Highly efficient infrared (IR) stealth materials with low emissivity and thermal insulation features are urgently demanded in many fields. However, these two characteristics are difficult to be realized by an individual compound due to the high thermal conductivity of low emissivity materials (e.g. metal materials) and the high emissivity of excellent thermal insulation materials (e.g. polymer foam and aerogel). Herein, we demonstrated a new strategy to fabricate low emissivity/thermal insulation IR stealth composites with asymmetric structure based on a combination of silver-plated hollow glass microsphere (HGM-Ag) and waterborne polyurethane (WPU) through one-step density-driven filler separation coupled with freeze-drying method. The composites were constructed from the HGM-Ag concentrated on the top of the composites as low emissivity layer and the bottom layer with low thermal conductivity about 0.044 W m⁻¹ K⁻¹ served as the thermal insulation layer. The emissivity of the composites can be reduced from 0.943 to 0.713 by adding HGM-Ag. Benefitting from the well-interconnected 3-dimensional structure, the HGM-Ag/WPU porous composites also display outstanding mechanical property. We believe this work will provide a new strategy for designing highly efficient IR stealth materials based on synergetic mechanism of reducing emissivity and thermal insulation.

在许多领域，迫切需要具有低发射率和隔热功能的高效红外（IR）隐形材料。然而，由于低发射率材料（例如金属材料）的高导热率和优异的绝热材料（例如聚合物泡沫和气凝胶）的高发射率，很难通过单独的化合物实现这两个特性。在此，我们展示了一种新策略，该策略通过一步密度驱动填充剂将镀银空心玻璃微球（HGM-Ag）和水性聚氨酯（WPU）结合起来，制造具有不对称结构的低辐射/隔热IR隐形复合材料分离结合冷冻干燥方法。^-1 K ^-1用作隔热层。通过添加HGM-Ag，复合材料的发射率可以从0.943降低到0.713。得益于良好互连的三维结构，HGM-Ag / WPU多孔复合材料还显示出出色的机械性能。我们相信这项工作将为基于降低辐射率和隔热性能的协同机制设计高效的红外隐身材料提供新的策略。