USA: Levitating glass. Molten droplets highlight future

29.03.2004

29.03.2004


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NASA is developing new materials for electronics, medical equipment and other important technical areas. For unique designs need to them in the process of creation is not touched not only the human hand, but in general any instruments. At NASA has setup that allows it to do.

Imagine that you are very certain heat the raw material, and then refrigerate the mixture to create a new material.

From what you have done any capacity to melt, it somehow comes into chemical or physical interaction with your agent and inevitably contaminate it.

This means that you will not be able to accurately determine the properties of the new material.

Another, no less important consequence is that your sample will have characteristics different from those that you planned, writing the original "recipe."


Is it possible to carry out all stages of the experiment, no touching the sample? Comes to mind weightlessness and space station, but there is an easier way out.

Since 1997, the Marshall Space Center (Marshall Space Flight Center) operates an amazing device — "Electrostatic levitator."

Until now, he regularly brings effective and you may say, spectacular scientific results.

The heart of the device — the vacuum chamber with six electrodes. The feed pellets are suspended in the center of the chamber in a strong electrostatic field.

To make up for the electric charge of the sample (which loses electrons in strong heating) is a special deuterium arc lamp.

Intersect at right angles lasers are used to control the position of the sample in space. Computers regulate the charge on the electrodes to keep the ball exactly in the center of the chamber.

And, again, a powerful laser heats it to a molten state. Also, remote scientists study the properties of the resulting alloys in liquid and in a frozen state.

Only when all the experiments were carried out, a drop can be cooled down with a clear conscience to take up.

The main purpose of the device — the creation of unusual varieties of glass, metal alloys, ceramics, and analysis of their properties.

Now with the Marshall Center collaborates small private firm Containerless Research, Inc (CRI). It is thanks to levitatoru she invented REAl-glass.

REAl — an acronym meaning "rare earth aluminum oxide" (Rare Earth and Aluminum oxides). These glasses consist of a mixture of several rare earth oxides, alumina and silica small impurity.

This material is selected application. For example, in medicine.

"Most surgical lasers use expensive crystals, such as sapphires, — says Dr. Richard Weber (Richard Weber), one of the leaders of CRI. — These crystals are not only expensive, but also severely limit the available range of wavelengths and energy. REAl-glass potentially give surgeons more choices.

The new lasers will allow much more flexible to adjust the radiation on the basis of what is best suited for a particular type of surgery. "

Weber's work is funded by NASA. And it is not casual — new glass and ceramic materials may be indispensable for the creation of space ships of the future. And also — the new scientific instruments.

In general, a variety of materials obtained through levitatoru, over time, may significantly improve the technique in various areas.

For example, there will be new optical communications system for the Internet, or lasers to pattern metal car parts.

According to Weber, after the new properties of the material and its production process studied in detail, can be calculated as the same material to produce a conventional method — for casting in molds.

It just opens up a new piece of glass on the conveyor path.

Incidentally, among the studied materials levitatore to have such an unusual class of these, as the metallic glass.

This metal or metal alloy which is at room temperature in the solid state exists in the form of an amorphous aggregate (such as glass) and not in the form of lattice, which is traditionally considered perhaps the most important feature of metals.

The secret of its production is that the sample is cooled ultra pure, floating in a vacuum, without touching the walls.

And since there is no nucleation and external mechanical perturbations metal droplet remains liquid even at temperatures well below the melting point.

Then, at some point it suddenly hardens (a fraction of a second), thereby emitting a flash of light. And it turns metallic glass.

Such other materials have magnetic properties, as well — much harder and more durable than the same substance in conventional crystalline form.

Metallic glasses are already used in the production of some products (eg, high-end sports equipment such as tennis rackets), but the potential of the unusual material has not been exhausted.

Equally interesting bioactive glass and which, when introduced into the body, ultimately breaks when its work has been done. Microscopic amounts of the glass, they say in NASA, can be used for the treatment of cancer.

Of course, the most interesting glass samples can be created in microgravity — in space. Such experiments (on board the shuttle) has already been carried out.

Now Weber plans to continue his research, using ground-based levitator to create unusual alloys and further purifying the resulting material is already in the world on the International Space Station.

By the way, on the Moon and elsewhere in the cosmos many source components for the production of glass. So, for the development of future colonies on other planets is very important to understand — how to create the most unusual of his species.

Electrostatic levitator just helps U.S. scientists in this study.

All the more so if the first levitatore balls melt could not be more than three millimeters (not enough power support fields), then over time, scientists have built a larger installations

In particular, enable to produce a limited batch of new material in the form of, say, a cylinder with a diameter centimeters and a length of six inches. And this is a step toward commercial production of "space", levitating glass on Earth.

Battery News, 26.03.2004 9:25
Source: Membrana

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