Scientists levitate ultra-pure glass
By Tariq Malik
( SPACE.com) -- An experiment originally designed to fly on the International Space Station led a team of researchers to develop a completely new type of glass, a material formed while floating in mid-air in a NASA laboratory on Earth.
Using static electrical fields to levitate the material, scientists were able to construct a pure glass, free of any contamination typically associated with containers. It could serve as the centerpiece for new medical and industrial lasers, as well as have broadband Internet applications.
"I think there's a lot of potential for this glass," said Rick Weber, director of the Glass Products Division of Containerless Research, Inc., which invented a whole family of the new transparent material. "We've got a wide composition field, so one [glass] can be tuned for a particular use."
Weber said that the new glass is currently being put through its paces for applications in high-density lasers and low-cost, compact broadband devices.
The new material known as REAL glass -- short for Rare Earth Aluminum oxide -- was first developed at NASA's Electrostatic Levitator laboratory at Marshall Space Flight Center in Huntsville, Alabama.
Scientists there routinely use static electricity to levitate objects. Inside a vacuum chamber, lasers zap the experiments to turn them into floating molten balls of material that can later cool without any interference from a crucible or container.
"In an oven or container of any sort you have contact with the container wall, and at high temperatures a sample can interact with those walls, absorbing specks of dust and having a chemical reaction with the container," said Jan Rogers, a scientist at the Marshall center.
By melting and cooling levitating material, scientists can understand not just its formation, but its inherent physical properties.
At the most fundamental level, making REAL glass employs the same method used by glassmakers for centuries. Scientists still mix together materials, melt them and then cool them until solid. But levitation allows researchers to tailor types of glass with traits such as chemical stability, infrared transmission and laser activity.
"Other glasses tend to have just one of those properties and at least one weakness," Weber said. "They could be really good at infrared transmission, but dissolve in water so you wouldn't want a window made out of it."
Laser applications are key for the new glass, since the material could help amplify light into a concentrated beam to cut metal for car assembly or human tissue during surgery. Such components could also provide a range of wavelengths that give surgeons more precise control of beam intensity, Weber added.
Once Containerless Research scientists understood the basics of REAL glass formation, they were able to adapt the technology away from its dependency on electrostatic levitation. The step was a crucial one for commercial purposes, since NASA's facility is only powerful enough to levitate tiny sample materials up to three millimeters wide and 70 milligrams in weight.
"So we're not talking about golf balls and pineapples here," Weber said of the production capabilities. "For commercial purposes, we needed at least rods and plates of the glass."
Weber's team was able to devise a small-scale production plan that uses platinum crucibles to melt REAL glass and cooling forms that shape it into commercial rods and plates without taking away the materials positive properties.
Other scientists have used some form of levitation, though not exactly Weber's approach, for making glass on Earth and in space. Delbert Day, a NASA-funded researcher at the University of Missouri-Rolla, for example, used sound waves to levitate glass samples in order to study high-quality glass. He also designed microgravity experiments for the space shuttle.
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