Magnetic Properties Of Nanocomposites Research Articles

Swift Heavy Ion Induced Modification in Physical Properties of Poly Methylmethacrylate (PMMA)/Nickel (Ni) Nanocomposites

We have These films were irradiated with 85 MeV C-ions at the fluences of 1 x 1011 and 1 x 1012 ions/cm2. Changes in the optical, structural, dielectric, magnetic and thermal properties of (PMMA)/Ni nanocomposites of different concentrations of nickel nanoparticles (5%, 10%, 15%) due to swift heavy ion irradiation were studied by means of UVvisible spectroscopy, X-ray diffraction, impedance gain phase analyzer, SQUID and differential scanning calorimetry. Optical properties like band gap were estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength range 200-800 nm. It was found that the band gap value shifted to lower energy on doping with metal nanoparticles. Differential scanning calorimetry analysis revealed a decrease in the glass transition temperature upon irradiation, which may be attributed to the scissioning of polymer chain due to ion beam irradiation which is also corroborated with XRD analysis. Surface morphology of the pristine and irradiated films was studied by scanning electron microscopy (SEM). The breakage of chemical bonds resulted in an increase of free radicals, unsaturation etc. as revealed from FTIR analysis. The dielectric properties were observed to enhance with an increase in metal compound concentration as well as with irradiation dose. This may be due to metal/polymer bonding and conversion of polymeric structure into hydrogen-depleted carbon network. Zero-Field-Cooled (ZFC)/Field-Cooled (FC) magnetization and magnetic hysteresis measurements were performed using a superconducting quantum interference device (SQUID) magnetometer from temperatures ranging from 5 K to 300 K, to investigate the magnetic properties of nanocomposites. The changes in topography of surfaces were also observed upon irradiation.

Controlled synthesis and magnetic properties of monodisperse Ni1−xZnxFe2O4/MWCNT nanocomposites via microwave-assisted polyol process

Ni1−xZnxFe2O4/MWCNT nanocomposites (x=0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1) with controllable composition have been successfully synthesized via microwave-assisted polyol process using triethylene glycol solution (TREG) as solvent. Experimental results demonstrated that monodisperse face-centered cubical Ni1−xZnxFe2O4 nanoparticles with average size (6nm) had been attached on the MWCNTs. The composition of ferrite nanoparticles can be controlled through adjusting the atomic ratios of the nickel and zinc salts in the mixed nitrate solution. The magnetic properties of nanocomposites with different Zn contents were measured by vibrating sample magnetometer (VSM). The saturation magnetization (Ms) of Ni1−xZnxFe2O4/MWCNT nanocomposites gradually increases when the x is less than 0.5 while decreases when the x is larger than 0.5. Ms reached maximum value when the x is 0.5. The coercivity (Hc) of nanocomposites is low at room temperature, which exhibits characteristic of superparamagnetic.

Effect of polymer matrix on the magnetic properties of polymer bonded magnets filled Fe3O4 nanoparticles

The effect of binder on the magnetic properties of polymer bonded magnets (PBMs) was studied. Five PBMs containing 5 wt% of Fe3O4 nanoparticles were prepared by melt extrusion in a twin screw extruder. The selecting bonders were polypropylene, nylon 66, high impact polystyrene, polycarbonate and acrylonitrile butadiene styrene. Compression moulded samples were prepared. TEM images show a good dispersion for nylon 66 comparing to other nanocomposites. Dynamic intersection frequency (ωc) which is related to crossing of G′ and G″ curves showed that there was a more homogeneity in the nylon 66 and PP nanocomposite comparing to that of other nanocomposites. The curves of saturation magnetization strength (Bs), residual magnetic flux density (Br), and coercive force (Hc) versus surface energy were plotted for different nanocomposites. The magnetic properties of nanocomposites had relationship with the rheological properties and also the surface energy of the matrices.

