彭蒙惠英语 Amazing Aerogel 2

New uses for old ideas

　　Surprisingly， some types of aerogel have been around a long time. Introduced in the 1930s， the first aerogels were the result of a bet between chemists Samuel S， Kistler and Charles Learned to see who cold remove the liquid from a jar of jelly without causing the jelly to shrink.

　　There are， of course， a number of ways to remove liquid from a gel. You can let it dry in the air， like wet laundry， or you can use the same process as food companies do when they make the pieces of fruit in breakfast cereal-freeze drying.

　　Unfortunately， both of these methods result in changes to the gel's microstructure. In Kistler's case， it meant an unacceptable shrinkage of the jelly； for Dr. Tsou it would have meant damaging that fibrous microstructure that can stop cometary particles.

　　To avoid these structural changes， aerogels are made using supercritical drying， a process in which temperature and increased to the point that it becomes impossible to distinguish between liquid and gas. Then the pressure is quickly dropped， causing a rapid removal of liquid without altering the gel's solid structure-and thus， avoiding jelly shrinkage.

　　With the help of Dr. Tsou's aerogel， NASA Stardust program successfully returned the first pristine cometary samples to earth in January 15， 2006. since that time aerogel has become anything but redundant. NASA has already found a second use for it-insulating electronics on the Mars landers. With its strength， low density and ability to insulate from sound， heat and electricity， aerogel is sure to play a major role in manufacturing， construction and technology for years to come.

　　Word

　　Redundant （adj） unnecessary because it is no longer needed

　　Insulating （v） to cover and surround something with a material or substance in order to stop heat， sound or electricity form escaping or entering.

　　Mars landers （n phr） a space vehicle designed to land on the planet Marts