Reinforced silica-carbon nanotube monolithic aerogels synthesised by rapid controlled gelation

Abstract

Manuscript Click here to download Manuscript AeroSic-Paper_JSST_30.docx Click here to view linked References HIGHLIGHTS • Homogeneous SiO2-carbon nanotube monolithic aerogels were obtained by rapid controlled gelation • The carbon nanotubes were homogeneously dispersed in the highly porous silica matrix • The hybrid aerogels kept outstanding structural features and densities below 80 mg/cm in all cases • The Si-O-C covalent bonding between carbon nanotubes and silica matrix was prompted by FTIR • The carbon nanotubes turned the aerogels into 100% stiffer and 60% more deformable materials ABSTRACT This work introduces a new synthesis procedure for obtaining homogeneous silica hybrid aerogels with carbon nanotube contents up to 2.50 wt.%. The inclusion of nanotubes in the highly porous silica matrix was performed by a two-step sol-gel process, resulting in samples with densities below 80 mg/cm 3. The structural analyses (N2 physisorption and SEM) revealed the hierarchical structure of the porous matrix formed by nanoparticles arranged in clusters of 100 nm and 300 nm in size, specific surface areas around 600 m 2 /g and porous volumes above 4.0 cm 3 /g. In addition, a relevant increase on the mechanical performance was found, and an increment of 50% for the compressive strength and 90% for the maximum deformation were measured by uniaxial compression. This reinforcement was possible thanks to the outstanding dispersion of the CNT within the silica matrix and the formation of Si-O-C bridges between nanotubes and silica matrix, as suggested by FTIR. Therefore, the original synthesis procedure introduced in this work allows the fabrication of highly porous hybrid materials loaded with carbon nanotubes homogeneously distributed in the space, which remain available for a variety of technological applications.

Thermal Gelation for Synthesis of Surface-Modified Silica Aerogel Powders

“…Both homogeneous gelation and surface modification are required to obtain high-quality hydrophobic silica aerogel powders (with low bulk density and high pore volume) [ 20 ]. Generally, hydrophobic silica aerogels are synthesized through gelation of silica sol or silicic acid solution and subsequent solvent exchange (SE) and surface modification (SM) using hydrophobizing agents.…”

Silica-Based Aerogel Composites Reinforced with Reticulated Polyurethane Foams: Thermal and Mechanical Properties

“…The obtained aerogel showed a higher Young’s modulus, reaching values above 201.5 kPa, higher porosities and lower densities than the pure aerogels. Another example is the work of Piñero et al [ 10 ] in which functionalized CNTs are included into the silica formulations, achieving a significant stiffening effect on the resultant monoliths. Different reinforcing fibers have also been used in several works such as polymeric fibers [ 11 , 12 , 13 ], or glass fibers [ 14 , 15 , 16 ].…”

Mechanical characterization of sol-gel alumina-based ceramics with intragranular reinforcement of multiwalled carbon nanotubes

“…Among all the synthesis strategies, the sol-gel method has been considered for ceramic fabrication [20,21], and more recently, for the fabrication of alumina-based CMCs with CNTs [9,14,15]. The aim is to achieve a good dispersion of the CNTs by a rapid, controlled gelation though the use of liquid precursors, control of the pH, and the assistance of high-power ultrasound [22]. In addition, this method may promote intragranular placement of the CNTs, as they are present during the very first steps of the formation of the ceramic grains [9,14,15].…”