A lightweight, supercompressible and superelastic aramid nanofiber/nanocellulose-derived carbon aerogel with in-plane micro-wrinkle honeycomb structure for thermal insulation

Abstract

Nanofiber carbon aerogels with 3D interconnected microfibrillar networks exhibit fascinating physical properties and present great application potential. However, it is still a challenge to fabricate superelastic nanofiber carbon aerogels owing to their extremely dilute brittle interconnections and poor fiber toughness after carbonization. Herein, aramid nanofibers (ANF)/nanocellulose (CNF) dual-fibrous carbon aerogels are prepared, which exhibited supercompressibility and superelasticity due to the "skeleton-binder" synergistic effect of ANF and CNF and the design of in-plane micro-wrinkle honeycomb structure. The "skeleton-binder" synergistic effect improves interfacial interactions of nanofibers and optimizes the stress distribution of carbon aerogel. The highly ordered honeycomb structure with in-plane microwrinkles, formed by the bidirectional freezing and the difference in volume shrinkage during the carbonization between CNFs and ANFs, endows the CNF/ANF carbon aerogel with negative Poisson's ratio and high energy absorption capacity. These strategies significantly improve the overall mechanical properties of ANF/CNF carbon aerogel including the elasticity and fatigue resistance. As a result, the ultralight carbon aerogel (3.46 mg/cm³) exhibits excellent supercompression (undergoing an extreme strain of 95%) and elasticity (a stress retention up to 81.38% at 90% strain with 500 cycles and 96.15% at 50% strain with 10000 cycles). The nanofiber carbon aerogel shows excellent multifunctional properties in flexible piezoresistive sensor and anisotropic thermal insulation materials, including a desirable sensitivity (as high as 48.74 kPa⁻¹) and an instant response time (∼40 ms), an anisotropy factor of 3.69 and an ultralow radial thermal conductivity (0.012 W m⁻¹ K⁻¹). These properties make dual-fibrous carbon aerogels highly attractive in pressure sensors and thermal management applications.