MAX phases are considered a material of the future. They combine the advantages of ceramic and metals and could be used in turbines or in space travel. So far, there is no suitable process for the industrial production of the material. An ancient trick from cooking is supposed to change that: the salt crust.
MAX phases combine the positive properties of ceramic and metals:
For the industry to be able to process MAX phases in larger quantities, it needs the material in powder form. Production has so far been complex and expensive. MAX phases only form at over 1,000 degrees Celsius. To prevent the materials from reacting with the atmospheric oxygen and oxidising, they are produced in a vacuum or in a protective atmosphere consisting of argon.
In the MAXCOM* project, Jülich materials experts Apurv Dash and Prof. Jesus Gonzalez-Julian have developed an amazingly simple method for producing MAX phases. The researchers from the Institute of Energy and Climate Research (IEK-1) immerse the raw materials in a salt bed (potassium bromide) (1). The principle is known from cooking: the salt crust prevents aromas and nutrients from disappearing from fish, meat or vegetables during cooking. In the MAX phases, on the other hand, the crust protects against oxygen penetration. A special protective atmosphere is therefore not necessary, a normal oven is sufficient for heating. The salt also acts as a separating agent, preventing the various components of the MAX phases from caking and ensuring that fine-grained powder is produced. The salt melts upon heating (2), which solidifies during cooling (3). The salt can then be dissolved with water and washed away (4). The powder is then dried (5).
* MAXCOM has been funded by the Federal Ministry of Education and Research for five years since 2016.
Photos: Forschungszentrum Jülich/Tobias Schlöﬂer, Illustrations: SeitenPlan, Video: Falling Walls Foundation