Electrical Magnetic Properties Research Articles

The synthesis and combined electrical–magnetic and toxic dye sequestration properties of a Cr(iii)-metallogel

The present communication deals with the synthesis, characterization of a Cr-based metallogel and explores its electrical-magnetic properties. The proton conductivity and toxic dye sequestrations have also been investigated.

Analysis of the new ternary phase with C6Cr23 structure in Mg-Co-B system by Rietveld method and physical properties of its Ni-substituting effect

• New ternary Mg 1.4 Co 21.6 B 6 compound was firstly reported. • The crystal structure of Mg 1.4 Co 21.6 B 6 was determined by Rietveld XRD method. • The instability of Mg 1.4 Co 21.6 B 6 at elevated temperatures has been discussed. • Physical properties of Ni-substituting Mg 1.4 Co 21.6 B 6 have been investigated. A new ternary Mg 1.4 Co 21.6 B 6 compound in the Mg-Co-B system was synthesized via a conventional solid-state reaction method and the effect of Ni-substitution on its crystal structure, thermal stability, solid solubility and physical properties were systematically investigated. The crystal structure of the Mg 1.4 Co 21.6 B 6 compound was fully determined by the X-ray diffraction technique with Rietveld refinement method. It is found that Mg 1.4 Co 21.6 B 6 crystallizes in the form of C 6 Cr 23 structure type (space group: Fm-3m (No.225), a = 10.5617(2)Å, Z = 4). The results showed that the 4a sites have been occupied completely by Co atoms in present compound which with M 2-x Ni 21+x B 6 form belonging to the W 2 Cr 21 C 6 -type. When Mg 1.4 Co 21.6 B 6 is repeatedly sintered at elevated temperatures, it becomes unstable and decomposes into Co 3 B and Mg. The lattice parameters of the Mg 1.4 Co 21.6 B 6 solid solution alters dramtically with increasing Ni substitution, with no regular trend being observed. The electrical and magnetic performances of the 3.6Mg:3Co:17Ni:6B and 3.6Mg:3Co:18Ni:6B (nominal compositions) samples suggest that both samples are typical ferromagnetic materials. The temperature in the maximum drop of the ρ(T) curve decreases as a function of the Ni content. Base on the correlation between the critical temperature and Ni content, a linear fitting equation is obtained and the critical temperature of Mg 1.4 Co 21.6 B 6 calculated utilizing the linear fitting equation. The findings in this work may provide certain reference values for material science on electrical magnetic properties and other references for researching the material further.

Nanostructured quaternary Ni1-xCuxFe2-yCeyO4 complex system: Cerium content and copper substitution dependence of cation distribution and magnetic-electric properties in spinel ferrites

Quaternary Ni 1-x Cu x Fe 2-y Ce y O 4 complex nano-ferrites system with different cerium content ratio and copper substitution degree were synthesized via co-precipitation wet chemical technique. The newly obtained nanoparticles, with general formula Ni 1-x Cu x Fe 2-y Ce y O 4 (where x = 0.0, 0.3, 0.6 and y = 0.00, 0.03, 0.05, 0.08 and 0.10) were heated up to 600 °C to stabilize the specific crystalline spinel structure. The limit of cerium content was quantitively determined to be around 0.08 and up to 0.10. Furthermore, the powders were pelletized in a 13 mm wide pellets and thermally treated at 950 °C. The thermal treatment affected even more the phases segregation process, as CeO 2 was identified in the sample with lowest degree of cerium insertion – 0.03. Also, a difference in color and size of pelletized samples was noticed after the 950 °C thermal treatment. The Rietveld refinement, crystal structure confirmation, morphology magnetic and electrical properties of samples have been deeply studied. The cation distribution carried out from Rietveld refinement confirms the occupancy of (Fe 3+ ) on tetrahedral sites and [Ni 2+ ], [Cu 2+ ], [Fe 3+ ] and [Ce 2+ ] on octahedral sites in the crystal lattice. Preliminary information regarding the cation distribution in spinel structures were suggested by FTIR spectral results, precisely in the 650-520 cm −1 region, as a consequence of peak shape and lack of shiftiness of M Td – O bond. Spherical-shaped quaternary nano-ferrites of 17–28 nm were determined from FE-SEM analysis and the samples composition was confirmed by EDX analysis. Hysteresis loops shows modifications in coercivity, magnetization and magnetic remanence with Ni 2+ and Cu 2+ ions doping in Ni 1-x Cu x Fe 2-y Ce y O 4 complex systems with typical ferrimagnetic behavior. Dielectric measurements were employed in order to determine the electrical permittivity, dielectric losses and conductivity values in a 10 Hz – 1 MHz frequency range.

