Full
DING Donghai (1983-), male, Associate Professor, Postdoctor. E-mail: dingdongxauat@163.com
Outline
In order to evaluate the absorbing properties of B4C ceramic absorber, B4C powder was fabricated via combustion synthesis with carbon black and boron oxide as raw materials, and Mg as a reductant. The microstructure of the products was characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The samples for dielectric test were prepared with B4C powder as an absorber and paraffin as a binder, respectively. The complex permittivity of samples containing different amount of B4C absorber was tested by a rectangular waveguide method at X band (8.2 GHz-12.4 GHz), and the reflection loss values were calculated based on the transmission line theory. The results show that the impurities such as MgO and Mg3B2O6 can be removed by pickling. The grain size of the product is 0.4-1.0 μm with an oblique hexagonal structure. The real and imaginary parts of the complex permittivity increase with the increase of the content of B4C powder. When the content is 50% (mass fraction), the real and imaginary parts are 19.33 and 10.40, respectively. The calculated results show that the optimum electromagnetic wave absorption performance can be obtained at B4C powder content of 33%. The minimum reflection loss value is -21.1 dB when the thickness is 2.3 mm, and the effective bandwidth reaches 2.95 GHz. It is indicated that B4C powder could be a promising candidate as a high-temperature microwave absorber.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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