Rare earth-doped mixed Ni-Cu-Zn ferrites as an effective photocatalytic agent for active degradation of Rhodamine B dye

In this study, a series of Gd^(3+)-doped mixed Ni-Cu-Zn ferrites with composition of Zn_(0.5)Ni_(0.3)Cu_(0.2)Fe_(2-x)Gd_(x)O_(4)(x = 0, 0.025, 0.05, 0.075, 0.1) was prepared using self-ignition sol-gel method. The prepared nanoparticles with an average size ranging from 22 to 26 nm show a single-phase cubic structure belonging to the spinel matrix. A rise in the Gd^(3+)concentration leads to an increase in crystallite size and lattice parameter. In Fourier transform infrared spectra, two main absorption bands belonging to the spinel structure are observed. The high-frequency bands(v_(1)) represent the tetrahedral complex, while the lowfrequency bands(v_(2)) signify the octahedral complex. The optical bandgap of the nanoferrites is found within the range of 2.91 to 2.41 eV, depending on their size. The magnetic characteristics of the material,such as saturation magnetization and coercivity are significantly altered with the concentration of Gd^(3+)in the solution. Using Rhodamine B(RhB) as a model organic pollutant, an in-depth investigation of the photocatalytic activity of the compounds was carried out. The present outcomes show that adding an adequate amount of Gd^(3+)significantly enhances the number of hydroxyl radicals produced by the ferrite,in turn, increasing the photocatalytic activity of the material. Mechanism elucidated by scavenger studies reveals that ·OH and holes are the primary reactive radicals responsible for the degradation process.Prepared photocatalysts show an insignificant performance loss in five consecutive cycles. Thus, it is concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater.

Study on Magnetic Responsibility of Rare Earth Ferrite/Polyacrylamide Magnetic Microsphere

In inverse microemulsion, rare earth ferrite/polyacrylamide magnetic microsphere were prepared and their magnetic responsibility were studied by magnetic balance. Results indicate that the magnetic responsibility of microsphere relates to magnetic moment of rare earth ion, and it can be improved by the addition of dysprosium ion of high magnetic moment. Dysprosium content has an effect on magnetic responsibility of dysprosium ferrite/polyacrylamide magnetic microsphere. The microsphere displays strong magnetic responsibility when the molar ratio of Dy3+/iron is 0.20.

ⅢA-ⅡB multicomponent perovskite rare earth ferrites with promising electromagnetic wave absorption properties

Perovskite-type rare-earth ferrites(REFeO_(3))are promising materials for absorbing electromagnetic(EM)wave pollution.However,insufficient dielectric loss and poor impedance matching are key factors that limit the broader implementation of REFeO_(3).Herein,a series of multicomponent perovskite-type ferrites with strong EM wave absorption capabilities was prepared.Through the synergistic effect of chemical constitution regulation and entropy regulation,optimization of the dielectric loss and impedance matching is achieved by strengthening the structural defect mechanism,thus further adjusting the EM wave absorption performance.Compared with(LaGdSmNdBa)FeO_(3)(HE-1)and(LaGdPrSmNdBa)FeO_(3)(HE-2),(LaGdBa)FeO_(3)(ME-1)and(LaGdSmBa)FeO_(3)(ME-2)exhibit favorable performance,with optimal minimum reflection loss(RL_(min))of-56.35 dB(at 11.12 GHz)and-63.25 dB(at 7.22 GHz)and effective absorption bandwidth(EAB)of 4.46 and 4.72 GHz,respectively.This multicomponent design provides a new strategy for the development of EM wave absorption materials.

