Preparation of Dysprosium Ferrite/Polyacrylamide Magnetic Composite Microsphere and Its Characterization

Using the technique of microemulsion polymerization with nano-reactor, dysprosium ferrite/polyacrylamide magnetic composite microsphere was prepared by one-step method in a single inverse microemulsion. The structure, average particle size, morphology of composite microsphere were characterized by FTIR, XRD, TEM and TGA. The magnetic responsibility of composite microsphere was also investigated. The results indicate that the magnetic composite microsphere possess high magnetic responsibility and suspension stability.

The structural and magnetic properties of barium ferrite powders prepared by the sol-gel method

In this paper, M-type hexagonal barium ferrite powders are synthesized using the sol-gel method. A dried precursor heated in air is analyzed in the temperature range from 50 to 1200 ℃ using thermo-gravimetric analysis and differential scanning calorimetry. The effects of the additives and the cacinating temperature on the magnetic properties are investigated, and the results show that single-phase barium ferrite powders can be formed. After heat-treating at 950 ℃ for 4h with 3 wt% additive, the coercivity and saturation magnetization are found to be 440 Oe and 57.9 emu/g, respectively.

Magnetic and microwave absorbing properties of M-type barium ferrite/graphene oxide composite microwave absorber

In order to improve the absorbing properties of M- type barium ferrite absorbing materials, M-type barium ferrite/graphene oxide composites with different graphene oxide contents were synthesized by the sol-gel autocombustion method. X-ray diffraction （XRD）, a scanning electronic microscopy （ SEM ）, a physical properties measurement system （PPMS-9）, and a vector network analyzer were used to analyze their structure, surface morphology, magnetic and absorbing properties, respectively. The results show that the absorbing band of the composite absorbing material is widened and the absorbing strength is increased compared with the pure M-type barium ferrite. The sample with the content of doped graphene oxide of 3% has the minimum reflectivity at 10 to 18 GHz frequencies. Hence, the doped graphene oxide effectively improves the absorbing properties of M-type barium ferrite.

Effect of Al-substitution on phase formation and magnetic properties of barium hexaferrite synthesized with sol-gel auto-combustion method

Al-substituted barium ferrite powders were synthesized using the sol-gel auto-combustion method according to the molecular formula BaAlxFe12-xO19 （x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0）. Compared with non-substituted barium ferrite annealing at 1000 ℃, the vibrating sample magnetometer （VSM） measurement manifested that the optimum magnetic properties formation temperature of Al-substituted barium ferrite was 1 100 ℃. The data from X-ray diffractometer （XRD） showed that with increasing x, the lattice constants （a and c） decreased as well as the unit-cell volume Vcell. Magnetic measurement of non-substituted and Al-substituted powders annealed from 900 ℃ to 1 200 ℃ exhibited that the maximum magnetization M （10 kOe）, the remanent magnetization Mr and the coercivity Hc depended strongly on the chemical composition of powder as well as the annealing temperature. When annealing at 1 100 ℃, BaAl0.5Fe11.5O19 of high coercivity Hc （6584 Oe） was produced. Meanwhile, M （10 kOe） and Mr were 42.83 emu/g and 25.65 emu/g, respectively.

Preparation and characterization of composite microspheres of nano zinc ferrite/poly(D,L-lactide-co-alanine)

Magnetic nano zinc ferrite fliuds were synthesized using an improved liquid phase chemical method, which would be used to replace tradditional iron oxides magnetic material. A novel copolymer （PLAA） with D, L-lactide （D, L-LA） and alanine was synthesized using stannous octoate as initiator. Magnetic polymer microspheres were fabricated with nano zinc ferrite fluid coated with alanine modified poly lactide. These as-prepared zinc ferrite fluids, modified poly lactide and magnetic composites, were characterized with X-ray diffraction diffractometer, FT-IR spectrometer, nuclear magnetic resonance spectrometer, scanning electron microscope, transmission electron microscope, vibrating sample magnetometer, and thermogravimetric analyzer. The results demonstrate that the as-prepared zinc ferrite is spinel type of ZnFe2O4 nano crystals with particle size of 20-45 nm and magnetization of 32×10^-3 A.m2. Alanine is copolymerized with lactide, and the prepared composite magnetic microsphere is coated with the modified polylactide, with mass fraction of 45.5% of PLA, particle size ranging from 80-300 nm, and magnetization of 10.6×10^-3 A·m^2, which suggests ZnFe2O4 enjoys a stable magnetization after being coated by polymer.

