A near-invisible silica gel that would serve as a thermal barrier in cryogenic fuel tanks, boot soles and sun films may sound like a magical product straight from a sci-fi.
But it’s a tangible reality that researchers of the Indian Space Research Organization at its Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, have made possible.
The yet to be christened product, the hydrophobic silica aero gel as it is known now, is supposed to have low thermal conductivity and density and high specific surface area and can be applied on any surface.
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With its “exotic properties,” silica aero gels are attractive candidates for many unique thermal, optical, acoustic, catalytic and chemical applications and are best known for their “super-insulating property.”
Silica aero gels can be made in chunks (granular), beads, powder and tape or sheet form, and may be used as the application demands, according to VSSC.
As air fills the gel up to 95 per cent of its size, it comes as super lightweight material. The air molecules trapped inside the gel would act as insulators, and its heat conductivity is close to zero. They could be used for coating the windows of houses and vehicles as they would let in 95 per cent of the light that falls on the surface and fully deflect the heat.
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“The researchers stumbled upon the exotic properties of the gel during their search for a super thermal insulator for the cryogenic fuel tanks of rockets. The temperature on the surface of the rockets is likely to be between 300 and 400 degree Celsius during its flight, and the cryogenic fuel needs to be insulated. Thus, the gel was developed,” explained K. Sivan, director, VSSC.
As the gel acts as a thermal barrier, it could be used as a protective component of clothes and boots of solders stationed in extremely cold regions such as Siachen and Kargil. The weight of military clothes could be brought down to ordinary dresses after applying the gel over it thus giving the much required freedom of movement for the soldiers. To coat a jacket may require around 500 grams of gel. “Discussions are on with some textile developers for the design of cloths by applying gel over it,” said Dr. Sivan.
“Besides apparel for soldiers, the gel could also be used for heavy duty dresses used by researchers working in Arctic/Antarctic expeditions. For insulating cryogenic fuel tanks, 2.8 kg of gel is required. It needs to be produced in large quantities for commercial use and discussions are on with some entrepreneurs,” he explained.
“ISRO has offered the knowhow of the technology to suitable entrepreneurs in India and the benefits from the transfer of technology would go to the country,” he said.
The other applications of the material include acoustic insulations, building and pipeline insulation and window facades as translucent panels which allow natural light but not heat for hot areas where air conditioners are and trapping heat in cold places.
It would also be used for controlling oil spills and vibration. Other applications include acoustic damping materials and insulation in refrigerators, fillers or additives in paints, sealants, adhesives, cement, coatings, foams, and for increasing the heat resistance of the material, according to VSSC sources.