Structural Analysis and Magnetic Properties of Gd-Doped Li-Ni Ferrites Prepared Using Rheological Phase Reaction Method

A series of Gd-doped Li-Ni ferrites with the formula of LiNi0.5GdxFe2-xO4 where x = 0.00 - 0.08 in steps of 0.02, were prepared by thermolysis of oxalate precursors obtained by rheological phase reaction. The structure, morphology, and the magnetic properties of the samples were characterized by powder X-ray diffraction （XRD）, atomic force microscopy （AFM） and a vibrating sample magnetometer （VSM）. A single spinel phase was obtained in the range of x = 0.00 - 0.04. The lattice parameters of the Gd-doped samples were larger than that of pure Li-Ni ferrite, and increased in the range of 0.00 ≤ x ≤ 0.04, then decreased up to x = 0.08, because of the formation of the secondary phase （Gd- FeO3）. All samples were spheric particles with an average size of about 100 nm, but agglomerated to some extent. The hysteresis loops indicated that the saturation magnetization decreased gradually with increasing Gd content, while the variation of coercivity was related to the microstructure of the Gd-doped samples.

Magnetic properties of La-Zn substituted Sr-hexaferrites by self-propagation high-temperature synthesis

The La-Zn substituted SrM-type ferrites with the composition of Sr1-xLaxFe12-xZnxO19 （x=0-0.4） were prepared by self-propagating high-temperature synthesis （SHS）. The single SrM phase was detected by XRD in the as-received samples by controlling the Fe contents in the reagents. The substitution of La^3＋and Zn^2＋ obviously increased the magnetic properties of the as-prepared samples. The maximum improvements of Br, Hcb and （BH）m were 14.4%, 15.3% and 30.7%, respectively compared with that of the samples without La-Zn substitution. Microstructure observation by SEM showed that the SHS method benefited forming the better particle features and achieving the higher Hcj in comparison with the traditional firing method.

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.

Synthesis and Characterization of Gadolinium Doping M-type Hexagonal Barium Ferrite Ultrafine Powders

The hexagonal BaGd x Fe 12- x O 19 ( x =0.1～1.0) nano sized powders with M type structure were synthesized by the sol gel auto combustion high temperature synthesis method. The effects of pH of the solution, the molar ratio of nitrate/citric acid and the calcination temperature on the synthesis of the ferrites were investigated. The crystal structure, grain size, shape and magnetic properties were studied by means of XRD, TEM and vibrating sample magnetometer.The results show that under the conditions of pH 7.0 or so, mole ratio of citrate/nitrate (1～3) and calcination temperature of 850 ℃ for 1 h, M type BaGd x Fe 12- x O 19 ultrafine powders with a particle size of less than 100 nm can be obtained, and the coercive force reaches 430 kA·m -1 at x =1.0, which is far greater than that of barium ferrite (BaFe 12 O 19 ).

Influences of La^(3+) Substitution on Structure and Electromagnetic Properties of Nanocrystalline Nickel Ferrites

Nanocrystalline nickel ferrites with substitution of Fe3+ by rare-earth La3+, according to the formula NiLaxFe2-xO4 (with x=0, 0.05, 0.1 and 0.15), were prepared by polyacrylamide gel method. Influences of the amount of La3+ substitution on the structure and electromagnetic properties of NiLaxFe2-xO4 compounds were systematically investigated by DSC-TG, XRD, TEM and wave-guide method. XRD results indicated that the pure spinel-type crystal structure of the NiLaxFe2-xO4 (x=0 and 0.05) was obtained at 500 ℃. TEM results showed that the average particle sizes of NiFe2O4 and NiLa0.1Fe1.9O4 particles were about 10 and 15 nm, respectively. The complex permittivity and complex permeability was measured in the frequency range of 8.2～12.4 GHz. The results revealed that the nanocrystalline NiLaxFe2-xO4 had both dielectric loss and magnetic loss in the frequency range of 8.2～12.4 GHz. The tgδε and tgδm of NiLaxFe2-xO4 (with x=0 and 0.05) decreased with the increase of La3+ ions content, and some strong resonance peaks of the tgδε and tgδm of NiLaxFe2-xO4 (with x=0.1 and 0.15) appeared because of the secondary phases (LaFeO3) and more lattice defects.

