experimental results.     

Preparation of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-C18 nano-magnetic composite materials and their cleanup properties for organophosphorous pesticides

Magnetic Fe₃O₄-C18 composite nanoparticles of approximately 5–10 nm in size were synthesized and characterized by IR spectroscopy, atomic absorption spectroscopy, X-ray diffraction, and transmission electron microscopy. The magnetic Fe₃O₄-C18 composite nanoparticles were applied for cleanup and enrichment of organophosphorous pesticides. Comparative studies were carried out between magnetic Fe₃O₄-C18 composite nanoparticles and common C18 materials. Residues of organophosphorous pesticides were determined by gas chromatography in combination with a nitrogen/phosphorus detector. The cleanup and enrichment properties of magnetic Fe₃O₄-C18 composite nanoparticles are comparable with those of common C18 materials for enrichment of organophosphorous pesticides, but the cleanup and enrichment are faster and easier to perform. Figure Presumed mechanism for the adhesion of the OPs to the Fe₃O₄-C18 magnetic nanoparticles     

Sol-gel preparation and spectroscopic study of the pyrophanite MnTiO<Subscript>3</Subscript> nanoparticles

The nanosized xerogel of titanium dioxide (TiO₂) and manganese oxides (MnO₂, Mn₂O₃, Mn₃O₄) was prepared by the sol-gel method using manganese chloride (MnCl₂·4H₂O) and titanium isopropoxide (Ti(O-iPr)₄) as precursors in cetyltrimethylammonium bromide (CTAB)/ ethanol/H₂O/HCl micelle solutions, following the calcinations of the produced powders at difference temperatures. The nanostructure and phase composition of these nanoparticles were characterized with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The spectroscopic characterizations of these nanoparticles were also done with UV-Vis spectroscopy and laser Raman spectroscopy (LRS). XRD patterns show that the pyrophanite MnTiO₃ phase was formed at the calcinations temperature of 900°C. The TEM images show that the nanoparticles are almost spherical or slight ellipose and the sizes are 50 nm on average. The UV-Vis spectra show that the nanosized MnTiO₃ have significant absorption bands in the visible region. There are new absorption peaks of MnTiO₃ nanoparticles in LRS compared with the pure TiO₂ powder.     

Surfactant Assisted Hydrothermal Synthesis of Superparamagnetic ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanoparticles as an Efficient Visible-Light Photocatalyst for the Degradation of Organic Pollutant

Super paramagnetic ZnFe₂O₄ nanoparticles were prepared by a surfactant assisted (ethylamine) hydrothermal method along with heat treatment. The nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, high resolution scanning electron microscopy, Transmission electron microscopy, vibrating sample magnetometer and diffuse reflectance spectra technique. From the analyses, influence of calcination temperature on the structural, vibrational, morphological, magnetic and optical properties of ZnFe₂O₄ nanoparticles were investigated. The ZnFe₂O₄ nanoparticles with an average particle size of 17 nm showed high photocatalytic activity in the degradation of methylene blue (90 %). This work demonstrates that ZnFe₂O4 can be used as a potential monocomponent in visible-light photocatalysis for the degradation of organic pollutants. Furthermore, the products were super paramagnetic and could be conveniently separated within 15 min and recycled by using simple magnet, which is very beneficial for the degradation of organic pollutants.     

Flash microwave synthesis of trevorite nanoparticles

Nickel ferrite nanoparticles have several possible applications as cathode materials for rechargeable batteries, named “lithium-ion” batteries. In this study, NiFe₂O₄ was prepared by microwave induced thermohydrolysis. The obtained nanoparticles were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), BET method, transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). All the results show that the microwave one-step flash synthesis leads in a very short time to NiFe₂O₄ nanoparticles with elementary particles size close to 4-5 nm, and high specific surfaces (close to 240 m²/g). Thus, microwave heating appears as an efficient source of energy to produce quickly nanoparticles with complex composition as ferrite.     

