Aerogels thermal insulation

Keywords Fumed Silica / Aerogels / Thermal Insulation... 

Thermal Insulation. In addition to their low thermal conductivity, as discussed in the section above, siUca aerogels can be prepared to be highly transparent in the visible spectmm region. Thus, they are promising materials as superinsulating window-spacer. To take further advantage of its... 

Silica aerogels, a newly developing type of material, also have been produced as thermal insulations with superinsulation characteristics. The nanometer-size cells limit the gas phase conduction that can take place. The aerogels are transparent to visible light, so they have potential as window insulation. The use of superinsulations at present is limited by cost and the need to have a design that protects the evacuated packets or aerogels from mechanical damage. 

The main disadvantage of gels is their high porosity. This property may be used to improve the thermal insulation of aerogels, but in most cases it is con-... 

Although the aerogel loses its optical transparency by this measure, its thermal insulation is strongly enhanced. Total conductivities for nonevacuated aerogels of the order of 0.014 W/(m K) are achievable. This is considerably lower than in CFC-blown polyurethane (PU) foams, the best nonevacuated thermal insulators available today [48]. 

Figure 4 Spectral specific extinction (absorption) of pure silica aerogel (dashed), silica aerogel doped with 5% carbon black (dotted), and RF aerogel (solid). Note that the transmission window in pure silica aerogel between 3 and 5 j4m leads to a dramatic increase in thermal radiative transport and renders pure Si02 aerogels ineffective as thermal insulators above 100°C. The integration of an opacifier markedly improves the thermal resistance of Si02 aerogels.

One of the most promising applications of SiOa aerogels is their use as transparent thermal insulation. Extensive studies of transparent aerogels have shown that the thermal resistance as well as the solar transmission are sufficiently high to make these materials most suitable for passive solar usage [72]. However,... 

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