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Kristin Persson is one of the experts behind the Materials Project, the new computational tool aimed at taking the guesswork out of new materials discoveries. Credit: Roy Kaltschmidt, LBL.

Right after I wrote my first post on the availability of the new Materials Project computation-database-search toolkit, I belatedly learned that the National Energy Research Scientific Computing Center has also been playing a big role in the development and operations underlying the effort (along with MIT, Lawrence Berkeley National Lab and University of Kentucky are also partners).

In fact, NERSC’s participation was right under my nose, just not in plain sight. It turns out that the center is serving as the online host for the Materials Project, a role it has taken on as part of its mission to create gateways for various science communities. Here’s a brief description NERSC provides of the gateway concept

NERSC is helping build web interfaces to access [high performance] computers and storage systems. These gateways allow scientists to access data, perform computations and interact with NERSC resources using web-based interfaces and technologies. The goal is to make it easier for scientists to use NERSC while creating collaborative tools for sharing data with the rest of the scientific community.

NERSC engages with science teams interested in using these new services, assists with deployment, accepts feedback, and tries to recycle successful approaches into methods that other teams can use.

[…]

NERSC is providing scientific groups with the building blocks to create their own science gateways and web interfaces into NERSC. Many of these interfaces are built on top of existing grid and web technologies.

[…]

Science gateways can be configured to provide public unauthenticated access to data sets and services as well as authenticated access if needed. The following features are available to projects that wish to enable gateway access to their data through the web. Other features can be made available on request.

(It’s worth noting that materials science has been on the NERSC’s radar for some time and, according to this overview (pdf) of the NERSC, has been allocating the largest chunk of its “workload”—17 percent—to materials science since 2008.)

Kristin Persson, who works at the LBL and who is described as one of the founding scientists behind the Materials Project, repeats the Google analogy I mentioned yesterday. She says in a story on the NERSC website, “Our vision is for this tool to become a dynamic ‘Google’ of material properties, which continually grows and changes as more users come on board to analyze the results, verify against experiments and increase their knowledge. So many scientists can benefit from this type of screening. … Materials innovation today is largely done by intuition, which is based on the experience of single investigators. The lack of comprehensive knowledge of materials, organized for easy analysis and rational design, is one of the foremost reasons for the long process time in materials discovery.”

In the same story, NERSC computer engineer Shreyas Cholia provides some of the history of the MP. Cholia says, “The Materials Project represents the next generation of the original Materials Genome Project, developed by [Gerbrand] Ceder’s team at MIT. The core science team worked with developers from NERSC and Berkeley Lab’s Computational Research Division to expand this tool into a more permanent, flexible and scalable data service built on top of rich modern web interfaces and state-of-the-art NoSQL database technology. … At NERSC, we have a long history of engaging with science teams to create web-based tools that allow scientists to share and access data, perform computations and interact with NERSC systems using web-based technologies, so it was a perfect match.”

Also, for more details on Ceder’s thoughts about high-throughput computation, density functional theory and materials development, check out this 2010 presentation (pdf) he made at the Oak Ridge National Lab.

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Large-format lithium-ion battery displayed at 2010 Paris Motor Show. Credit: Dow Kokam.

Coincidentally, there is another news item out of Oak Ridge National Lab, this one regarding a new $5.5 million pact between Dow Kokam and ORNL “to develop and commercialize advanced lithium-ion batteries” that is being touted as an example of the new Advanced Manufacturing Partnership.

ORNL has developed unique and specialized battery know-how, and with this new agreement the lab will essentially supplement the Dow Kokam’s staff R&D efforts.

A news release from the lab mentions the two entities have been doing joint R&D work since early 2010 and says the new efforts will come in the areas of electrochemical and microstructural analysis, in-line quality control process development, raw material characterization and processing battery components, technology evaluation and technical strategic advice.