2-pyrrolidone - capped Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocrystals

Water-soluble Mn₃O₄ nanocrystals have been prepared through thermal decomposition in a high temperature boiling solvent, 2-pyrrolidone. The final product was characterized with XRD, SEM, TEM, FTIR and Zeta Potential measurements. Average crystallite size was calculated as ∼15 nm using XRD peak broadening. TEM analysis revealed spherical nanoparticles with an average diameter of 14±0.4 nm. FTIR analysis indicated that 2-pyrrolidone coordinates with the Mn₃O₄ nanocrystals only via O from the carbonyl group, thus confining their growth and protecting their surfaces from interaction with neighboring particles.      

Synthesis and Electrocatalytic Properties of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanocrystallites with Various Morphologies

Co₃O₄ crystallites with particle, plate-, tube-, rod- and sheet-like morphologies were successfully prepared by the calcination of the corresponding precursors synthesized via a precipitation or hydrothermal procedure. The morphologies of the precursors and Co₃O₄ nano-tubes were detected by field emission scanning electron microscopy (FE-SEM). The as-obtained Co₃O₄ samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and special surface area measurement (BET). The electrocatalytic activity of p-nitrophenol reduction with the Co₃O₄ products decorated on a glassy carbon electrode (GCE) was tested, respectively, using cyclic voltammetry (CV) in a basic solution. The results indicated that p-nitrophenol was reduced with higher current density but almost at a constant potential on the Co₃O₄/GCE in contrast with that on a bare GCE at the same conditions. The highly catalytic activity of the as-prepared Co₃O₄ in a basic solution suggested their wide applications in environmental treatment or organic synthesis.     

Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>/Bi<Subscript>2</Subscript>MoO<Subscript>6</Subscript> heterostructures with enhanced visible light photocatalytic activity for the degradation of rhodamine B

Highly efficient visible-light-driven Ag₃PO₄/Bi₂MoO₆ hybrid photocatalysts with different mole ratios of Ag₃PO₄ were prepared via sonochemical method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that product are cubic Ag₃PO₄ nanoparticles supported on orthorhombic Bi₂MoO₆ nanoplates. Under visible light irradiation (>420 nm), the Ag₃PO₄/Bi₂MoO₆ photocatalysts displayed the higher photocatalytic activity than pure Bi₂MoO₆ for the decolorization of rhodamine B (RhB). Among the hybrid photocatalysts, 10% Ag₃PO₄/Bi₂MoO₆ exhibited the highest photocatalytic activity for the decolorization of RhB due to the efficient separation of electron–hole pairs.     

One-Pot Synthesis of Novel Amino-Functionalized Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Hybrid Microspheres for Cu(II) Removal from Aqueous Solutions

In this work, we report the development of novel amino-functionalized Fe₃O₄ hybrid microspheres adsorbent from a facial and one-step solvothermal route by using FeCl₃·6H₂O as a single iron source and 3-aminophenoxy-phthalonitrile as ource of amino groups. During solvothermal process, the nitrile groups of 3-aminophenoxy-phthalonitrile would bond with the Fe₃O₄ through the phthalocyanine cyclization reaction to form the amino-functionalized Fe₃O₄ magnetic nano-material, which was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermo-gravimetric analyzer (TGA). From the scanning electron microscope (SEM) and transmission electron microscopy (TEM) observation, the resulting monodispersed amino-functionalized Fe₃O₄ hybrid microspheres with the diameters of 180–200 nm were synthesized via the self-assembly process. More importantly, as-prepared Fe₃O₄ nano-materials with abundant amino groups exhibited high separation efficiency when they were used to remove the Cu(II) from aqueous solutions. Furthermore, the adsorption isotherms of Fe₃O₄ nano-material for Cu(II) removal fitted the Langmuir isotherm model, in which the calculated maximum adsorption capacity could increase from 5.51 to 16.25 mg g^–1 at room temperature. This work demonstrated that the amino-functionalized Fe₃O₄ magnetic nano-materials were promising as efficient adsorbents for the removal of heavy metal ions from wastewater in low concentration.     