Preparation of magnetic polyurethane rigid foam nanocomposites

Super paramagnetic Fe3O4@SiO2 nanoparticle was incorporated into polyurethane rigid foams in order to prepare new corresponded magnetic nanocomposite foams via one-shot method. The core–shell-structured nanoparticles were prepared by sol–gel method and characterized by transmission electron microscopy, X-ray diffraction, as well as Fourier transform infrared spectroscopy techniques. Magnetic nanoparticles were used up to 3 % in the foam formulations and the samples prepared successfully. Thermal, mechanical, and magnetic properties of nanocomposites were studied and the results showed superior properties in comparison with pristine foams.

Application of magnetic phase analysis for the study and control of the composition and properties of Fe/C nanocomposites

This work discusses the aspects of the production and study of the properties of Fe/C nanocomposites with high iron content up to 50 wt %, which are a carbon matrix with Fe and Fe3C nanoparticles. A method for the adjustment of magnetic characteristics and the phase composition of the material after synthesis is proposed. The result shows the efficiency of applying a magnetic phase analysis to study the properties of magnetic nanocomposites. It has been demonstrated that the dynamic observation of the magnetization intensity as a function of temperature makes it possible to control the phase ratio in the system Fe-Fe3C-C.

Magnetic Properties of Nanocomposites Formed by Magnetic Nanoparticles Embedded in a Non-Magnetic Matrix: A Simulation Approach

In this work, simulations of magnetic properties of nanocomposites formed by magnetic nanoparticles embedded in a non magnetic matrix are presented. These simulations were carried by means of the Monte Carlo Method and Heisenberg model. Properties as magnetization and Hysteresis loops were obtained varying different parameters as the nanoparticle size, distance between nanoparticles and temperature. The model employed includes interaction between ions belonging to each nanoparticle and also the interaction between nanoparticles. Results show that the magnetization and the coercive force decrease as a function of the nanoparticles distance.

Synthesis and Characterization of Co-Ni and Fe$_{3}$O$_{4}$-Pd Nanocomposites

Co-Ni needle-like and Fe3O4-Pd spherical nanoparticles were prepared by water-in-oil microemulsion (W/O). The as-synthesized nanoparticles have been encapsulated by silica (SiO2) and polyvinyl alcohol (PVA) in N2 atmosphere. Their structure and magnetic properties were evaluated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). The influence of structural modifications to the magnetic properties of nanocomposites has been investigated. Powder X-ray diffraction analysis indicated the formation of face-centered cubic phase for both Co-Ni and Fe3O4-Pd systems. The average crystallite size for the studied samples has been calculated in the range of 7-26 nm. TEM images revealed the morphology of the particles as needle-like nanoparticles for Co-Ni alloy and spherical for Fe3O4-Pd system. The magnetization curves of nanocomposites at room temperature demonstrated coercivity values between 8.2 and 15.5 kA/m for Co-Ni nanocomposites and superparamagnetic behavior of Fe3O4-Pd nanocomposites due to the small-size effect of nanoparticles.

Preparation and Structural Characterization of Vulcanized Natural Rubber Nanocomposites Containing Nickel-Zinc Ferrite Nanopowders

Single-phase polycrystalline mixed nickel-zinc ferrites belonging to Ni0.5Zn0.5Fe2O4 were prepared on a nanometric scale (mean crystallite size equal to 14.7 nm) by chemical synthesis named the modified poliol method. Ferrite nanopowder was then incorporated into a natural rubber matrix producing nanocomposites. The samples were investigated by means of infrared spectroscopy, X-ray diffraction, scanning electron microscopy and magnetic measurements. The obtained results suggest that the base concentration of nickel-zinc ferrite nanoparticles inside the polymer matrix volume greatly influences the magnetic properties of nanocomposites. A small quantity of nanoparticles, less than 10 phr, in the nanocomposite is sufficient to produce a small alteration in the semi-crystallinity of nanocomposites observed by X-ray diffraction analysis and it produces a flexible magnetic composite material with a saturation magnetization, a coercivity field and an initial magnetic permeability equal to 3.08 emu/g, 99.22 Oe and 9.42 x 10(-5) respectively.