The release also connects the agreement to the AMP, noting it “aligns directly with goals outlined in the recent report titled “Ensuring American Leadership in Advanced Manufacturing.” The report was prepared by the President’s Council of Advisors on Science and Technology and the President’s Innovation and Technology Advisory Committee. A key recommendation of the 25-member panel was to “invest to overcome market failures, to ensure that new technologies and design methodologies are developed here, and that technology-based enterprises have their infrastructure to flourish.”

Dow Kokam is jointly owned by Dow Chemical Co., TK Advanced Battery LLC and Groupe Industriel Marcel Dassault. The company is focused on developing “large-format” (i.e., transportation-scale) batteries, based on Li-ion technologies primarily using a nickel manganese cobalt composition.

The funding for the ORNL support work likely links back to a recent $4.9 million DOE grant to Dow Kokam to develop Li-ion cells that have energy densities greater than 500 Watt-hours per liter.

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Electrochemical strain microscopy images ion mobility. The overlay shows electrochemical activity of platinum nanoparticles on a yttria-stabilized zirconia surface, showing ionic activity along the triple phase boundaries. Credit: ORNL

My favorite part of the TV hospital drama, House, is the beginning when the failure occurs. The show opens with the patient-of-the-week doing normal stuff and the camera cuts to the deconstruction going on unbeknownst inside the unlucky patient’s body. The camera zooms around, darting through veins, leaping across synapses, undulating in the ebb and flow within until—zonk!—something goes terribly wrong. The crackerjack team of doctors sure could use a probe like the one the show’s producers have—one that shows from within how things flow, interact and fail. Instead they have the brilliant but irascible Dr. House.

There are times when materials scientists, too, would benefit from getting an inside view. It can be especially helpful to be able to characterize a material dynamically and capture the material’s response as it is happening. For example, the key reaction in a solid oxide fuel cell is the oxygen reduction reaction that occurs at the triple phase boundary. The triple phase boundary (pdf) is where the solid electrolyte, catalyst and gas are in contact. It’s where the action is in a fuel cell with the oxygen reduction reaction at the cathode and the hydrogen oxidation reaction at the anode, converting chemical energy into electricity.

The TPB is a very difficult region to characterize. If the electrochemical reactions could be observed or imaged, it should be possible to understand the fundamental mechanisms controlling the material’s performance and to design improved materials.

“If we can find a way to understand the operation of the fuel cell on the basic elementary level and determine what will make it work in the most optimum fashion, it would create an entirely new window of opportunity for the development of better materials and devices,” says Amit Kumar in an ORNL press release.

Kumar is lead author of a new paper out of Oak Ridge National Laboratory that describes a new technique—electrochemical strain microscopy—that allows scientists to directly measure oxygen reduction/evolution reactions and oxygen vacancy diffusion on ion conducting solid surfaces, like yttria-stabilized zirconia.

ESM measures electrochemical reactivity and ionic current in solids on a scale of ten nanometers or less. By applying a periodic bias to a scanning probe microscopy tip in contact with the surface, ionic movement is induced, the surface deforms and the deformations are mapped. As explained in an article (pdf) by Asylum Research, a partner with ORNL on developing the technique, “The intrinsic link between concentration of ionic species and/or oxidation states of the host cation and molar volume of the material results in electrochemical strain and surface displacement.”

Regarding the importance of the capability afforded by ESM, coauthor and ACerS member Sergei Kalinin says, “When you want to understand how a fuel cell works, you are not interested in where single atoms are, you’re interested in how they move in nanometer scale volumes. The mobile ions in these solids behave almost like a liquid. They don’t stay in place. The faster these mobile ions move, the better the material is for a fuel cell application. Electrochemical strain microscopy is able to image this ion mobility.”

The technique can be used to characterize ionic conductivity for other applications as well, such as lithium batteries, metal-air batteries and semiconductors.

Kalinin, co-theme leader for Functional Imaging on the Nanoscale at ORNL, says in an email to us, “The ORR/OER directly underpin the operation of fuel cells and metal–air batteries, and hence their probing on the level of a single electrocatalytic nanoparticle or structural defect is of direct interest for energy storage and conversion. Furthermore, these processes can severely affect (through oxygen nonstoichiometry) the functionality of the materials of interest for condensed matter physics community. After all, materials used in fuel cells—manganites, cobaltites, etc.—are the same as those studied for colossal magnetoresistance or nanoscale phase separation.”

