Lightweight porous materials for electromagnetic interference (EMI) shielding applications are reviewed. EMI shielding refers to the capability of a material to protect from electromagnetic fields (EMFs) generated by electronic devices. Traditionally conducting metals are used in EMI shielding applications, which are slowly being replaced by conducting polymer based shields. This review is narrowly focused on understanding the approaches related to porous high EMI shielding composite materials that have very low density values. While metallic fillers can increase the EMI shielding capabilities of polymers, they also increase the weight, which can be offset by inducing the porosity in the matrix. Porosity is found to be effective in providing higher shielding effectiveness at low filler volume fraction due to concentrating the filler in the solid polymers. However, use of gas porosity results in composites with low mechanical properties. This problem can be alleviated to some extent by reinforcing polymer foams with lightweight conductivefillers such as carbon nanofibers (CNFs), carbon nanotubes (CNTs) and graphene. But the properties of pores such aspore size and distribution cannot be effectively controlled in such cases. Syntactic foams containing hollow particle fillers seem to be the best combination of EMI shielding capabilities and mechanical properties. These composites can be either filled with a second phase conducting filler, or hollow particles can be coated with a conducting layer, or hollow particles made of conducting materials can be used as fillers. The hollow particle wall thickness and volume fractions can be optimized to obtain the desired combination of properties in syntactic foams to enable their multifunctional applications.

A review of porous lightweight composite materials for electromagnetic interference shielding

Tensile and wear behaviour of in situ Al-7Si/TiB2 particulate composites

Fabrication and characterisation of Al–7Si–0.35Mg/fly ash metal matrix composites processed by different stir casting routes

Dynamic compressive behaviour of cellular materials: A review of phenomenon, mechanism and modelling

Mechanical and thermal characteristics of high density polyethylene-fly ash Cenospheres composites

The dense and homogeneous 30 vol.%TiB2P/Al composite was successfully fabricated by squeeze casting technology, and its friction and wear properties were investigated. Results show that in dry sliding wear mode, friction coefficient of TiB2P/Al composite at the steady stage was only about 0.16–0.17, while that of SiCP/Al composite fabricated by the same method was 0.7. In addition, wear volume of TiB2P/Al composite was less than that of SiCP/Al composite. The TiB2P/Al composites exhibited higher wear resistance. No obvious characteristics of adhesion or abrasion wear were observed on worn surfaces of TiB2P/Al composites. All of these properties might be attributed to the oxidation of TiB2 and the formation of boric acid film on the sliding surfaces.

Friction and wear properties of TiB2P/Al composite

Fly-ash cenosphere particles were used as mixture in aluminum matrix composite by squeeze casting method [1]. The electromagnetic interfering shielding effectiveness (EMISE) was investigated in the frequency range from 0.03 MHz to 1.5 GHz. It showed the SE value of Al2024/cenospheres composite (ACC) is higher than that of aluminum alloy, and comparative to traditional material 1J50. Unlike 1J50, the mechanism of EMI shielding for ACC is reflection and multiple reflections. Analyzed by XRD and SEM, chemical reactions may occur between the matrix and cenosphere particles during the casting procedure, but it affects the shielding effectiveness little.

Electromagnetic interfering shielding of aluminum alloy–cenospheres composite

Effects of thermal cycling on mechanical properties of AlNp/Al composite

A structure factor k was used to investigate the relations between aspect ratio of ligaments and yield strength of open-cell Fe–Ni foams. The results indicated yield strength of Fe–Ni open-cell foam increased with the decreasing aspect ratio of ligaments, and varying cross-section of ligaments had distinct effect on compressive properties of Fe–Ni open-cell foams. The yield strength predicted by the uniform cross-section ligament model ( k  = 1) agreed well with experimental values within the relative density of 2.5–5%, while the varying cross-section of ligaments with k  = 0.85 was suitable for the foams with relative density lower than 2.5%.

Zuoyong Dou

Papers

Friction and wear properties of TiB2P/Al composite

Electromagnetic interfering shielding of aluminum alloy–cenospheres composite

Effects of thermal cycling on mechanical properties of AlNp/Al composite

Compressive properties of open-cell Fe–Ni foams