A feasible approach for preparing remanence enhanced NdFeB based permanent magnetic composites

NdFeB based permanent magnetic nanocomposites were prepared by depositing soft magnetic Fe, Co, or Fe65Co35 nanoparticles on the melt spun NdFeB powders with near single phase composition by a chemical reduction method. The effects of the reduction process, the composition, and the concentrations of metal ions on the magnetic properties of nanocomposites were investigated. Introducing and increasing soft nanoparticle content improved the remanence and maximum energy product of the nanocomposites at the expense of coercivity. Fe65Co35 coated NdFeB powders had higher remanence and energy product than Co or Fe coated powders. The inter-grain exchange coupling between hard and soft magnetic grains was demonstrated by the smooth demagnetization curve with high remanent polarization. Remanence enhanced bulk magnets were also fabricated by consolidating the nanocomposite powders using spark plasma sintering (SPS) technique.

Investigations on structural and magnetic properties of cobalt ferrite/silica nanocomposites prepared by the coprecipitation method

Magnetic nanocomposites consisting of cobalt ferrite nanoparticles embedded in silica matrix were prepared by the coprecipitation method using metallic chlorides as precursors for ferrite. Subsequently composites were annealed at 100, 200 and 300°C for 2h. The samples were structurally characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The magnetic properties were measured in the temperature range of 10–300K using vibrating sample magnetometer (VSM). The effects of thermal treatment on structural and magnetic properties of nanocomposites were investigated. When the samples were annealed, CoFe2O4 nanocrystallites were observed in the SiO2 matrix, whose size increases with increase in annealing temperature. The coercivity and saturation magnetization of nanocomposite (annealed at 300°C for 2h) are much higher than that of bulk cobalt ferrite. The realization of adjustable particle sizes and controllable magnetic properties makes the applicability of the CoFe2O4 nanocomposite more versatile.

Surface spin disorder effects in magnetite and poly(thiophene)-coated magnetite nanoparticles

Chemically synthesized magnetite and poly(thiophene)-coated magnetite nanoparticles and the correlations between their magnetic, structural, and microstructural properties are investigated. A typical superparamagnetic behavior was observed for faceted nanoparticle agglomerates of magnetite and nanocomposite. In nanocomposites, the polymer layer causes a sharp decrease in the spin disorder, which reduces the anisotropy constant significantly. This happens because the intimate contact between magnetite and poly(thiophene) leads to charge transfer from the polymer to the core via polaron interactions, causing a structural rearrangement of the nanoparticles and suppression of the spin movement at the surface. As this dynamic interaction can tune the core dimensions, the magnetic properties of nanocomposites can be tuned by controlling the core size through polymer coating. These characteristics can be exploited to design high-performance magnetically tunable nanodevices and applied in many areas of biomedicine (DNA separation, drug targeting, immune detection, and magnetic nanoparticle hyperthermia in cancer treatment).

Influence of calcinations temperature on physical properties of the nanocomposites containing spinel and CuO phases

Nanocomposites containing spinel and CuO phases have been synthesized by sol–gel method using Cu(II), Ni(II) and Fe(III) in a basic medium. The effect of calcinations temperature on the physical properties of the nanocomposites has been investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), micro-Raman spectroscopy (RS), differential scanning calorimetery (DSC)/thermogravemetric analysis (TGA), diffuse reflectance spectroscopy (DRS), scanning electron microscope (SEM), high resolution transmission electron microscope (HR-TEM) and vibrating sample magnetometer (VSM). The XRD pattern of nanocomposites synthesized at different calcinations temperature reveals spinel and CuO phases. The particle size of the nanocomposites is increasing with increasing the calcinations temperature. The band gap of synthesized nanocomposites has been calculated using DRS method. The prepared nanocomposites exhibit semiconducting nature with band gap values, 1.9–2.24 eV. The magnetic properties of nanocomposites are also measured at room temperature and the values of saturation magnetization (Ms), remanent magnetization (Mr) and coercivity are found enhanced with the calcinations temperature.