The Role of Y<Subscript>2</Subscript>O<Subscript>3</Subscript> and MgO Additives on the Photoluminescence Properties of Si<Subscript>3</Subscript>N<Subscript>4</Subscript> Nanoparticles

The current research addressed synthesizing and studying photoluminescence studies of β-Si₃N₄ nanoparticles. The effect of MgO and Y₂O₃ as the typical additives on photoluminescence behaviour was evaluated. The β-Si₃N₄ with MgO and Y₂O₃ additive specimens were fabricated by a solid state technique (ball-milled method). The as-prepared products were characterized by X-ray diffraction technique, transmission electron microscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman analysis. The results showed that after ball-milled process, hexagonal β-Si₃N₄ with MgO or Y₂O₃ as the additives with the size distribution of 45–50 nm was obtained. The optical properties of the as-synthesized product were also investigated by photoluminescence and diffuse reflection spectroscopy. The obtained results confirmed that employing MgO as an additive, in comparison to the Y₂O₃, could enhance emission properties in the synthesized silicon nitride nanoparticles. The obtained results also showed that MgO–Si₃N₄ pair acted as FRET system to enhance the emission intensity of β-Si₃N₄ nanoparticles.     

Synthesis and characterization of TiO<Subscript>2</Subscript>-montmorillonite nanocomposites and their photocatalytic activity

TiO₂ nanoparticles have been synthesized on the surface of exfoliated montmorillonite at a low temperature in benzyl alcohol medium. According to X-ray diffraction (XRD), N₂ adsorption-desorption isotherm and transmisson electron microscopy (TEM), it was found that the intercalation of TiO₂ nanoparticles destroyed the ordered structure of montmorillonite to some extent, and the crystallites of the nanocomposites are assembled to form a house-of-cards structure. The size of the nanoparticles in the interlamellar space is about 4 nm. The nanocomposites exhibited excellent photocatalytic activity in methylene blue degradation due to the synergetic effect of the adsorptive ability to organic compound of cetyl trimethylammonium bromide—montmorillonite and the catalytic ability of TiO₂ nanoparticles in it.     

Particle size,morphology, and properties of transition metal ferrospinels of the MFe<Subscript>2</Subscript>O<Subscript>4</Subscript> (M = Co,Ni, Zn) type,produced by glycine-nitrate combustion

Ferrites-spinels of the MFe₂O₄ type (M = Co, Ni, Zn), produced by glycine-nitrate combustion were studied. A physicochemical study of ferrite samples was performed by X-ray fluorescence analysis, scanning electron microscopy, X-ray phase analysis, and X-ray spectroscopy. The average size of the coherent scanning region was found to be (nm): 28 ± 2 for CoFe₂O₄, 32 ± 2 for NiFe₂O₄, and 26 ± 2 for ZnFe₂O₄. Magnetic characteristics were determined by the NMR method. The specific residual magnetization, specific saturation magnetization, and coercive force were, respectively, 14.1 A m² kg^?1, 20.1 A m² kg^?1, 31800 A m^?1 for CoFe₂O₄; 4.4 A m² kg^?1, 23.1 A m² kg^?1, 6550 A m^?1 for NiFe₂O₄; and 5.1 A m² kg^?1, 18.3 A m² kg^?1, 3200 A m^?1 for ZnFe₂O₄. Their magnetic properties show that the resulting ferrospinel powders can be used in the following fields of technology: CoFe₂O₄ in those areas where heat transfer is necessary (hyperthermia) and in development of data storage media; NiFe₂O₄ and ZnFe₂O₄ in those areas where low heat exchange is necessary, ZnFe₂O₄ for fast remagnetization and NiFe₂O₄ as a core or shell for transportation of other substances. The ferrospinel samples compare well in magnetic properties with their foreign commercial analogs, which makes these compounds commercially viable.     

