Synthesis Of Ultra-light, Mechanically Strong And Thermally Insulating Aerogels

Abstract

Synthesis of Ultra-Light, Mechanically Strong and Thermally Insulating Aerogels Thermal insulation is considered one of the main factors of reducing heat and energy consumption in buildings. There are many insulation materials used to reduce energy consumption and heat loss in buildings, such as: cellulose, glass wool, rock wool, polystyrene, urethane foam.., etc. Unfortunately, most of these materials have problems with their durability, effectiveness and cost. Aerogels being ultra-light, highly porous and highly thermal insulating materials are being considered for applications as varied as thermal and sound insulation for aerospace applications, as absorbents for environmental remediation and as supports for catalysts [1-4]. However, the major problem with aerogels is their mechanically fragility that impeded their commercialization and limited their fabrication in the form of granules or panels of limited thickness. Aerogel production is a slow and tedious process. Wet gels, termed aquogels or alcogels depending on the solvent can be rapidly synthesized following well-established procedures [5,6] but drying is time-consuming. Because of capillary forces the solvent cannot be evaporated without cracking and shrinking the monolith. We want to share very interesting results of a novel synthesis approach through which mechanically strong aerogels can be fabricated just in few hours instead of few days. The other novelties associated with our process is one pot synthesis for both native and cross-linked aerogels and no need for time consuming process of multiple solvent exchanges. This also significantly truncate large volume of fresh solvent required during the conventional synthesis process. The results are of particular importance, since they dramatically shorten fabrication times for monoliths with large sizes of native and, most importantly, of cross-linked aerogel. We have synthesized samples using base- and acid-catalyzed chemistries, varied alkoxide concentration and, for cross-linked aerogels, monomer concentration. Depending on alkoxide concentration, native oxide aerogels had densities between about 0.06 and 0.17 g.cm-3 and surface areas between about 300 and 500 m2.g-1. Figure 1 shows our synthesized Aerogels. Our group has been developing alternative fabrication methods which enable to produce custom parts which are made mechanically strong by reinforcing the regions of highest solicitation with a polymer. We have fabricated custom parts that may be used as insulation of selected parts of internal combustion engines, passive fire protection of structural elements in building, and lightweight footwear for extreme cold conditions. We also have developed cost-effective and scalable procedures for fabricating these custom- shaped aerogels.