Lightweight microcellular polyurethane (TPU)/carbon nanotubes (CNTs)/ nickel-coated CNTs (Ni@CNTs)/polymerizable ionic liquid copolymer (PIL) composite foams are prepared by non-solvent induced phase separation (NIPS). CNTs and Ni@CNTs modified by PIL provide more heterogeneous nucleation sites and inhibit the aggregation and combination of microcellular structure. Compared with TPU/CNTs, the TPU/CNTs/PIL and TPU/CNTs/Ni@CNTs/PIL composite foams with smaller microcellular structures have a high electromagnetic interference shielding effectiveness (EMI SE). The evaporate time regulates the microcellular structure, improves the conductive network of composite foams and reduces the microcellular size, which strengthens the multiple reflections of electromagnetic wave. The TPU/10CNTs/10Ni@CNTs/PIL foam exhibits slightly higher SE values (69.9 dB) compared with TPU/20CNTs/PIL foam (53.3 dB). The highest specific EMI SE of TPU/20CNTs/PIL and TPU/10CNTs/10Ni@CNTs/PIL reaches up to 187.2 and 211.5 dB/(g cm−3), respectively. The polarization losses caused by interfacial polarization between TPU substrates and conductive fillers, conduction loss caused by conductive network of fillers and magnetic loss caused by Ni@CNT synergistically attenuate the microwave energy.

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Ingenious microstructure design and appropriate multicomponent strategies are still challenging for advanced electromagnetic interference (EMI) shielding materials with excellent shielding effectiveness (SE) and reliable mechanical properties in harsh environments and low filling levels. In this study, nickel@multiwalled carbon nanotubes/alumina (Ni@ CNTs/Al 2 O 3 ) ceramic composites with segregated structures and electric/magnetic-coupling networks anchored by CNTs and magnetic Ni nanofillers were prepared by hot-press sintering. CNTs/Al 2 O 3 ceramic composites exhibit a percolation threshold of only about 0.32013 vol %, which is lower than those of other reported CNTs/Al 2 O 3 composites with segregated or uniformly dispersed structures. The electrical conductivity and EMI SE of 9CNTs/Al 2 O 3 ceramic composites with 9 vol % (4.76 wt %) CNT content were 103.1 S/m and 33.6 dB, respectively. In addition, EMI SE and toughness were both enhanced by the synergistic effect of Ni nanoparticles and CNTs. In the unit of a segregated structure, a three-dimensional (3D) electric/magnetic-coupling network effectively captures and attenuates electromagnetic wave energy by electrical conduction, dielectric loss, and magnetic loss. On the other hand, the pull-out of CNTs and deflection of cracks distributed along the segregated structures synergistically enhance the fracture toughness of Ni@CNTs/Al 2 O 3 ceramic composites. High-performance 3Ni@5CNTs/Al 2 O 3 ceramic composites with 5 vol % (2.64 wt %) and 3 vol % (0.76 wt %) CNT contents have been achieved, whose EMI SE is 41.8 dB, density is 90.99%, flexural strength is 197.83 ± 18.62 MPa, and fracture toughness is 6.03 ± 0.23 MPa•m 1/2 . This efficient method provides a promising way to fabricate EMI shielding ceramic composites with high mechanical properties.

Polyurethane/multiwalled carbon nanotube (PU/MWCNT) composite foams containing MWCNTs with long length (MWCNT-L and Ni@MWCNT-L) and MWCNTs with short length (MWCNT-S) were prepared using an environmentally friendly water-blown method. The influence of different MWCNTs on the foaming process, morphologies, electrical conductivity, and mechanical and electromagnetic interference (EMI) shielding performances has been studied. The PU foams with MWCNT-L and MWCNT-S hybrid fillers (PU/MWCNT-L-S) display a more uniform cell structure compared with PU/MWCNT-L foams at the same filler loading because the short rod of MWCNT-S with mechanical sensitivity can help MWCNT-L eliminate the physical barrier during the foaming process. Conductance, polarization, and magnetic losses in PU/Ni@-2L-CNT-2L-4S foam can scatter and reflect electromagnetic waves inside the cellular microstructure and eventually transform into heat in the conductive networks. PU/Ni@-2L-CNT-2L-4S exhibited a density of 0.30 g/cm3 and excellent specific EMI shielding efficiency of 102.7 dB/(g/cm3) over the X-band.

Silicone rubber (SR)/polyolefin elastomer (POE) blends containing ionic liquids modified with carbon blacks (CB-IL) and multi-walled carbon nanotubes (CNT-IL) were prepared by melt-blending and hot pressing. SR/POE/CB-IL and SR/POE/CB-CNT-IL composites showed co-continuous structural morphologies. The cation–π interactions between ILs and CNTs were stronger than those between ILs and CBs due to the large length and high surface area of CNTs, which promoted better dispersion of carbon fillers. SR/POE/CB-CNT-IL composites showed higher EMI SE than SR/POE/CB-IL composites containing identical filler contents because the CNTs with larger aspect ratios helped form more electrically-conductive networks.

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Strength and toughness are two vital and contradictory properties, especially in alumina structural ceramics. This mutual exclusion limits the widespread application of advanced alumina ceramics in harsh environments. To deal with this issue, self‐toughening alumina bulk ceramics without any ductile phase and with a unique combination of excellent toughness and reliable strength by combining the foam ceramics with hot‐pressing sintering are prepared. Foam ceramics with honeycomb cellular structures are prepared by particle‐stabilized foaming. Then, the foam ceramics is directly hot pressed sintered, in which the cellular structure is fractured into fragments and completely dense under pressure. Equiaxed grains that constituting the fragments grow anisotropically into plate‐like grains with a large diameter–thickness ratio during hot‐pressing sintering. Plate‐like grains improve the material's fracture toughness by exerting a toughening mechanism similar to that of fibers. The self‐toughening alumina ceramics exhibit a unique combination of high flexural strength (874 ± 31 MPa) and high fracture toughness (6.2 ± 0.1 MPa m1/2). The Vickers hardness also can reach 21 GPa. Herein, a new strategy with relatively simple processing to fabricate high‐performance ceramics based on the widespread ceramic processing techniques are provided.