Research Achievements: Pure Natural Wood Like Aerogel With Thermal Insulation And Fire Resistance Properties Extracted From Wood

As a widely used material and abundant resource, wood has been used for thousands of years due to its low density, low heat conduction, good mechanical properties and sustainability. In recent years, based on the understanding of wood structures, various wood like materials with unique physical properties and wide applications have also been developed. Among them, aerogel with excellent thermal insulation performance is one of the important research topics. Wood like aerogels based on plastics and resins are limited by poor biodegradability, resulting in the accumulation of waste and environmental problems. However, wood like aerogels based on existing nanostructure units are limited by their lack of sustainability and high cost. Therefore, in order to solve the problem of unsustainable materials at present, developing new building elements with low cost, low energy consumption and environmental protection will play an important role in the development of wood like aerogels.

Recently, Yu Shuhong, an academician of the Chinese Academy of Sciences and a professor of the University of Science and Technology of China, reported that a bottom-up strategy was adopted to prepare pure natural wood like aerogel with excellent thermal insulation and fire resistance properties using natural biomass and natural minerals as raw materials. Relevant research results were published in German Applied Chemistry under the title of Anal natural wood inspired aerogel.

The researchers used ingenious surface chemical control methods to activate the surface of micron sized sawdust particles under mild conditions, thus exposing cellulose nanofibers (Fig. 1a). The nanofibers on the surface of these particles significantly enhanced the interaction between particles, and combined with unidirectional freezing technology, a strong and durable wood like aerogel was constructed. This aerogel has an orientation channel structure similar to that of natural wood (Fig. 1b-g). At the same time, this wood like structure can reduce the thermal conductivity of the aerogel, making it have an ultra-low radial thermal conductivity of 17.4 mW m-1K-1, superior to existing cellulose based aerogel materials and various commercial sponges (Fig. 2a-c). In addition, the addition of natural clay nanoflakes has greatly improved the fire resistance of this aerogel, which can withstand the flame at 1300 ℃ for at least 20 minutes without being burned through (Fig. 2d-h).

This all natural wood like aerogel has better heat insulation and fire resistance than natural parsa wood and most commercial sponges, and is expected to become an ideal substitute for existing commercial thermal insulation materials. In addition, the natural raw material source and low energy consumption and low emission preparation process of all natural wood like aerogel make it have good biodegradability and sustainability, which can reduce the negative impact of thermal insulation materials on the environment in the process of production, use and waste.

The research work has been supported by the national key research and development plan, the key projects of the National Natural Science Foundation of China, the collaborative innovation plan of Chinese universities, the major science and technology projects of Anhui Province, the special funds for the basic scientific research business fees of the central universities, and the key research and development projects of Anhui Province.

Fig. 1. Preparation and structure of all natural aerogels. (a) Schematic diagram of the nanoparticle surface of sawdust particles and the construction process of wood like structure; (b-d) natural wood and its orientation channel structure; (e-g) all natural sponge and its orientation channel structure.

Figure 2. Thermal insulation and fire resistance of all natural aerogels. (a) The thermal insulation performance of all natural aerogels was compared with that of reported cellulose based and wood based aerogels; (b) Ashby diagram shows the comparison between the thermal insulation performance of all natural gas gel and various commercial sponges; (c) The mechanism of excellent thermal insulation performance of all natural gas gel is explained from three heat transfer forms of heat radiation, heat convection and heat conduction; (d-g) The microstructure of different parts of wood like aerogels after flame burning; (h) The radial and axial thermal conductivity changes of aerogels after high-temperature carbonization.