Ultrawide Band Microwave Absorption Properties of Ultrasound Processed CrO2--Paraffin Wax Composites

概要

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The microwave absorption properties of ultrasound processed CrO2--paraffin wax composites are investigated in the frequency range of 0.1--18 GHz by the coaxial method. By analysis and comparison between ultrasound processed sample and the unprocessed sample, we discovered that the ultrasound treatment will induce a thin insulating Cr2O3 shell over the CrO2 rods to form a core/shell structure that performs excellent in microwave absorption. An optimum reflection loss of $-50.9$ dB was found at 5.2 GHz with a matching thickness of 3.4 mm for 70 wt % CrO2--paraffin wax composite. Moreover, the frequency range of which the reflection loss is less than $-20$ dB spreads from 4.0 to 8.7 GHz with the corresponding absorption thickness ranges from 2.3 to 4.0 mm. The comparison among our result and other reported ones indicates that, in addition to its common applications, the CrO2 after certain process may have potential in microwave absorption. More profoundly, the technique of ultrasound process employed in this report may suggest a new method to induce, according to different needs, crystalline phase transition for a various range of metastable chemicals.
2011-03-25