CoYbxFe2-xO4 (x = 0.00, 0.025, 0.05, 0.075, 0.10) spinel ferrites were synthesized by co-precipitation technique. Structural, dielectric and magnetic properties were measured. X-ray diffraction analysis showed that all the prepared spinel ferrites possessed cubic spinel structure. Dielectric constant, AC conductivity and dielectric loss decreased with the addition of rare earth ions. The impedance analysis explained the role of grains and grain boundaries with in prepared samples. Cole-Cole plots helped to measure the values of grains and grain boundary's resistance. The magnetic properties proved the soft nature of these ferrites. Saturation magnetization and remanence decreased while coercivity was enhanced with the addition of ytterbium concentration. All these parameters suggested that these prepared samples might be suitable for high frequency applications. 相似文献
The complicated structure of human blood has been characterized based on relaxation time, τ, and the Cole-Cole parameter, α, obtained from dielectric measurements. As previously reported by different authors, the experimental data show net deviation from the classical Debye model with certain distribution of relaxation times (Dτ). Plots of α versus width of the relaxation rate distribution of micro-particles inside the blood show that Dτ drastically affects the dielectric properties of the fluid. The mathematical function of Dτ is found to be Gaussian and we find that the α values of normal blood have net lower magnitude than that of diabetic blood. These results suggest that glucose in blood increases the broadness of the parameter α, which have significant importance in diabetic-biosensor manufacture. 相似文献
New compound showing a direct SmA*–SmCA* phase transition was synthesised. As far as authors know there are a few pure compounds showing para- and antiferroelectric phases without SmC* between them. Direct current (DC) field applied into a planar-oriented cell induces ferroelectric SmC* phase in an investigated compound. Typical for SmC*, Goldstone mode starts to be detectable. DC field also shifts down the temperature of a SmCA* phase creation. Moreover, modes in the appearing antiferroelectic phase are enhanced by DC field. This paper shows and discusses relations between modes detected in SmA*, SmCA* and SmC* (SmC* phase – nucleated by DC field) phases. Parameters of observed modes are calculated using the Cole–Cole relaxation model and a calculation procedure useful especially for high frequency relaxations (higher than 200 kHz). 相似文献
The dielectric constant of aqueous MgCl2 solution has been determined in the frequency range 0.2 MHz to 20 GHz at 298 K using the dielectric relaxation spectroscopy method. The behavior is well described according to four Cole-Cole terms whose evolution with composition is analyzed. The static dielectric constant and relaxation times decreases with the increasing aqueous MgCl2 solution concentrations. Only one H-bonded water cluster with the aqueous MgCl2 solution relaxes is reported during the cutoff relaxation time. A distinct ion–water cooperative interaction is observed, and water molecules perturbed by ion contribution on dielectric constant beyond the first hydration shell are obtained. 相似文献
In this paper we study properties of numerical solutions of Burger’s equation. Burgers’ equation is reduced to the heat equation on which we apply the Douglas finite difference scheme. The method is shown to be unconditionally stable, fourth order accurate in space and second order accurate in time. Two test problems are used to validate the algorithm. Numerical solutions for various values of viscosity are calculated and it is concluded that the proposed method performs well. 相似文献
Non magnetic material Ca2+ as a substitute in Cobalt ferrite (Co1?xCaxFe2O4x?=?0.00, 0.05, 0.10 & 0.15) is prepared by self auto combustion method. The synthesized samples were carried out for various characterizations such as X-ray diffraction, Field emission scanning electron microscope (FE-SEM), Dielectric measurement and Magnetic property. X-ray diffraction reveals the values of crystalline size, lattice parameter and x-ray density by using the standard formula. The saturation magnetization (Ms) decreases from 63.92 to 43.17 emu/g for x?=?0.00 to 0.15 and the coercivity (Hc) increases gradually from 819.85 to 1312.32?Oe with the increase in Ca2+ concentration. The dielectric properties of synthesized nano materials were carried out at room temperature. The dielectric parameters such as tangent loss, Cole–Cole plot (Impedance, Modulus), and AC Conductivity were determined for various Ca2+ concentration. The frequency dependent dielectric dispersion behaviour of all the samples can be explained by the Maxwell–Wagner two-layer model along with Koop's phenomenological theory. As a result, Ca2+ substituted Cobalt ferrite is enhanced with their dielectric and magnetic property which is suitable for a memory device, recording media application and high frequency device. 相似文献
The superparamagnetic 8-nm Fe3O4 nanoparticles were successfully prepared by chemical oxidation process. For the complex permittivity, the dual dielectric relaxation processes have been proved by two overlapped Cole–Cole semicircles, and the natural resonance frequency is 3.03 GHz for the complex permeability. The maximum reflection loss value reaches −55.5 dB at 6.11 GHz with 3.85 mm in the thickness of the absorbers for the superparamagnetic 8-nm Fe3O4 nanoparticles which is better than that of 150 nm and 30 nm Fe3O4 nanoparticles. It is believed that the superparamagnetic 8-nm Fe3O4 nanoparticles can be used as a kind of candidate for microwave absorber. 相似文献
Summary: The study of the structure and the rheological properties of poly(propylene) (PP)/montmorillonite (MMT)/maleinated PP (MAPP) composites strongly suggests that a silicate network may form under certain conditions. Network formation could not be proven unambiguously with the usual techniques, i.e., with TEM and by plotting the frequency dependence of viscoelastic properties. Cole‐Cole plots detect the network very sensitively. A certain number of silicate layers are needed to create a house‐of‐cards structure. A threshold concentration of MAPP exists in the investigated system, which depends on the silicate content.
Cole‐Cole representation of the viscoelastic properties of PP/OMMT/MAPP nanocomposites. 相似文献