Electrical and magnetic properties of La0.7Ca0.3MnO3 nanoparticle prepared by reactive milling method

La0.7Ca0.3MnO3 nanoparticle in an orthorhombic structure with space group of Pnma was prepared by a combination of the reactive milling method and annealing at 900 °C for 1 h in air. The mean crystal size determined through the powder x-ray diffraction data is 18 ± 2 nm. Based on the dependences of the resistivity and the magnetisation on temperature and applied magnetic field, the electrical-magnetic properties, the magnetoresistance and the magnetocaloric effects have been investigated. It shows La0.7Ca0.3MnO3 nanoparticle undergoes a metal-insulator and a ferromagnetic-paramagnetic phase transitions at T MI = 252 K and T C = 253 K, respectively. The temperature dependences of resistivity of material in the absence and presence of 4 kOe in a range of 30–300 K were fitted to the phase segregation model. The magnetoresistance and the magnetocaloric effects related to the double-exchange interactions taking place around T MI and T C were observed, corresponding to the values of the magnetoresistance MR = 9.29% and the maximum magnetic entropy change ∣ΔS max∣ = 0.18 J/kg.K under an applied magnetic field of 4 kOe. Besides, the low field magnetoresistance value at low temperature region and the change of the specific heat of La0.7Ca0.3MnO3 nanoparticle have also been concerned.

Layer-by-layer assembly of PDMS-coated nickel ferrite/multiwalled carbon nanotubes/cotton fabrics for robust and durable electromagnetic interference shielding

The military and industry have multiple needs for Electromagnetic interference (EMI) shielding textiles, but it is still a huge challenge to realize integration of inorganic nanomaterials and fabric with good interface adhesion. Therefore, carefully chosen EMI materials and preparation techniques are key to provide commercially acceptable fabrics. Herein, a flexible and durable EMI shielding cotton fabric was fabricated by a layer-by-layer assembly of multiwalled carbon nanotubes (MWCNTs) and nickel ferrite (NiFe2O4) nanoparticles, following by an organic poly (dimethylsiloxane) (PDMS) coating. Benefiting from the strong interfacial interactions between MWCNTs and NiFe2O4, the efficient electrical, magnetic and thermally conductive pathways were successfully constructed on the cotton fabric. The resultant composite fabrics exhibited high electrical-magnetic properties, superior EMI shielding effectiveness of ≈ 84.5 dB in X-band with a 0.96 mm thickness, and markedly enhanced thermal conductivity (2.52 W m− 1K− 1). Furthermore, the external PDMS coating not only imparted a water-resistant feature, but also improved the structural and performance stability while maintaining satisfactory air permeability. Based on these results, the layer-by-layer assembly approach can be viewed as an efficient tool to fabricate protective textiles against EMI radiation pollution. A new surfactant assisted acid prehydrolysis process for enhancing biomass pretreatment.

Preparation and electrical-magnetic properties of Co0.6Cu0.16Ni0.24Fe2O4/MWCNTs composites

Co0.6Cu0.16Ni0.24Fe2O4/multi-walled carbon nanotube nanocomposites (CCNF/MWCNTs) were synthesized by solution filling method. The phase structure, thermal stability, morphology and electrical-magnetic properties of the samples were characterized by means of modern testing technology. The effect of iron concentration, filling time, sintering temperature on their electrical and magnetic performance was discussed. The results indicated that conductivity was related to the content of MWCNTs, while the magnetism correlated with the volume fraction of the filled CCNF in the composites. When the optimal condition satisfied the filling time of 18 h, ferric concentration of 0.25 mol L−1 and sintering temperature of 350°C, the prepared composite had the best magnetic loss performance, and its minimum reflection loss reached −22.47 dB on 9.76 GHz, the available bandwidth was beyond 2.0 GHz. Hence, the obtained composite can be used as advancing absorption and shielding material due to its favorable microwave absorbing property.