Magnetic properties of samarium and gadolinium co-doping Mn-Zn ferrites obtained by sol-gel auto-combustion method

Mn-Zn ferrites doped with different contents of Sm^（3＋） and Gd^（3＋） ions were prepared by sol-gel auto-combustion method and characterized by Fourier transform infrared spectroscopy（FTIR）, thermogravimetric analysis（TG）, X-ray diffraction（XRD）, scanning electron microscopy（SEM） and vibrating sample magnetometer（VSM）. When samples were calcined in a relatively low temperature below 1100 °C, secondary phases（α-Fe_2O_3） could be identified. Therefore, in order to acquire pure and better crystallinity, the suitable calcining temperature of powders was selected at 1200 °C. It was also found that all the samples consisting of ferrite phases of typical spinel cubic structure and average crystallite sizes between 31.5 and 38.2 nm were obtained after calcining at 1200 oC for 4 h. The lattice parameters increased almost linearly with increasing Sm content. A dense microstructure was obtained after sintering at 1250 °C for 4 h. Through the analysis of magnetic properties, hysteresis loops for all the samples were narrow with low values of coercivity and retentivity, indicating the paramagnetic nature of these samples. And saturation magnetization Ms strongly depended on the type of additive to reach a maximum of 47.99 emu/g for x=0.015, which showed a great promise for hyperthermia applications.

Enhanced saturation magnetization in La^(3+) doped NiCo ferrites prepared by sol-gel auto-combustion method

Lanthanum doped nickel-cobalt nano ferrites with chemical formula Ni_(0.5)Co_(0.5)LaxFe_(2-x)O_(4)(x=0.05,0,10,0.15 and 0,20) were prepared using a simple sol-gel auto combustion method.The basic structural properties were determined by X-ray diffraction method and the formation of single phased spinel ferrite was confirmed.The crystalline size decreased from 25 to 11 nm and lattice parameter a increases with increase of La doping.The surface morphology of these ferrites was observed by field-emission scanning electron microscopy(FESEM) and agglomerated irregular grains are observed with increase of the rare earth element La doping.Energy-dispersive X-ray spectroscopy(EDX) result confirms the presence of the required elements.The Fourier transform infrared spectroscopy(FTIR) spectrum indicates the formation of the spinel ferrite structure with M-O bonds.Optical direct band measurements from ultraviolet-visible spectroscopy(UV-Vis) spectroscopy indicate that the direct band gap decreases from 1.39 to 1.19 eV for x=0.05 to x=0.15,then increases to 1.28 eV for x=0.20.The room temperature magnetic properties of these ferrites were studied by a vibrating sample magnetometer(VSM).The enhanced saturation magnetization of 49.73 emu/g is observed for x=0.10 and then saturation magnetizations are gradually decreased for x=0.15 and x=0.20.Interestingly the remanent magnetization and coercivity also follow the same trend.

Tunable zeroth-order resonator based on a ferrite metamaterial structure

This paper proposes a tunable zeroth-order resonator on a composite right/left-handed transmission line consisting of a transversely magnetized ferrite substrate periodically loaded by microstrip inductors. Based on the propagation theory of edge guided modes, the analysis procedure of this structure is introduced. The numerical results demonstrate the tunability of the resonant frequency by changing the DC bias magnetic field applied to the ferrite. In contrast to previous work, the proposed structure is easy to design and fabricate and does not require a chip component.

