| Summary: | 碩士 === 國立中正大學 === 化學工程所 === 98 === The novel urchin-like α-Fe2O3 materials was grown by a simple and one–step thermal oxidation of Fe powders at 300 oC in air atmosphere. The urchin-like α-Fe2O3 materials was consisted of α-Fe2O3 nanoflakes with the single crystalline and aligned perpendicular to the Fe powder. As a result of the TGA/DTA analysis, the radial growth of the nanoflakes was attributed to the thermal oxidation rate. We proposed a growth mechanism for the thermal growth of the urchin-like α-Fe2O3.
In regard to the applications, we demonstrated the good field emission (FE) performance of the urchin-like α-Fe2O3 by the systemetic experiments and simulation analysis. The low turn-on field of 3.1 V/μm, high Emission Spot Density (ESD) of large area (2×2cm) and stable FE performance for 22 h test of the urchin-like α-Fe2O3 nanostructure can be achieved.
The electromagnetic (EM) wave absorption properties of 2-mm-thick urchin-like α-Fe2O3-epoxy composites were studied in the range of 2-40 GHz using a free-space antenna-based system. The 60 wt % urchin-like α-Fe2O3 composites exhibited dual-frequency EM wave absorptions of -26.2 and -21.0 dB at 9.7 and 25.2 GHz, respectively. The minimum reflection loss of -33.8 dB was achieved at 7.8 GHz for the composites containing 70 wt% urchin-like α-Fe2O3. The good EM wave absorption performance would be attributed to the network and special urchin-like geometric structure of urchin-like α-Fe2O3 materials.
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