Carbon Aerogel Composites Prepared by Ambient Drying and Using Oxidized Polyacrylonitrile Fibers as Reinforcements

Abstract

Carbon fiber-reinforced carbon aerogel composites (C/CAs) for thermal insulators were prepared by copyrolysis of resorcinol-formaldehyde (RF) aerogels reinforced by oxidized polyacrylonitrile (PAN) fiber felts. The RF aerogel composites were obtained by impregnating PAN fiber felts with RF sols, then aging, ethanol exchanging, and drying at ambient pressure. Upon carbonization, the PAN fibers shrink with the RF aerogels, thus reducing the difference of shrinkage rates between the fiber reinforcements and the aerogel matrices, and resulting in C/CAs without any obvious cracks. The three point bend strength of the C/CAs is 7.1 ± 1.7 MPa, and the thermal conductivity is 0.328 W m(-1) K(-1) at 300 °C in air. These composites can be used as high-temperature thermal insulators (in inert atmospheres or vacuum) or supports for phase change materials in thermal protection system.

Correlation between morphology and electrical conductivity of dried and carbonized multi-walled carbon nanotube/resorcinol–formaldehyde xerogel composites

“…Difference in degree of shrinkage between the nanotube aggregates and the polymer matrix phases usually leads to large residual stress and then to crack nucleation and propagation [28]. This can decrease the mechanical strength of the composite and, in the worst cases, may lead to breakage.…”

“…7 Semi-log plot of relative electrical conductivity of the composites with respect to MWCNT volume fraction: experimental data (filled circle) and EMT fit (-) supercapacitors [29], as well as applications in thermal insulation [28]. Table 3 demonstrates that the introduction of nanotubes into the xerogel structure of both RF and C did not have a significant effect on porous properties of the composite.…”

Infrared-opacified Al2O3–SiO2 aerogel composites reinforced by SiC-coated mullite fibers for thermal insulations

“…Aerogels are nano-porous solid materials with high surface area, high porosity, and low density [1]. Due to their unique nanometer network and nano-porous structure, which suppress the gaseous thermal conduction significantly, the gaseous thermal conductivity of aerogels is very low [1,2].…”

“…Due to their unique nanometer network and nano-porous structure, which suppress the gaseous thermal conduction significantly, the gaseous thermal conductivity of aerogels is very low [1,2]. However, the total thermal conductivity of aerogels is still high at high temperatures; the reason is that the radiative conductivity k rad , increases in proportion to the third power of temperature.…”

Morphological characterization and impedance spectroscopy study of porous 3D carbons based on graphene foam-PVA/phenol-formaldehyde resin composite as an electrode material for supercapacitors

“…13,14 These structures are produced by different techniques which may include hydrothermal polymerization and carbonization of mixtures of polymers and carbon from different sources 15 and template-directed growth. 16 Recently, a threedimensional graphene/polymer-based hydrogel with exceptional properties was reported by Zhang et.…”