Comparative study of MoSi2-borosilicate glass coatings on fibrous ceramics prepared by in-situ reaction method and two-step method

Two infrared radiating coatings with borosilicate glass as binder and MoSi2 as emittance agent were prepared on mullite fibrous ceramics by an in-situ reaction method and a two-step method, respectively. The in-situ reaction coating was prepared from Si, B2O3 and MoSi2, in which borosilicate glass was obtained through the in-situ reaction of Si, B2O3 and O2. By contrast, the two-step method included the preparation of borosilicate glass powders by a melt-quench technique and then coating preparation with MoSi2 and the glass powders. The structure, phase composition, thermal endurance, infrared radiation property and impact resistance of the two coatings were compared. The results showed that the in-situ reaction coating was denser, and much less MoSi2 therein was oxidized during sintering (11.3%) than that in the two-step coating (67.0%), resulted from the oxygen diffusion barrier formed by molten B2O3 at approximately 450 °C. The in-situ reaction coating possessed better thermal endurance due to its higher MoSi2 content and denser structure. In addition, the in-situ reaction coating had higher emissivity (0.787) and better impact resistance (0.051 J) than the two-step coating (0.706, 0.038 J).