Water-repellent ceramic could enhance industrial processes

Researchers in the US have found a way to make durable ceramic materials repel water and so become more useful in industrial processes.

A team from the Massachusetts Institute of Technology (MIT) used rare-earth metals to make a type of ceramic — a material that is usually hydrophilic, meaning it attracts water — with an electronic structure that actually repels water.

Many water-repellent or hydrophobic materials, which can enhance industrial processes such as water condensation in desalination and electric power plants, are easily susceptible to wear and tear, particularly under high temperatures.

The MIT team’s new material managed to combine the durability of ceramics with the hydrophobic properties of weaker materials such as thin polymer coatings.

‘We showed, for the first time, that there are ceramics that are intrinsically hydrophobic,’ said associate professor Kripa Varanasi, one of the researchers whose work is published this week in the journal Nature Materials.

The rare-earth oxides from which the new ceramics are made are exotic materials, and interestingly their wetting properties have not been studied, he said in a statement.

Fellow researcher Gisele Azimi added: ‘Even if they are damaged, they can sustain their hydrophobic properties.’ This is because the hydrophobicity is an intrinsic chemical property.

The team studied oxides made from 13 of the 14 elements classed as rare earth (excluding the radioactive promethium) by compacting and heating them to nearly their melting point in order to fuse them into solid, ceramic form — a process called sintering — and found all 13 had similar hydrophobic properties.

By exposing the ceramics to a steam environment similar to that in a power-plant condenser, the researchers found the ceramics retained their hydrophobicity even after exposure to abrasion and temperatures of 1,000ºC. They also found the ceramics were much harder than many other materials currently used in rough industrial settings.

The scientists then coated nanotextured surfaces with the ceramics in order to demonstrate extreme water repellency where droplets bounced off the surface.

‘These materials therefore provide a pathway to make durable superhydrophobic surfaces as well, and these coatings can be fabricated using existing processes,’ said Azimi.

Such extreme non-wetting properties coupled with durability could find use in steam turbines and aircraft engines, he added.