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Double-layer microwave absorber based on nanocrystalline CoFe2O4 and CoFe2O4/PANI multi-core/shell composites

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24 feb 2017

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XRD patterns of samples S1, S2, S3 and S4.
XRD patterns of samples S1, S2, S3 and S4.
TEM (a, b, d, f) and SEM (c, e) images of the sample S1 (a), S2 (b), S3 (c, d) and S4 (e, f).
TEM (a, b, d, f) and SEM (c, e) images of the sample S1 (a), S2 (b), S3 (c, d) and S4 (e, f).
Schematic illustration of the synthesis process of CoFe2O4/PANI multi-core/shell composites.
Schematic illustration of the synthesis process of CoFe2O4/PANI multi-core/shell composites.
Hysteresis loops at room temperature for sample S2, S3 and S4.
Hysteresis loops at room temperature for sample S2, S3 and S4.
Variation of complex permittivity and permeability of sample S2, S3 and S4 with frequency.
Variation of complex permittivity and permeability of sample S2, S3 and S4 with frequency.
Sketch map of incidence of electromagnetic wave in multi-layer absorber.
Sketch map of incidence of electromagnetic wave in multi-layer absorber.
Absorption curves of the layers with thickness d = 2.0 mm (a), 2.5 mm (b), and variation of dielectric loss tangent (c) and magnetic loss tangent (d) of sample S2, S3 and S4 with frequency.
Absorption curves of the layers with thickness d = 2.0 mm (a), 2.5 mm (b), and variation of dielectric loss tangent (c) and magnetic loss tangent (d) of sample S2, S3 and S4 with frequency.
Absorption curves of the double-layer absorbers with a total layer thickness d = 2.0 mm (a), 2.5 mm (b).
Absorption curves of the double-layer absorbers with a total layer thickness d = 2.0 mm (a), 2.5 mm (b).

Microwave absorption properties of single layer (S2-S4) and double-layer (S5-S11) absorbers with total thickness of 2_0 mm and 2_5 mm_

SampleMaterialThickness [mm]Total thickness [mm]Min. R [dB]R peak [GHz]Bandwidth R < –10 dB [GHz]
S2Calcined ferrite2.02.0–3.211.7
2.52.5–4.811.8
S3Ferrite/PANI composite2.02.0–17.417.014.9 – 18.0 (3.1)
2.52.5–16.612.111.1 – 14.5 (3.4)
S4Ferrite/PANI composite2.02.0–19.016.214.1 – 18.0 (3.9)
2.52.5–23.613.110.8 – 14.5 (3.7)
S5Layer 1: S20.52.0–28.816.213.8 – 18.0 (4.2)
Layer 2: S41.5
S6Layer 1: S21.02.0–22.316.214.2 – 18.0 (3.8)
Layer 2: S41.0
S7Layer 1: S21.52.0–11.617.315.9 – 18.0 (2.1)
Layer 2: S40.5
S8Layer 1: S20.52.5–28.812.810.3 – 15.8 (5.5)
Layer 2: S42.0
S9Layer 1: S21.02.5–31.112.810.3 – 15.8 (5.5)
Layer 2: S41.5
S10Layer 1: S21.52.5–22.413.211.1 – 15.8 (4.7)
Layer 2: S41.0
S11Layer 1: S22.02.5–11.211.711.5 – 12.0 (0.5)
Layer 2: S40.5