Glycolic acid assisted one-step synthesis of Cu–Ni–Fe metal oxide nanocomposites by sol–gel-combustion method: Structural, spectroscopic and magnetic studies

The present article reports the synthesis of copper, nickel and iron-based metal oxide nanocomposites by sol–gel method using disproportion of Cu(II) and Fe(III) in basic media. The synthesized nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy (RS), differential scanning calorimetery (DSC)/thermogravemetric analysis (TGA), field-emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM) and vibrating sample magnetometer (VSM). The XRD patterns of nanocomposites confirm the presence of spinel, CuO and FeO phases. The particle size of the nanocomposite has been calculated using HR-TEM micrographs and found to be in the range of 10–120 nm. The magnetic properties of nanocomposites were measured at room temperature. The values of saturation magnetization (Ms) and remanent magnetization (Mr) were increasing with increase of iron concentration.

Magnetic Studies of CoFe<SUB>2</SUB>O<SUB>4</SUB>/SiO<SUB>2</SUB> Aerogel and Xerogel Nanocomposites

The evolution of the structural and magnetic properties of nanocomposites formed by cobalt ferrite particles dispersed in xerogel and aerogel silica matrices (CoFe2O4/SiO2) have been studied as a function of the temperature of preparation and the amount of ferrite dispersed in the matrix. Wet samples with different amounts of CoFe2O4 in SiO2 matrix were prepared by sol-gel process in monolithic form. Xerogel and aerogel samples were prepared by controlled and hypercritical drying, respectively, and heated at various temperatures between 300 and 1100 degrees C. Superparamagnetic behavior has been observed by magnetization studies at room temperature for xerogels prepared at low temperature. Aerogel samples showed significant superparamagnetic fractions for all thermal treatment temperatures as determined by Mössbauer spectroscopy. Magnetization of the nanocomposites at 10 KOe applied field varied from 1 to 19 emu/g and the coercivity from 90 to 2320 Oe, respectively, for the different morphologies and textures of the analyzed material. The results show that besides the magnetization and coercivity depend on crystallite size, parameters such as ferrite content, porosity and drying conditions greatly influence the nanocomposite magnetic behavior.

Magnetic and electronic transport properties of nanocomposites of superconducting Mo carbides’ nanoparticles embedded in a ferromagnetic carbon matrix

The electronic transport and magnetic properties of nanocomposites, in which nanoparticles of superconducting (SC) molybdenum carbides are embedded in a ferromagnetic (FM) carbon matrix to form a three-dimensional SC-FM network, are studied. The high-resolution transmission electron microscope observation shows that the carbon in the nanocomposites is in both ordered and disordered forms. The magnetic properties of the nanocomposites are ruled by the ferromagnetic carbon matrix. The temperature dependence of electrical resistivity of the nanocomposites is dominated by the carbon matrix, showing the semi-conductivity. The special I-V curves near the zero voltage bias of the nanocomposites are observed at low temperatures, due to the influence of contact barriers between molybdenum carbides and the carbon matrix.

Preparation and characterization of thermosensitive polymers grafted onto silica-coated iron oxide nanoparticles

In this study, multifunctional nanoparticles containing thermosensitive polymers grafted onto the surfaces of 6-nm monodisperse Fe 3O 4 magnetic nanoparticles coated by silica were synthesized using reverse microemulsions and free radical polymerization. The magnetic properties of SiO 2/Fe 3O 4 nanoparticles show superparamagnetic behavior. Thermosensitive PNIPAM (poly( N-isopropylacrylamide)) was then grafted onto the surfaces of SiO 2/Fe 3O 4 nanoparticles, generating thermosensitive and magnetic properties of nanocomposites. The sizes of fabricated nanoparticles with core–shell structure are controlled at about 30 nm and each nanoparticle contains only one monodisperse Fe 3O 4 core. For thermosensitivity analysis, the phase transition temperatures of multifunctional nanoparticles measured using DSC was at around 34–36 °C. The magnetic characteristics of these multifunctional nanoparticles were also superparamagnetic.

