Study of the Dielectric Behaviour of Cr-Doped Zinc Nano Ferrites Synthesized by Sol-Gel Method

The series of Cr-Zn nano ferrites having the general composition CrxZnFe2-xO4 (0 ≤ x ≤ 0.5) have been synthesized successfully in the nanocrystalline form using the sol-gel method. The samples were sintered at 900°C for 3 hours. The effect of chromium substitution on dielectric properties of Zn-ferrites is reported in this paper. The analysis of XRD patterns revealed the formation of single phase cubic spinel structure for all the Cr-Zn ferrite samples. The FTIR spectra show two strong absorption bands in the range of 400 - 600 cm-1, which corroborate the spinel structure of the samples. The average grain size was found to be in the nanometer range and of the order of 43 - 63 nm obtained using TEM images. The lattice parameter and crystallite size decrease with increase in Cr concentration (x). The investigation on dielectric constant (ε'), dissipation factor (D) and ac conductivity (σac) was carried out at a fixed frequency 1 kHz and in the frequency range of 100 Hz to 1 MHz at room temperature using LCR meter. The plots of dielectric constant (ε') versus frequency show the normal dielectric behavior of spinel ferrites. The value of ac conductivity (σac) increases with increase in frequency for all the compositions. The appearance of the peak for each composition in the dissipation factor versus frequency curve suggests the presence of relaxing dipoles in the Cr-Zn nano ferrite samples. It is also found that the shifting of the relaxation peak towards lower frequency side with an increase in chromium content (x) is due to the strengthening of dipole-dipole interactions. The composition and frequency dependence of the dielectric constant, dielectric loss and ac-conductivity are explained based on the Koop’s two-layer model, Maxwell-Wagner polarization process, and Debye relaxation theory.

Effect of Bi3+ Ion Substitution on Magnetic Properties of Cobalt Nano Ferrites Prepared by Sol-Gel Combustion Method

Bismuth substituted cobalt nano ferrites with the chemical composition Co Bix Fe2-x O4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method. The phase identification of prepared samples is characterised by X-ray powder diffraction (XRD) method, which confirms the formation of a single phase fcc spinal structure. The mean crystallite sizes of all prepared samples were obtained within the range of 21 (±5) nm. Transmission Electron Microscopy (TEM) images also confirmed the crystallite size of all the synthesised samples was in nano range. With the effect of Bi3+ ion substitution on spinal cobalt ferrite, the magnetic properties were investigated by using Vibration Sample Magnetometer (VSM). The obtained hysteresis (M-H) curves of all the samples were analysed under the applied magnetic field of range ± 10 K Oe at 300 K. The magnetic properties such as saturation magnetisation (Ms), remnant magnetization (Mr) and coercivity (Hc) values are tabulated, which show a decrease in trend as the bismuth ion concentration increases. This is due to the addition of Bi3+ ion in the place of Fe3+ ion (octahedral site) and hence the Bi3+-Fe3+ ion interaction predominates as compared with the Fe2+-Fe3+ ion interaction. The data obtained from magnetic studies, the variation among the magnetic properties have been investigated for all the prepared samples.

Influence of Cr³⁺Ion on the Dielectric Properties of Nano Crystalline Mg-Ferrites Synthesized by Citrate-Gel Method

Mixed Mg-Cr Nano ferrites having the compositional formula MgCrxFe2-xO4 (where x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) were synthesized using Citrate-Gel auto combustion method. Structural characterization was carried out by XRD Analysis which confirmed the formation of single phase cubic spinel structure without any impurity peak. The dielectric properties such as Dielectric constant (ε'), Dielectric Loss tangent (tan δ) and AC conductivity (σAC) of Mg-Cr nano ferrites were studied at room temperature in the frequency range of 2 Hz - 2 MHz using Agilent E4980A Precision LCR meter. The dielectric constant, loss tangent and AC conductivity shows a normal behavior with frequency. A qulitative explanation is given for composition and frequency dependance of the dielectric constant, dielectric loss tangent and AC conductivity of the nano ferrite. The loss tangent for the synthesized samples was found to be decreased from 0.09 to 0.054 in higher frequency region showing the potential applications of these materials in high frequency micro wave devices. On the basis of these results the explanation of dielectric mechanism in Mg-Cr ferrites is suggested.

