Aerogels possess unique microstructural characteristics, such as high specific surface area and high porosity. They are chemically stable, have low thermal conductivity, are resistant to high temperatures, can operate over a wide temperature range, and have a long service life. In recent years, researchers in China, the United States, Europe, and other regions have developed various new types of aerogels, including biomass-based aerogels, by improving the aerogel preparation process.
Aerogel is a metamaterial that is extremely lightweight; even if placed on a flower’s stigma, it would not bend it. Currently, a wide variety of aerogels have been developed, ranging from soft to rigid and from conductive to insulating, with broad applications. Steam pipeline networks have extremely high requirements for corrosion resistance and thermal insulation; the pipelines for the Xinxiang Steam Pipeline Network Project in Henan Province have selected high-temperature centrifugal glass wool and nano-aerogel composite insulation materials. Wang Xing, the project’s technical director, stated that the thermal insulation performance of nano-aerogel is 2 to 5 times that of traditional insulation materials, which can significantly improve construction quality and efficiency while reducing construction costs.
As the solid material with the lowest thermal conductivity and smallest density known to date, aerogel is considered the “king of thermal insulation” in the materials field and has already been applied in sectors such as aerospace and petrochemicals. For example, aerogel has been used in the engines and surface of the Tianwen-1 probe and Mars rover, the high-temperature gas systems of the Long March 5 Y4 carrier rocket, and the thermal protection of the Chang’e-4 probe’s thermal battery. Since China proposed its “dual carbon” goals, the application scenarios for aerogel have continued to expand alongside ongoing technological innovation.
Features high heat resistance, high elasticity, and strong adsorption properties
Aerogel is a novel, nanoscale, porous solid material in which the combined volume of all pores accounts for the vast majority—even 99%—of the aerogel’s total volume. It possesses unique microstructural characteristics, including a high specific surface area, high porosity, nanoscale pores, and low density. It is chemically stable, has low thermal conductivity, is heat-resistant, highly elastic, strongly adsorbent, water-repellent, suitable for a wide range of operating temperatures, and has a long service life.
“Aerogel can be thought of as a nanoscale version of a porous sponge,” says Wang Bei’er, a technical expert in the field of aerogel. Its pore sizes range from 20 to 50 nanometers. Since air molecules are approximately 70 nanometers in size—larger than the diameter of aerogel pores—air flows through aerogel with extremely low efficiency. Combined with the material’s high specific heat capacity, which minimizes heat radiation transfer, aerogel exhibits excellent thermal insulation properties.
Aerogels are primarily classified into three categories: inorganic aerogels, organic aerogels, and organic-inorganic hybrid aerogels. Among these, inorganic aerogels are composed mainly of inorganic materials, including elemental aerogels, oxide aerogels, and sulfide aerogels. Organic aerogels, on the other hand, are based on organic materials and primarily include phenolic aerogels, cellulose aerogels, polyimide aerogels, chitosan aerogels, and chitosan-cellulose aerogels. Organic-inorganic hybrid aerogels leverage the respective advantages of organic and inorganic materials to achieve specialized functionalization of the aerogel.
In 2021, *Science* magazine listed aerogels as one of the top ten trending scientific and technological advancements, describing them as “versatile new materials that can change the world.” Wang Bei’er noted that aerogels are the only material among the top ten new materials selected by *Science* that has already been widely implemented in practical commercial applications.
The aerogel preparation process primarily consists of two steps: first, preparing a gel via the sol-gel process, and then using specific drying methods to replace the liquid within the gel with gas, thereby producing the aerogel.
Data indicates that manufacturing costs account for approximately 45% of the cost structure in the aerogel industry. Zheng Song, Assistant to the Chairman of Suzhou Jinfu Technology Co., Ltd., noted that reducing aerogel costs is a key focus for the industry. Currently, one of the primary approaches is the implementation of automated production lines, and cost reductions will open up more application scenarios.
Biomass-based aerogels are becoming a hot topic of research
According to an assessment by the China National Petroleum Pipeline Technology Research Center, taking the thermal insulation of 350°C steam pipelines as an example, compared to traditional insulation materials, the thickness of aerogel insulation layers can be reduced by two-thirds, saving more than 40% in energy consumption and reducing carbon dioxide emissions by 125 tons per kilometer of pipeline annually.
