Runsheng Huang

Giant magnetoresistance of bulk polycrystalline La0.833Na0.167MnO3 with Ag2O addition

Abstract A series of bulk polycrystalline samples of La 0.833 Na 0.167 MnO 3 with Ag 2 O addition were prepared by conventional solid-state reaction processing in air. The mol proportion between La 0.833 Na 0.167 MnO 3 and Ag 2 O is 1: x ( x =0, 0.04, 0.08, 0.125, 0.25, and 0.50). X-ray diffraction patterns show that the sample for x =0, i.e., pure La 0.833 Na 0.167 MnO 3 , contains a single perovskite phase and that the samples for x >0 are composed of two phases (a magnetic perovskite phase and a nonmagnetic Ag-rich phase). It is found that, in this series of polycrystalline samples, a maximum magnetoresistance occurs for x =0.25, i.e., for a composite of the two phases. The corresponding magnetoresistance ratio is about 27% at room temperature. The enhancement of the magnetoresistance effect in such an inhomogeneous granular system can be attributed to the spin dependent scattering of electrons at the interface of the two phases.

Dispersion of magnetic metals on expanded graphite for the shielding of electromagnetic radiations

The composites of nanoparticles of magnetic metals Co, Ni, and Ni–Fe dispersed on the nanolayers of expanded graphite (EG) were prepared by the impregnation of EG with ethanol solutions of metal acetates, followed by drying and reduction in H2. Such composites combined the properties of high electric conductivity of EG and magnetic conductivities of dispersed metals, and thus exhibited the high shielding effectiveness in a wide range of frequencies. Specifically, the composite containing 30%Ni and 70%EG reached the shielding effectiveness of 70–105dB at frequencies from 300kHzto1.5GHz.

Morphology control of nanohelix by electrospinning

We developed a simple approach to design and fabricate precisely controlled coiled nanofibers via the micromanufacture of electrospun nanofibers. The fabrication set-up was specially designed so that one stream of polyvinyl pyrrolidone (PVP) sol with ferric nitrate was electrospun into a fiber bundle. This bundle acted as an axis that was collected between two opposite rotating needles while another stream of PVP sol, containing copper nitrate, was electrospun around the fiber bundle axis to form a coil. By altering the elements in the precursor solution, copper microsolenoids with magnetite (Fe3O4) cores were fabricated followed by annealing and deoxidation.

The Influence of Plasma Induced by

At the different radioactivity, temperature, pressure, heights, and incident angles, the influences of the electromagnetic wave propagating in the α-decay radionuclide layer (RNL) coated on a perfect electric conductor system were simulated by the finite-difference time-domain method. The maximum electron density ionized by 5.45-MeV α-particles is ~1.8 × 1011 per cubic centimeter when the radioactivity is 10 Ci/cm2. The decrease of the reflectivity at altitude is much better than at ground and the decreasing amplitudes could reach 1-20 dB in the frequency range from 300 MHz to 40 GHz at an altitude of 10000 m. In addition, the same RNL would significantly reduce the back scattering bistatic radar cross section (RCS) of the platform. The decrease of RCS along the direction of the originally strongest reflection wave is nearly 25.5 dB when the incident angle is 60°.

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A simple liquid-reduction method to prepare the metallic particles/expanded graphite (EG) composites has been developed and the electromagnetic shielding effectiveness (SE) of the materials is studied. With this method, we have successfully implanted the nanoparticles of Ni, Cu, and Ag into EG. It is shown that their SE at low frequencies is significantly increased by dispersing the metallic particles on EG, especially for the composites of 30% metal content. At the frequency range of 300 kHz-1 GHz, with the surface density only 0.096 g/cm2, the SE can reach as high as 70-105 dB. Compared with the EG, the SE has gained 17 dB at 300 kHz.