Ultralight Biomass Aerogels with Multifunctionality and Superelasticity Under Extreme Conditions

Abstract

Biomass aerogels are highly attractive candidates in various applications due to their intrinsic merits of high strength, high porosity, biodegradability, and renewability. However, under low-temperature harsh conditions, biomass aerogels suffer from weakened mechanical properties, become extremely brittle, and lose functionality. Herein, we report a multifunctional biomass aerogel with lamella nanostructures (∼1 μm) fabricated from cellulose nanofibers (∼200 nm) and gelatin, showing outstanding elasticity from room temperature to ultralow temperatures (repeatedly bent, twisted, or compressed in liquid nitrogen). The resultant aerogel exhibits excellent organic solvent absorption, thermal infrared stealth, and thermal insulation performance in both normal and extreme environments. Even at dry ice temperature (−78 °C), the aerogel can selectively and repeatedly absorb organic solvents in the same way as room temperature with high capacities (90–177 g/g). Excellent heat insulation and infrared stealth performances are achieved in a wide temperature range of −196 to 80 °C. Further, this aerogel combines with the advantages of ultralow density (∼6 mg/cm3), biodegradability, flame retardancy, and performance stability, making it a perfect candidate for multifunctional applications under harsh conditions. This work greatly broadens application temperature windows of biomass aerogels and sheds light on the development of mechanically robust biomass aerogels for various applications under extreme conditions.

Rigid and Fire-Resistant All-Biomass Aerogels

“…Based on combustion tests, thermal stability tests, and residue characterizations, the fire resistance mechanism of PG/PA-based aerogels could be considered as follows: (1) the natural flame retardancy of PG and PA materials made the aerogels difficult to be ignited in both small-fire tests (LOI and UL-94) and large-fire tests (CONE); (2) in the process of combustion, the release of bound water in PG and PA diluted the concentration of combustible gas and absorbed heat; (3) the hybrid char layers containing N and P were formed by the interaction between PG and PA, limiting the transfer of heat and combustible volatiles and further decreasing the release of heat and smoke from aerogel; − (4) with increasing MMT, the melt viscosity of the aerogel increased and a dense char layer containing C, N, P and Si was formed, resulting in a remarkable improvement in fire resistance for PG-based aerogels. − …”

Protein-Based Flexible Conductive Aerogels for Piezoresistive Pressure Sensors

“… 31 , 32 Recently, some examples of gelatin-based aerogels with elastic properties have been reported, employing mixtures of gelatin and polymeric materials like poly(vinyl alcohol) (PVA) or cellulose or conductive materials (graphene oxide or Mxene). 33 − 36 …”

“…The development of novel methods for aerogel preparation have resulted in a range of novel low-density materials suitable for a wide range of applications including energy storage and conversion, − sensing, , catalysis, , and environmental remediation. − There is much recent interest in development of sensors that can detect mechanical deformations, − and aerogels and foams have also been developed for such applications. − In contrast to its popularity for forming hydrogels, employment of gelatin for preparation of aerogels is comparatively rare, and early studies focused on building 3D structures suitable for tissue engineering . In recent years, gelatin-based aerogels have been investigated as adsorbents (e.g., for oil or metal ions). , Recently, some examples of gelatin-based aerogels with elastic properties have been reported, employing mixtures of gelatin and polymeric materials like poly­(vinyl alcohol) (PVA) or cellulose or conductive materials (graphene oxide or Mxene). − …”

Ambient Pressure Drying to Construct Cellulose Acetate/Benzoxazine Hybrid Aerogels with Flame Retardancy, Excellent Thermal Stability, and Superior Mechanical Strength Resistance to Cryogenic Temperature

“…Cellulose aerogels have attracted extensive interest as a novel kind of green biodegradable nanoporous material. − Cellulose aerogels combine the environmental friendliness, biocompatibility, and biodegradability of cellulose and the characteristics of traditional aerogel materials such as low density, high specific surface area, and high porosity . Therefore, this green nanoporous material has a great application potential in thermal insulation, adsorption separation, biomedical field, and as a carrier …”