A Special Material or a New State of Matter: A Review and Reconsideration of the Aerogel

Abstract

The ultrahighly nanoporous aerogel is recognized as a state of matter rather than as a functional material, because of its qualitative differences in bulk properties, transitional density and enthalpy between liquid and gas, and diverse chemical compositions. In this review, the characteristics, classification, history and preparation of the aerogel were introduced. More attention was paid to the sol-gel method for preparing different kinds of aerogels, given its important role on bridging the synthetic parameters with the properties. At last, preparation of a novel single-component aerogel, design of a composite aerogel and industrial application of the aerogel were regarded as the research tendency of the aerogel state in the near future.

CNF-reinforced polymer aerogels: Influence of the synthesis variables and economic evaluation

“…5. Pure PVA showed bands in the regions 3600-3000 cm À1 (OAH stretching vibration of hydroxyl group), 3000-2850 cm À1 (saturated CH 2 /CH 3 groups, stretching vibration), 1800-1550 cm À1 (C@O stretching), 1500-1300 cm À1 (CH stretching) and 1200-940 cm À1 (CAOAC and CAC stretching vibrations) [57,61]. Both the pure PVA and the CNF-reinforced polymer aerogels prepared with different solvents presented the same peaks.…”

“…Sample GEL PVA(1% CNF) presented lower Tg, E 0 and E 00 modulus values than sample GEL PVA(0.25% CNF), which could be attributed to that the CNF distribution in the PVA matrix was heterogeneous, leading to a worse interaction between PVA and CNF. The mechanical resistance of CNF-reinforced polymer aerogels here described make these materials to be potentially used as building materials [1,57].…”

Strengthening effect of nanofibrillated cellulose is dependent on enzymatically oxidized polysaccharide gel matrices

“…Such porous materials are called either aerogels, supercritically dried gels (Kistler, 1931), cryogels, freeze-dried/ lyophilized gels (Lozinsky et al, 2003), or foams (Han, Zhou, Wu, Liu, & Wu, 2013). However, the term aerogel is becoming generally accepted for porous gel structures, regardless of whether they are lyophilized or supercritically dried (Borisova et al, 2015;Du, Zhou, Zhang, & Shen, 2013;Pääkkö et al, 2008). During the last few decades, aerogels have drawn increasing attention as thermal and acoustic insulating materials as well as due to their excellent properties for water uptake, pharmaceutical and biomedical media, tissue engineering scaffolds, and packaging materials.…”

“…During the last few decades, aerogels have drawn increasing attention as thermal and acoustic insulating materials as well as due to their excellent properties for water uptake, pharmaceutical and biomedical media, tissue engineering scaffolds, and packaging materials. As a result, numerous methods and techniques have been developed, so various types of raw materials can be used to form aerogels (Du, Zhou, Zhang, & Shen, 2013). Recently, research efforts have focused on the development of materials from environmentally compatible renewable resources.…”

Synthesis of a novel Al2O3–SiO2 composite aerogel with high specific surface area at elevated temperatures using inexpensive inorganic salt of aluminum

“…It can slowly consume the protons in an acidic condition and mildly facilitate the condensation mildly. The sol-gel mechanism can be described as follows [12][13][14]:…”