Permeability and electromagnetic-interference characteristics of Fe–Si–Al alloy flakes–polymer composite

Abstract

A magnetic sheet made of Fe–Si–Al flakes was found to have excellent permeability and electromagnetic-interferences characteristics in a quasimicrowave band. The flakes prepared by attrition were embedded in a polymer with their planes lying parallel to the sheet plane. This sheet exhibits a peculiar dual dispersion in permeability. The Curie temperature of the flakes increases with increasing specific surface area of the flakes. This suggests the composition of the flakes changes to excess Fe by oxidation of Si and Al. This deviation from the Sendust composition brings an increase of a magnetoelastic effect and the dual frequency dispersion seems to be associated with stress caused by attrition. On the basis of these results, flakes with more desirable permeability characteristics were produced from raw powder with less Fe content. Consequently, we could fabricate a magnetic composite that possesses superior noise suppressing effect in a quasi-microwave band.

Nanoparticle-assisted microwave absorption by single-wall carbon nanotubes

“…Examples of such structures include Ba hexaferrite nanocrystals 10 and micron-size ferrite powders 11,12 in a rubber matrix, Fe-Si-Al alloy flakespolymer composites, 13 and CaCoTi ferrite-epoxy composites. 14 Microwave absorption in these materials is thought to be mainly due to magnetic resonance and interfacial electric polarization.…”

Magnetic Properties and Microwave Absorption Properties of Polymer-Protected Cobalt Nanoparticles

“…Magnetic nanoparticles were prepared by the thermal decomposition of dicobalt octacarbonyl: Co 2 (CO) 8 . Poly(Nvinyl-2-pyrrolidone) (PVP), which molecular weight was 55000, was used to disperse magnetic nanoparticles and to control their particle size.…”

“…Co 2 (CO) 8 and PVP (5.557 g = 0.05 mol) were dissolved in ethylene glycol (200 ml), and then heated to • C (198…”

“…Co 2 (CO) 8 and PVP were mixed as Co/PVP (mole/unit mol) = 0.05, 0.10 and 0.50. A color change of the solution from light red brown to black occurred during this process.…”

“…Some materials, such as ferrites with spinel, 2, 3) M 4,5) and W-type 6) structure or metallic magnetic materials, have been applied to microwave absorbers. Especially, resin composites of metallic magnetic materials [7][8][9] have been paid much attention as microwave absorbers in the frequency range of 1-5 GHz. Because they have large values of saturation magnetization and show high relative complex permeability in this frequency range, which leads thinner thickness of absorbers.…”