Additively manufactured Ti600 lattice sandwich structures with ultra-low thermal conductivity: theoretical model and experiment

The high-temperature alloy Ti600 is a promising candidate for lightweight thermal insulation, particularly when fabricated into lattice sandwich structures via additive manufacturing. However, accurately predicting thermal performance of these complex geometries remains a challenge. This study developed a theoretical model to predict their equivalent thermal conductivity (ETC), supported by simulations and experiments. The model considered two main heat transfer mechanisms: solid conduction and cavity radiation. Solid conduction ETC was modeled based on the shortest heat transfer path and an improved relative density formula, showing high accuracy even in dense structures. Radiative ETC was estimated using a four-node thermal resistance network, which included finite dimensions and adiabatic boundary conditions, making it more realistic. Parametric analysis showed that higher relative density predominantly increased solid conduction, while higher temperature and more layers enhanced thermal radiation. Based on these findings, a novel structure with a low relative density (0.42 %) and an SiO₂ fiber aerogel-filled core was designed to reduce conduction and radiation. This optimized structure achieved excellent thermal insulation, with an ETC of 0.0365 W/(m K) at room temperature and 0.119 W/(m K) at 600 °C. This represents an 85.9 % reduction in thermal conductivity at 600 °C from the initial air-filled structure’s value of 0.843 W/(m K). This integrated approach of modeling, simulation, and design offers valuable insights for developing lightweight, high-performance materials for extreme thermal environments.