The paper "Aerogel as an Engineering Material and Its Effectiveness" is a perfect example of a case study on engineering and construction. Aerogel is manufactured from titania, silica, alumina, etc and is usually filled with vacuum, water, air, or alcohol as stipulated by Aegerter (2011). Additionally, the surface is then modified by the use of carboxyl, amine, and agents for silane coupling, agents for chelating, enzymes, and other substances (Mortensen, 2007). Properties of Aero-gel include; Have an extremely low density of approximately 0.003g/cm3. Has very high porosity ranging from 82% to 99.8% It has a very low thermal conductivity.
(0.02W/m-k) It has an index of a fraction that is extremely low (usually less than 1.05) Its dielectric constant is very low usually k=1.0 to 2.0. Its specific surface area is very high ranging between 500m2 /g and 200m2/g. 2 Examples and images of materials Aerogels are manufactured through the technology of sol-gel and have different types including; cellulose, oxides such as zirconia and quartz, polymers, starch, and basically any material that has gelling qualities. Monolithic Silica Aerogel(Aegerter, 2011) Monolithic silica aerogel (Aegerter, 2011) 2.1 Production of Aerogels Aerogels are formed through two major stages: One process involves the production of the wet gel and the second stage involves the drying of the wet gel resulting in the formation of aerogel by the use of Silicon Alcoxide precursors such as tetraethyl orthosilicate as noted by Ashby and Schodek (2009).
The use alkoxides are used to improve the various properties of the gel and also for the elimination of the appearance of the unneeded by-products of salt. Moreover, it facilitates an increased control of the product. Si (OCH2CH3)4 (Lid) + 2H2O Lid =SiO2 (solid) + 4HOCH2CH3 (Lid) The silicon alkoxide concentration used during the process determines the eventual aerogel density and the process is carried out in ethanol.
The use of catalysts is essential in the formation of aerogel because at room temperature the reaction is very slow and takes many days or even weeks before the process is completed. The properties of the eventual aerogel product and its physical and microstructure characteristics are determined by the nature and amount of catalyst applied (Mortensen, 2007). Ammonia is used as a basic catalyst while catalysts that are acidic include hydrochloric and portico acid. Gels prepared in a single process involves base or acid-catalyzed TEOs.
Whether Aerogels are two-stage or single-stage, the varying formation conditions result in critical modifications to the aerogel product. Nonetheless, the two-stage process is preferred to one stage. 2.1.1 Soaking and Aging The condensation and hydrolysis effect of Si (OCH2CH3)4 reactions is deemed complete when the gel point is attained by the sol but this is not the truth. To facilitate silica system strength, enough gelation time needs to be provided (Mortensen, 2007). The process should be gradual and should be advanced by managing the content of the water and PH of the coating fluid.
For gels catalyzed by the base aging procedure, it involves soaking the gel in water or alcohol for two days. Thereafter, drying of the gel takes place preceded by the aging of the gel. This is obtained through soaking of the gel in alcohol to such a time when all water disappears. 2.1.2 Drying through the super-critical process.