Structural and Magnetic Properties of La-Doped Li-Ni Ferrite

A series of polycrystalline La-doped Li-Ni ferrites LiNi_ 0.5La_xFe_ 2-xO_4 (where x=0.0～0.08 in steps of 0.02) were prepared by thermolysising of oxalate precursors which were obtained by rheological phase reaction. Results were observed by powder X-ray diffractometer (XRD) on samples indicate that all doped ferrites have the major spinel phase, and the single spinel phase is obtained in La content x≤0.04. The lattice parameter increases in the range of x=0～0.04, then decreases up to x=0.08. The hysteresis loops show that the value of saturation magnetization is less than that of the pure Li-Ni ferrite except for x=0.04, while the coercivity increases with the La content.

Synthesis and characterization of La doped M-type hexagonal barium ferrite fine powders

The hexagonal BaLa x Fe 12- x O 19 fine powders with M type structure were synthesized by sol gel method. The pH of the solution, the molar ratio of nitrate to citric acid and the calcination temperature were investigated to clarify the forming conditions of the ferrites. The crystal structure, grain size, form and magnetic properties were studied by means of XRD, SEM and vibrating sample magnetometer. It is concluded that at pH of 7.0 or so, molar ratio of nitrate to citric acid of 1/3 and calcination temperature of 850 ℃(1 h), 1 000 ℃, M type BaLa x Fe 12- x O 19 fine powders with a particle size of less than 300 nm was obtained. [

Synthesis and characterization of Nd doped M-type hexagonal barium ferrite ultrafine powders

The hexagonal BaNd x Fe12?x O19(x=0.1?1.0) fine powders with M-type structure were synthesized by sol-gel auto-combustion high-temperature synthesis method. The structure of powders, gels’ combustion and magnetic properties of powders were respectively studied by means of X-ray diffractometer (XRD), differential thermal analysis-thermogravimetric analysis (DTA-TG) and vibrating sample magnetometer (VSM). The powders before and after combustion and calcination at 450–850 °C with different mole ratio of Nd to Ba (0.1–1.0) were compared in terms of XRD. In addition, the effects of different synthesis conditions on magnetic properties of powders were also discussed. The results show that at pH 7.0 or so, mole ratio of citrate to nitrate (1–3) and calcination temperature of 850 °C for 1 h, M-type BaNd x Fe12?x O19(x=0.1?1.0) fine powders can be obtained, and the coercive force reaches 436880 A·m?1 at x=1, which is far greater than that of barium permanent ferrite (BaFe12O19).

Preparation and Characterization of La Doped Ferrite Using Marine Manganese Nodules as Raw Materials

A kind of La doped ferrite was prepared with marine manganese nodules derived from East Pacific sea-bottom as raw material, NaOH as fluxing reagent, La(NO3)3 as doping agent, by calcination at 1000 ℃ for 5 h. XRD analysis showed that the ferrite products were of a spinel structure, and that its molecular formula could be expressed as MnFe2-xRxO4. SEM images proved that these ferrites showed octahedral and cubic aspects. It was found that there is some relationship between the La doping amount and the magnetic property of the ferrite. When the La doping amount was 0.03, the susceptibility of the ferrite was maximal. The as-prepared La doped ferrite is a kind of soft magnetic material that is easy to be magnetized with rather weak coercive force.

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.

