The development of aeroengine with a high thrust-weight ratio poses great challenges for current top-coating thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs) in service. Medium/high-entropy ceramics are highly promising candidate material for advanced TBCs/EBCs owing to their low thermal conductivity, high melting point, high-temperature stability, and calcium–magnesium–alumino–silicate (CMAS) resistance. Most feedstock powder used for medium/high-entropy TBCs/EBCs is prepared via traditional spray drying, which cannot fully exploit the advantages of multicomponent ceramics. The density, sphericity, inner structure, and flowability of feedstock powder affect their melting state during the thermal spraying process, which strongly affects the microstructure and properties of the deposited coatings. Therefore, the deposited coatings exhibit phase segregation, amorphous phases, and microstructure defects owing to unpredictable variations in feedstock powder with random morphologies and structures. Here, the structure and properties of feedstock powder prepared by state-of-the-art granulation technologies and their influences on the deposited coatings were systematically investigated, which can provide guidance for configuration optimization of feedstock powder and the manufacturing accuracy of the deposited coating. This review aims to bridge the gap between cutting-edge ceramics and advanced engineering technologies, thus providing concrete background knowledge and crucial guidelines for designing and developing TBCs/EBCs.

Advanced magnesium alloys with light weight and high strength have been widely used in aerospace industry and hydrogen storage and transportation. However, magnesium alloys have certain safety risks, due to their active chemical properties and low ignition point. These characteristics make them susceptible to potential explosions and deflagrations. Therefore, in response to the limitations of magnesium alloys for current thermal protection technology, we developed an expansive ceramic heat insulation coating that can be applied through integrated spraying at room temperature. The flame retardant performance and mechanism of the coating have been systematically studied. The coating demonstrates an expansion rate up to 300%, effectively reducing the back temperature to below 500 ℃. Additionally, the coating exhibits a mass loss rate ranging from 30% to 40%, maintaining a wreckage strength of 110-190 kPa. When subjected to flame ablation at 1100 ℃, the expansive ceramic heat insulation coating shows exceptional flame retardant and thermal insulation capabilities, without degradation in mechanical strength. The incorporation of expanded carbon layer and expanded graphite introduces a multi-scale pore structure in the coating, which effectively hinders the conduction of heat and oxygen. Furthermore, the dense and robust structure formed owing to the exceptional mechanical properties and self-healing properties of MoAlB (MAB) phase significantly enhances the wreckage strength. Such coating demonstrates outstanding comprehensive flame retardancy even in extreme environments.

Spiral fibers were considered to be an ideal toughening phase of ultra-high torsional release effect. In this work, ZrB₂ (Z)–20 vol% SiC (S) spiral fiber (ZS_sf) with controllable structure was prepared by a combination approach of liquid rope effect and non-solvent-induced phase separation. Dominantly depended on the kinematic viscosity (η), dropping height (H), and flow rate (Q), the geometric parameters of ZS_sf involving filament diameter (d) and coil diameter (D) were followed the relationship of d ≈ 0.516×10⁻³Q^1/2H^−1/4 and D ≈ 0.25×10^–3(Q/H)^1/3, respectively, within the optimized η of 10–15 Pa·s. Three different microstructures of ZS_sf were achieved by adjusting the polymer/solvent/non-solvent system assisted with phase diagram calculation, including dense, hollow, and hierarchical pore structures. The ZrB₂–SiC with 1 wt% ZS_sf composites prepared by hot isostatic pressing (HIP) exhibited a ~30% increase in fracture toughness (K_IC, 4.41 MPa·m^1/2) compared with the ZrB₂–SiC composite, where the microscopic fracture toughness of the ZS_sf was ~80% higher than that of the matrix. The fibers with a ~10 nm in-situ-synthesized graphite phase amongst grain boundaries of ZrB₂ and SiC changed the fracture mode, and promoted the crack deflection and pull-out adjacent the interface of matrix and the fiber.