Mechanically Strong, Scalable, Mesoporous Xerogels of Nanocellulose Featuring Light Permeability, Thermal Insulation, and Flame Self-Extinction

Abstract

Scalability is a common challenge in the structuring of nanoscale particle dispersions, particularly in the drying of these dispersions for producing functional, porous structures such as aerogels. Aerogel production relies on supercritical drying, which exhibits poor scalability. A solution to this scalability limitation is the use of evaporative drying under ambient pressure. However, the evaporative drying of wet gels comprising nanoscale particles is accompanied by a strong capillary force. Therefore, it is challenging to produce evaporative-dried gels or "xerogels" that possess the specific structural profiles of aerogels such as mesoscale pores, high porosity, and high specific surface area (SSA). Herein, we demonstrate a structure of mesoporous xerogels with high porosity (∼80%) and high SSA (>400 m 2 g −1 ) achieved by exploiting cellulose nanofibers (CNFs) as the building blocks with tunable interparticle interactions. CNFs are sustainable, wood-derived materials with high strength. In this study, the few-nanometer-wide CNFs bearing carboxy groups were structured into a stable network via ionic inter-CNF interaction. The outline of the resulting xerogels was then tailored into a regular, millimeter-thick, board-like structure. Several characterization techniques highlighted the multifunctionality of the CNF xerogels combining outstanding strength (compression E = 170 MPa, σ = 10 MPa; tension E = 290 MPa, σ = 8 MPa), moderate light permeability, thermal insulation (0.06−0.07 W m −1 K −1 ), and flame self-extinction. As a potential application of the xerogels, daylighting yet insulating, load-bearing wall members can be thus proposed.

Design, Synthesis, and Use of High Temperature Resistant Aerogels Exceeding 800 oC

“…For example, carbon materials cannot be used as precursors for HTRAs, such as graphene and carbon nanotubes (CNT), because they will undergo oxidative decomposition in an aerobic conditions at high temperatures. [41,42] Polymers [43][44][45][46][47][48][49][50][51][52][53] cannot be used as candidate precursors neither, although some aromatic heterocyclic polymers exhibit thermal stability in an oxygen-free thermal decomposition temperature up to 550 ℃ (e.g. polyimide aerogels and aramid aerogel).…”

Design of a Waste Paper‐Derived Chemically ‘Reactive’ and Durable Functional Material with Tailorable Mechanical Property Following an Ambient and Sustainable Chemical Approach

“…Furthermore, some compressible spongy materials with porous network have already been demonstrated for prospective applications as thermal insulators. [38][39][40] In general, the existing approaches for deriving functional superhydrophobic materials from waste paper primarily depends on the high temperature pyrolysis process, [32][33][34][35][39][40][41][42] which is an energy consuming, sophisticated approach that leads to secondary pollution. Hence, a facile, economic design for converting waste paper into a chemically 'reactive' sponges with the scope to tailor both the mechanical property and chemistry would provide an avenue for a) develloping eco-friendly/economic thermal insulators, b) prospective use in efficient remediation of oil spillages and c) controlled droplet manipulation.…”

“…Furthermore, the previously reported approaches lacked the ability to tailor the compressive modulus of the synthesized materials, which could prove beneficial for obtaining the ideal substrate for repetitive and prolonged oil/water separation performance of the paper derived materials. Furthermore, some compressible spongy materials with porous network have already been demonstrated for prospective applications as thermal insulators [38–40] . In general, the existing approaches for deriving functional superhydrophobic materials from waste paper primarily depends on the high temperature pyrolysis process, [32–35,39–42] which is an energy consuming, sophisticated approach that leads to secondary pollution.…”

Nanocellulose Xerogel as Template for Transparent, Thick, Flame-Retardant Polymer Nanocomposites

“…Recently, we developed optically transmissive mesoporous CNF xerogels with high porosity (70-80%) and high SSA (>350 m 2 g −1 ) [16,17]. Xerogels are porous materials produced through the ambient pressure drying of wet gels.…”