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In this work, the engineered polyaniline (PANI)/epoxy composites reinforced with PANI-M (physical mixture of PANI spheres and fibers) exhibit significantly enhanced electromagnetic wave absorption performance and mechanical property. Due to the synergistic effect of PANI fillers with different geometries, the reflection loss of 10.0 wt% PANI-M/epoxy could reach − 36.8 dB at 17.7 GHz. Meanwhile, the mechanical properties (including tensile strength, toughness, and flexural strength) of PANI/epoxy were systematically studied. Compared with pure epoxy, the tensile strength of epoxy with 2.0 wt% PANI-M was improved to 86.2 MPa. Moreover, the PANI spheres (PANI-S) and PANI fibers (PANI-F) were prepared by the chemical oxidation polymerization method and interface polymerization method, respectively. The characterizations including scanning electron microscope, Fourier transform infrared spectra, and X-ray diffraction were applied to analyze the morphology and chemical and crystal structures of PANI filler. This work could provide the guideline for the preparation of advanced engineered epoxy nanocomposites for electromagnetic wave pollution treatment. Graphical abstract

Al matrix composite, reinforced with the in situ synthesized 3C–SiC, MgAl2O4, and MgO grains, was produced via the casting process using phenolic resin pyrolysis products in flash mode. The contents and microstructure of the composites’ fracture characteristics were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties were tested by universal testing machine. Owing to the strong propulsion formed in turbulent flow in the pyrolysis process, nano-ceramic grains were formed in the resin pyrolysis process and simultaneously were homogeneously scattered in the alloy matrix. Thermodynamic calculation supported that the gas products, as carbon and oxygen sources, had a different chemical activity on in situ growth. In addition, ceramic (3C–SiC, MgAl2O4, and MgO) grains have discrepant contents. Resin pyrolysis in the molten alloy decreased oxide slag but increased pores in the alloy matrix. Tensile strength (142.6 ± 3.5 MPa) had no change due to the cooperative action of increased pores and fine grains; the bending and compression strength was increasing under increased contents of ceramic grains; the maximum bending strength was 378.2 MPa in 1.5% resin-added samples; and the maximum compression strength was 299.4 MPa. Lath-shaped Si was the primary effect factor of mechanical properties. The failure mechanism was controlled by transcrystalline rupture mechanism. We explain that the effects of the ceramic grains formed in the hot process at the condition of the resin exist in mold or other accessory materials. Meanwhile, a novel ceramic-reinforced Al matrix was provided. The organic gas was an excellent source of carbon, nitrogen, and oxygen to in situ ceramic grains in Al alloy.