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The Miracle of Air: What percentage of air is in aerogels?
Aerogels, this eye-catching and wonderful material, have been active in the scientific community since the 1930s. Having received widespread attention for its unique properties and amazing application potential, airgels are porous synthetic materials whose liquid components are replaced by gases and do not collapse significantly in structure. So, exactly what percentage of this magical substance is air?
Aerogels are one of the lowest density solids in the world, with many aerogel samples having an air composition of up to 99.98%.
The magic of airgels lies in their lightweight structure and excellent thermal conductivity. This material is effective in resisting heat conduction, convection and radiation, making it an excellent insulating material. For example, the thermal conductivity of silica airgels is as low as 0.003 W·m−1·K−1, which makes it extremely potential in areas such as construction and aerospace.
In fact, the manufacture of aerogels can be traced back to 1931, when the then scientist Samuel Stephens Kistle took the opportunity of a bet to successfully replace the liquid part of a solid with a gas for the first time, and No significant contraction was caused. However, the structure of airgels is not simple, although it has a "gel" in its name, but in fact its texture is firm and dry, with very different physical characteristics from traditional gels.
Even extremely light airgels can still create permanent dents if sufficient pressure is applied, but this is somewhat improved using more modern modified airgel structures.
The porous structure of the airgel enables it to carry large amounts of air, which is also the basis for its excellent insulating properties. Despite the different air compositions of different types of aerogels, the porosity of most aerogels ranges from 90% to 99.8%, which means that about 97% of the volume therein is air. Such a structure is not only lightweight, but also effectively resists heat transfer.
The cockroach properties as well as insulating properties of airgels not only make it play a core role in refrigeration technology, but are also widely used in aerospace engineering. Another breakthrough application of this material is its ability to effectively capture tiny particles to achieve filtration. Aerogels have also shown amazing results in many experiments with environmental filtration.
Because airgels are composed of air and solid structures, they are prone to degradation after contact with water, which has also driven scientists to find solutions that can effectively waterproof.
The waterproofing properties of airgels are a hotspot for further research. This material is usually hydrophilic and relatively easy to absorb water, so it is particularly important to chemically treat it during preparation so that its surface can remain hydrophobic for a long time. Some technology companies are focusing on developing waterproof aerogels, which will further expand the application of the material.
Another important topic about aerogels is their production process. Aerogels are produced primarily by a sol-gel process, which includes three steps: sol generation, aging, and drying. In these three processes, it becomes important to control the size and surface area of the pores, which directly affects the performance of the final aerogel.
Although the preparation process is relatively complex, the use of techniques such as supercritical drying can effectively avoid the collapse of the airgel structure and maintain its flexibility and lightness.
With the advancement of technology, the application of airgels in daily life is becoming more and more common. For example, their use in insulation can help homes reduce energy consumption and improve protective performance. While in the aerospace field, aerogels are used to protect sensitive electronic instruments from extreme temperatures. Furthermore, with the rise of environmental awareness, airgels have also been included in the choice of sustainable materials.
Aerogels that combine scientific and engineering techniques not only demonstrate their uniqueness, but are more likely to change our way of life in the future. What other new uses can such an amazing material be developed?
