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ILP Institute Insider

August 18, 2014
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Designing Better Surfaces for Energy

Solid core material is almost a given for technology. But just because the guts are right doesn’t guarantee success. It’s the surface layer that can hold the key in some applications, but its importance is still easy to overlook. This area is where Bilge Yildiz keeps her focus. The Associate Professor of Nuclear Science and Engineering and PI of the Laboratory for Electrochemical Interfaces looks at the surface and how it acts in harsh environments.
Bilge Yildiz
Associate Professor
Nuclear Science & Engineering
High temperatures, reactive fluids and mechanical stresses all conspire to alter material behavior, and, with it, performance. When it comes to something like clean fuel production and energy conversion, bad surfaces slow down reactions and lower output. With a nuclear power plant or oil pipelines, the consequence is faster rates of corrosion. Yildiz wants to reverse those processes, and through her laboratory and computational work, she and her research group have been making inroads by being able to study and understand the interaction of material and environment on the atomic and nanoscale, and ultimately make better, more resilient materials for energy technology.

Looking at the Outside
The key to mitigating the corrosion of materials is to understand the passive outer layer of film that natively forms and serves to protect the base material. If that can be done, the layer can be engineered to last longer. And while it sounds obvious, industry testing and predictive models on corrosion have been rudimentary, relying mostly on empirical data rather than solid physical mechanisms, Yildiz says. One obstacle has been the difficulty of probing these very surfaces in inhospitable, hard-to-reach environments. In answer to that, Yildiz has designed a specialized instrument, a scanning tunneling microscope, which works in situ, in temperatures up to 600 degrees Celsius, and which offers a new way of visualization at the nanometer and atomic scales.

She’s used the device to study pyrite, which has brought an essential finding. The mineral is insulating in its bulk, and relying on just that information, which essentially has been the standard course, would lead to the conclusion that the corrosive process would be slow. But by looking at pyrite’s surface, Yildiz found that it easily transfers electrons, forms defects and can accelerate corrosion. This gap exists, and, by knowing this, smarter choices can now be made. “It’s very important input in designing and developing models to predict the rates at which these materials would corrode and ultimately degrade and fracture,” she says.

Blowing Off Hydrogen
A side product of metal corrosion caused by water is that the water splits and releases hydrogen. One of two things then happens. The hydrogen can leave the surface or it becomes incorporated into the bulk of the material and degrades the load-bearing properties via hydrogen embrittlement. The former is desirable; the latter isn’t. “Hydrogen in the bulk of the materials has been studied for a long time, but the key may be to just not let it enter through the surface,” Yildiz says. Again, it’s a confined interface in a harsh environment, but those qualities make understanding the hydrogen entry process, and the potential to control it, even more necessary.

Yildiz has performed computational work on how hydrogen absorption and transport can take place through this surface layer from the environment into the bulk metal. Surveying different compositions that could be used to alter the physical properties of the passive surface film, the results predicted physical descriptors that are tunable by composition to stop or minimize the entry of hydrogen through this critical interface. While this work was performed for zirconium alloys, it can now be extended to a wide range of metals that suffer from hydrogen embrittlement, and Yildiz is collaborating with industrial partners to implement the new materials. “The aim is to make materials that are more durable by stopping hydrogen at the surface and avoid its entry into the metal,” she says.

Boosting Energy
Yildiz also works on electrochemical energy conversion in high temperature fuel cells and electrolytic cells. In this field, she’s looking at the same properties as with metallic interfaces, namely how the oxide surface chemistry affects either efficiency or degradation. For fuel cells, the goal is to enable clean and sustainable electricity generation. With electrolyzers, the goal is to connect them to nuclear reactors or concentrated solar plants in order to provide the necessary heat to electrolyze steam and carbon dioxide, and generate hydrogen or synthetic gas. Such potential would be of interest to the nuclear industry, she says, because it’s one means to expand the applicability of nuclear energy beyond electricity to making fuels that would work for something like transportation.

Furthermore, these systems can run reversibly, i.e. both as a fuel cell and electrolyzer, providing for large-scale energy storage capability, in conjunction with renewable and nuclear energies. Currently, American nuclear plants run with a base load that can’t respond to fluctuations in demand. The cell would not only generate electricity, but also store energy in the form of produced fuel. Add that to the plant’s existing electricity, and peaking behavior in the demand curve can be addressed and supplied, she says.

