Ultralight and Hydrophobic Palygorskite-based Aerogels with Prominent Thermal Insulation and Flame Retardancy

Abstract

Clay-based aerogel is a promising material in the field of thermal insulation and flame retardant, but obtaining claybased aerogel with high fire resistance, low thermal conductivity, hydrophobicity, and mechanical robustness remains a challenge. In this work, palygorskite-based aerogel was successfully fabricated via combining with a very small proportion of alginate to form a distinctive hierarchically meso−microporous structure. By employing ethanol solution (EA) replacement method and freeze-drying process, the resultant aerogel exhibited ultralow density (0.035−0.052 g/cm 3 ), practical mechanical strengths (0.7−2.1 MPa), and low thermal conductivity of 0.0332−0.165 W/mK (25−1000 °C). The hydrophobicity of aerogel was achieved by simple chemical vapor deposition of methyltrimethoxysilane (MTMS). The Pal-based aerogel showed good performance in both fire resistance with high limiting oxygen index up to 90%, and heat resistance with tolerance of flame up to 1000 °C for 10 min. This renewable Palbased aerogel with a 3D framework is a promising material to be applied in fields of construction and aerospace for thermal insulation and high fire resistance.

Calcium-Doped Boron Nitride Aerogel Enables Infrared Stealth at High Temperature Up to 1300 °C

“…High-temperature thermal conductivities of Ca-BN aerogel were further measured by a hot disk thermal analyzer, and their values were about 0.14 and 0.15 W mK −1 at 900 and 1000 °C, respectively, lower than that of most aerogel materials in the previous reports [ 28 – 32 ], such as Al 2 O 3 aerogel (0.298 W mK −1 at 800 °C) [ 28 ], core–shell Al 2 O 3 aerogel/mullite fiber composite (0.16 W mK −1 at 1000 °C) [ 29 ], palygorskite-based aerogels (0.165 W mK −1 at 1000 °C) [ 30 ], aluminum borate foams (0.228 W mK −1 at 1000 °C) [ 31 ] and BN/SiOC aerogel (0.215 W mK −1 at 1000 °C) [ 32 ]. Therefore, Ca-BN aerogel exhibits great potential in high-temperature insulation.…”

Design, Synthesis, and Use of High Temperature Resistant Aerogels Exceeding 800 oC

“…Apparently, aerogels with efficient thermal insulation (low thermal conductivity ~0.010 W/mK) and extremely low density (~0.016 mg/cm 3 ) are ideal candidates in the aerospace field. [182][183][184] Besides, many industrial fields face extremely high operating temperatures during the production process. For example, the internal operating temperature of the conversion equipment and connecting pipelines in the hydrogen production plant is usually above 700 ℃, and the tank calciner is heat-treated in the absence of air.…”

Biorefinery Approach for Aerogels

“…The moisture resistance was shown to be improved by, for example, chemical vapor deposition of methyltrimethoxysilane after freeze-drying to produce ultralight (0.036 g/cm 3 ), hydrophobic and flame-retardant porous alginate with low thermal conductivity (0.332−0.0165 W/mK, 25−1000 °C) and a surface area up to 146 m 2 /g [252]. Also, nanorod clay (palygorskite) was combined with alginate to achieve fire and heat resistance.…”