Synthesis, magnetic and electromagnetic wave absorption properties of porous Fe3O4/Fe/SiO2 core/shell nanorods

Abstract

Porous Fe3O4/Fe/SiO2 core/shell nanorods were fabricated, in which the diameter of the pores was 5–30 nm. The magnetic and electromagnetic properties were investigated. The temperature dependent magnetic measurements showed that these nanorods were ferromagnetic with a Verwey temperature of 129 K. The electromagnetic data indicated that effective complementarities between the dielectric loss and the magnetic loss were realized, suggesting that they have excellent electromagnetic wave absorption properties. Thus the porous core/shell nanorods could be used as a kind of candidate absorber.

Synthesis, characterization and microwave absorption of carbon-coated Cu nanocapsules

“…An optimal RL value of -40.0 dB, corresponding to 99.99 % absorption, is observed at 10.52 GHz for a layer 1.9 mm thickness. It is worth noting that the absorbent with a thickness of 1.1 mm has RL values exceeding -20 dB at high frequencies in broad frequency ranges, which is thinner than the previous reported results [3][4][5][8][9][10][16][17][18][19][20][25][26][27] . As shown in Figure 3b, for all frequencies within the 1-18 GHz range, RL values exceeding -20 dB can be obtained by selecting an appropriate thickness of the absorbent layer between 1.1 and 10.0 mm.…”

“…Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) images were obtained on a JEOL JEM-2010 transmission electron microscope at an acceleration voltage of 200 kV. The paraffin-Cu nanocapsules composite was prepared by uniformly mixing Cu nanocapsules with paraffin, as described in detail elsewhere [2][3][4][5][6][7][8][9][10][16][17][18][19][20] , by homogeneously mixing the nanocapsule with paraffin and pressing them into cylindershaped compacts. Then the compact was cut into toroidal shape with 7.00 mm outer diameter and 3.04 mm inner diameter.…”

“…A broad arena in engineering applications is also attributed to these particles and is attracting an increasing number of scientists.Carbon-coated Cu nanocapsules for sensor applications had been produced using a modified flame spray synthesis unit under highly reducing conditions 13 . Zhang et al reported the synthesis of carboncoated Cu nanocapsules by means of an arc discharge method in a CH 4 atmosphere, which consists of carboncoated Cu nanocapsules and onion-like fullerenes 2 . Since then, significant progress has been made in the syntheses of carbon-coated Cu nanocapsules.…”

“…In recent years, with the development of local electronic devices, microwave communication, and the rising pollution of electromagnetic (EM) interference, materials with EM-wave absorption in a wide frequency range, with strong absorption, low density, and low cost are more and more desirable 3 . The EM-wave absorption properties of magnetic material-based nanocomposites and heterostructured nanocomposites have been intensely investigated, because of the synergetic effect between magnetic and dielectric losses [4][5][6][7] . Among the candidates for EM-wave absorbers, magnetic nanocapsules with carbon as shells have attracted intensive interest on account of the following facts: (1) the large saturation magnetization and high Snoek limit, (2) the suppression of the eddy current phenomenon, and (3) being composites with different kinds of EM-absorber materials 8 .…”

Controlled synthesis and shape-dependent electromagnetic wave absorption characteristics of porous Fe3O4 sub-micro particles

“…Recently, Pengand et al [36,37] have developed an oxidation route to fabricate hollow Fe 3 O 4 nanoparticles. However, Fe 3 O 4 based materials have been seldom reported for the attenuation of EM waves [7,10,15]. In general, for biomedical applications, such as magnetic labeling of cells, the sizes of Fe 3 O 4 materials are expected to be below 20 nm because they are superparamagnetic and are very light in magnetic resonance imaging [24].…”