Effects of Cu and Co Substitution on the Properties of NiZn Ferrite Thin Films

Cu- and Co-substituted NiZn ferrite thin films, Ni0.4-xZn0.6CuxFe2O4 and Ni0.5Zn0.5CoxFe2-xO4 （0≤x≤0.2）, are synthesized by sol-gel process. The crystallographic and magnetic properties of Cu- and Co-substituted NiZn ferrite thin films have been investigated. The lattice parameter decreases with Cu substitution and increases with Co substitution. The saturation magnetization decreases and the coereivity increases with the increase of Cu substitution. Moreover, the saturation magnetization gradually increases with the increase of Co substitution when x≤0.10, but decreases when x〉0.10. Meanwhile, the coereivity initially decreases with the increase of Co substitution when x≤0.10, but increases when x〉0.10.

Microstructure and Microwave Absorption Properties of Y-Substituted Ni-Zn Ferrites

The Yttrium ions substituted Ni-Zn ferrites powders were prepared using a sol-gel technique. The crystal structure, magnetic properties and microwave absorption properties of the Ni-Zn ferrites powders were studied by X-ray diffraction, vibrating sample magnetometer and vector network analyzer. The results show that the microwave absorption properties of the Ni-Zn ferrites can be improved effectively with the substitution of Y ions. The minimum reflection loss of the Yttrium ions substituted Ni-Zn powder reaches –34.8 dB, with the –20 dB bandwidth over 2 GHz. The Yttrium substitution can improve microwave absorption properties of Ni-Zn ferrite due to smaller grain dimension and the higher specific

Magnetic Properties and Microstructure of La-substituted Ba-ferrite Composites

A Self-Propagating Combustion Synthesis (SPCS) method, citrate SPCS method, was used to synthesize crystalline powders of La-substituted barium hexaferrit, according to the formula Ba1-xLaxFe11.5Cr0.5O19(x=0～0.25). The structures, morphologies and ferromagnetic properties of La3+ substituted composites were characterized by powder X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM) and Vibrating Sample Magnetometer (VSM). XRD results showed that it was possible to obtain single-phase barium ferrite powders at 1100 ℃ and La content x<0.2. From the SEM, it was observed that the particles calcined at 1100 ℃ had a plate-like hexagonal shape. The results of magnetic mensuration revealed that the magnetic properties of La-substituted samples were obviously affected by La content .With the increasing of the La content, the saturation magnetization of Ba1-xLaxFe11.5Cr0.5O19 (x=0～0.25) increased from 50.1 to 56.2 emu·g-1, and coercivity increased from 1411.1 Oe to 1544.6 Oe.

Structural,magnetic,and acidic properties of cobalt ferrite nanoparticles synthesised by wet chemical methods

A detailed investigation on the effect of preparation method on the structural,magnetic,and acidic properties of cobalt ferrite nanoparticles prepared by sol-gel and co-precipitation is presented.Citric acid and ethylene glycol were used as gelling agents,while sodium hydroxide and aqueous ammonia were used as precipitating agents.The resulting ferrites were calcined at 450℃ and 750℃.Sharper X-ray diffraction(XRD)peaks were observed for the samples calcined at 750℃,indicating greater crystallinity of the samples calcined at higher temperature.Average crystallite sizes fell in the ranges of 7.1-21.1 nm and 30.4-42.1 nm for the samples calcined at 450℃ and 750℃,respectively.The infrared spectra revealed two main absorption bands,the high frequency bandν1 around 600 cm^(-1) and the low frequency bandν2 around 400 cm^(-1) arising from stretching vibrations of the oxygen bond with the metal in the tetrahedral(A)and octahedral(B)sites in the spinel lattice.Agglomeration of particles was observed in the scanning electron microscopy(SEM)images.Magnetic parameters of CoFe_(2)O_(4) nanoparticles greatly depended on calcination temperature and preparation techniques.Ammonia temperature programmed desorption(TPD)measurements indicated that weak acid sites predominate medium strength sites,while the number of strong acid sites is the least.Cumulative acidity decreased for the samples calcined at higher temperature.The results underline the effect of preparation conditions on the morphology,crystallite size,and magnetic properties of nano ferrites.

