Search

The effects of Si+4 and Zn+2 substitutions on the structural and magnetic properties of Cu1−xZnx+ySiyFe2−2yO4 ferrites prepared by double sintering ceramic technique have been investigated. From X-ray diffraction analysis, it was found that substitution of Zn and Si enhanced sintering process and crystallization. The XRD peaks increase by increasing Zn and Si content. On the other hand, the initial permeability decreases sharply at Curie temperature for all samples, which makes Zn/Si co-doped CuFe2O4 spinel ferrites a very promising candidate for magnetic switches, magnetic temperature transducers (MTT), and for fabrication of temperature sensitive controller devices. The important change of Curie temperature of CuFe2O4 compound occurs by simply controlling the content of Zn and Si within CuFe2O4 and results in obtaining magnetic materials with desired Curie temperature. Magnetic hysteresis loop measurements show that the samples have soft magnetic character.

The current work involves the use of flash auto combustion procedure to synthesize nano-ferrites Mn0.6Zn0.4LaxFe2-xO4, (x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) annealing at 500 °C for 4 h. X-ray Diffraction (XRD), Fourier transition infrared spectroscopy (FTIR), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structural properties of produced samples. Scanning electron microscopy (SEM) was utilized to examine the surface morphology of the samples at various Lanthanum concentrations. From XRD, the spinel cubic structure for all samples with few traces of secondary phase at high La concentrations is assured. The crystallite size is estimated to be in the nanoscale range of 13.16–18.13 nm using the Debye–Scherrer formula. The appearance of characteristic vibrational bands near 460 cm−1 and 563 cm−1, which correspond to the octahedral and tetrahedral sites, respectively, confirms the formation of the spinel structure. SEM micrographs show that the grains are nearly irregular in shape, and the accumulation of La+3 ions at the grain boundaries exerts tensile strength and pressure on the grain itself, reducing the grain size. The particle size estimated by TEM coincides well with the crystallite size determined by XRD. The thermogravimetric analysis, (TGA), was used to investigate the thermal properties of the nanoferrites from room temperature to 1000 °C. In comparison to the other samples, the sample with x = 0.04 has greater thermal stability and the TEM measurement indicates that this sample has the smallest particle size. Therefore, we can assert that the thermal stability improves as the particle size decreases. The magnetic permeability was measured in the temperature range 303–773 K at a fixed frequency of 10 kHz and at various La contents. The sample with x = 0.04 has a minimal permeability value, showing that the separation brought on by La ions has diminished the super exchange contact between magnetic ions. [ABSTRACT FROM AUTHOR]

The effects of poly (vinylidene fluoride, PVDF) on barium zirconate titanate nanoparticles has been studied. Different concentrations of (BZT-PVDF) nanocomposites using the formula [x (PVDF)/(1 − x) BZT] (where x = zero, 0.2, 0.4, 0.6, 0.8 and 1) were prepared using the hot pressing method. The BZT nanoparticle was prepared using the tartrate precursor route method. The Dc resistivity as a function of reciprocal temperature (1000/T) K−1 for the composite samples has been studied. The dielectric constant (ε) increases with the amount of BZT, which can be described as the increase of interfacial space charge polarization between (PVDF-BZT) nano-composites and the increase in the ionic mobility of the polymer. The ferroelectric hysteresis of prepared nano-composites has been investigated. The increase of BZT content raises the slope of the hysteresis loop and hence the dielectric polarization, which may be attributed to the dominance of smaller grain size and tetragonality. The increasing in dielectric properties for the prepared samples is very useful in industrial applications, such as sensors, actuators and transducers. [ABSTRACT FROM AUTHOR]

The Ni-Al ferrite nanoparticles are synthesized by the flash auto-combustion method, and PANI is synthesized by the situ-chemical oxidative polymerization method. NiAl-ferrite/PANI/ x (PANI) Nanocomposite Films (x = 0.6 and 0.8) were prepared using a solution casting process. The X-ray results of the NiAlxFe2-xO4/PANI composite manifest that the Ni-Al ferrite fully interacted with PANI molecules and the Ni-Al ferrite particles are embedded in the PANI chains from TEM and SEM images. The dielectric parameters ϵ′, ϵ″ and tan δ decreased with the increase in the frequency of the applied field. The modulus M″ spectra of the investigated samples show two relaxation peaks in two frequency regions. In Cole–Cole plot of M′ versus M″, a semicircular trend is observed, i.e. a non-Debye criterion. The presence of PANI in the NiAl0.6Fe1.4O4/PANI composite films reduces the magnetic properties of the composite samples leading to the decrease of saturation magnetization and remanence magnetization. [ABSTRACT FROM AUTHOR]

In this investigation, it is used a phenomenological model to predict the thermomagnetic properties through making simulation of experimental isofield thermo-magnetization curve for Sc doped Th2NiC2 superconductors. Consequently, the magnetocaloric effect (MCE) of Sc doped Th2NiC2 superconductors, in the vicinity of superconducting phase transition, is simulated, calculating MCE parameters. The results show that MCE of Sc doped Th2NiC2 superconductors are inverse type in temperature range of superconducting phase transition. The behavior of MCE in Th1.9Sc0.1NiC2 and Th1.8Sc0.2NiC2 samples recommends that they can fruitfully be utilized as very low-temperature magnetic refrigerants between 7 and 11 K especially in radiation detectors for outer space research. [ABSTRACT FROM AUTHOR]

A phenomenological model (PM) is applied to simulate the magnetocaloric effect (MCE) of Ca3Co2O6 (CCO). On the basis of PM, MCE parameters of CCO are concluded as results of simulation for magnetization vs. temperature under 5 T magnetic field. The maximum value of absolute value of magnetic entropy change is 2.21 J/Kg.K. The values of full-width at half-maximum, relative cooling power and refrigerant capacity are 64 K, 141 and 101 J/Kg, respectively, finding that CCO is a prospective material in magnetic refrigeration (MR) over cryogenic temperature between 0 and 100 K. CCO sample could work as an adequate magnet in MR with limited eddy and little loss of hysteresis. Thus, magnets like CCO sample can do a significant role in the fabrication of various eco-friendly devices. It is recommended that CCO sample is a significant and promising magnet in MR for liquefying nitrogen gas. [ABSTRACT FROM AUTHOR]