The paper is “Measuring oxygen reduction/evolution reactions on the nanoscale,” A. Kumar, et. al., Nature Chemistry 3, 707-713 (2011) doi:10.1038/nchem.1112
Published online 14 August 2011

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Computational modeling of carbon supercapacitors with the effects of surface curvature included. Credit: Jingsong Huang, ORNL

A fair number of recent posts have been about nanostructured porous materials (PCCMs, diamond aerogel, tunable gold). The interesting characteristics of these materials necessarily depend on the porosity: What is not there makes the material what it is. The massive surfaces, bulk surfaces actually, can act in surprising ways and it is important not to discard seemingly anomalous results, as a recent story out of Oak Ridge National Lab shows.

The ORNL work goes back to a paper published in 2006 by ACerS Fellow Yury Gogotsi, professor of MSE at Drexel University, in Science (doi 0.1126/science.1132195). Gogotsi’s group was studying carbon supercapicitors, and were particularly interested in a carbide-derived carbon class of porous carbon materials. Carbide-derived carbon is synthesized by subjecting metal carbides to high-temperature chlorination, which removes the metals and metalloids as chlorides, leaving behind a nanoporous carbon structure comprising 50-80% open volume. The pore structure of CDCs can be carefully controlled to within a very narrow size disribution; average pore size can be tuned to within 0.05 nm for pores in the 0.5-3.0 nm range.

Supercapacitors (sometimes called electrical double-layer capacitors) are energy storage devices that store charge by adsorbing ions on the surface of highly porous materials taking advantage of the electrostatic separation between electrolyte ions and electrodes with high surface areas to up the capacitance. The ability to synthesize CDCs with huge porosity in a tightly controlled size range, makes them prime candidate materials for energy storage, and the payoff could be significant — typical dielectric capacitors have capacitances in the range of microfarads per gram of active material, while supercapacitors can have capacitance values in the tens of Farads.

Gogotsi’s work took a turn for the unexpected with the discovery that capacitance increased, a lot, for pore sizes smaller than the solvated ions. As the paper reports, “Decreasing the pore size to a value approaching the crystallographic diameter of the ion led to a 100% increase in normalized capacitance.” The anomalous effect was attributed to a distortion of the solvation shell around the ion, similar to the distortion of a balloon when it’s squeezed through an opening smaller opening. The distortion places the ion closer to the electrode, increasing capacitance.

Such a startling anomaly was questioned at the time, according to the ORNL story. A team of computational modelers, computational chemists Bobby Sumpter and Jingsong Huang and computational physicist Vincent Meunier, used ORNL’s supercomputers to model interactions between ions and the porous carbon surface at the nanoscale using density functional theory.

Computational modeling refers to a spectrum of computer modeling and simulation methods that sort out roughly by scale. Density functional theory, more generally categorized as “electronic structure methods,” models on the smallest physical scale — atomic structure up to crystal structure (which, amazingly, spans orders of magnitude of scale). Most engineers and scientists are very familiar with the component-scale computer modeling methods of finite element, finite difference, finite volume analysis, etc. Same idea, different scale. (An emerging field of materials science known as “integrated computational materials engineering,” is generating a lot of interest, and we hope to give it more attention in subsequent posts.)

Through simulation, the ORNL team was able to determine that the ion “easily pops out of its solvation shell and fits into the nanoscale pore.” Sumpter explained that the ion actually desolvates in the bulk, driven by electrostatic potential and van der Waals forces pulling it into the porosity and “…in fact it’s very easy for it to get in.” And, Sumpter says, the model they developed explained all the data.

Because nanoscale porous materials have huge surface areas, they also tend to have a lot of topography with a variety of concave and convex curvatures. The simulation research revealed that the topography can make an enormous difference in capacitance. For example, positive curvature surface mounds can store and release ions much quicker than negative curvature holes.