Synthesis and Characterization of Copper Substituted Nickel Nano-Ferrites by Citrate-Gel Technique

Mixed Copper substituted Nickel nano-ferrites having the chemical formula Ni1-xCuxFe2O4 (where x = 0, 0.2, 0.4, 0.6, 0.8, 0.9 and 1.0) were synthesized by citrate gel technique. The crystal structure characterization and morphology were investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). An elemental composition of the samples were studied by energy dispersive X-ray Spectroscopy (EDS). Lattice parameter, X-ray density, Volume of the Unit Cell and The values of the hopping length for octahedral (dB) and tetrahedral (dA) sites were calculated. The observed results can be explained on the basis of composition.

Characterization of Chromium Substituted Cobalt Nano Ferrites Synthesized by Citrate-Gel Auto Combustion Method

Co-Cr nano-ferrites, having the chemical formula CoCrxFe2-xO4 (where x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0), were synthesized by the Citrate-gel auto combustion method. Synthesized powders were sintered at 500°C for 4 hours in an air and were characterized by XRD, SEM and EDS. XRD analysis showed cubic spinel structure of the ferrites and the crystallite sizes (D) were found in the range of 6 - 12 nm. The values of lattice parameter (a) decreased and X-ray density (dx) increased with the increase of Cr content. Scanning Electron Microscopic (SEM) studies revealed nano crystalline nature of the samples. An elemental composition of the samples was studied by Energy Dispersive Spectroscopy (EDS). The observed results can be explained on the basis of composition and crystal size.

Nano Copper Ferrite Catalyzed Sonochemical, One-Pot Three and Four Component Synthesis of Poly Substituted Imidazoles

A simple, multi component, one-pot method has been reported for the synthesis of poly substituted imidazoles in presence of magnetically separable and recyclable spinel nano copper ferrite as heterogeneous catalyst by the cyclo-condensation of benzil, aromatic aldehyde, ammonium acetate and substituted amines under ultrasonic irradiation. This method of preparation has many advantages compared to those methods which are previously reported in the literature. This methodology offers simple experimental procedure, milder reaction conditions and environmentally benign approach.

Magnetic Nano Cobalt Ferrite Catalyzed Synthesis of 4H-Pyrano[3,2-h]quinoline Derivatives under Microwave Irradiation

A microwave irradiated magnetically separable nano cobalt ferrite catalyzed green method for the synthesis of 4-phenyl-4H-pyrano[3,2-h]quinolin-2-amine and 2-amino-4-phenyl-4H-pyrano[3,2-h] quinoline-3-carbonitrile derivatives through cyclization of aromatic aldehyde, acetonitrile/malononitrile and 8-hydoxyquinoline is developed and presented in this paper. The cubic magnetic cobalt ferrite nano particles were synthesized by sol-gel citrate precursor method and characterized by FT-IR, XRD, SEM and TEM techniques and the structures of the synthesized pyranoquinoline derivatives were assigned by IR, MASS and 1H NMR techniques. The reaction is carried out in a domestic microwave oven with a heat-resistant microwave safe glass container with a lid.

Nano Nickel-Cobalt Ferrite Catalysed One-Pot Multi-Component Synthesis of Xanthenediones and Acridinediones

1,8-Dioxo-octahydroxanthenes (4a-4f) and 1,8-dioxohexahydroacridines (5a-5c) were synthesized by novel, simple and eco-friendly method with higher yields in the presence of magnetically separable nano nickel-cobalt ferrite catalyst (Ni0.5Co0.5Fe2O4). The former, 1,8-dioxo-octahydroxanthenes have been synthesized from dimedone and different aromatic aldehydes, while the latter from this mixture are along with ammonium acetate. The main advantage of this method is that the nano catalyst can be reused up to five reaction cycles without losing the catalytic activity.

