Do you know what is the lightest solid in the world? A piece of paper, a feather or a grain of rice? Neither, but a material called aerogel, which is lighter than air and looks like a frozen cloud of smoke. Having said that, people can't help wondering, what is aerogel? Why is it the lightest solid in the world?
First, we need to know what gel is. Gel is a kind of elastic semi-solid liquid with high concentration, which becomes gel after losing fluidity under the action of polymer. The most common gel in life is jelly, which has a delicate three-dimensional network structure and contains more than 99% water. 193 1 year, inspired by jelly, American scientists removed liquid from silica gel through extreme drying process, replaced it with masonry, and filled its grid gaps, thus forming silica aerogel. Its composition, like glass, is silica, but the content of silica is less than 1%, and the rest 99.8% is air. It is one of the lowest density materials known in the world. After more than 90 years of development, aerogels have various types, such as silicon series, carbon series and metal series.
In fact, as long as the gel can keep its original shape after drying, it can be called aerogel. Although it looks fragile, it is actually very durable and can withstand the pressure of thousands of times its own quality. For example, a two-gram aerogel can support 2.5 kilograms of bricks. In addition, its nano-scale grid structure has strong air insulation ability, which is 39 times stronger than the best glass fiber.
This is why aerogels become excellent cold-proof materials. The three-nanometer-thick aerogel winter clothes can resist the light attack of cold air at-196 degrees Celsius, and because the main component is air, the thermal conductivity and refractive index of aerogel are very low, and the melting point is as high as 1400 degrees Celsius. Someone has done such an experiment. Put a petal on the aerogel sheet and bake the aerogel with a gun. You can clearly see that the petals are slowly withering, but the aerogel facing the flame has not changed. This feature also makes aerogels an indispensable material in space exploration. Its thermal insulation performance can minimize the heat generated by the friction between the spacecraft and the atmosphere, thus better protecting the spacecraft and prolonging its service life.
At present, aerogels have been used in many space probes in China, such as "Zhu Rong" and "Tianwen-1". In this technology, we were limited from the beginning to independent innovation, and then to self-reliance. Scientists in China showed us the speed of China. In 20 13, the research group of Professor Gao Chao from the Department of Polymer Science of Zhejiang University developed an ultra-light aerogel carbon sponge with a density of 0. 16mg/cm3, which is about 1/7 of the air density, setting a new record for the lightest material in the world.