Transparent Insulators with a Tough Nanocellulose Skeleton Formed via Freeze-Drying

Area of Science:

• Materials Science
• Sustainable Energy
• Nanotechnology

Background:

• Significant heat loss in buildings and vehicles hinders low-carbon society goals.
• Transparent insulators are crucial for reducing heat loss through windows.
• Silica aerogels, a conventional option, suffer from unscalable production and brittleness.

Purpose of the Study:

• To develop novel transparent and thermally insulating materials.
• To overcome the limitations of conventional silica aerogels.
• To create scalable, mechanically robust transparent insulators.

Main Methods:

• Developed transparent cryogels using cellulose nanofibers (CNFs) via freeze-drying.
• Suppressed nanofiber agglomeration by rapid freezing of tert-butyl alcohol (t-BuOH)-exchanged gels.
• Extended the synthesis approach to chitin nanofibers (ChNFs) to demonstrate universality.

Main Results:

• CNF cryogels achieved 80-90% visible-light transmittance and a thermal conductivity as low as 0.023 W/m·K.
• ChNF cryogels showed similar high transparency (∼80%) and low conductivity (0.022 W/m·K).
• The developed cryogels are mechanically strong and suitable for scalable production.

Conclusions:

• Cryogels derived from CNFs and ChNFs are effective transparent insulators.
• These materials offer a promising, scalable alternative to silica aerogels.
• The cryogels are ideal for interspace materials in double-glazed windows for energy-efficient applications.