Crystalline-amorphous Ni3P@Nix(POy)z core–shell heterostructures as corrosion-resistant and high-efficiency microwave absorbents

Highlights: • Crystalline-amorphous Ni₃P@Ni_x(PO_y)_z core–shell heterostructures have been fabricated via thermal phosphating strategy. • Ni₃P@Ni_x(PO_y)_z achieves superior microwave absorption performance at the ultrathin thickness of 1.3 mm. • The crystalline Ni₃P/amorphous Ni_x(PO_y)_z interface effectively enhances the interfacial polarization ability. • Electrochemical analysis was developed to evaluate corrosion properties. • The composite exhibits excellent corrosion resistance in acid, alkali, and salt environments. The search for high-efficiency and anti-corrosive microwave absorption (MA) materials plays a paramount role in improving the environmental adaptability and survivability of military targets in the harsh chemical conditions. However, it still faces huge challenges and lacks systematic research. Herein, a well-designed heterostructure composed of crystalline Ni₃P core and amorphous Ni_x(PO_y)_z shell was successfully fabricated through a facile annealing and thermal phosphating strategy. Electrochemical analysis demonstrated that the Ni₃P@Ni_x(PO_y)_z heterostructures delivered strong corrosion resistance in acid, alkaline, and salt environment owing to the presence of surface amorphous Ni_x(PO_y)_z layer. Meanwhile, crystalline Ni₃P/amorphous Ni_x(PO_y)_z interface could trigger intensive interfacial polarization relaxation to strengthen microwave attenuation. Furthermore, abundant lattice defects, polar Ni-P bond, decreased band gap and intrinsic magnetism of Ni₃P crystal endowed the Ni₃P@Ni_x(PO_y)_z heterostructures strong reflection loss (−43.1 dB), moderate absorption bandwidth (3.0 GHz) and ultra-thin thickness (1.3 mm). This work may provide an insight into the evaluation and development of corrosion-resistant microwave absorbents.