Nanocomposite aerogels

Nanocomposite aerogels mainly consist as homogeneous dispersions of nanoparticles in an aerogel matrix. The preparation of nanocomposite aerogels can be... 

Cai J, Liu SL, Feng J, Kimura S, Wada M, Kuga S, Zhang LN (2012) Cellulose-silica nanocomposite aerogels by in situ formation of silica in cellulose gel. Angew Chem Int Ed 51 2076-2079... 

The incorporation of nanoparticies as a way to increase the possibility of the use of aerogels as innovative functional materials and the challenges in the controlled preparation of nanocomposite aerogels is reviewed in this chapter. 

The different strategies that have been adopted to synthesize nanocomposite aerogels follow two general approaches, depending on whether the nanophase (or its precursor) is added during or after the sol-gel process. 

In the following, some recent examples of nanocomposite aerogels will be reviewed with the aim of pointing out some significant advances in the preparation of functional... 

Figure 16.1. Schematic diagram of the different approaches for the chemical synthesis of nanocomposite aerogels.

Maghemite-silica nanocomposite aerogels were prepared by van Raap et al. using different precursors (TEOS and TMOS) and different pressure-temperature drying... 

Figure 16.8. ZFC-FC magnetization curves of the CoFe204-Si02 nanocomposite aerogel with 5 wt% loading of cobalt ferrite (reproduced from [28] by permission of American Chemical Society).

While almost all papers on nanocomposite aerogels containing metal oxide nanoparticles dispersed in an insulating matrix refer to silica-based systems, a few examples are also available for other matrices. 

The preparation of nanocomposite aerogels made out of zero-valent metal or alloy nanoparticles in an insulating aerogel matrix has attracted a great deal of effort in view of the preparation of materials for catalysis, biomedicine, optoelectronics, and sensors. As it is the case for aU sol-gel nanocomposites, silica is by far the most investigated matrix for supporting metal/alloy nanoparticles, although alumina, titania, chromia, and polymer supports have also been proposed. 

Since every preparation route has specific advantages and drawbacks, it is not possible to define a general strategy for obtaining nanocomposite aerogels. Nevertheless, metal and metal oxide nanoparticles supported on aerogel matrices with given compositional and microstructural features have been effectively prepared. 

Casu A, Casula ME, Corrias A, Falqui A, Loche D, Marras S (2007) Magnetic and structural investigation of highly porous CoFe204-Si02 nanocomposite aerogels. J Phys Chem C 111 916-922... 

Carta D, Corrias A, Mountjoy G, Navarra G (2007) Structural study of highly porous nanocomposite aerogels. 

Loche D, Casula MF, Falqui A, Marras S, Corrias A (2010) Preparation of Mn, Ni, Co ferrite nanocomposite aerogels by an urea-assisted sol-gel procedure. J Nanosci Nanotechnol 10 1008-1016. doi 10.1166/ jnn.2010.1907... 

Casula MF, Corrias A, Paschina G (2002) FeCo-Si02 nanocomposite aerogels by high temperature supercritical drying. J Mater Chem 12 1505-1510... 

Carbon Nanotube-Polymer Nanocomposite Aerogels and Related Materials Fabrication and Properties... 

In this chapter, the recent advances in the field of carbon nanotube/polymer nanocomposite aerogels and related materials are described. An emphasis is paid to the relationship between the preparation method and the most characteristic properties of these materials such as density, surface area, electrical conductivity, mechanical strength, and so forth. 

NANOCOMPOSITE AEROGELS CONTAINING A HIGH CONCENTRATION OF CARBON NANOTUBES... 

Another original approach for fabrication of nanocomposite aerogels based on CNTs and chemically cross-linked polymers was described by Zou, Liu, and Karakoti (2010). The authors first disperse MWNTs by poly(3-hexylthiophene)-b-poly(3-(trimethoxysilyl)propyl methacrylate) (P3HT-PTMSPMA) due to the n-n interaction between nanotubes and P3HT, form a physical gel and, then, cross-link the polymer layer by hydrolysis and condensation of PTMSPMA blocks (Figure 8.3). 

The general trend seen in the studies focused on nanocomposite aerogels containing a high concentration of CNTs is that the polymers serve as structure binders, that is, they reinforce the material, but do not dominate the physico-mechanical properties. As a typical example, the addition of polymers, which are nsnally insulators, decreases the electrical conductivity of CNT aerogel to a certain extent bnt the values reported are still in the range of those accepted for conducting materials. 

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