Preparation and characterization of CoFe_2O_4/TiO_2 magnetic composite films

CoFe2O4/TiO2 magnetic composite films were prepared using the sol-gel method with tetrabutyltitanate and metallic chlorates as starting materials. The effects of heat treatment temperatures on micro- structures and on magnetic properties were studied. The microstructure and properties of the samples at different heat treatment temperatures were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, polarized microscopy and vibrating sample magnetometry. The results show that crystals of different substances grow up independently. Cobalt ferrite is evenly embedded into the titanium dioxide matrix in the prepared composite films. The magnetism of the composite films is enhanced with an increase of the heat temperature.

Selective microwave absorption in Nd3+ substituted barium ferrite composites

Microwave(MW)frequency based wireless communications and electronic devices became prospective due to several ramifications.To meet this need,a series of neodymium ions(Nd3+)substituted barium ferrite composites with composition(20)BaO:(80-x)Fe2 O3:(x)Nd2 O3(0≤x≤3 mol%)was prepared at1100℃using solid-state reaction method.We evaluated the effect of various Nd3+ions contents on the surface morphology,structure,and magnetic properties of the as-synthesized barium ferrite composites.Meanwhile,microwave reflection loss,complex permittivity and permeability were determined using the transmission/reflection line method in the X-band(8-12 GHz).SEM image of the composites shows that the surface morphology consists of rough and porous microstructures.XRD patterns of the un-doped composites reveal the existence of BaFe12O19(hexagonal)and Fe21.333O32(tetragonal)crystalline phases.Furthermore,a new hexagonal crystalline phase of Ba6 Nd2 Fe4 O15 with the crystallite sizes between 15 and 67 nm is observed due to Nd3+ions substitution in the composite.The saturation magnetization of the composite containing 2 mol%of Nd3+does not exhibit any significant alteration compared to the one devoid of Nd3+.The complex relative permitivity and permeability of the achieved composites enriched in Ba6 Nd2 Fe4 O15 and BaFe2 O4 phases disclose significant MW frequency dependence.The composites also display selective MW absorption in the X-band which could be useful for diverse applications.

Effect of Substitution of Al for Fe on Magnetic Properties and Particle Size of Ni-Co Nanoferrite

Nanocrystalline Al doped nickel-cobalt ferrite [Ni0.6Co0.4Fe2-xAlxO4 (x = 0.0, 0.1, 0.3, 0.5 and 0.7)] powders have been synthesized by sol-gel auto-ignition method and the effect of non-magnetic aluminum content on the nanosize particles and magnetic properties has been studied. The X-ray diffraction (XRD) revealed that the powders obtained are single phase with inverse spinel structure. The calculated grain size from XRD data have been verified using transmission electron microscopy (TEM). TEM photograph shows that the powders consist of nano meter sized grain. The size of nanoparticles decreases as the non magnetic Al content increases. Magnetic hysteresis loops were measured at room temperature with maximum applied magnetic field of 20 KOe. As aluminum content increases, the measured magnetic hysteresis curves became narrow and saturation magnetization (Ms), and coercive force (Hc) decreased. The reduction of magnetization with the increase of aluminum content is caused by non-magnetic Al3+ ions and weakened interaction between sub-lattices.

Effect of Annealing Temperature on the Structural and Magnetic Properties of NiFe₂O₄Nanoferrites

Nanocrystalline NiFe2O4 spinel ferrites were synthesized by sol-gel method. The structural and magnetic properties were investigated using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometer (VSM). Annealing temperature showed prominent effect on the grain size. The average grain size of NiFe2O4 was observed to increase from 31 nm to 54 nm as the annealing increased from 500℃ to 1000℃. The IR spectra showed the absorption bands corresponding to stretching of tetrahedral and octahedral bands. The magnetic properties were observed to depend strongly on the annealing temperature.

