Entity

Time filter

Source Type

United States

News Article
Site: http://phys.org/chemistry-news/

Called ion soft-landing, the high-precision technique resulted in electrodes that could store a third more energy and had twice the lifespan compared to those prepared by a conventional method, the researchers report today in Nature Communications. Straightforward to set up, the method could eventually lead to cheaper, more powerful, longer-lasting rechargeable batteries. "This is the first time anyone has been able to put together a functioning battery using ion soft-landing," said chemist and Laboratory Fellow Julia Laskin of the Department of Energy's Pacific Northwest National Laboratory. The advantages come from soft-landing's ability to build an electrode surface very specifically with only the most desirable molecules out of a complex mixture of raw components. "It will help us unravel important scientific questions about this energy storage technology, a hybrid between common lithium rechargeable batteries and supercapacitors that have very high energy density," said lead author, PNNL chemist Venkateshkumar Prabhakaran. Although lithium ion rechargeable batteries are the go-to technology for small electronic devices, they release their energy slowly, which is why hybrid electric vehicles use gasoline for accelerating, and take a long time to recharge, which makes electric vehicles slower to "fill" than their gas-powered cousins. One possible solution is a hybrid battery that crosses a lithium battery's ability to hold a lot of charge for its size with a fast-charging supercapacitor. PNNL chemists wanted to know if they could make superior hybrid battery materials with a technology—called ion soft-landing—that intricately controls the raw components during preparation. To find out, Laskin and colleagues created hybrid electrodes by spraying a chemical known as POM, or polyoxometalate, onto supercapacitor electrodes made of microscopically small carbon tubes. Off-the-shelf POM has both positively and negatively charged parts called ions, but only the negative ions are needed in hybrid electrodes. Limited by its design, the conventional preparation technique sprays both the positive and negative ions onto the carbon nanotubes. Ion soft-landing, however, separates the charged parts and only sets down the negative ions on the electrode surface. The question that Laskin and team had was, do positive ions interfere with the performance of hybrid electrodes? To find out, the team made centimeter-sized square hybrid batteries out of POM-carbon nanotube electrodes that sandwiched a specially developed ionic liquid membrane between them. "We had to design a membrane that separated the electrodes and also served as the battery's electrolyte, which allows conduction of ions," said Prabhakaran. "Most people know electrolytes as the liquid sloshing around within a car battery. Ours was a solid gel." They tested this mini-hybrid battery for how much energy it could hold and how many cycles of charging and discharging it could handle before petering out. They compared soft-landing with conventionally made hybrid batteries, which were made with a technique called electrospray deposition. They used an off-the-shelf POM containing positively charged sodium ions. The team found that the POM hybrid electrodes made with soft-landing had superior energy storage capacity. They could hold a third more energy than the carbon nanotube supercapacitors by themselves, which were included as a minimum performance benchmark. And soft-landing hybrids held about 27 percent more energy than conventionally made electrospray deposited electrodes. To make sure the team was using the optimal amount of POM, they made hybrid electrodes using different amounts and tested which one resulted in the highest capacity. Soft-landing produced the highest capacity overall using the lowest amount of POM. This indicated the electrodes used the active material extremely efficiently. In comparison, conventional, sodium-based POM electrodes required twice as much POM material to reach their highest capacity. The conventionally-made devices used more POM, but the team couldn't count them out yet. They might in fact have a longer lifespan than the soft-landing produced electrodes. To test that, the team charged and discharged the hybrids 1,000 times and measured how long they lasted. As they did in the previous tests, the soft-landing-based devices performed the best, losing only a few percent capacity after 1000 cycles. The naked supercapacitors came in second, and the sodium-based, conventionally made devices lost about double the capacity of the soft-landed devices. This suggests that the soft-landing method has the potential to double the lifespan of these types of hybrid batteries. The team was surprised that it took so little of the POM material to make such a big difference to the carbon nanotube supercapacitors. By weight, the amount of POM was just one-fifth of a percent of the amount of carbon nanotube material. "The fact that the capacitance reaches a maximum with so little POM, and then drops off with more, is remarkable," said Laskin. "We didn't expect such a small amount of POM to be making such a large contribution to the capacitance." They decided to examine the structure of the electrodes using powerful microscopes in EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility at PNNL. They compared soft-landing with the conventionally made, sodium-POM electrodes. Soft-landing created small discrete clusters of POM dotting the carbon nanotubes, but the conventional method resulted in larger clumps of POM clusters swamping out the nanotubes, aggregates up to ten times the size of those made by soft-landing. This result suggested to the researchers that removing the positive ions from the POM starting material allowed the negative ions to disperse evenly over the surface. As long as the positive ions such as sodium remained, the POM and sodium appear to reform the crystalline material and aggregate on the surface. This prevented much of the POM from doing its job in the battery, thereby reducing capacity. When the team zoomed out a little and viewed the nanotubes from above, the conventionally made electrodes were covered in large aggregates of POM. The soft-landed electrodes, however, were remarkably indistinguishable from the naked carbon nanotube supercapacitors. In future research, the team wants to explore how to get the carbon materials to accept more POM, which might increase capacity and lifespan even further. More information: Venkateshkumar Prabhakaran et al. Rational design of efficient electrode–electrolyte interfaces for solid-state energy storage using ion soft landing, Nature Communications (2016). DOI: 10.1038/NCOMMS11399