稀土Ce对高强工程机械用钢夹杂物和高温塑性的影响

通过向高强工程机械用钢中加入稀土合金,研究了Ce对夹杂物和高温塑性的影响。通过扫描电镜、能谱分析、夹杂物自动分析系统和热力学计算对夹杂物的类型、数量和尺寸进行分析。利用Gleeble1500热模拟机测定了实验钢的高温塑性,并使用光学金相显微镜和扫描电镜观察断口形貌及组织。结果表明,加入Ce后,钢中夹杂物由不规则的Al_(2)O_(3)、MnS和Al_(2)O_(3)+MnS复合夹杂物转变为球状或椭球状的Ce_(2)O_(2)S和CeS,数量增多,尺寸减小了37.64%。650~1050℃范围内含Ce钢的断面收缩率均高于无Ce钢,具有更好的高温塑性。这是由于Ce处理生成的小球状稀土夹杂物减轻了应力集中,与基体能够协调变形,同时它们能够诱导晶内铁素体形核,最终高温塑性得到改善。

Enhancement of coercivity,permeability,and dielectric properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ferrites for memory and high frequency devices

Spinel cubic ferrites have huge applications in me mory and high frequency devices.For the improvement of these modern devices,the magnetic coercivity,permeability,and dielectric properties of a ferrite are the important issues.This article focuses on improving the magnetic coercivity,magnetic permeability,and dielectric properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ferrites,where x=0.00,0.06,and 0.10.The X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),field emission scanning electron microscopy(FESEM),energy dispersive X-ray(EDX),vibrating sample magnetometer(VSM),and an impedance analyzer were used to characterize the structural,magnetic,and dielectric properties of the samples.The XRD patterns indicate the formation of spinel cubic structure of the samples with a secondary peak(EuFeO_(3))for Eu doped samples.The densities and porosities of the samples follow an inverse trend,where the doped samples’lattice parameters are increased with the increment of rare earth Eu concentration.The FTIR analysis also proves the spinel cubic phase of the samples.The average grain size of the ferrites is obtained via FESEM images,and it is increased from 121 to 198 nm.VSM analysis confirms that doping of the Eu content also changes other hysteresis loop properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ferrites.Particularly,the coercivity of the Eu doped samples is greater than that of the mother alloy(x=0.00).The EDX study shows that there is no impurity contamination in the ferrites.The permeability and dielectric measurements show an improved quality factor of the Eu-doped samples with low magnetic and dielectric losses.Frequency dependent resistivity and impedance analysis also show the improved nature.From the observed properties of the samples,all the investigated ferrites might be strong candidates for potential applications in memory devices,magnetic sensors,and high frequency applications.

S44535铁素体不锈钢高温氧化行为

为了探究稀土La对S44535铁素体不锈钢高温氧化行为的影响,采用加速氧化对添加0.26%La的S44535钢在800、900、1000℃下的静态空气中进行高温氧化研究。采用恒温氧化法对比S44535铁素体不锈钢在三种温度下的氧化动力学曲线,用扫描电镜(SEM)、能谱分析仪(EDS)和X射线衍射(XRD)对钢的氧化层进行表征分析,探究了稀土La对铁素体不锈钢高温抗氧化性能的影响。结果表明,氧化产物主要为Cr2O3和MnCr2O4,随着温度的升高,表面氧化膜增厚且更加致密,其外层富含Mn,内层富含Cr,说明稀土改变了氧化膜的生长方式,且呈现出较为优异的高温抗氧化性能。

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.

Correlation between structural phase transition and physical properties of Co^(2+)/Gd^(3+)co-substituted copper ferrite

The doping of the spinel ferrites with selective cations usually improves the properties of the parent ferrite.The effect of Co^(2+)/Gd^(3+)co-substitution on the microstructure,optical,and magnetic properties of Cu1-xCoxFe2-xGdxO4 prepared by the citrate-nitrate auto-combustion synthesis was investigated.Characterization of the samples was performed with powder X-ray diffraction(XRD),Raman and Fouriertransform infrared(FTIR)spectroscopy,field-emission scanning electron microscopy,X-ray energydispersive spectroscopy,UV-Vis spectroscopy,and a vibrating sample magnetometer.The results of XRD,Raman,and FTIR analysis show a gradual structural phase transition from a tetragonal(I41/amd)structure to a cubic(Fd3m)structure.The bandgap energy of the studied samples is in a range of 1.57-1.75 eV with a minimum in sample x=0.06 and then increases.Magnetic investigations show that the presence of Co^(2+)/Gd^(3+)cations in an octahedral site of the copper ferrite structure could increase saturation magnetization and coercive field from 567.9 Oe and 23.62 emu/g to 929.4 Oe and 28.27 emu/g,respectively.

