Another week, and another new use for the rare earth elements. Mechanical engineering postdoctoral researcher Gisele Azimi, and Associate Professor Kripa Varanasi, along with two graduate students and another postdoctoral researcher at the Massachusetts Institute of Technology (MIT) have announced a big advance in hydrophobic materials. Hydrophobic materials are materials that prevent water from spreading over a surface, and sticking to it. The surface turns the water into tiny water shedding droplets that hardly touch the surface at all. Up till now, hydrophobic materials are mostly thin polymer coatings that degrade when heated, and quickly suffer from abrasion. A big and costly limitation in industry.
Not anymore thanks to MIT, where they have developed a new class of hydrophobic ceramics. Guessing correctly that the rare earths would be hydrophobic, the team set out to test 13 of the 14 rare metals with the normally hydrophilic (water attracting) ceramics. Ceramic have the advantage of being very resistant to extreme temperatures and wear, which is why they were used on the NASA space shuttle. Promethium wasn’t tested due to its radioactivity.
“We thought they should all have similar properties for wetting, so we said, ‘Let’s do a systematic study of the whole series,’” said Professor Varanasi, who is the Doherty Associate Professor of Ocean Utilization
Using powder oxides of 13 rare metals, the team made sintered pellets by compacting and heating them towards their melting point fusing them onto a solid ceramic material. The team was able to demonstrate that all 13 metals produced hydrophobic ceramics that retained their hydrophobicity even when subjected to abrasion and heated to 1,000 degrees centigrade. We’ll leave the last word to the researchers at MIT:
“These materials therefore provide a pathway to make durable superhydrophobic surfaces as well, and these coatings can be fabricated using existing processes. This makes it amenable to retrofit existing facilities,” Ms. Azimi stated. Professor Varanasi added, “no one has really addressed the key challenge of robust hydrophobic materials. We expect these hydrophobic ceramics to have far-reaching technological impact.”
From the MIT press release:
“Water-shedding surfaces that are robust in harsh environments could have broad applications in many industries including energy, water, transportation, construction and medicine. For example, condensation of water is a crucial part of many industrial processes, and condensers are found in most electric power plants and in desalination plants.”
My guess is that this will quickly develop into a big new market for the cheaper rare earth elements. Time to take another look at Molycorp and Lynas perhaps.
Rare earth oxides make water-repellent surfaces that last
Ceramic forms of hydrophobic materials could be far more durable than existing coatings or surface treatments.