Experimental and Numerical Energy Assessment of a Monolithic Aerogel Glazing Unit for Building Applications

In the last few decades, the attention of researchers has been focused on the characterization of aerogels in order to improve the thermal performance of transparent building envelopes. Granular aerogel is already spread in the market thanks to the easy manufacturing system, whereas the difficulty in producing monoliths without defects, cracks, and inhomogeneity limited the diffusion of monolithic aerogel systems. A new production process for the monolithic panels was developed at Union College (Schenectady, NY, USA); it is a rapid supercritical extraction technique which allows a reduction in production time (only a few hours) and results in less solvent waste. Panes with maximum dimensions of about 100 × 100 mm were fabricated and composed in a unique glazing system, with external dimensions 300 × 300 mm. The thermal characterization of the innovative monolithic aerogel glazing system (simple float glazing 4.7-mm-thick monolithic aerogel pane 15-mm-thick simple float glazing 4.7 mm thick), which was carried out by means of a Small Hot Box apparatus, showed a thermal transmittance value of about 1.1 W/(m2K). Data was used in dynamic simulations of a typical non-residential building. They showed that the new investigated solution allows a valuable reduction with respect to a low-e double glazing system in terms of heating energy demand (about 5–7% for Helsinki, 8–12% for Paris, and 10–15% for Turin), for different window-to-wall ratios.

Synthesis and Characterization of Copper-Nanoparticle-Containing Silica Aerogel Prepared via Rapid Supercritical Extraction for Applications in Three-Way Catalysis

ABSTRACTCopper-alumina and copper-silica aerogels formed by impregnation of a copper(II) salt into an alumina or silica wet gel before supercritical extraction have been found to contain copper in multiple oxidation states: Cu0, Cu+1 and Cu+2. These aerogels are effective at catalyzing the reduction of NO and the oxidation of HCs and CO under conditions similar to those found in automotive three way catalysts. In this work we have developed a preparation method incorporating Cu0, Cu+1 and Cu+2 nanoparticles directly into silica aerogels. Nanoparticles in the form of (a) Cu0 nanorods (100 nm diameter, 10-20 μm length); (b) Cu+1 nanoparticles (350 nm diameter); and (c) Cu+2 nanoparticles (25-55 nm diameter) were added (0.5-15% by weight) to separate precursor mixtures consisting of tetramethyl orthosilicate, methanol, water and ammonia. These precursor mixtures were then processed using a rapid supercritical extraction (RSCE) method to form aerogels. The resulting aerogels show evidence of nanoparticles dispersed throughout the silica aerogel structure. Addition of Cu+1 and Cu+2 nanoparticles decreases the surface area of the aerogels significantly. X-Ray diffraction shows that regardless of initial oxidation state of the nanoparticles, crystalline Cu0 is detected after RSCE processing to 290 °C. Following heat treatment at 700 °C, crystalline Cu+2 is detected. The copper containing silica aerogels are found to be catalytically active with light-off temperatures (50% conversion) for NO and CO at 400 °C in three-way catalytic applications.