Strong and machinable carbon aerogel monoliths with low thermal conductivity prepared via ambient pressure drying

Abstract

Carbon aerogels are among the most attractive porous carbon materials currently, but their real-world applications are greatly limited by their high cost, complicated preparation process and low mechanical properties. Herein, we report a very facile route to prepare lightweight but mechanically strong carbon aerogel monoliths (CAMs), through a sol-gel polymerization of linear phenolic resin and hexamethylenetetramine (HMTA), followed by ambient pressure drying and carbonization. The good capability of linear phenolic resin with ethanol could induce the formation of large polymer particle and good particle connectivity, affording robust network to suppress the collapse during the ambient drying. The synthesis is scalable and flexible, permitting a facile tailor of density, porous structure and mechanical strength by adjusting the ratio of phenolic resin to HMTA and phenolic resin concentration. The obtained CAMs possess macroporous/microporous hierarchical structure with low density as low as 0.07 g cm -3 , high mechanical strength of 0.9-5.0 MPa and low thermal conductivity (0.032-0.069 W m -l K -1 ). Further CO 2 activation can greatly develop the microporosity without sacrificing the monolithic structure. Moreover, as-prepared CAMs can be fabricated in large sizes, as well as being post-machined into many shapes and sizes for potential applications.

Mechanical and thermal insulation properties of isocyanate crosslinked resorcinol formaldehyde aerogel: Effect of isocyanate structure

“…As a result, solid conductivity is considered as a main heat transfer mechanism. Solid conductivity is governed by the density of aerogels . The presence of crosslinking agents increases the neck size and enhanced the connection of the secondary particles.…”

“…Although some of those monoliths had greatly decreased surface areas, changing the solvent used to produce the gels from methanol to ethanol increased the surface area in one instance from 6 to 220 m 2 g −1 with little influence on the modulus, elastic recovery, porosity, and density. Jia et al . reported a new route to prepare a lightweight carbon aerogel with high mechanical strength as a thermal insulator.…”

Carbon Aerogels for Environmental Clean‐Up

“…Carbon aerogels, the 3D porous network structure formed by carbon nanomaterials, have received widespread attention since they were firstly obtained, due to their fascinating physical properties, including low apparent density, large specific surface area, abundant pore structure, high electrical conductivity, good chemical stability, and environmental compatibility. Based on the above characteristics, a kaleidoscope of carbon aerogels has been fabricated and used widely in energy storage,, thermal insulation, environmental clean‐up,, chemical sensors,, and biomedical and pharmaceutical applications , . As shown in Figure , the number of publications concerning carbon aerogel have been increasing in the past decade.…”

Tribo‐Tunneling DC Generator with Carbon Aerogel/Silicon Multi‐Nanocontacts

“…[3,[5][6][7][8][9][10] The tribo-tunneling transport tip-enhanced current generation, as reported by Liu et al [3,6] using conductive-atomic force microscope (C-AFM), show that the tribo-tunneling current density ( J) output can be boosted by the nano-sized contact (tip radius R ≈ 30 nm) up to 10 6 A m −2 due to the enhanced electronic excitation and strong localized electric field E. It has been reported that a micro-tip (tip radius R ≈ 30 µm) sliding system produces a current density of 35 A m −2 while larger tip radius (R ≈ 100-300 µm) yields a current density of 10 A m −2 in the test probe sliding system. [11] It has been widely used for nanocomposite, electrodes, desalination filters, and heterogeneous catalysis due to its large surface area. The metal micro-tips also cause substrate surface scratching, which impacts the sustainability of the power generation.…”

“…[11] It has been widely used for nanocomposite, electrodes, desalination filters, and heterogeneous catalysis due to its large surface area. [11] It has been widely used for nanocomposite, electrodes, desalination filters, and heterogeneous catalysis due to its large surface area.…”