Polyaniline/Li 0.25Ni 0.5La xFe 2.25 − xO 4 nanocomposites: Preparation and tailoring the magnetic property

Polyaniline/Li 0.25Ni 0.5La x Fe 2.25 − x O 4 nanocomposites were synthesized by a simple, general and inexpensive in situ polymerization method. The structural, morphological and magnetic properties of nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, scanning electronmicroscopy (SEM) and magnetic measurements. XRD and FTIR revealed the presence of Li 0.25Ni 0.5La x Fe 2.25 − x O 4 in the nanocomposites. SEM micrographs showed that the nanocomposites exhibited spherical morphology with particle sizes in the range of 50–100 nm. The magnetic measurements indicated that magnetic property of resulting nanocomposites can be tailored by controlling the different La content in spine ferrite.

Preparation and magnetic properties of Zn [sbnd]Cu [sbnd]Cr [sbnd]La ferrite and its nanocomposites with polyaniline

Nanosized Zn 0.6Cu 0.4Cr 0.5Fe 1.5− x La x O 4 ( x = 0 ∼ 0.06 ) ferrites doped with La are synthesized by a rheological phase reaction method. Polyaniline (PANI)/ferrite nanocomposites are prepared by in situ polymerization method. The structure, morphology and ferromagnetic property of ferrite powders and nanocomposites are characterized by X-ray powder diffractometer (XRD), transmission electron microscope (TEM), Fourier transform infrared spectra (FTIR), UV–visible spectroscopy (UV), thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM). The results indicate that the PANI and nanosized ferrite powders can be combined effectively. The polymers can reduce the agglomeration of nanosized ferrite particles to some extent, which is good for the dispersedness and stabilization of nanoparticles. The PANI/ferrite nanocomposites under applied magnetic field exhibit the hysteretic loops of the ferromagnetic nature. The magnetic properties of nanocomposites are tailored by controlling the ferrite content.

Synthesis and Magnetic Properties of Nanocomposite Magnets Self-Organized from FeB-Nd-Nb Metallic Glasses

ABSTRCTChange of the magnetic property of Fe-B-Nd-Nb alloys was investigated with replacing Nb by a glass forming element Zr under constant quenching rate as well as heat treatment conditions. As a result, the coercivity significantly increases up to 1207 kA/m when the half of Nd is replaced by Zr, which is presumably due to grain refinement of the Nd2Fe14B phase. The self-organized nanograin magnets are attractive for future applications since their coercivity can be further improved by reducing the grain size via optimizing the Zr concentration, the quenching rate and the subsequent heat treatment condition.

XANES and USXES investigations of interatomic interaction at the grain boundaries in nanocomposites (Co 41Fe 39B 20) x(SiO 2) 1− x

Interatomic interaction in amorphous (Co 41Fe 39B 20) x (SiO 2) 1− x nanocomposites was investigated with the use of X-ray absorption near-edge structure (XANES) technique that is one of the most sensitive to the chemical surrounding of the elements in multi-component compounds. XANES spectra of Fe L 2,3-edges, Co L 2,3-edges, B K-edge, Si L 2,3-edges and O K-edge demonstrated the presence of interatomic interaction between the elements of metallic and dielectric components of the nanocomposite. These interactions result in a formation of the complex multi-phase system and its electron structure should have an influence on the electrophysical and magnetic properties of nanocomposites. Particularly, transformation of the fine structure of iron L 2,3-edges spectra represents the change of ratio of two- and three-valence iron atoms in oxides and/or silicates. The presence of CoO and complex boron oxides in nanocomposites was also detected. Therefore, electroconductivity within the boundaries of a single grain of nanocomposite (nanoferrite) with a possible composition of FeO·Fe 2O 3·CoO·B x O y is due to the transitions of electrons not only between Fe 2+ and Fe 3+ ions but also between the ions of Co 2+, Fe 2+ and Fe 3+. At the same time, dielectric component represents a mixture of silicon oxide and silicates of transition metals.