耐海洋腐蚀的双层稀土掺杂铁氧体/聚氨酯吸波复合材料

目的开发一种防腐性和吸波性能均良好的新型复合材料。方法制备了一种新型的双层吸波复合材料,其中匹配层使用30%(质量分数)稀土铁氧体粉的Ce-铁氧体/TPU复合材料,吸收层则使用70%(质量分数)稀土铁氧体粉的Ce-铁氧体/TPU复合材料。在制备过程中,首先将稀土铁氧体粉和TPU树脂按照一定的比例混合,并通过机械搅拌使其均匀分散。然后,将混合物填充在模具中,并进行高温热压处理,以实现复合材料的固化和成型。结果通过数值计算,发现双层吸收体的微波吸收性能比其组分有很大的提高。与此同时,在总厚度保持不变的条件下,充分利用30%~70%的层厚度比例进行调节以改善有效吸收带宽的情况,并基于RL(反射损耗)优化了厚度3.5 mm/1.5 mm的30%~70%双分子层。当频率为15.76 GHz时,最大RL峰为-26.4 dB,有效吸收带宽达12.32 GHz(5.68~18 GHz)。通过适当的阻抗匹配和多种损耗形式,可以显著提高30%~70%双层吸收体的微波吸收性能。结论将30%(质量分数)稀土铁氧体粉的Ce-铁氧体/TPU复合材料和70%(质量分数)稀土铁氧体粉的Ce-铁氧体/TPU复合材料组合形成双层后,其电磁性能明显上升,达到了良好的阻抗匹配。其中30%(质量分数)稀土铁氧体粉的Ce-铁氧体/TPU复合材料的耐腐蚀性能略高于70%(质量分数)稀土铁氧体粉的Ce-铁氧体/TPU复合材料的,将二者组合后,其防腐性能也有所提升,由此制得的双层材料的耐腐蚀性和吸波性能均得到了提升。

Tuning structural,electrical,dielectric and magnetic properties of Mg-Cu-Co ferrites via dysprosium(Dy^(3+))doping

In current research work,Dy3+substituted Mg0.5Cu0.25Co0.25Fe2-xDyxO4(0.0≤x≤0.04 with the step interval of 0.01)soft ferrites were synthesized by the sol-gel auto combustion method.The prepared samples were characterized by the techniques using X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared(FTIR)spectroscopy,curre nt-voltage(Ⅰ-Ⅴ)measurement,LCR meter,vibrating sample magnetometer(VSM)and Raman.XRD data reveal that the average crystallite size is 49.71 nm and the lattice constant is 0.83703 nm for sample x=0.03.The non-uniform grain growth was demonstrated by micrographs and impurity-free elemental composition was observed from EDX analysis.The DC resistivity has an increasing and decreasing trend in ferromagnetic and paramagnetic regions with an increase in temperature.Moreover,the high resistivity is observed with the order of 1010Ω·cm,and the activation energy is 0.944 eV for samples x=0.03.The dielectric parameters including dielectric constant,dielectric losses,and impedance gradually decrease with the increase in frequency from 8 Hz to 8 MHz.The minimum dielectric loss at high frequency is found for sample x=0.03.The coercivity(Hc)and saturation magnetization(Ms)are found in the ranges of 520.82-544.02 Oe and 20.5841-21.1473 emu/g,respectively.These observations confirm that dysprosium(x=0.03)doped MCC-soft ferrites may be applicable in transformer cores,microwave absorbance,and telecommunication devices.