A new vision in thermal insulation: A comprehensive review of silica aerogel coatings with sustainable potential

With the escalating global energy consumption and rapid urbanisation, the issue of building energy consumption has become increasingly prominent. The development of high-efficiency and economical thermal insulation materials has emerged as a pivotal factor in achieving the goals of energy saving and emission reduction. Recently, silica aerogels (SAs), characterized by their unique nanoporous structure, low density, high surface area, and excellent thermal insulation performance, have emerged as a pioneering "new vision" in the field of insulation with silica aerogel-based insulation coatings standing out as top candidates for building insulation applications. These coatings can achieve a thermal conductivity as low as 0.050 W/(m·K), significantly surpassing conventional thermal insulation coatings and also exhibit high solar reflectance (>90%) and superhydrophobicity, which cooperatively contribute to reducing building heating and cooling energy consumption. The manufacturing process of silica aerogels, including key steps such as the sol-gel synthesis, aging treatment, and drying, directly determines the final product's microstructure and properties. To address the inherent challenges of aerogels (e.g., agglomeration and inadequate hydrophobicity) and further explore their sustainable potential, researchers have been dedicated to the development of environmentally benign and low-toxicity silicone-based source precursors. Moreover, various modification strategies have been proposed to enhance the mechanical properties of aerogel coatings, including pore structure modulation and second-phase material addition. Further research focuses on composite and modification strategies to cooperatively optimize the superior insulation of aerogels and key coating application properties. Finally, SA coatings' extensive applications in multiple fields, such as building energy efficiency, industrial equipment, and optics, are comprehensively summarized. This review systematically highlights the latest research progress, technical bottlenecks, and future development trends of SA coatings, fully demonstrating their remarkable application potential and practical value in advancing sustainable thermal insulation technologies and promoting energy conservation and environmental protection.