Structure and Physical Properties of Nanocomposite Coatings

Nanocomposite structures composed of crystalline and/or amorphous phases are of rapidly growing interest. With the real-time control of the deposition parameters, functionally graded thin films can be produced. These coatings have enhanced mechanical, magnetic and interesting electric properties compared to conventional single-phase coatings. Tailored physical properties can be produced and reproduced only if detailed knowledge of the structure and the atomic processes, taking place during film formation, is available. Nanoscale composite films are often produced by physical deposition methods. In these films the nanosize of the crystalline grains is ensured by the formation of a continuous covering layer of the (amorphous) matrix during growth, blocking the growth of the crystallites. Model systems of metal/amorphous carbon or carbon-nitride films as well as metal/metal-oxide nanocomposites will be shown as examples.The physical and technical background of hard and multifunctional nanocomposite materials...

The low frequency internal friction and electric magnetic properties in La0.7Pb0.3MnO3 bulk materials

Abstract The polycrystalline samples of La 0.7 Pb 0.3 MnO 3 synthesized by the sol–gel method were studied by the low frequency internal friction measurements and the resistance and ac susceptibility measurements. There are two internal friction peaks at 258 and 198 K, respectively, the peak positions of which do not shift with frequency but the peak heights of which decrease with increasing frequencies. The modulus softening is evident at the corresponding temperatures. Corresponding to the two internal friction peaks, there are two resistance peaks, and a sharp rise and a following continuous decrease of ac susceptibility. It is suggested that the high temperature peaks correspond to the paramagnetic (PM) to ferromagnetic (FM) transition, while the low temperature peaks originate from the process of an anti-ferromagnetic phase (AFM) separating from the ferromagnetic matrix (phase separation) in polycrystalline materials. The peak positions of internal friction and resistance will move towards higher temperature when the sample was annealed in flowing oxygen, and the low temperature peaks become smaller.

Synthesis and electrical–magnetic properties of polyaniline composites

Synthesis and electrical–magnetic properties of polyaniline composites

Synthesis and electrical-magnetic properties of polyaniline composites

Composites of polyaniline (PANI) with both conducting and ferromagnetic feature were synthesized by an improved method proposed by the authors. The electrical and ferromagnetic properties of the composites were measured as a function of the concentration of KOH solution used during polymerization. The conductivity of the composites at room temperature decreases with the increase of the concentration of KOH; the maximum conductivity of 8.0 × 10−1 S/cm can be obtained when 25 wt % of concentration of KOH was used. For a high concentration of KOH, ferromagnetic properties of the composites including a high saturated magnetization (∼ 10.0 emu/g) depending on the concentration of KOH solution and a lower coercive force (Hc ≈ 0) independent of the concentration of KOH solution were observed. It has been demonstrated that magnetic particles (Fe3O4) with nanometer size in the composites can be attributed to the ferromagnetic properties of the composites observed. For a lower concentration of KOH solution, on the other hand, the magnetic properties of the composites can be decomposed to Curie susceptibility χc depending on the temperature and Pauli susceptibility χP independent of the temperature. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2799–2805, 1998

Structure, valence state and magnetic properties of LnGa 1-x V x O 3

Recently considerable attention has been paid to the ABO_3 type RE complexoxides since they have special electrical-magnetic properties, good catalytic behaviour andgas sensitive behaviour. One of them is ABO_3 type RE gallate system, which has some

RF Coupler Technology for Fusion Applications

Radio frequency (rf) oscillations at critical frequencies have successfully provided a means to convey power to fusion plasmas due to the electrical-magnetic properties of the plasma. While large rf systems to couple power to the plasma have been designed, built, and tested, the main link to the plasma, the coupler, is still in an evolutionary stage of development. Design and fabrication of optimal antennas for fusion applications are complicated by incomplete characterizations of the harsh plasma environment and of coupling mechanisms. A brief description of rf coupler technology required for plasma conditions is presented along with an assessment of the status and goals of coupler development.