Micro-nano structured high-temperature thermal insulating solid coating composites and simulation of their heat conduction mechanisms

High-temperature thermal management materials are widely applied in extreme environments, including thermal power, nuclear power and hydrocracking industries, where the surface temperature can reach 400 ℃. Nevertheless, conventional solid coating-based thermal management materials suffer from insufficient heat resistance and limited thermal insulation, failing to meet the demands of such high-temperature conditions. Herein, a hybrid composite coating was designed and fabricated using amino-phenoxy phthalonitrile (APN)/bismaleimide (BMI) blends as organic matrix. By introducing heat-shielding silicon carbide (SiC) particles, together with micropores derived from pyrolyzed polyethylene glycol (PEG) and mesopores constructed by γ-aminopropyltriethoxysilane (APTS)-modified nanoscale m-SA, a “barrier-turbulence-scattering” system with micro-nano multi-scale porous structure was established (m-SA + SiC/APN-BMI). It was melt-coated at some arbitrary temperature between 95.64 ℃ and 151.12 ℃ with viscosity below 3000 Pa·s, followed by gradient curing at 180 ℃/2 h, 220 ℃/2 h, 260 ℃/2 h and 300 ℃/0.5 h. The lightweight porous coating exhibited a density of 0.34 g·cm − 3 and a porosity of 67.47%, attributed to micropores of thermal decomposition from 50 vol% PEG and mesopores of 35 wt% m-SA. It possessed a thermal conductivity of 0.053 W·m − 1 ·K − 1 at 400 ℃, enabling high-temperature thermal management. The cross-linked coating anchored on steel substrates, giving an adhesion strength of 2.03 MPa (pull-off method). Finally, macro-microscale finite element modelling (FEM) was implemented. Macroscopic simulations validated the numerical predictions agreed with time-temperature variation of the coating on a hot stage, captured by thermal imaging. Microscopic FEM analyses elucidated internal heat conduction pathways, verifying the “barrier-turbulence-scattering” heat-transfer mechanism of the coating at 400 °C.