Data shows that in 2021, demand for aerogel in the oil and gas sector accounted for 56% of total demand, Another 18% was used for industrial insulation, 9% for construction, and 8% for transportation. The National Advisory Committee on the Development Strategy of New Materials Industry noted in the *2022 Aerogel Industry Research Report* that the use of aerogel flame-retardant materials in battery cell modules for new energy vehicles can increase the battery pack’s high-temperature resistance to over 800 degrees Celsius. With the development of the new energy vehicle industry and other sectors, aerogels have found widespread application in new energy vehicles and the energy storage industry, and demand is expected to continue rising.
The aerogel industry is developing rapidly. Li Weike, an analyst at the Institute of International Technology and Economics under the Development Research Center of the State Council, said that in recent years, researchers in China, the United States, Europe, and other regions have developed various new types of aerogels—such as biomass-based aerogels, graphene aerogels, and polymer aerogels—by improving aerogel preparation processes. It is worth noting that biomass is widely available, low-cost, and rich in carbon sources. Using biomass to prepare eco-friendly porous carbon fiber aerogels is an economical and sustainable production method, making biomass-based aerogels a current research hotspot.
For example, the team led by Academician Yu Shuhong at the University of Science and Technology of China has developed a superelastic cellulose aerogel. This cellulose aerogel exhibits superelasticity and excellent fatigue resistance that remain constant across a temperature range from room temperature to -196°C, demonstrating significant thermal insulation potential in harsh environments. Furthermore, since the materials used in its preparation are all biomass-derived, it holds promise for addressing environmental pollution caused by energy-intensive technologies and petrochemical materials, making it an ideal alternative to traditional non-renewable aerogels.
A research team led by Researcher Lu Yun at the Institute of Wood Industry, Chinese Academy of Forestry Sciences, used wood as a matrix and combined inorganic and organic aerogels with a wood scaffold matrix to pioneer the third-generation wood cellulose aerogel. By modulating the cellulose in wood and biomass waste, they increased the specific surface area of the cellulose by seven orders of magnitude. The material exhibits an oil adsorption capacity of 75 to 300 times its own mass, requires 50% to 75% less volume, and is both biodegradable and renewable.
Aerogel Development Enters the “Fast Lane”
The development of aerogels has received continuous support from national policies. In 2014 and 2015, the National Development and Reform Commission (NDRC) included aerogels in the *National Catalog of Key Energy-Saving and Low-Carbon Technologies* for two consecutive years, marking the beginning of their initial promotion and application. In June 2018, aerogels were designated as part of the emerging building materials industry. In September of the same year, the first national standard for aerogels, *Nanopore Aerogel Composite Thermal Insulation Products*, was issued. In 2020, the “Technical Standards for Aerogel Thermal Insulation Coating Systems” came into effect; in 2021, the “Opinions of the Central Committee of the Communist Party of China and the State Council on Fully, Accurately, and Comprehensively Implementing the New Development Philosophy and Effectively Advancing Carbon Peaking and Carbon Neutrality” proposed promoting the research, development, and application of new materials such as aerogels.
As aerogel application technologies continue to mature, the development of aerogels has entered the “fast lane.” However, Li Weike noted that current aerogel research still faces several challenges, such as a rapid increase in thermal conductivity under high-temperature conditions and poor adhesion to reinforcing matrix materials like fibers; the production process involves the use of numerous organic solvents, which can easily cause environmental pollution; and aerogels are difficult to recycle, hindering sustainable development.
Furthermore, aerogel production is costly, resulting in high product prices. The *2022 Aerogel Industry Research Report* indicates that production costs are primarily driven by silicon sources, equipment depreciation, and energy consumption. Effectively reducing costs depends not only on breakthroughs in preparation processes but also on the large-scale industrialization of low-cost raw materials.
Aerogels are rare materials capable of simultaneously meeting multiple requirements such as fire resistance, water resistance, thermal insulation, and sound insulation. Li Weike noted that the development and application of aerogels remain in a process of continuous exploration, with future research primarily focused on developing new types of aerogels, including cellulose aerogels, graphene aerogels, perovskite-structured aerogels, and aerogels made from non-metallic elements.
