Failure is a main headache for thermal barrier coatings (TBCs). Typically, whether failure occurs depends on a competition between cracking driving force (negatively related to strain tolerance) and cracking resistance. However, it is difficult to simultaneously enhance these two properties in conventional mono-structures, since they often need totally opposite structures. In this work, a novel structure was designed to co-enhance strain tolerance and cracking resistance in thick TBCs. The novel structure appears to have tri-modal features. The macro-columnar structure was tailored to enhance the strain tolerance, the meso-gradient structure in individual columns was porosity-distributed from bottom to top to enhance the cracking resistance, and the micro-lamellar structure was deposited to further tolerate strain and to prevent heat flux. Firstly, the tri-modal-featured structure was tailored in 2000 μm thick TBCs. Thermal cyclic test showed that the life span was nearly 4 times and 9 times that of the conventional one-way designs of columnar and gradient TBCs, respectively. Secondly, a finite element model was developed to investigate the mechanism responsible for the long life span. Co-operation in lowering driving force and increasing cracking resistance significantly retards the cracking behavior in thick coatings. Finally, dominant factors for the tri-featured structures were discussed and optimized to further extend the life span of thick TBCs. Overall, the matching design between strain tolerance and cracking resistance provides a fundamental way for durable protection in thick TBCs.

To meet the demands for high thrust-to-weight ratios and reusability, rocket engines require thermal barrier coatings (TBCs) capable of withstand 1800 °C for prolonged durations. This study presents a novel quaternary rare earth-stabilized cubic zirconia (RSZ) material and systematically optimizes double-ceramic-layer (DCL) RSZ/yttria-stabilized zirconia (YSZ) coating architectures. The optimized structure—with a total thickness of 350 μm and a YSZ-to-RSZ thickness ratio of 1 : 1—exhibits outstanding thermal shock resistance at 1800 °C, achieving a lifespan of 15 cycles and thereby satisfying the performance benchmark for rocket engines under such extreme conditions. In this optimized configuration, failure proceeds through sintering-induced localized spallation, a comparatively gradual process that contributes to prolonged coating durability. These findings highlight the strong potential of RSZ/YSZ coatings for application in next-generation rocket engines operating at 1800 °C.

The lifetime of Si bond coats in environmental barrier coatings (EBCs) is constrained by phase transition-induced cracking at the SiO₂ scale. In this study, reactive self-consumption and lattice solid solution strategies are employed to address this limitation via Si–Yb₄Al₂O₉ composite coatings. The formation of an Yb₂Si₂O₇ layer, through the consumption of the thermally grown SiO₂ scale and Yb₄Al₂O₉, reduces the SiO₂ thickness and significantly lowers the cracking driving force. Furthermore, the incorporation of Al into the SiO₂ lattice stabilizes high-temperature β-SiO₂, preventing phase transition-induced cracking. The proposed coating demonstrated an oxidation lifetime 20 times longer than that of pure Si at 1370 °C, highlighting its potential as an EBC bond coating.

Double-layered thermal barrier coatings (DL-TBCs) have been developed to meet multiple service requirements, such as low thermal conductivity, high thermal stability, and high fracture toughness. Conventional DL-TBCs are often designed on the basis of equal total thickness to have long lifespans, which may weaken the thermal insulation. The reason is that the single-scale designed structure often has opposite effects on the thermal and mechanical properties. To enhance both the thermal insulation and lifespan, this work designed durable DL-TBCs at multiple scales under equivalent thermal insulation. The macroscopic thickness ratio of the top layer to the bottom layer was tailored to optimize the total and single thicknesses, and the microscopic pore size in the top layer was tailored to resist sintering. Six groups of samples with different thickness ratios were prepared. The thermal cycling test revealed that the lifespan of DL-TBCs first increases but then decreases with increasing thickness ratio. The optimized thickness ratio is 2:3 for DL-TBCs, which have the largest lifespan among the six groups. The cross-sectional morphologies revealed that the failure mode changed from the spallation of the top layer to the delamination of the total double layers. The long lifespan of the optimized DL-TBCs stems from the cotailored thickness ratio and porous structure in the top layer to lower the total cracking driving force.