News Article
Site: http://phys.org/technology-news/

The Electricity Infrastructure Operations Center at Pacific Northwest National Laboratory will host the web portal and repository for realistic grid data developed under a new ARPA-E program. Credit: Pacific Northwest National Laboratory Say you have a great new theory or technology to improve the nation's energy backbone—the electric grid. Wouldn't it be great to test it against a model complete with details that would tell you how your ideas would work? But it's a challenge, because existing sets of data are too small or outdated; and you don't have access to real data from the grid because of security and privacy issues. To overcome this issue, the Department of Energy's Pacific Northwest National Laboratory is helping to create open-access power grid datasets for researchers and industry. DOE's Advanced Research Projects Agency—Energy has awarded PNNL $3 million for two projects in a new program—Generating Realistic Information for the Development of Distribution and Transmission Algorithms or GRID DATA. In one project, PNNL will develop a sustainable data evolution technology or SDET. First, researchers will gather features and metrics from many private datasets provided by the laboratory's industry partners. The team includes the National Rural Electric Cooperative Association, GE Grid Solutions (formerly Alstom Grid), PJM Interconnection—an eastern regional transmission organization, the California Independent System Operator and Avista, a western utility. Datasets essentially describe the physical power grid and the transactions that occur on it. Data points can include how long it takes to ramp up a power plant, the resistance to flow on a power line, maximum power a certain plant can generate, connectivity—how electricity moves from point to point, the configuration of the grid at any given point, and much more. The combination of these elements is vast and they all determine the performance of the grid, which has been made more complex with the relatively recent addition of factors such as renewables and intelligent devices. So, researchers are seeking new methods to make it operate reliably for the least amount of expense to owners, operators and ratepayers. "Creating algorithms to optimize the grid essentially comes down to a challenging mathematical problem," said Henry Huang, an engineer at PNNL. "It's like the old saying 'garbage in, garbage out.' We need to get the right numbers—realistic numbers—into the algorithms needed for modeling so that utilities and grid operators feel confident in adopting new technologies being developed to modernize the grid." PNNL, together with partners, will develop data creation tools and use them to generate large-scale, open-access, realistic datasets. Finally, they will validate the datasets that are created using industry tools provided by GE Grid Solutions. The data creation tools as well as the datasets will be made available through a data repository, which also will be created by the second PNNL project awarded by ARPA-E. PNNL will partner with the National Rural Electric Cooperative Association to build a power system model repository, which will host the open-access power grid models and datasets. This Data Repository for Power System Open Models With Evolving Resources, or DR POWER, approach will review, annotate, and verify submitted datasets while establishing a repository and a web portal to distribute open-access models and scenarios. It will include the ability to collaboratively build, refine, and review a range of large-scale realistic power system models. It will also include datasets created by other GRID DATA projects. For researchers, this represents a significant improvement over current small-scale, static models that do not properly represent the challenging environments encountered by present and future power grids. The repository and the web portal will be hosted and maintained in PNNL's Electricity Infrastructure Operations Center.


