High Emissivity MoSi2-SiC-Al2O3 Coating on Rigid Insulation Tiles with Enhanced Thermal Protection Performance

Abstract

High emissivity coatings with sol as the binder have the advantages of room temperature curing, good thermal shock resistance, and high emissivity; however, only silica sol has been used in the current systems. In this study, aluminum sol was used as the binder for the first time, and MoSi2 and SiC were used as emittance agents to prepare a high emissivity MoSi2-SiC-Al2O3 coating on mullite insulation tiles. The evolution of structure and composition at 1000–1400 °C, the spectral emissivity from 200 nm to 25 μm, and the insulation performance were studied. Compared with the coating with silica sol as a binder, the MoSi2-SiC-Al2O3 coating has better structural uniformity and greater surface roughness and can generate mullite whiskers at lower temperatures. The total emissivity is 0.922 and 0.897, respectively, at the wavelength range of 200–2500 nm and 2.5–25 μm, and the superior emissivity at a low wavelength (<10 μm) is related to a higher surface roughness and reduced feature absorption. The emissivity reduction related to the oxidation of emittance agents at a high temperature (−10.2%) is smaller than that of the silica-sol-bonded coating (−18.6%). The cold surface temperature of the coated substrate is 215 °C lower than the bare substrate, suggesting excellent thermal insulation performance of the coating.

Preparation of Asymmetric Al2O3-SiO2 Janus Nanoparticles in Aqueous Phase and Its Interfacial Property

“…Therefore, the equivalent rod-like model proposed by Briard et al [38] can be applied to the particle size measurement of asymmetric Al 2 O 3 -SiO 2 Janus nanoparticles. The equivalent diameter can be calculated using Equation (4).…”

“…In recent literature, various methods such as the sol–gel method, hydrothermal method, co-precipitation method, and mechanical mixing method have been employed to combine Al 2 O 3 and SiO 2 into composite materials to overcome the limitations of their individual use. This amalgamation aims to enhance several key properties including mechanical strength, thermal stability, chemical resistance, electrical properties, and surface properties [ 1 , 2 , 3 , 4 ], but the Al/Si components in these Al 2 O 3 -SiO 2 composites are not separated. Therefore, an important research question involves developing a method to obtain Al 2 O 3 -SiO 2 nanoparticles with separated Al and Si components.…”