Fabrication of the Urchin-like Alpha-Fe2O3 and Their Field Emission and Electromagnetic Wave Absorptions

• Main Authors: Hsin-Chih Yu, 余欣熾
• Other Authors: Yuan-Yao Li
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/16521572919087846960

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.