Ultra-pure glass created in levitation lab

Spherical samples float in midair within the Electrostatic Levitator, thanks to static electricity generated by six electrodes. A laser beam heats the sample until it melts into a tiny levitating ball.
Spherical samples float in midair within the Electrostatic Levitator, thanks to static electricity generated by six electrodes. A laser beam heats the sample until it melts into a tiny levitating ball.NASA / MSFC / E. Given
/ Source: 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 midair in a NASA laboratory on Earth.

Using static electricity 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, and could have broadband Internet applications as well.

"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 told Space.com that the new glass is currently being put through its paces in several validation projects for applications in high-density lasers, and as the glass components for low-cost, compact broadband devices.

Levitating glass
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, Ala.

Scientists there routinely use static electricity to allow their experiments to defy gravity inside a vacuum chamber, then zap them with lasers to turn them into floating molten balls of material that can later cool without any interference from a crucible or container.

"The ESL is a very pure way to look at what a material does," said Jan Rogers, a facility scientist for the Electrostatic Levitator. "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."

By melting and cooling a levitated material, scientists can understand not just its formation, but its inherent physical properties. Surface tensions keeps molten samples together, which, when cool, coalesce into tiny spheres.

At the most fundamental level, making REAL glass uses the same method used by glass-makers for centuries — namely, mixing materials together, melting them, then cooling them into a solid. But it’s the levitation that gives REAL glass its kick. The process allowed researchers to imbue their glass with a number of attractive properties, 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 REAL glass, since the material could serve as the "gain medium," a component that amplifies light into a concentrated beam capable of cutting metal for car assembly or human tissue during surgery. REAL glass laser gain media could provide a range of available wavelengths to give surgeons more control of beam intensity, depending on tissue type and surgery, he added.

Consumer glass
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 a tenth of an inch (3 millimeters) wide and 0.002 ounces (70 milligrams) in weight.

"So we're not talking about golf balls and pineapples here," Weber said of the levitator's 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 into commercial rods and plates, all without taking away the materials positive properties.

A glassy side project
Containerless Research scientists did not originally seek to develop REAL glass outright when they approached NASA with a proposed space station experiment. That proposal, which used the Marshall lab as a proving ground before reaching the orbiting outpost, sought to explore the properties of molten oxides and aluminates.

"Most of my customers are spaceflight candidates," Rogers said of the researchers who use the facility. "Some of them have experiments for the ISS, where they would be using the next-generation levitator."

That instrument, an electromagnetic levitator for space-based material science studies, is being developed for the European Space Agency's Material Science Laboratory aboard the station's Columbus module. The module was scheduled to be delivered via the space shuttle in October 2004, though NASA does not expect another shuttle flight until at least March 2005.

"When the appropriate instrumentation is available, we still hope to conduct that flight experiment," Weber said.

Other scientists have used some form of levitation, though not exactly Weber's approach, for glass making, both 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 higher-quality glasses. He also designed microgravity experiments for the space shuttle.