Thiol-functionalized Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> microspheres with superparamagnetism and their adsorption properties for Au(III) ion separation

Thiol-functionalized Fe₃O₄/SiO₂ microspheres (Fe₃O₄/SiO₂-SH) with high saturation magnetization (69.3 emu g^–1), superparamagnetism, and good dispersibility have been prepared by an ethylene glycol reduction method in combination with a modified Stöber method. The as-prepared composite magnetic spheres are characterized with fourier transform infrared spectroscopy (FT-IR), zeta potential, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and superconducting quantum interference magnetometer, and tested in separation of Au(III) ions from aqueous solutions. The data for Au(III) adsorption on Fe₃O₄/SiO₂-SH are analyzed with the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models, and the pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics models. The adsorption behaviors of Au(III) on Fe₃O₄/SiO₂-SH follow the Langmuir isotherm model, and the adsorption process conforms to the pseudo-second-order kinetic model. The maximum adsorption capacity of Au(III) on Fe₃O₄/SiO₂-SH is 43.7 mg g^–1. Acetate anions play an important role yet Cu(II) ions have little interference in the adsorption of Au(III) on the adsorbent. A satisfactory recovery percentage of 89.5% is acquired by using an eluent with 1 M thiourea and 5% HCl, although thiols have a high affinity to Au(III) ions based on the hard-soft acid-base (HSAB) theory by Pearson.     

Electrospinning fabrication of mesoporous nano Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript>@activated carbon fiber membrane for hybrid removal of phenol from waste water

A mesoporous iron–titanium mixed-oxides@activated carbon(AC) fiber membrane was fabricated by an electrospinning method and applied to the treatment of phenol waste water. The physical and chemical properties of the composite fiber membrane were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption, UV–Vis light diffuse reflectance spectroscopy (DRS), Raman spectroscopy, respectively. The results indicate that the composite nanofiber membrane is composed of α-Fe₂O₃, anatase TiO₂ and activated carbon phases with a specific surface area of 231 m² g^–1 and narrow pore size distribution of 3–6 nm. DRS reveals that the composite membrane has high photons absorption from both ultraviolet light and visible light irradiation owing to the combination of Fe₂O₃, TiO₂ and carbon. The prepared nano Fe₂O₃–TiO₂@AC fiber membrane can act as an efficient reusable photocatalyst and adsorbent for 100% remo val of phenol pollutant. This hybrid technique is hopeful to be widely used in the treatment of various organic waste waters.     

Nanocomposite based on epoxy and MWCNTs modified with NiFe2O4 nanoparticles as efficient microwave absorbing material

In order to make a microwave absorbent material with good dielectric and magnetic properties, well dispersed microwave absorbing hybrid epoxy polymer composites containing nickel doped Fe₃O₄ nanocrystals coated on carbon nanotubes (NiFe₂O₄‐MWCNTs/epoxy) were synthesized by the combined precipitation‐hydrothermal method in 1‐30 wt.% of nanoparticles. Nickel possess well interaction with microwave radiation and represents fine electromagnetic interference (EMI) shielding and by dopping it into ferrite spinel structures, does not show any tendency to oxidation. Well‐dispersed NiFe₂O₄–MWCNTs/epoxy nanocomposite prepared by new in‐situ polymerization method. First, NiFe₂O₄–MWCNT nanoparticles ultrasonicated in acetone and after mixing with epoxy resin ultrasonicated again. Finally, hardner added to the composite and tuned temperature for evaporating solvent. X‐ray diffraction (XRD) and energy dispersive spectroscopy (EDS) confirmed the synthesizing NiFe₂O₄ nanoparticles. Saturation magnetization value of NiFe₂O₄‐MWCNTs is about 29 emu/g with very low remanence and coercivity content, which revealed that the NiFe₂O₄‐MWCNTs is ferromagnetic nanocrystal. Transmission electron microscopy (TEM) used to characterize the distribution of NiFe₂O₄ nanocrystals on the surface of MWCNTs. The TEM images show that NiFe₂O₄ nanocrystals have a mean size of 12 nm, and completely coated on the exterior surface of MWCNTs. The obtained results of reflection loss revealed that the maximum values of reflection loss of the NiFe₂O₄‐MWCNTs/epoxy increase by enhancing the content of nanoparticles until 10 wt.% and decreases in 30 wt.%.