Aerogel

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FIBRE REINFORCED AEROGEL BLANKET

THERMAL INSULATING MATERIAL

SAIKAT KUMAR SAHUBEM/626WHAT IS AEROGEL?

Aerogel is basically a synthetic porous ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas.Aerogels are sometimes also known by different names such as frozen smoke, solid smoke, solid air, or blue smoke owing to translucent nature and the way light scatters in the material.

Aerogels are typically characterized by low density solid, low optical index of refraction, low thermal conductivity, low speed of sound through materialsPREPARATION OF AEROGELSAerogel synthesis involves the following three steps-

Sol-Gel Preparation- The gel is prepared using silicon precursors, such as tetra methyl ortho silicate (TMOS), tetra ethyl ortho silicate (TEOS), methyl tri ethoxy silane (MTES), silicon alkaoxide, etc. The silica gel can be prepared by mixing tetra ethoxy silane Si(OC2H5)4 with ethanol and water to make it polymerize and thus producing a water based silica gel.

Si(OCH2CH3)4 (liq.) + 2(H2O) (liq.) SiO2 (solid) + 4(HOCH2CH3) (liq.)

Then a solvent, such as methanol, is used to extract and replace the liquidPREPARATION OF AEROGELS

Aging of the Gel- It provides strength to the structure of gel. The gel prepared earlier is aged. After jellification, the gel is left undisturbed in the solvent to complete the reaction. After completion of reaction the aerogel product is formed.

Drying- The solvent has to be removed while preserving the solid aerogel network. This can be done by supercritical drying. Aerogel materials are typically prepared by removing the solvent contained in a gel matrix by extraction in a supercritical fluid medium. The gel solvent system can be extracted from the wet gel with an appropriate solvent. Liquid carbon dioxide is the most popular extraction solvent because it is inexpensive.PREPARATION OF AEROGELS

AEROGEL PROPERTIES

Aerogels are highly porous solid materials which can consist of 99% air.Aerogels have an unusual combination of high porosity and small pore size.Inside the structure of the aerogel, air molecules are prevented from touching. Thus, heat transfer is impossible.In their original, brittle state, aerogels cannot be used for facade insulation. This is why aerogel can be mixed with plasters to prepare a thermal insulating plaster or an insulation board can be made with fibre mat and aerogel.Aerogel also has a very low density (0.030.35g/cm3).Sound velocity in aerogel is also low, which is approximately 100m/s.

FRAB- Fibre Reinforced Aerogel Blanket

Since aerogels cannot be used for facade insulation, it is casted into a fibrous batting, which provides mechanical integrity. Typically polyester, glass, carbon, or ceramic fibre can be used as blanket. The process includes the following steps-

Before drying the wet gel is filled into the blanket.

Then the solvent is removed via CO2 extraction and dried.

The blanket is rolled onto a spool.

FRAB- Fibre Reinforced Aerogel BlanketFRAB- Fibre Reinforced Aerogel BlanketThicknesses of the blankets are normally 2, 5, 10, 15, 20, 30, 40 mm.Thermal conductivity varies between 0.015 W/mK to 0.018W/mK.This blanket has excellent vapor permeability.It has good impact sound absorption.It does not contain any ozone depleting substances.Available Sheet size: 580 x 390 mm

Health Aspects:It is not expected to pose a carcinogenic risk.Silica is inert when ingested, and unlikely to be absorbed through the skin.Typical dust loading in fab-shop is