Burnt Bread Makes Strong Carbon Foam?

Researchers of the American Chemical Society (ACS) have developed a strong, lightweight carbon foam from baked bread. This type of foam has many structural and insulating applications in aerospace engineering, energy storage and temperature maintenance. The bread-based innovation surpasses current foams, which lack strength and are heavier, costlier and more challenging to make in an environmentally friendly way. In order to meet these challenges, ACS introduced a super-toasted bread technique for creating the carbon foam. Carbon foam structures are similar to aerogels. They are lightweight due to their 3D network, can tolerate high temperatures and adjust their thermal and electrical properties. Many different materials, such as graphene sheets (2D layers of carbon atoms) and biomass such as banana peels, can be used to make these foams.

However, these materials lack stability and have invariable inner structures. Yibin Li, Qingyu Peng and colleagues at ACS developed a versatile, low-cost and green method to produce a strong carbon foam.

How Bread Transforms into Carbon Foam

The researchers used a standard bread recipe, mixing flour, yeast and water, kneaded and baked. The bread was then subjected to a laboratory tube furnace under argon gas conditions to produce the hard carbonized foam. Argon gas is abundant in nature—making it economical to create this type of furnace environment—and prevents graphite from burning at the high temperatures the process demands.

By conducting spectroscopy tests on the carbon foam derived from bread, the researchers showed that the final product was mechanically stiff and shielded against electromagnetic interference. This test was especially important to understand the foam's limitations in applications for energy storage and insulation.

Compared to previously made carbon foams, this new type developed by ACS has lower flammability and is cheaper and easier to make. To meet the different requirements for particular applications, the makeup of the foam can be changed by varying the recipe, for example, changing the yeast and water content.