Decolorization of Disperse Dyes Using Immobilized Laccase Enzyme on Nano Zinc Ferrite from Single and Binary Systems

In this paper, immobilized laccase enzyme on nano zinc ferrite was used in order to decolorize disperse dyes from single and binary systems. In this case, disperse dyes such as Disperse red 60 (DR60), Disperse blue 56 (DB56) and Disperse yellow 54 (DY54) were selected as model dyes. Several parameters such as enzyme concentration, pH and dye concentration and their effect on decolorization of dyes from single and binary systems were studied. According to the experimental results, the optimized immobilized laccase enzyme concentration, reaction time and pH for decolorization of DR60, DB56 and DY54 from single and binary systems were 500 mg/L (for DR60 and DY54) and 400 mg/L (for DB56), 20 min and 3, respectively. Moreover, Dye decolorization kinetics followed Michaelis-Menten Model. Finally, the results showed that enzymatic process using immobilized laccase enzyme on nano zinc ferrite was effective method to decolorize disperse dyes from single and binary systems.

Preparation and Characterization of Cu-Zn Nano-Structural Ferrite Thin Films Produced by Pulsed Laser Deposition (PLD)

Cu-Zn ferrite nano thin films were deposited from a target of Cu-Zn ferrite onto a sapphire substrate using XeCl excimer laser operating 308 nm with an energy of 225 mJ and a frequency of 30 Hz. Films were deposited from the target onto sapphire (001) substrates heated to 650℃ in an oxygen atmosphere of 100 mTorr. The laser beam was incident On the target face at an angle of 45°. Studies on crystal structure were done by X-ray diffactometry (XRD). The surface texture, cross-section morphology and grain size was observed by JEOL-JSM-6400 scanning electron microscopy, atomic force microscopy (AFM) and magnetic force microscopy (MFM) [Model DI 3000, Digital instruments].

Effect of Annealing Temperature on Prepared Nanoparticles Li-Ferrite Using Positron Annihilation Lifetime Technique

Lithium ferrite nanoparticles were synthesized by a sol-gel auto-combustion method. For prepared samples, the nanograins were increased with increasing the annealing temperature. Positron annihilation lifetime spectroscopy (PALS) was used to study defects at different sites for nanograins Li-ferrites. The analysis of the PAL spectrum indicated two lifetime components τ1 and τ2 for the annihilation of the positrons, and their corresponding relative intensities I1% and I2%. For nanoparticles Li-ferrite there are correlations between: 1) I2, τ2, annealing temperature and the total porosity (Pt) with the grain size;2) I1, μi, Ms and the homogeneity with grain size.

CNTs/Ferrite/PVDF复合材料的电磁波吸收特性

本文采用水热合成法在碳纳米管(CNTs)表面包覆了一层组分为Ni0.2Cu0.2Zn0.6Fe1.96O4的尖晶石型纳米铁氧体(Ferrite)颗粒,并应用共混法制备了碳纳米管/铁氧体/聚偏二氟乙烯(PVDF)三相复合材料。使用矢量网络分析仪在8-18GHz的频率范围内对复合材料的复介电常数和复磁导率进行了测试,并由此计算出复合材料的反射损失率。测试结果表明,复合材料在宽约为几个GHz的频段内反射损失超过了10dB,碳纳米管/铁氧体/聚偏二氟乙烯复合材料呈现出非常良好的电磁波吸收性能。

Preparation and Sinterability of Mn-Zn Ferrite Powders by Sol-Gel Method

Mn-Zn spinel ferrites were synthesized by sol-gel method. Effects of calcined temperature on structure and particle size of MnZnFe2O4 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicate that the ultra fine Mn-Zn ferrite exhibits a spinel crystal structure. SEM images show that the powder fired at 900℃for 2 h has an average diameter of 60 ~ 90 nm. The particle size becomes larger with the increasing of calcined temperature and the distribution of particle becomes even more homogeneous. Sintering behaviors of synthesized ferrite powders depend on the powder characteristics and high temperatures have induced the good crystallization of particles.

Influenced of Cu²⁺Doped on Structural, Morphological and Optical Properties of Zn-Mg-Fe₂O₄Ferrite Prepared by Sol-Gel Method

The Zn0.5CuxMg0.5-xFe2O4 (where x = 0.0, 0.1, 0.2, 0.3 and 0.4) was prepared by sol-gel route and characterized in detail in terms of their structural, morphological, elemental and optical properties as a function of Cu concentration. X-ray diffractometer (XRD) results confirmed the formation of cubic spinel-type structure with average crystallized size in the range of 30.56 to 40.58 nm. Lattice parameter was found to decrease with Cu concentration due to the smaller ionic radius of Cu2+ ion. The HR-SEM images show morphology of the samples as prismatic shaped particles in agglomeration. The elemental dispersive X-ray Spectroscopy (EDX) confirmed the elemental composition of the as-prepared spinel ferrite material with respect to the initial concentration of the synthetic composition used for the material. The Fourier transform infrared (FTIR) spectroscopy confirmed the formation of spinel ferrite and showed the characteristics absorption bands around 463, 618, 876, 1116, 1442, 1622 and 2911 cm-1. The energy band gap was calculated for the samples were found to be in the range of 4.87 to 5.30 eV.