News Article
Site: http://www.scientificcomputing.com/rss-feeds/all/rss.xml/all

RICHLAND, WA — Say you have a great new theory or technology to improve the nation's energy backbone — the electric grid. Wouldn't it be great to test it against a model complete with details that would tell you how your ideas would work? But it's a challenge, because existing sets of data are too small or outdated; and you don't have access to real data from the grid because of security and privacy issues. To overcome this issue, the Department of Energy's Pacific Northwest National Laboratory is helping to create open-access power grid datasets for researchers and industry. DOE's Advanced Research Projects Agency has awarded PNNL $3 million for two projects in a new program — Generating Realistic Information for the Development of Distribution and Transmission Algorithms or GRID DATA. In one project, PNNL will develop a sustainable data evolution technology or SDET. First, researchers will gather features and metrics from many private datasets provided by the laboratory's industry partners. The team includes the National Rural Electric Cooperative Association, GE Grid Solutions (formerly Alstom Grid), PJM Interconnection — an eastern regional transmission organization, the California Independent System Operator and Avista, a western utility. Datasets essentially describe the physical power grid and the transactions that occur on it. Data points can include how long it takes to ramp up a power plant, the resistance to flow on a power line, maximum power a certain plant can generate, connectivity — how electricity moves from point to point, the configuration of the grid at any given point, and much more. The combination of these elements is vast and they all determine the performance of the grid, which has been made more complex with the relatively recent addition of factors such as renewables and intelligent devices. So, researchers are seeking new methods to make it operate reliably for the least amount of expense to owners, operators and ratepayers. "Creating algorithms to optimize the grid essentially comes down to a challenging mathematical problem," said Henry Huang, an engineer at PNNL. "It's like the old saying 'garbage in, garbage out.' We need to get the right numbers — realistic numbers — into the algorithms needed for modeling so that utilities and grid operators feel confident in adopting new technologies being developed to modernize the grid." PNNL, together with partners, will develop data creation tools and use them to generate large-scale, open-access, realistic datasets. Finally, they will validate the datasets that are created using industry tools provided by GE Grid Solutions. The data creation tools, as well as the datasets, will be made available through a data repository, which will be also be created by the second PNNL project awarded by ARPA-E. PNNL will partner with the National Rural Electric Cooperative Association to build a power system model repository, which will host the open-access power grid models and datasets. This Data Repository for Power System Open Models With Evolving Resources, or DR POWER, approach will review, annotate, and verify submitted datasets while establishing a repository and a web portal to distribute open-access models and scenarios. It will include the ability to collaboratively build, refine, and review a range of large-scale realistic power system models. It will also include datasets created by other GRID DATA projects. For researchers, this represents a significant improvement over current small-scale, static models that do not properly represent the challenging environments encountered by present and future power grids. The repository and the web portal will be hosted and maintained in PNNL's Electricity Infrastructure Operations Center.