Again, it comes down to understanding the material surfaces, in this instance for improving the productivity and durability of the device. It is desirable to have faster reaction and conversion rates for these technologies to produce electricity and fuels. But without knowing what’s on the surface of the material, since that’s where reactions occur, the rates can’t be accelerated. Through her work, Yildiz has been able to identify the surface behavior and design materials to accelerate reaction rates for better performance and also increase the lifetime. This means that the technology can be made more efficient, more durable and more economical when coupled to other energy sources such as nuclear, solar or wind.

“While this is a new technology,” Yildiz says, “it can become a game-changer in large-scale energy storage.”

Research News

August 18, 2014

Recycling old batteries into solar cells

This could be a classic win-win solution: A system proposed by researchers at MIT recycles materials from discarded car batteries — a potential source of lead pollution — into new, long-lasting solar panels that provide emissions-free power.

The system is described in a paper in the journal Energy and Environmental Science, co-authored by professors Angela M. Belcher and Paula T. Hammond, graduate student Po-Yen Chen, and three others. It is based on a recent development in solar cells that makes use of a compound called perovskite — specifically, organolead halide perovskite — a technology that has rapidly progressed from initial experiments to a point where its efficiency is nearly competitive with that of other types of solar cells.

“It went from initial demonstrations to good efficiency in less than two years,” says Belcher, the W.M. Keck Professor of Energy at MIT. Already, perovskite-based photovoltaic cells have achieved power-conversion efficiency of more than 19 percent, which is close to that of many commercial silicon-based solar cells.

MIT Sloan
Management Review

August 14, 2014

How Social Media Can Amplify Your “Media Ecosystem”

In your company, there may be people who ask, “What does our Twitter feed deliver to the bottom line?”

It’s a reasonable question. How do you measure the investment a company makes in maintaining its social media presence?

At Mondelez International, a $35 billion company created from the split of Kraft Foods and whose brands include Oreo cookies, Cadbury chocolates and Trident gum, they’ve flipped that question on its head.

Sensors aren’t sensitive enough yet to pick up a direct correlation because of Twitter. Instead, the company tracks how social media is amplifying the bigger pieces of its media activity.

In a Q&A with MIT Sloan Management Review, Mondelez’s B. Bonin Bough, vice president of global media and consumer engagement, explains what he means when he says that social media amplifies the media ecosystem.

“What does Twitter do to TV? We see that when we use Twitter and TV [ads] together, that would actually increase [the effectiveness of] television. And that’s something that’s big enough to be measured. So what we’re doing is we’re looking more at attribution modeling versus direct correlation of that one specific channel.”

The numbers are big: On TV alone, a campaign for Trident gum would have gotten the company to 18% of its target demographic, Bough says, “but adding Twitter gets us a 50% reach.” His team takes the core TV products, such as commercials, and pushes them out to consumers to watch on their phones when they’re not in front of the television.

“While they’re searching for video on their mobile device, while they’re closer to point of purchase, which is another key opportunity for these channels to work together, we begin to bring media closer to the point of buying. We can affect consumer behavior in a more direct way,” Bough says.

“If on average CPGs [consumer packaged goods] are spending 70% on television, and you could make that 70% investment work twice as hard, that’s a pretty dramatic and significant impact to the bottom line,” he adds.

Mobile, Bough says, is a tremendously important platform for a company like Mondelez. “We’re a snacking company, it’s about impulse buying. And the device that you have with you throughout the entire consumer journey, and that can most likely trigger impulse buying, is the mobile phone. So we made a pretty, pretty aggressive commitment to moving 10% of our media into mobile, because we knew that it was not only something that was important, but something that we wanted to get really good at.”

For more thoughts on how companies can best use social media, including details on how Mondelez is using geo-location marketing to target customers on their morning commutes and how the company’s Mobile Futures program helped to bring innovation into the company, see the full Q&A with Bough.

This article draws from “The Multiplier Effect of Social Business Tools,” an interview with B. Bonin Bough (Mondelez International) by David Kiron (MIT Sloan Management Review ). It appeared online on April 23, 2014, at MIT Sloan Management Review.