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Rare earth metals increase water-repellent properties over time

As the world becomes more technology-driven and our population continues to increase, demand is also increasing for rare earth metals. These elements are metals found in rare earth minerals and are – as you might have guessed… rare. They are used in the catalytic converters and batteries that drive our car, in the production of screens and lamps, and as a contrast agent in MRIs, among many other uses.

In 2013, American researchers reported that surfaces coated with rare earth oxides become water-repellent (hydrophobic), opening up many more applications for the already popular metals.

Recently, researchers from the University of Basel, the Swiss Nanoscience Institute, and the Paul Scherrer Institute published new information on rare earth metal hydrophobicity in the journal Scientific Reports.

They worked with the company Glas Tröesch in order to study the hydrophobic properties of rare earths in more detail. By coating glass samples with rare earth oxides, nitrides, and fluorides, they could analyze how the surfaces then reacted to water exposure.

Interestingly, the researchers were unable to detect any hydrophobic properties when the coating was freshly deposited. Only after rare earth oxides came into contact with air did the glass surfaces begin to exhibit hydrophobic properties.

The scientists determined that gaseous hydrocarbons were absorbed from the air by the surface and then reacted with the oxides, making carbonates and hydroxides. The presence of these compounds increased the surfaces’ roughness and reduced wetting by water.

Professor Ernst Meter, from the Department of Physics at the University of Basel, expressed his shock at this discovery, saying, “We were surprised that the hydrophobic effect was caused by the surface aging.” They were even more surprised that this chemical reaction was able to take place at room temperature.

Although the examined materials are unsuitable for industrial production of water-repellent glass surfaces, knowing that rare earth metals can react with compounds in the ambient air is important for this growing industry. Catalytic processes – like the ones that take place in your car’s catalytic converter and thus help reduce harmful emissions – frequently take place at room temperature. Continuing research into the properties of these important rare earth metals will only serve to benefit an already booming industry as we move into the future.

By Connor Ertz, Staff Writer

Source: University of Basel

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