Nanostructure of Aerogels and Their Applications in Thermal Energy Insulation

Abstract

The recent global energy context has been recognized as evidence for the need to reduce our energy consumption, to prolong fossil fuel supplies and minimize shortage, and to decelerate greenhouse gas transpiration. Over the past few years, using an insulator and decreasing its thermal conductivity have been recognized as the most effective way to reduce energy consumption. Aerogels as superinsulating materials permit reduction of the heat exchange between two environments while producing facile sol−gel and diverse drying routes. Aerogels have intrigued scientists and engineers due to their unique nanocharacteristics, such as low density, fine internal void spaces, and openpore geometry, which originate from sol particles in a 3D random network. Noteworthy are aerogel-based materials that have a supreme potential as thermal insulation owing to their very low thermal conductivity based on trapped air in the meso-/ nanoporous structure. Indeed, aerogels have great appeal in terms of their thermal efficiency, producing simplicity and performance reliability as compared with a traditional insulator. In this work, we will review the main milestones along with the concept of aerogels and then discuss some new trends, strategies, and opportunities in employing various morphological and nanostructural control methods to improve the performance of aerogels, especially enhancing insulation efficiency or decreasing thermal conductivity. The focus will be on (I) tailoring the porous structure of a carbon-based aerogel such as graphene oxide and reduced graphene oxide to accommodate high thermal behavior and (II) designing strategies to achieve intrinsically superinsulating materials in synthesized polymer and bio-based materials, with/without embedding an additional component.

Lightweight, Anisotropic, Compressible, and Thermally-Insulating Wood Aerogels with Aligned Cellulose Fibers

“…In addition, the gaseous thermal radiation of wood aerogel-8 h also played a significant role [42]. The multilayer structure of wood aerogel-8 h separated channels for gas transmission, and the large amount of nanopores in the cell walls further restricted the movement of gas molecules, leading to poor gaseous radiation thermal conductivity [12,43]. The low density, multilayer structure, and exposed nanopores reduced the thermal conductivity from 0.113 W/mK of the natural wood to 0.033 W/mK of the wood aerogel-8 h (Figure 7c).…”

“…Bio-based aerogels are produced from natural plant resources and degrade in the natural environment. Bio-based materials include cellulose, starch, pectin, and their derivatives [12]. Among them, cellulose is the most abundant polysaccharide polymer, being directly extracted from renewable biomass resources (wood, bamboo, and straw) and possessing high mechanical strength, high specific surface area, abundance of functional groups, and good biodegradability [13][14][15][16].…”

Synthesis and design of polyurethane and its nanocomposites derived from canola‐castor oil: Mechanical, thermal and shape memory properties

“…In comparison to carbon nanotube (CNT), graphene also has exhibited lower percolation threshold, which is defined as a specific filler amount that leads to the vast improvement in electrical and thermal properties, owing to the unique structure and features. [ 13,18,19 ] Thus, the desirable properties can be obtained and controlled with the addition of graphene as a filler to the PU matrix.…”

Fabrication, Structure, Performance, and Application of Graphene-Based Composite Aerogel

“…In short, the introduction of graphene-based materials improves the thermal performance of aerogel and provides a scheme to overcome the problem of energy consumption [ 65 ], which gives it great application potential in thermal insulation materials, flame retardant materials, and electronic devices.…”