A 3D α-Fe₂O₃nanoflake urchin-like structure for electromagnetic wave absorption

Abstract

An α-Fe(2)O(3) nanoflake urchin-like structure is formed via the thermal oxidation of micrometre-sized iron spheres in air at temperatures of 300-400 °C. The material consists of α-Fe(2)O(3) nanoflakes grown perpendicularly to the sphere surface, a layer of a mixture of α-Fe(2)O(3) and Fe(3)O(4) as the oxidation shell, and an iron core. The ranges of the tip diameters of the nanoflakes are 20-30 nm (300 °C), 30-50 nm (350 °C), and 60-100 nm (400 °C). A composite consisting of the α-Fe(2)O(3) nanoflake urchin-like structure and an epoxy resin exhibits an excellent electromagnetic (EM) wave absorption ability. A small tip diameter (20-30 nm) and a high density (3 × 10(13) nanoflakes m(-2)) lead to a good network structure and good EM wave absorption. A minimum reflection loss (RL) of -33.8 dB (99.93% of EM wave absorption) at 7.8 GHz can be achieved using a 70 wt% urchin-like material as the filler in the resin matrix. In addition, a composite containing 60 wt% unchin-like material exhibits dual-frequency EM wave absorption. The peaks of the minimum RL values are located at 9.7 GHz (-26.2 dB) and 25.2 GHz (-21.0 dB). The unique morphology of the α-Fe(2)O(3) nanoflake urchin-like material is believed to be a key factor in the enhancement of the EM wave absorption.

Formation of urchin-like CuO structure through thermal oxidation and its field-emission lighting application

“…In addition, thermal decomposition [47], solid stabilized emulsion [48], and a facile reflux method [49] have been applied in forming urchin-like CuO structures. However, according to our literature review, no study has examined the formation of urchin-like CuO by using thermal oxidation, although an urchin-like Fe 2 O 3 microstructure was reported in our previous study [50,51].…”

Facile Size‐Controllable Synthesis of Colorful Quasi‐Cubic α‐Fe2O3 Materials from Nanoscale to Microscale and Their Properties Related to the Size Effect

“…[11,28] To correlate the dielectric constant with the nanosize of synthesized hematite nanocubes, we selected three typical samples with different sizes (samples 1, 3, and 5). [11,28] To correlate the dielectric constant with the nanosize of synthesized hematite nanocubes, we selected three typical samples with different sizes (samples 1, 3, and 5).…”

“…As we know, iron oxides were used as traditional wave absorption materials, and are still considered to be an ideal wave absorption material with the development of nanotechnology. [11,28] To correlate the dielectric constant with the nanosize of synthesized hematite nanocubes, we selected three typical samples with different sizes (samples 1, 3, and 5). The frequency dependency of the selected samples in paraffin wax composites with a loading of 50 wt % of hematite nanomaterials was measured and the results are shown in Figure 12 a,b.…”

“…[7] On the other hand, the control of size and shape of nanocrystals can be achieved by appropriate adjustment of the synthesis parameters, such as solvent, surfactant, temperature, reaction time, and so forth. [11] Considering the strong connection between properties and nanostructure, a certain amount of effort has been devoted to the controllable synthesis of a-Fe 2 O 3 nanoparticles. Therefore, a facile and environmentally friendly synthesis of nanomaterials is highly encouraged.…”

“…These advantages make hematite relevant in many scientific and technical applications, such as materials for lithium storage capability, [9] lithium-ion batteries, [10] and electromagnetic wave absorption. [11] Considering the strong connection between properties and nanostructure, a certain amount of effort has been devoted to the controllable synthesis of a-Fe 2 O 3 nanoparticles. Various morphologies were synthesized successfully, including nanoflasks, [12] nanowires, [13] nanorods, [14] nanobelts, [15] and hollow nanospheres.…”