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Silica Aerogel Is Limited Due To Its Fragile

Feb 23

Aerospace materials

Silica Aerogel is a material with unique properties which are especially useful in Silica Aerogel in Insulation applications due to its light weight, low thermal conductivity and high transparency. It consists of a three-dimensional network of silica particles which are interlocked in an intricate, pearl necklace-like structure which gives the material its unique attributes. These characteristics make it an attractive replacement for a variety of current insulation materials which are either flammable or have low thermal insulation performance. Silica aerogels are typically produced by removing the liquid from silica gels under supercritical conditions which results in the formation of a highly porous, yet solid, low-density material.

Due to their high thermal insulating properties, the demand for silica aerogels has grown considerably in recent years. In order to maximize the potential of these new materials, it is important to understand the physical mechanisms that govern their thermal behavior. This can be achieved by the use of various experimental techniques such as gas adsorption, mercury porosimetry and small angle X-ray scattering.

The gaseous thermal conductivity of aerogels depends on the pore size and connectivity. It also depends on the crystalline structure of the silica and its composition. In addition to this, the material's density and the ambient pressure influence the thermal conductivity. In particular, low-density aerogels exhibit lower thermal conductivity than their dense counterparts.

Moreover, the mechanical strength of silica aerogel is limited due to its fragile, brittle nature. However, efforts are being concerted to improve this property. The adsorption of polymers and other additives can enhance the mechanical properties of silica aerogels. Furthermore, combining silica aerogels with fiber materials can significantly improve the strength and elasticity of these lightweight materials.

Light scattering is another factor that limits the utility of silica aerogels as insulation materials. The scattering effect is dependent on the size of the crystalline particles as well as the wavelength of the incident light. As such, different wavelengths of light will scatter with varying magnitudes. Nevertheless, scattering can be reduced by the application of chemical modifications on the surface of the material.

Currently, the most popular materials used for insulation are organic polymer foams like phenolic and polyurethane foams. However, these materials are flammable which poses a serious fire risk for airplanes. Silica aerogels on the other hand are a safe alternative. Their vapor permeability and low thermal conductivity makes them an ideal choice for military aircraft.