International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 05 Issue: 03 | Mar-2018 www.irjet.net p-ISSN: 2395-0072 © 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 4098 A Review on Aerogel An Introduction Ghodake Sagar S. 1 , Londhe Babasaheb C. 2 1 Department of Mechanical Engineering,S.N.D.COE &RC,Maharastra,India 2 Asso.Prof.,Department of Mechanical Engineering,S.N.D.COE &RC,Maharastra,India -----------------------------------------------------------------------***------------------------------------------------------------------------------ Abstract – Aerogel is a solid with extremely low density and low thermal conductivity. Nicknames include frozen smoke, solid smoke, solid air, or blue smoke owing to its translucent nature and the way light scatters in the material. It look like expanded polystyrene to the touch. It can be made from a variety of chemical compounds. by extracting the liquid component of a gel through supercritical drying Aerogel is produced. This liquid can be slowly dried off without changing the solid matrix in the gel, as would happen with conventional evaporation. The first aerogels were produced from silica gels.. Aerogel does not have a designated material with set chemical formula but the term is used to group all the material with a certain geometric structure. Aerogel has become a material of interest to scientists in recent decades due to its unique physical properties that give it the potential to improve technologies in a variety of fields. In particular, aerogels offer the lowest densities and the lowest thermal conductivities of any known solid. Since then, many other types of aerogels have been created, including carbon-based and clay-based aerogels. Silica-based aerogels are the simplest and most widely studied type of aerogel, with new uses and applications arising ever. The goal was to create a reliable, non-toxic method, using inexpensive materials Key Words: Aerogel, Material, silylating agents, Airglass, Alcogel 1.INTRODUCTION )n ͳͻ͵ͳ, ǮSteven Kistlerǯ made a bet with a colleague that he could prove a wet gel contained a solid matrix the same size and shape of the gel. To do this he began with a gel and extracted the liquid, leaving a low-density solid behind. Using an autoclave to drive the liquid past its critical point he was able to conquer the obstacle of surface tension which would otherwise rip apart the internal solid structure of the gel. His successful wager produced the first silica-based aerogel. For half a century this curious material went relatively unnoticed, due to the notorious difficulties and safety issues involved in its creation . In the early years, fabricating aerogels meant sending alcohol to volatile pressures and temperatures in order for it to reach its supercritical point and allow for the supercritical-extraction of the gel. Then, in the ͳͻͺͲǯs, interest was renewed when a French scientist, attempting to improve the fabrication process for the French government, developed a process which used less-toxic materials. He switched out methyl alcohol and Tetra Methyl Ortho Silicate (TMOS) for the safer pairing of ethyl alcohol and Tetra Ethyl Ortho Silicate (TEOS). The next breakthrough came in the early ͳͻͻͲǯs when liquid carbon dioxide replaced the ethyl alcohol involved in the gel before the sample was taken through the supercritical process. This allowed scientists to bypass the dangerous pressures and temperatures needed to send the pure ethanol past its supercritical point. Liquid carbon dioxide has the relatively mundane requirements of 305 K and 1050 psi to be brought to its supercritical point. To obtain hydrophobic low density and low thermal conductivity aerogels for thermal insulation and liquid marble formation purpose, various sol-gel parameters, processing parameters namely washing, shaking, various solvents, silylating agents and drying method were varied along with doping the gel with TiO2 powder. Aerogel is a typical nano-porous thermal insulation material with open-cell structure. Due to the excellent properties, aerogel is widely applicable in industry fields such as astronautics, thermal insulation and so on. However, the extremely low porosity and complicated structure make it a challenge to accurately predict the effective thermal conductivity and enhance the insulation performance. The experimental measurements of the aerogel thermal conductivity under different pressure and temperature. Most of the present researches adopted some regular structure to represent the aerogel structure, which can simplify the heat transfer analysis of materials, but also contain artificial parameters and ignore the stochastic characteristic of aerogel material. In the aspect of numerical study, used the macroscopic numerical method to obtain the thermal conductivity, whereas using traditional numerical methods is hard to solve the micro-scale heat transfer problem. the open-cell micro-porous random structure of aerogel was reconstructed basing on the solid-phase growth principle, which has no artificial parameters and guarantees the stochastic characteristic of aerogel material. Then the lattice Boltzmann method was adopted to predict the aerogel effective thermal conductivity. The increase of building energy consumptions driven by the higher expectations for indoor comfort, together with concerns for the rise in GHG emissions, are pushing the research and design interest toward energy saving in buildings. The development of new insulating materials is among the most promising options. The aerogels are considered one of the most promising family of materials for insulating purposes, given their high thermal insulation. They are dried gels with such a high porosity that they have lower thermal conductivity than air. Moreover, they are