One of the most requested materials in our collection is the aerogel. To be specific aerogel is not a material but a process to create a material. Back in around 1929-1930 Dr. Samuel Kistler invented the aerogel process when he was working on solidifying amino acids in a process that sounds very similar to that for aerogels.
"It occurred to Dr. Alling that if a solution of amino acids, in some solvent whose critical temperature was not so high as to decompose them, were gradually brought into the neighborhood of the critical temperature, crystallization might be induced since the solubility decreases rapidly as that temperature is approached, and the log of the viscosity decreases inversely as the log of the temperature…I therefore proposed to i....nvestigate the precipitation of compounds from solution as the critical point is approached, paying special attention to indications of supersaturation. I have made a careful study of the literature and at my earliest opportunity intend to conduct experiments in the laboratory designed to demonstrate the feasibility of this method of crystallization...."
Here from the first article in Nature Magazine form May 1931:
"The procedure that we have adopted is as follows :The jelly is first formed in a suitable liquid in diluteform. The liquid is then replaced by another which does not dissolve the structure and has a reasonably low critical temperature. Alcohol has proved quite satisfactory for most of the inorganic gels, ether has advantages in the case of easily reduced substances, and propane was used for all of the organic jellies. In making the replacement, it is necessary that each liquid used be completely miscible with both that which precedes and that which follows it. For example, water may be replaced by alcohol and then by ether. Mere evaporation would inevitably cause shrinkage. However, the jelly is placed in a closed autoclave with an excess of liquid and the temperature is raised above the critical temperature of the liquid, while the pressure is maintained at all times at or above the vapour pressure, so that no evaporation of liquid can occur and consequently no contraction of the gel can be brought about by capillary forces at its surface. When the critical temperature is passed, the liquid has been converted directly into a permanent gas without discontinuity. The jelly has had no way of ‘ knowing ‘ that the liquid within its meshes has become a gas. All that remains is to allow the gas to escape, and there is left behind a coherent aerogel of unchanged volume."
Fast forward to the 1970s when safer and more efficient methods of production were found Aerogels again took hold of the imagination of the scientific world. In the 1980s and 1990s scientists continued to work with the process and hone the elements until it was commercially viable. Around the same time NASA started to use aerogel on its space missions to insulate the computers and electronic aspects of the spaceships. NASA also utilized the aerogel tiles to capture dust from the comet WIld 2 in 1999.
So for something so fragile and light the silica aerogel has a very robust history.
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