It’s not just geeky fun, though. The ORNL team had already worked with Rice University to use atom-thick sheets of carbon materials to create a supercapacitor prototype that is transparent, flexible and can be wrapped around a finger. As Sumpter said in the story, “…we’ve gone all the way from modeling electrons to making a functional device that you can hold in your hand.”

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Houses in Thailand typically have steep roofs and may benefit from new, cooler ceramic tile pigment. Credit: Wikipedia.

A two-degree temperature drop in room temperature may not sound like a lot, but it can make a huge difference in a nation’s aggregate energy costs and investments. This is particularly true in a warm climate nation with many ceramic tile rooftops and a developing economy, such as Thailand. The (relatively) easy solution is to use a white TiO₂-based pigment, which has a high near-infrared reflectance (87%). The problem is that not everyone likes white roofs. White isn’t a huge problem for flat roof that can’t be seen, but getting widespread adoption of white tiles for pitched roofs visible from below can be a problem for aesthetic and cultural reasons.

But, as reported on in ACerS’ International Journal of Applied Ceramic Technology (doi:10.1111/j.1744-7402.2010.02599.x), there is now a green color alternative to white for roof tiles. A new paper in ACT discusses the discovery by a trio of Thai ceramic reseachers investigating “cool materials” (a generic term for building materials that make use of pigments that have high near-infrared solar reflectance or low NIR solar absorptance) of a green-hued, heat-blocking alternative to white-glazed tiles.

The group, working out of King Mongkut’s University of Technology and Suratthani Rajabhat University, started with a chromium oxide pigment base, which by itself has a medium-high NIR reflectance (50-57%). In Thailand, where steep, tinted roofs are preferred, Cr₂O₃ is of interest not only because of its reflectance but also ceramic glazes containing it can provide shades of green, which, tend to be dull and dark.

To see if some brighter colors and more reflective compositions are possible, the researchers added varying amounts of TiO₂, Al₂O₃ and V₂O₅ to the Cr₂O₃ and synthesized a test group of 39 different compositions. These compositions were then calcined and formed into test disks, whereupon their reflectance was measured using a UV–Vis–NIR spectrophotometer.

As it turned out, one particular sample — “S9″ — composed of (by weight percent) 80% Cr₂O₃, 4% TiO₂, 14% Al₂O₃ and 2% V₂O₅ stands out because it has a NIR solar reflectance of 82.8%, i.e., close to the reflectance of TiO₂.

To test the S9 sample under more realistic conditions, the group constructed two identical test “houses” built so that heat could only penetrate through the roof tops. One house was covered with 50 pieces of S9-glazed ceramic roof tile. For control purposes, the other house was roofed similarly, but with tiles glazed with a commercially available green pigment. Reflectance and temperature measurements were then recorded over a five-day summer period.

As expected, they found the NIR reflectance of S9-coated tiles was relatively high, 76.3%, compared to the control-coated tiles (65.7%).

In regard to the thermal tests, temperatures were taken at three locations within each house. They found that the house with the S9-coated tiles stayed cooler than the control house by about 2°C across the three measured positions.

The group’s work was supported by several institutions and governmental agencies, including the Energy Policy and Planning Office, Ministry of Energy; the Commission on Higher Education under the Strategic Scholarships for Frontier Research Networks for Thai Doctoral Degree Program; and National Research University.

By the way, for Oak Ridge National Lab’s Building Envelopes Program (a.k.a., “Roofs and Walls”) has many resources and calculators for researchers and consumers related to “developing technologies that improve energy efficiency and environmental compatibility of residential and commercial buildings.”

As a final note, it should be pointed out that while the benefits of cool roof technologies vary depending on geographic location among other things, they are not necessarily only of interest to nations and people living in topical or semitropical regions. While the addition of insulation may be more cost effective in many cooler climes, even New York City seems to have a fairly robust effort called NYC°CoolRoofs (and is part of the “100 Cool Cities Global Initiative”).

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