Xiaowei Hong

Lanthanum and Neodymium Doped Barium Ferrite-TiO₂/MCNTs/poly(3-methyl thiophene) Composites with Nest Structures: Preparation, Characterization and Electromagnetic Microwave Absorption Properties.

We report herein the synthesis of a novel nest structured electromagnetic composite through in-situ chemical polymerization of 3-methyl thiophene (3MT) in the presence of the BaFe11.92(LaNd)0.04O19-TiO2 (BFTO) nanoparticles and MCNTs. As an absorbing material, the BFTO/MCNTs/P3MT/wax composites were prepared at various loadings of BFTO/MCNTs/P3MT (0.2:0.10:1.0 ~ 0.2:0.30:1.0), and they exhibited strong microwave absorption properties in the range of 1.0–18 GHz. When the loading of BFTO/MCNTs/P3MT is 0.2:0.30:1.0, the composite has a strongest absorbing peak at 11.04 GHz, and achieves a maximum absorbing value of −21.56 dB. The absorbing peak position moves to higher frequencies with the increase of MCNTs content. The mechanism for microwave absorption of these composites has been explained in detail.

Synthesis and electromagnetic properties of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites

Abstract Doped BaFe11.92(LaNd)0.04O19/titanium dioxide composites have been prepared by the gel-precursor self-propagating combustion process. The characterization of the composites are performed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Differential thermal analysis-thermo gravimetry (DTA–TG), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and network analyzer. Both XRD and FT-IR indicate that the doped BaFe11.92(LaNd)0.04O19/titanium dioxide composites are successfully synthesized and there are some interactions between BaFe11.92(LaNd)0.04O19 and titanium dioxide. DTA–TG analysis of BaFe11.92(LaNd)0.04O19/titanium dioxide composites shows that the composite gel decomposition process mainly includes two stages: the first stage is the crystallized water and the residual moisture evaporation; the second stage is the nitrate and citric acid decomposition reaction. SEM demonstrates that the doped BaFe11.92(LaNd)0.04O19/titanium dioxide solid solution has formed. The magnetic parameters indicate that the electromagnetic properties of the composites could be well adjusted by the mass ratio of BaFe11.92(LaNd)0.04O19 and titanium dioxide. When the mass ratio of BaFe11.92(LaNd)0.04O19 and titanium dioxide is 4:5, the composites have the best magnetic loss. The composites with the mass ratio 6:5 of BaFe11.92(LaNd)0.04O19 and titanium dioxide. BaFe11.92(LaNd)0.04O19 and titanium dioxide possess good dielectric loss. The introduction of titanium dioxide enhances the dielectric loss and widens the frequency bands. The composites will be promising microwave absorption materials with wide frequency band.

La/Sm-doped Strontium-ferrite/poly-m-toluidine Composites Obtained by In Situ Polymerization

La/Sm-doped strontium-ferrite/poly-m-toluidine) (PMT) composites were synthesized by in-situ chemical polymerization of m-toluidine in the presence of La/Sm-doped strontium-ferrite particles. Structural, morphological and electro-magnetic properties of nanocomposites were performed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), four-probe conductivity tester and vibrating sample magnetometer (VSM). The results of XRD indicated that La3+ and Sm3+ had entered into the lattice of strontium ferrite. FTIR spectra demonstrated that there were interactions between ferrite particles and PMT. SEM studies showed that the composites presented the core-shell structure. Under applied magnetic field, nanocomposite exhibited the hystereric loops of the ferromagnetic behavior. The saturation magnetization and coercivity of nanocomposites varied with the content of (LaSm)(0.06)SrFe(11.88)O(19)particles.