Temperature-responsive self-healing coating with excellent resistances to oxidation and thermal shock from core-shell B2O3@SiO2 microcapsule

Abstract

Hierarchical design was applied to core-shell B2O3@SiO2 microcapsule, followed by fabrication of the SiC-B2O3@SiO2 coating by a combination of entrapping and hot dip processes. Among the C/C-SiC-BS2, C/C-SiC-BS4 and C/C-SiC-BS6 samples, the C/C-SiC-BS4 composite exhibits long-term antioxidant capabilities, with only a 2.30% mass loss as oxidized at 973 K for 1500 h, and 2.35% at 1073 K for 2600 h. Furthermore, after enduring 150 thermal shocks between 293 K and 1173 K, its mass loss is only 2.07%. The XRD patterns detected the existence of B2O3 and SiO2 phases, and the SEM and EDS analysis proved the borosilicate glass, indicating the excellent performances came from the synergistic self-healing effects of the B2O3, SiO2 phases, and borosilicate glass. Thus, within the temperature ranges from 873 K to 1273 K, the oxygen penetration shifts from osmotic state to defect diffusion in coating. This research emphasizes the significance of hierarchical designs for core-shell sacrificial phase in silicate coatings, thereby enhancing their long-term applicability.