Improvement of performance of foam perlite thermal insulation material by the design of a triple-hierarchical porous structure.

• Inorganic thermal insulation material with triple-hierarchical pores was designed. • A special heat treatment method was used to create different size of pores. • The density decreased by ∼15% and thermal conductivity decreased by ∼10%. • Softening coefficient (water resistance) was remarkably improved by ∼80%. Inorganic thermal insulation materials are incombustible, cheap, and perdurable, and can thus effectively avoid such shortcomings of organic materials. Nevertheless, the physical properties, such as thermal conductivity and apparent density, are usually not as good as the organic thermal insulation materials. In present work, we designed and synthesized a new kind of inorganic thermal insulation material with admirable and intriguing triple-hierarchical porous structures by combining the ambient temperature foam method and simple heat treatment. The final products contained triple-hierarchical pores in the range of hundreds of microns, several microns to tens of microns, and submicrons to several microns. Compared to products without heat treatment, the apparent density of this kind of inorganic thermal insulation material was 0.148 g·cm−3, which decreased by 15%, and the compressive strength was 0.30 MPa; the thermal conductivity reached 0.047 W· m −1· K −1 which reduced by 10%, and the softening coefficient (the ratio of the samples' strength under saturation with that in dry condition) was improved from 0 to ∼80%. Therefore, this work not only provided a new type of thermal insulation material with hierarchical pores, but also has great significance for the design of inorganic thermal insulation materials with high performance. Image, graphical abstract [ABSTRACT FROM AUTHOR]