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.

Hydrophobic materials — ones that prevent water from spreading over a surface, instead causing it to form droplets that easily fall away — can greatly enhance the efficiency of this process. But these materials have one major problem: Most employ thin polymer coatings that degrade when heated, and can easily be destroyed by wear.

MIT researchers have now come up with a new class of hydrophobic ceramics that can overcome these problems. These ceramic materials are highly hydrophobic, but are also durable in the face of extreme temperatures and rough treatment.

The work, by mechanical engineering postdoc Gisele Azimi and Associate Professor Kripa Varanasi, along with two graduate students and another postdoc, is described this week in the journal Nature Materials. Durability has always been a challenge for hydrophobic materials, Varanasi says — a challenge he says his team has now solved.

Ceramics are highly resistant to extreme temperatures, but they tend to be hydrophilic (water-attracting) rather than hydrophobic. The MIT team decided to try making ceramics out of a series of elements whose unique electronic structure might render the materials hydrophobic: the so-called rare earth metals, which are also known as the lanthanide series on the periodic table.

Since all of the rare earth metals have similar physico-chemical properties, the team expected that their oxides would behave uniformly in their interactions with water. “We thought they should all have similar properties for wetting, so we said, ‘Let’s do a systematic study of the whole series,’” says Varanasi, who is the Doherty Associate Professor of Ocean Utilization.

To test this hypothesis, they used powder oxides of 13 of the 14 members of that series (excluding one rare earth metal that is radioactive) and made pellets by compacting and heating them to nearly their melting point in order to fuse them into solid, ceramic form — a process called sintering.

Sure enough, when tested, all 13 of the rare earth oxide ceramics did display strong hydrophobic properties, as predicted. “We showed, for the first time, that there are ceramics that are intrinsically hydrophobic,” Varanasi says.

These rare earth oxides “are exotic materials, and interestingly their wetting properties have not been studied,” he says, adding that many of the properties of the entire series are not systematically documented in the scientific literature. “This paper also gives a whole host of the properties of rare-earth oxides.”

This includes, Azimi says, their morphology, surface chemistry, crystallographic structure, grain structure, sintering temperature and density — yielding “a catalog of information” about how to process and use these materials. The MIT researchers also showed that the materials have greater hardness than many others currently used in rough industrial settings.

Despite their name, rare earth metals are not particularly rare. “Some of them are as abundant as nickel or copper,” Azimi says — both of which are widely used industrially.

But separating rare earth metals from the minerals in which they are found can be costly and can leave toxic residues, so their production has been limited. China is currently the world’s major supplier of these elements, which have many high-tech applications.

The ceramic forms of rare earth oxides could be used either as coatings on various substrates, or in bulk form. Because their hydrophobicity is an intrinsic chemical property, Azimi says, “even if they are damaged, they can sustain their hydrophobic properties.”

To prove the point, the team exposed some of these ceramics to a steam environment, similar to what they would face in a power-plant condenser. Typical polymer-based hydrophobic coatings quickly degrade when exposed to steam, but the ceramics kept their hydrophobicity intact, Varanasi says. The materials sustained their hydrophobicity even after exposure to abrasion, as well as temperatures of 1,000 degrees Celsius, Azimi says

By coating nanotextured surfaces with these ceramics at MIT’s Microsystems Technology Laboratories, the team also demonstrated 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. This makes it amenable to retrofit existing facilities, Azimi says. Such extreme non-wetting properties coupled with durability could find applications in steam turbines and aircraft engines, for example.

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Some of the world’s most powerful magnets, not including electromagnets, are made from the rare-earth metals neodymium, samarium, or yttrium. As a result, Italian and Indian Research – Cheap and Safe Hydrogen Production are expensive, while magnets made of iron, ferrite magnets, are cheaper, but not nearly as strong.

Electric motors only function because of magnetism, and can be made up of arrangements of electromagnets and permanent magnets. By replacing ferrite magnets with neodymium magnets, an electric motor bound for an electric vehicle [EV] can be made smaller and lighter, weight being an important consideration in such an application.

In order to reduce dependency on rare-earth magnets, and therefore costs, Yaskawa Electric set out to produce an EV motor with a ferrite magnet core. The problem with the ferrite magnet, though, was strength, so Yaskawa had some work ahead of it to maximize the power output of the weaker core. First, the shape of the magnet had to be optimized to improve torque output.

Then, Yawaska made a change to the coil wiring itself. Instead of using the standard round-cross-section wiring, Yawaska switched to a rectangular-cross-sectioned wire, which stacks better on the rotor and stator. This resulted in a 30% increase in the number of windings they could put in the same space, increasing the power output over the standard round wire motor.

The resulting EV motor, about the same size as currently found in EVs and hybrids, weighs about 132 pounds and maxes out at 12,000 RPM. With a maximum power output of 80kW and 147 hp at zero rpm, the new motor fits in the range of what’s required for a small EV or hybrid vehicle.

By eliminating rare-earth magnets and combining new processing and optimization, the result is a cheaper motor, which would help to reduce costs of EVs and hybrids alike. Reducing costs would certainly help marketing these high-technology vehicles and help them gain acceptance in such a difficult market.

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China exported 16,265 metric tons of rare-earth ore, metals and compounds in 2012, official data Tuesday showed.

That is a decline of 3.5% from 2011 and far short of the 2012 export quota of 30,966 tons.

In spite of China's near-total domination of the world's supply of rare earths, a collective name for 17 metals used in high-technology applications like mobile telephones and missile systems, prices have fallen sharply for more than a year owing to waning demand and ample supply.

The value of Chinese rare-earth exports fell 66.1% from a year earlier to $906 million, according to data from the Hong Kong-based China Customs Statistics Information Center.

In December alone, China exported 3,252 tons of rare-earth ore, metals and compounds, it said.

China's Ministry of Commerce last month set the first batch of rare-earth export quotas for 2013 at 15,501 tons saying it will account for around half the full-year quota. A senior industry official had earlier suggested that the 2013 full-year quota would be around the same as last year's.

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Although they might have archaic-sounding names to the public, dysprosium, terbium, europium, neodymium and yttrium because of their rarity hold the secret to future technology as well as the success of clean energy and they are preoccupying the most powerful nations of the world.

Gaining access to these elements is a priority for U.S. energy strategy, which sees that China controls 95 percent of the production of the so-called rare earths, which are used in wind turbines, solar panels and the batteries of electric and hybrid vehicles.

With that situation in mind, the U.S. Energy Department mobilized scientists and experts from business and academia to seek solutions, a team that will be part of the new Critical Materials Institute.

Iowa-based Ames Laboratory and its director, Alex King, are heading up the project, which will receive $120 million in financing over the next five years.

The main aim of the CMI in the short term will be to detect possible deposits of these metals in the United States, as well as to work with existing operations to ensure that they are viable.

King gave the example of the Mountain Pass mine in California, which for decades was the biggest supplier in the world for rare metals but had to close in 2002 due to environmental problems.

The mine reopened in 2010, although it is facing a difficult market situation given China’s exercise of price controls by restricting rare earth exports.

That practice has been denounced by the European Union, the United States and Japan, while China insists that its intention is to put the brakes on excessive production to lessen environmental damage.

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