Cellulose/nanocarbon composite based multifunctional aerogels for thermal management

Abstract

Renewable resource-based aerogels have attracted numerous attention due to the requirement on sustainable multifunctional materials for thermal management. A series of cellulose and nanocarbon composite aerogels have been prepared from a blend of carboxylated cellulose nanofibril (CCNF) with carbon nanotube (CNT), graphene oxide (GO), or carbon fiber (CF) using directional freezing method. CCNF/nanocarbon aerogels from bidirectional freezing exhibit higher compression strength due to bridge structures that are induced by temperature gradient horizontally and vertically. Meanwhile, CCNF/carbon aerogels from bidirectional freezing also have thermal conductivity coefficient (λ) as low as 0.0308 W/(m·K), which increases to 0.0388 W/(m·K) after calcination. The dispersed linear carbon materials CF and CNT in CCNF matrix lead to thermoelectric, Joule heating and photothermal performance of CCNF/nanocarbon aerogels, which is also promoted by calcination. The Seebeck coefficient of CCNF/nanocarbon aerogels ranges from 0.027 to 0.067 mV/K and change into 0.037–0.044 mV/K due to the more uniform carbon network formed after high temperature treatment. A 5–15 V input voltage can induce a temperature increase of 62 ∼ 303 °C for composite aerogel after calcination. A laser with 0.3 W power can result in a rapid temperature increase even to 200 °C in seconds for composite aerogel with and without calcination. These kinds of CCNF/nanocarbon based composite aerogels exhibit ability in thermal management, including thermal insulation, thermoelectric, electric and photo induced heating, which are good candidates for multifunctional aerogels.