News Article
Site: http://www.materialstoday.com/news/

Inexpensive materials called metal-organic frameworks (MOFs) can pull gases out of air or other mixed gas streams, but fail to do so with oxygen. Now, a team of researchers has overcome this limitation by creating a composite of a MOF and a helper molecule in which the two work together to separate oxygen from other gases simply and cheaply. This work, reported in Advanced Materials, might prove of use in a wide variety of applications, including making pure oxygen for fuel cells and then using that oxygen in fuel cells, removing oxygen from food packaging, making oxygen sensors, and for many other industrial processes. The technique could also be used with gases other than oxygen by simply switching the helper molecule. Currently, industry uses a common process called cryogenic distillation to separate oxygen from other gases, but it is costly and uses a lot of energy to chill the gases. Also, it can't be used for specialty applications like sensors or getting the last bit of oxygen out of food packaging. A great oxygen separator would be easy to prepare and use, inexpensive and reusable. MOFs are materials containing lots of pores that can suck up gases like sponges suck up water. They have potential for use in nuclear fuel separation and in lightweight dehumidifiers. But of the thousands of MOFs produced to date, less than a handful can absorb molecular oxygen. And those MOFs chemically react with the oxygen, forming oxides that render the material unusable. "When we first worked with MOFs for oxygen separation, we could only use the MOFs a few times. We thought maybe there's a better way to do it," said materials scientist Praveen Thallapally at the US Department of Energy's Pacific Northwest National Laboratory (PNNL). The new approach that Thallapally and his colleagues at PNNL came up with involves using a second molecule to mediate the oxygen separation. This helper molecule should be attracted to, but chemically uninterested in, the MOF. Instead, the helper should react with oxygen to separate it from the other gases. The researchers chose a MOF called MIL-101 that is known for its high surface area – making it a powerful sponge – and its lack of reactivity: one teaspoon of MIL-101 has the same surface area as a football field. The high surface area comes from a MOF's pores, where reactive MOFs work their magic. MOFs that react with oxygen usually need to be handled carefully in the laboratory, but MIL-101 is stable at ambient temperatures and in the open atmosphere of a lab. For their helper molecule, Thallapally and his colleagues tried ferrocene, an inexpensive iron-containing molecule. The researchers made a composite of MIL-101 and ferrocene by simply mixing them and heating them up. Initial tests showed that MIL-101 took up more than its weight in ferrocene and at the same time lost surface area. This indicated that ferrocene was taking up space within the MOF's pores, where they need to be to snag oxygen molecules. Then the team tried sending gases through the black composite material. They found that the composite bound up a large percentage of oxygen, but almost none of the added nitrogen, argon or carbon dioxide. The material behaved this way whether the gases went through individually or as a mix, showing that the composite could separate oxygen from the other gases. Additional analysis showed that heating caused the ferrocene to decompose in the MOF pores to nanometer-sized clusters, making the iron available to react with oxygen. This reaction formed a stable mineral known as maghemite, all within the MOF pores. Handily, maghemite could be removed from the MOF, allowing the composite to be used again. Together, the results on the composite showed that a MOF might be able to do unexpected things – like purify oxygen – with a little help. Future research will explore other combinations of MOF and helper molecules. In addition to PNNL, other researchers taking part in this study hailed from Argonne National Laboratory and the University of Amsterdam in the Netherlands. This story is adapted from material from PNNL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.


