Microstructure and metal–dielectric transition behaviour in a percolative Al2O3–Fe composite via selective reduction

Abstract

Dou, S. (2013). Microstructure and metal-dielectric transition behaviour in a percolative Al2O3-Fe composite via selective reduction. RSC Advances, 3 (48), 26110-26115. Microstructure and metal-dielectric transition behaviour in a percolative Al2O3-Fe composite via selective reduction AbstractThe electromagnetic (EM) medium plays a key role in many areas, such as communications, stealth technology, etc. Different EM properties are required for different applications. In this paper, we have obtained tunable EM properties in an Al2O3-Fe composite via selective reduction. By adjusting the content of one functional component, the composite shows totally different EM properties, in accordance with the predictions of effective medium theory. Hybrid EM behaviour is obtained near the percolation threshold, which has a close relationship with its microstructure.

Negative permittivity behavior in the carbon/silicon nitride composites prepared by impregnation-carbonization approach

“…can equate with series of micro-capacitors [1]. The more interface areas resulting from the increase of carbon content, lead to the formation of more amounts of equivalent micro-capacitors in the composites, hence higher permittivity appears.…”

“…And the Si 3 N 4 ceramic composites containing pyrolytic carbon [4] or carbon fiber [5], exhibit excellent electromagnetic absorbing properties because of the good matching between permittivity and permeability. Oppositely, if permittivity and permeability of material aren't comparable, electromagnetic waves will be reflected back at the material surface, which is the primary mechanism of electromagnetic shielding [1,6]. Hence tunable permittivity and permeability of materials are desired to satisfy requirements of different applications.…”

“…Materials with different electromagnetic characteristic have been applied in various fields [1][2][3]. For example, porous Si 3 N 4 ceramic with low permittivity has been employed in missile radome due to their good electromagnetic waves transparency [2].…”

Ni/Al2O3/epoxy high-k composites with ultralow nickel content towards high-performance dielectric applications

“…Furthermore, the addition of Al(NO 3 ) 3 has no inuence on the transformation of Ni(NO 3 ) 2 into Ni, and nickel oxides were totally reduced into nickel during the reduction process. As we know, high temperature (>1000 C) may result in the reactions between nickel and alumina, [34][35][36] leading to the appearance of unexpected phases in the composites. In the present work, the Ni/Al 2 O 3 composites were prepared via a low temperature impregnation-reduction process.…”

Preparation and Electromagnetic Properties of an Electromagnetic Wave Absorber

“…Adopting microwave absorbing materials to convert the electromagnetic waves energy into heat is one of the most effective methods for eliminating the above-mentioned problems. Moreover, radar absorbing materials (RAM) play a significant role in military stealth technologies [3,4]. To satisfy the needs of military and commercial applications, therefore, the microwave absorbing materials have been extensively investigated [5][6][7][8].…”