Synthesis of Zn-SBA-15 as a new pigment for spacecraft white thermal control coatings

Thermal control coatings (TCCs) help to maintain the thermal equilibrium of spacecraft at a level acceptable for vital components, usually around 20°C. This is done by either minimizing the solar absorbance or maximizing the thermal emittance. In the present study, with the aim of introducing new TCCs with enhanced optical properties, two TCCs were prepared by incorporating presynthesized pigments including SBA-15 (mesoporous material) and Zn-SBA-15 into potassium silicate binder. After application and drying, the TCC containing SBA-15 showed very low hiding power, so optical tests for this TCC were not done. The results of solar absorptance measurements revealed that the TCC containing Zn-SBA-15 was a proper reflector in the ultraviolet (UV) radiation range, making it much less susceptible to solar radiation in comparison with conventional TCCs. Also, thermal emittance tests demonstrated that the surface of this TCC had greater ability to emit heat. Furthermore, lower pigment-to-binder ratio and dry film thickness were attainable with this TCC, leading to weight reduction, improvement of mechanical properties, and lower porosity.