Surface decoration of flexible Si₃N₄ nanowire membrane by hydroxyapatite micron-flake with excellent thermal insulation at 1300 °C

Flexible and excellent thermal insulation membranes are required as the thermal protection system materials of aerospace vehicles for next-generation space missions. Using ceramic membranes with ultralow thermal conductivity has been proved to be an effective way to protect the electronic components inside the fuselage. Herein, we decorate hydroxyapatite (HA) micron-flake onto Si₃N₄ nanowire membrane (SR), and investigate the thermal stability, fire-resistance and thermal insulating properties of the obtained SR decorated by HA micron-flake (SRHM). Surface decoration of HA micron-flake onto the SR results in the formation of well-interconnected junctions and the increase of interfacial thermal resistance. Due to the increased interfacial thermal resistance, the as-prepared SRHM exhibits good thermal insulation and outstanding fire-retardant performance. SRHM shows robust mechanical property with tensile strength value of 4.10 MPa, increased by 247.5% compared to the SR without the surface decoration by HA micron-flake. The thermal conductivity of SRHM is as low as 0.037 W m⁻¹ K⁻¹, reduced by 33.9% compared to the SR without the surface decoration by HA micron-flake. After SRHM is heated by a butane blow torch at 1300 °C for 30 min, no obvious change is observed in the macroscopic morphology. And the temperature of the backside for SRHM maintains at a stable temperature of ∼260 °C for 300 s, which is 1040 °C lower than that of the front side. Additionally, SRHM can protect the electronic components form being burnt under the heating of an alcohol lamp for 30 min. The successful preparation of such thermal insulating and fire-retardant SRHM will open up a new world for the widespread applications of ceramic membranes in the fields of aerospace vehicles.