Flame‐retardant cellulose nanofiber aerogel modified with graphene oxide and sodium montmorillonite and its fire‐alarm application

Thermal insulation materials (TIMs) are widely used to realize energy conservation in buildings, but most of the commonly used organic TIMs are flammable. A novel biomass‐based aerogel is produced by an environmentally friendly vacuum freeze‐drying method, and a facile approach is proposed to improve the flame‐retardant performance of cellulose nanofiber (CNF) aerogels by modifying them with graphene oxide (GO) and montmorillonite (MMT). GO and MMT form a barrier that blocks the contact between the composite aerogel and the external oxygen, achieving the flame‐retardation effect. Notably, based on the high‐temperature thermal reduction characteristic of GO, a fire‐alarm system that can provide an ultrasensitive and reliable fire‐warning signal is designed. A fire alarm of CNF‐MMT‐GO‐50% can be triggered in approximately 1.9 seconds and lasts for more than 137.0 seconds when the aerogels are attacked by fire. This work helps to develop advanced TIMs to solve the shortcomings of traditional organic insulation materials and supplies a newfangled idea for the design of fire‐alarm sensors, showing promising applications in building insulation, firefighting, and chemical industry.