Aerogel

Airgel is a very light substance, it has a solid consistency similar to a gel composed 98% of air and 2% of amorphous silicon, which is the main component of the glass.

Apparently it is a solid foam, which among other properties, such as to withstand high temperatures, it is also an excellent insulating substance. By virtue of its appearance is also called sand inflated, frozen smoke, solid smoke or blue smoke due to its transparency and its bluish color, aesthetically it looks like foam, although it doesn't have the same softness.

The airgel was created for the first time in 1931 by Steven Kistler that managed to exchange the liquid portion of a jelly eliminating it through the use of high values of pressure and temperature with a gas, then arriving to define a solid structure. The first experiment led to the birth of silica gel, and subsequent experiments have also led to the use of other substances such as aluminum, chromium, tin, etc. ... until the recent carbon aerogels.

Features and airgel technology

Airgel is nothing more than a gel of silicon dioxide, which through a series of processes of chemical nature, is transformed into a solid mass amorphous, three-dimensional, the size in millimeter.

Initially, the production costs were very high, reason why the first studies on this topic went rather slow, only subsequently the production costs were lowered, allowing the spread of airgel in various fields including the construction industry, in which, for its properties and for its nano porous structure, is used as thermal insulator, and as a good inhibitor convective because the air can not circulate inside.

Obviously the airgel is almost never used alone, but through a procedure which is called impregnation, is joined to a fibrous reinforcement, which provides flexibility, durability and usability of the element and without compromising the ability of insulation. Airgel, being essentially constituted by air, is considered as the lightest solid existing in nature.

Regarding the characteristic of transmitting sound and heat, it is very similar to the gas, which is why the values of the propagation of sound and heat are very low.

Types of Aerogel

Airgel is a product obtained from a series of chemical transformations depending on the type of material that we use, we can have different types of airgel.

The silica airgel is the most common type and the most widely used, one of its main features is to absorb infrared radiation. In this way it is possible to obtain materials that leave the sunlight to enter within the building whilst ensuring thermal insulation.

Carbon aerogel has the characteristic of a high porosity. It is usually produced in the form of composite sheets, which are essentially constituted by carbon fibers, impregnated with resorcinol-formaldehyde aerogels and pyrolysed.

Carbon airgel has a good electrical conductivity, therefore, the sheets made with this type of aerogels are used in capacitors. In addition,it also has the property of absorbing infrared radiation well, reflecting only 0.3% of it, this property allows it to be very efficient in storing solar energy.
Airgel alumina consists essentially of aluminum oxide, which is used as catalyst especially together with other metals, this type is rarely used in construction but is object of study of NASA.

Aerogel on the market

This product called airgel is not used in the building industry when newly produced, because of all the chemical processes that it suffers, but it is found in products that have reinforcement support consisting of geosynthetic in felted polyester, available in different thicknesses and density. The final product obtained is a flexible insulating mat as well as produced by RT Insulation and the AKTARUS GROUP, which has a reduced thickness, but at the same time offers high thermal performance.

An element of easy handling, strong enough and with excellent elasticity in compression. In addition, a specific treatment performed during production, makes the material hydrophobic, while maintaining high breathability to water vapor.

From the point of view of construction, the realization of these Aerogel blankets, considering their low thermal conductivity, the lowest ever obtained in a heat-insulating material, allows to obtain high thermal resistance with reduced thickness.

As we have seen, aerogels are materials that are applied differently depending on the type. In construction we can find them in granular form to give thermal insulation on the windows of the buildings. Transparent silica airgel would be very suitable as a material for the thermal insulation of windows, significantly limiting the dispersion of heat in buildings.

Airgel pros and cons

Surely this technology compared to that of the common insulating materials offers many advantages, including the reduction of space for insulation, a lower volume of material used, a reduction of costs of transportation and disposal with benefits then also on the environment, the use in small spaces because of the flexibility of the material, the possibility of realizing a continuous coating even on irregular structures.

Despite its excellent characteristics of thermal insulation, which makes it among the best materials from this point of view, when the glazing is filled with airgel rather than simply with air, there are also negative aspects:

- Reduction of light transmission of 25-30%;
- Reduction of the thermal transmittance between 40 and 60%;
-Image distortion;
-Poor color rendering, the light takes on different colors;
- High costs.