High-Tech Material in a Salt Crust
MAX phases are viewed as promising materials for the future, for example for turbines in power plants and aircrafts, space applications, or medical implants. A new method developed by scientists from Forschungszentrum Jülich now makes it possible to produce this desirable material class on an industrial scale for the first time.
MAX phases unite the positive properties of ceramics and metals. They are heat resistant and lightweight like ceramics, yet less brittle, and can be plastically deformed like metals. They are produced at temperatures much higher than 1,000 degrees Celsius. At such high temperatures, the materials would normally react with atmospheric oxygen and oxidize, which is why they are usually produced in a vacuum or in a protective atmosphere of argon. The Jülich method is astonishingly simple by comparison: the researchers encase the source material in a salt, potassium bromide, which melts during the production process. A vacuum or argon atmosphere for additional protection is no longer needed.
Methods using molten salt have been used for the powder production of non-oxide ceramics for some time. However, they require a protective argon atmosphere instead of atmospheric air, which increases both the complexity and production costs.
„Potassium bromide, the salt we use, is special because when pressurized, it becomes completely impermeable at room temperature. “We have now demonstrated that it is sufficient to encapsulate the source material tightly enough in a salt pellet to prevent contact with oxygen - even before the melting point of the salt is reached at 735 degrees Celsius. A protective atmosphere is this no longer necessary,” explains Apurv Dash.
The new method is not limited to a certain material. The researchers have already produced a multitude of different MAX phases and other high-performance materials. As a next step, the scientists are now planning to investigate industrial processes with which these powders can be processed further.