Aerogel superinsulation

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. 

K. Duer, S. Svendsen, Monolithic Silica Aerogel in Superinsulating Glazings, Solar Energy, 63, 259-267 (1998). 

Rigacci A, Marechal JC, Repoux M, Moreno M, Achard P (2004) lYeparation of polyurethane-based aerogels and xerogels for thermal superinsulation. J Non-Cryst Solids 350 372-378... 

Jensen KI, Kristiansen FH, Schultz JM (2005) Highly superinsulating and light transmitting aerogel glazing for superinsulating windows, Publi Final Report HILIT+ (Eu contract ENK-CT-2002-00648)... 

Duer K, Svendsen S (1998) Monolithic siUca aerogel in superinsulating glazings Sol Energy 63 259-267 Husing N, Schubert U (1998) Aerogels - Airy materials Chemistry, stracture, and properties. Angew Chem Int Ed 37 23 5... 

Despite those differences, it appears clear that those two aerogel families present a common huge potential for hybridization with their nanostructured silica homologues, which could lead to, among others, brand new reinforced superinsulating materials. 

Abstract The present chapter is focused on describing the intimate link which exists between aerogels and thermal superinsulation. For long, this applied field has been considered as the most pronusing potential market for these nanostructured materials. Most likely this old vision will become reality in the near future. 

Following a short presentation of the global need for superinsulation together with a closer look at the specific situation in the building sector, we propose within this synopsis a brief analysis of (1) the world s insulation markets, (2) superinsulating aerogel materials and their alternatives, (3) commercial aerogel insulation products available today, and (4) our estimation of their most likely applications worldwide in the future. We conclude this chapter with some first considerations on health, toxicity, and environmental aspects. 

Based on recent developments in the field, it can be stated that aerogels still offer the greatest potential for nonevacuated superinsulation systems and consequently must be considered as an amazing opportunity for sustainable development. This chapter of the handbook bridges the gap between those dealing with thermal insulation properties of aerogel materials in general (Chap. 21) and the various commercial products described in Part XV. 

VIP and VG offer outstanding thermal resistance because evacuation of the porous core material or the glazing cavity, respectively, results in a drastic reduction of heat transport by gas molecules. Aerogels on the contrary are nonevacuated superinsulators. Their low thermal conductivity is correlated with the pore structure of these materials. Before we briefly touch on the effect of the unique structural features of aerogels on heat transport, let us recapitulate the basics. Generally, heat is transferred by conduction, convection, and radiation. In porous materials there are five possible contributions to the total heat transfer, namely ... 

Most commercially relevant superinsulating Si02 aerogels have densities between 80 and 200 kg m. Their thermal conductivity values are dominated by conduction through the solid silica particle network at high densities and a combination of radiation and gaseous conduction through the air inside the pores at low densities. To produce the lowest conductivity materials, it is necessary to find an optimum between those two. It seems apparent that... 

Current Status of the Superinsulating Aerogels and Associated Components... 

All these properties have a strong influence on the thermal characteristics. For example, as previously described in this handbook by H.-P. Ebert (Chap. 23) and already underlined in the previous paragraphs of this chapter, the effective thermal conductivity is strongly dependent on the aerogel s apparent density [27]. Indeed superinsulating samples (e.g., X <0.020 W m K ) can only be found within a rather short range of densities (Figure 26.6), usually located between 0.10 and 0.20 g cm . ... 

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