CdS/α-Fe2O3 hierarchical nanostructures, where the CdS nanorods grow irregularly on the side surface of α-Fe2O3 nanorods, were synthesized via a three-step process. The diameters and lengths of CdS nanorods can be tuned by changing the ethylenediamine (EDA) and Cd ion concentrations. The magnetic investigations by superconducting quantum interference device indicate that the hierarchical nanostructures have an Morin transition at lower temperature (230 K) than that of the single bulk α-Fe2O3 materials (263 K). Importantly, the hierarchical nanostructures exhibit weakly ferromagnetic characteristics at 300 K. A sharp peak assigned to the surface trap induced emission are observed in room temperature PL spectra. Combining with the optoelectronic properties of CdS, the CdS/ α-Fe2O3 hierarchical nanostructures may be used as multi-functional materials for optoelectronic and magnetic devices.
CHEN YuJin1,2,3, SHI XiaoLing1, CAO MaoSheng1 & ZHU ChunLing4 1 School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
The influence of orientation on electromagnetic properties of basalt fibre/nickel core-shell heterostructures prepared by a simple electroless plating method is investigated. For comparison, the same investigation is also performed on naked basalt fibres. For electromagnetic measurement, the directions of basalt fibre/nickel and naked basalt fibres are parallel, random and perpendicular to the direction of external electric field, termed E || sample, random sample and E ⊥ sample, respectively. Electromagnetic anisotropy can be clearly observed in the basalt fibre/nickel core-shell heterostructures, while electromagnetic properties of naked basalt fibres are unrelated to the orientation. The E ⊥ basalt fibre/nickel shows the highest dielectric loss but the lowest magnetic loss, and E || basalt fibre/nickel exhibits the highest magnetic loss but the lowest dielectric loss. The dielectric loss of E ⊥ basalt fibre/nickel is several times as large as that of E || basalt fibre/nickel, which could be attributed to the increase of polarization relaxation time as a consequence of the nanosize-confinement effect. The magnetic loss of E || basalt fibre/nickel is even one order of magnitude higher than that of E⊥ basalt fibre/nickel, which originates mainly from the natural magnetic resonance of basalt fibre/nickel core-shell heterostructures.
This paper reports that single-phase γ-Y2Si2O7 is prepared via a sufficient blending and cold-pressed sintering technique from Y2O3 powder and SiO2 nanopowder. It studies the dielectric properties of γ-Y2Si2O7 as a function of the temperature and frequency. The γ-Y2Si2O7 exhibits low dielectric loss and non-Debye relaxation behaviour from 25 to 1400℃ in the range of 7.3-18 GHz. The mechanism for polarization relaxation of the as-prepared γ-Y2Si2O7 differing from that of SiO 2 is explained. Such particular dielectric properties could potentially make specific attraction for extensive practical applications.