The Electrical and Optical Properties of Zn0.5Li2xMg0.5-xFe2O4 Lithium Doped Nanoparticle Prepared by Coprecipitation Method

In this study, nano ferrite materials were produced to replace costive industrial materials [1]. Ferrite nanoparticles are the interesting material due to their rich and unique physical and chemical properties. They find applications in catalysis, bio-processing, medicine, magnetic recording, adsorption, devices etc. Using co-participation method, five nano ferrite samples Zn0.5Mg0.5-xLi2xFe2O4 (x = 0.00, 0.10, 0.20, 0.30 and 0.40) were prepared. The electrical and optical properties of the Zn0.5Mg0.5-xLi2xFe2O4 samples were studied using the Ultraviolet-visible (UV-Vis) spectroscopy. The results verified that the formation of the absorption coefficient of the five samples of Zn0.5Mg0.5-xLi2xFe2O4 increased with the increase of Lithium (Li2x). The energy band gap of the Zn0.5Mg0.5-xLi2xFe2O4 samples ranged from 3.28 to 3.12 eV [1]. The extinction coefficient (K) for five samples of Zn0.5Li2xMg0.5-xFe2O4 increased with the increase of Lithium (Li2x) at 338 nm from 0.074 to 0.207. The high magnitude of optical conductivity is (1.34 × 1012 sec-1) and the maximum value of electrical conductivity is 42 (Ω.cm)-1. This may due to the electrical and optical properties of lithium.

Physical Properties Study of Zn_(0.5)Mn_(0.5−x)Li_(2x)Fe_(2)O_(4) Nanoparticle Series that Prepared by Co-Precipitation Method

Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.

SAP、铁氧体与硫酸铁对水泥早强性能的影响

目的为提高瓦斯抽采效果,解决传统封孔水泥早期强度发展缓慢的问题。方法选用高吸水树脂(SAP)、纳米铁氧体和硫酸铁来制备新型封孔材料。通过抗压强度试验、流动度测试、凝结时间测试、X射线衍射(XRD)、热重分析、扫描电子显微镜(SEM)等手段对水泥试样进行结构分析及性能测试,研究三元早强剂对水泥基封孔材料的影响。结果与空白组相比,三元早强剂缩短了水泥的凝结时间,提高了水泥早期强度。1d抗压强度为10.13MPa,与空白组相比提高了51.87%。结论SAP的自养护效应和纳米铁氧体的晶核效应,可以促进水泥水化产物的生成,同时硫酸铁和纳米铁氧体中的铁离子为高价阳离子,对C-S-H形成的双电子层具有压缩作用,可以进一步促进C-S-H凝胶的生成,加快水泥水化速率,生成更多水化产物,填充孔隙,增加水泥密实度,提高早强性能,为水泥早强剂的设计提供了新思路。

隐身纳米吸波材料的研究进展

纳米吸波材料作为武器装备的重要隐身技术,对于提高其作战能力有着重要的作用。本文重点阐述了磁纳米、石墨烯、生物质碳基和碳纳米管等复合材料在吸波领域研究的最新进展,简要总结了不同类型吸波材料对电磁波的吸收机制。

纳米镍锌铜铁氧体在仿生机器人伺服电机编码器线缆中的应用

介绍了纳米镍锌铜铁氧体在仿生机器人伺服电机编码器线缆中的应用。首先分析了仿生机器人在复杂环境中的工作要求,特别是对信号传输稳定性的高需求。针对传统线缆存在的问题,提出了基于纳米材料的新型线缆设计方案,并详细讨论了纳米镍锌铜铁氧体材料的优势及其在线缆中的应用效果。最后,通过对比实验验证了新设计线缆在电磁屏蔽效能、机械性能和耐久性方面的优异表现,展望了纳米技术在机器人领域的广阔应用前景。