Electromagnetic Properties of Carbon Nanotube/BaFe<sub>12−x</sub>Ga<sub>x</sub>O<sub>19</sub>/Epoxy Composites with Random and Oriented Filler Distributions
The microwave properties of epoxy composites filled with 30 wt.% of BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub> (0.1 ≤ <i>x</i> ≤ 1.2) and with 1 wt.% of multi-walled carbon nanotubes (CNTs) were investigated i...
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| Autores principales: | , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/99e23e8a44454ad5af4b136eb9714bda |
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| Sumario: | The microwave properties of epoxy composites filled with 30 wt.% of BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub> (0.1 ≤ <i>x</i> ≤ 1.2) and with 1 wt.% of multi-walled carbon nanotubes (CNTs) were investigated in the frequency range 36–55 GHz. A sufficient increase in the microwave shielding efficiency was found for ternary 1 wt.%CNT/30 wt.% BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub>/epoxy composites compared with binary 1% CNT/epoxy and 30 wt.% BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub>/epoxy due to the complementary contributions of dielectric and magnetic losses. Thus, the addition of only 1 wt.% of CNTs along with 30 wt.% of barium hexaferrite into epoxy resin increased the frequency range where electromagnetic radiation is intensely attenuated. A correlation between the cation Ga<sup>3+</sup> concentration in the BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub> filler and amplitude–frequency characteristics of the natural ferromagnetic resonance (NFMR) in 1 wt.%CNT/30 wt.% BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub>/epoxy composites was determined. Higher values of the resonance frequency <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mrow><mi>r</mi><mi>e</mi><mi>s</mi></mrow></msub></mrow></semantics></math></inline-formula> (51.8–52.4 GHz) and weaker dependence of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mrow><mi>r</mi><mi>e</mi><mi>s</mi></mrow></msub></mrow></semantics></math></inline-formula> on the Ga<sup>3+</sup> concentration were observed compared with pressed polycrystalline BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub> (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mrow><mi>r</mi><mi>e</mi><mi>s</mi></mrow></msub></mrow></semantics></math></inline-formula> = 49.6–50.4 GHz). An increase in the NFMR amplitude on the applied magnetic field for both random and aligned 1 wt.% CNT/30 wt.% BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub>/epoxy composites was found. The frequency of NFMR was approximately constant in the range of the applied magnetic field, H = 0–5 kOe, for the random 1 wt.% CNT/30 wt.% BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub>/epoxy composite, and it slightly increased for the aligned 1 wt.% CNT/30 wt.% BaFe<sub>12–<i>x</i></sub>Ga<i><sub>x</sub></i>O<sub>19</sub>/epoxy composite. |
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