They note in a paper published on April 1 by Nature Communications that the material is an excellent candidate for producing lighter vehicle parts, and that this newfound understanding may lead to creation of other high strength alloys. Researchers at the Department of Energy's Pacific Northwest National Laboratory knew the titanium alloy made from a low-cost process they had previously pioneered had very good mechanical properties, but they wanted to know how to make it even stronger. Using powerful electron microscopes and a unique atom probe imaging approach they were able to peer deep inside the alloy's nanostructure to see what was happening. Once they understood the nanostructure, they were able to create the strongest titanium alloy ever made. At 45 percent the weight of low carbon steel, titanium is a lightweight but not super strong element. It is typically blended with other metals to make it stronger. Fifty years ago, metallurgists tried blending it with inexpensive iron, along with vanadium and aluminum. The resulting alloy, called Ti185 was very strong—but only in places. The mixture tended to clump—just like any recipe can. Iron clustered in certain areas creating defects known as beta flecks in the material, making it difficult to commercially produce this alloy reliably. About six years ago, PNNL and its collaborators found a way around that problem and also developed a low-cost process to produce the material at an industrial scale, which had not been done before. Instead of starting with molten titanium, the team substituted titanium hydride powder. By using this feedstock, they reduced the processing time by half and they drastically reduced the energy requirements—resulting in a low-cost process in use now by a company called Advance Materials Inc. ADMA co-developed the process with PNNL metallurgist Curt Lavender and sells the titanium hydride powder and other advanced materials to the aerospace industry and others. Much like a medieval blacksmith, researchers knew that they could make this alloy even stronger by heat-treating it. Heating the alloy in a furnace at different temperatures and then plunging it into cold water essentially rearranges the elements at the atomic level in different ways thereby making the resulting material stronger. Blacksmithing has now moved from an art form to a more scientific realm. Although the underlying principles are the same, metallurgists are now better able to alter the properties based on the needs of the application. The PNNL team knew if they could see the microstructure at the nano-scale they could optimize the heat-treating process to tailor the nanostructure and achieve very high strength. "We found that if you heat treat it first with a higher temperature before a low temperature heat treatment step, you could create a titanium alloy 10-15 percent stronger than any commercial titanium alloy currently on the market and that it has roughly double the strength of steel," said Arun Devaraj a material scientist at PNNL. "This alloy is still more expensive than steel but with its strength-to-cost ratio, it becomes much more affordable with greater potential for lightweight automotive applications," added Vineet Joshi a metallurgist at PNNL. Devaraj and the team used electron microscopy to zoom in to the alloy at the hundreds of nanometers scale—about 1,000th the width of an average human hair. Then they zoomed in even further to see how the individual atoms are arranged in 3-D using an atom probe tomography system at EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility located at PNNL. The atom probe dislodges just one atom at a time and sends it to a detector. Lighter atoms "fly" to the detector faster, while heavier items arrive later. Each atom type is identified depending on the time each atom takes to reach the detector and each atom's position is identified by the detector. Thus scientists are able to construct an atomic map of the sample to see where each individual atom is located within the sample. By using such extensive microscopy methods, researchers discovered that by the optimized heat treating process, they created micron sized and nanosized precipitate regions—known as the alpha phase, in a matrix called the beta phase—each with high concentrations of certain elements. "The aluminum and titanium atoms liked to be inside the nano-sized alpha phase precipitates, whereas vanadium and iron preferred to move to the beta matrix phase," said Devaraj. The atoms are arranged differently in these two areas. Treating the regions at higher temperature of a 1,450 degrees Fahrenheit achieved a unique hierarchical nano structure. When the strength was measured by pulling or applying tension and stretching it until it failed, the treated material achieved a 10-15 percent increase in strength which is significant, especially considering the low cost of the production process. If you take the force you are pulling with and divide it by the area of the material you get a measure of tensile strength in megapascals. Steel used to produce vehicles has a tensile strength of 800-900 megapascals, whereas the 10-15 percent increase achieved at PNNL puts Ti185 at nearly 1,700 megapascals, or roughly double the strength of automotive steel while being almost half as light. The team collaborated with Ankit Srivastava, an assistant professor at Texas A&M's material science and engineering department to develop a simple mathematical model for explaining how the hierarchical nanostructure can result in the exceptionally high strength. The model when compared with the microscopy results and processing led to the discovery of this strongest titanium alloy ever made. "This pushes the boundary of what we can do with titanium alloys," said Devaraj. "Now that we understand what's happening and why this alloy has such high strength, researchers believe they may be able to modify other alloys by intentionally creating microstructures that look like the ones in Ti185." For instance, aluminum is a less expensive metal and if the nanostructure of aluminum alloys can be seen and hierarchically arranged in a similar manner, that would also help the auto industry build lighter vehicles that use less fuel and put out less carbon dioxide that contributes to climate warming. More information: Arun Devaraj et al. A low-cost hierarchical nanostructured beta-titanium alloy with high strength, Nature Communications (2016). DOI: 10.1038/NCOMMS11176

Discover hidden collaborations