Preparation and Characterization of Nanocomposite MgFe_2O_4/SiO_2

Nanocomposites MgFe2O4/SiO2 were successfully synthesized by the sol-gel method in the presence of N, N-dimethylformamide （DMF）. The formation of pure MgFe2O4 was confirmed by powder X-ray diffraction （XRD） and electron diffraction. The structural evolution of MgFe2O4 nanocrystals was followed by powder X-ray diffraction and IR absorption spectroscopy. The formation of spinel structure of MgFe2O4 started at 800 ℃, and completed at 900 ℃, The transmission electron microscopy （TEM） measurements suggest that the particle sizes increase with the increasing annealing temperature, and the mean particle sizes of the spherical samples annealed at 800 ℃, 900 ℃ and 1 050 ℃ are ca. 3 nm, 8 nm and 11 nm, respectively. Magnetization measurements at room temperature and 78 K indicate supemaramagnetic nature of these MgFe2O4 nanocrvstals.

Effect of Gd3+-,Pr3+-or Sm3+-substituted cobalt-zinc ferrite on photodegradation of methyl orange and cytotoxicity tests

Gd3+-,Pr3+-or Sm3+-doped Co-Zn(Co0.5Zn0.5Fe2 O4)magnetic ferrites(i.e.,Co0.5Zn0.5Gd0.1Fe1.9O4,Co0.5Zn0.5Pr0.1Fe1.9O4 and Co0.5Zn0.5Sm0.1Fe1.9O4)were prepared using a facile sol-gel approach,and the structure,surface morphology and chemical composition of the products were studied by means of scanning electron microscopy(SEM),energy dispersive X-ray analysis(EDX),X-ray diffraction(XRD),UVvisible diffuse reflectance spectroscopy(DRS),photoluminescence(PL)spectroscopy,Fourier transform infrared spectroscopy(FT-IR)and vibrating sample magnetometer(VSM)spectroscopy.XRD patterns show the Co-Zn product is composed of cubic spinel phases with few impurities or secondary phases,and the average crystallite sizes of the samples are determined to be approximately^51—80,~99—181,~68—103 and^83—133 nm.Also the coercivity and remnant and saturation magnetizations,evaluated by vibrating sample magnetometer(VSM),are found to increase linearly with the incorporation of Gd3+,Pr3+and Sm3+in the product formulation.The CO1-xZnxFe2-yRyO4 photocatalyst sample is found to display a red shift in its absorption,and exhibits outstanding photocatalytic effects in the degradation of MO under ultraviolet(UV)light.This is attributed to the reduction of the band gap of cobalt-zinc ferrite due to the presence of rare earth ions.Further in vitro evaluations of the cytotoxic effects of the synthesized nanoparticles were performed on a HeLa cell line.

Sol-gel法制备纳米晶镍锌钴铁氧体／-氧化硅复合颗粒的研究

开发了用溶胶-凝胶法制备纳米晶镍锌钴复合铁氧体颗粒的技术，并对溶胶．凝胶工艺的影响因素进行了研究探讨。用扫描电镜（SEM）、电子探针（EPMA）和X射线衍射（XRD）对样品进行了表征，得到球状分布的纳米晶镍锌钴铁氧体／二氧化硅复合颗粒，并优化了制备工艺。

Fabrication and Magnetic Property of One-dimensional SrTiO_3/SrFe_(12)O_(19) Composite Nanofibers by Electrospinning

The composite nanofibers of SrTiO3/SrFel2O19 with a molar ratio of 1：1 and diameter about 120 nm were prepared by electrospinning. Effects of calcination temperature on the formation, crystallite size, morphology and magnetic property were studied by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. The binary phase of strontium ferrite and titanate was formed after being calcined at 900℃ for 2 h and the composite nanofibers were fabricated from nanograins of SrTiO3 about 24 nm and SrFel2O19 around 33 nm. The crystallite sizes for the nanofibers increase with increasing calcination temperature and the addition of SrTiO3 has an obvious suppression effect on SrFel2O19 grain growth. The specific saturation magnetization and remanence tend to increase with the crystallite size. With increasing calcination temperature from 900 to 1050℃, the coercivity increases initially, achieving a maximum value of 520.2 kA.m^-1 at 950℃, and then shows a reduction tendency.