Thermal diffusivity investigation of MoSi₂/Mo/MoSi₂ layered structure dedicated to green-powered rocket engine systems

The article presents the results of investigations into selected thermophysical properties, including the thermal diffusivity of the MoSi₂/Mo/MoSi₂ system, as a parameter characterising the ability to provide thermal insulation for structural elements dedicated to new technological solutions in rocket engines. The thermal conductivity value was calculated in the 25 to 1500 °C temperature range based on the obtained thermal diffusivity results. Systems of this type are used in newly designed combustion chambers of rocket engines using ecological, high-performance hypergolic propellants of a new type as fuel. The scope of the tests included the production of layered systems using the pack cementation method on the molybdenum surface and measurements of thermal diffusivity in two perpendicular directions, i.e. the in-plane method (along the surface of the silicide layer) and the laser-flash method, analysing thermal diffusivity in the direction perpendicular to the MoSi₂ top-surface. The measurements were performed using a final correction based on the silicide layer topology (roughness) analyses and an approximation method for thermal diffusivity analyses in layered systems with different thickness ratios of individual sublayers. Theoretical calculations were also performed using the DFT method, which enabled the determination of the thermal conductivity and diffusivity of the MoSi₂ crystal with an ideal crystal structure.