Pacific Northwest National Laboratory, University of Washington Team Up to Make the Materials of Tomorrow
Many innovations of 21st century life, from touch screens and electric cars to fiber-optics and implantable devices, grew out of research on new materials. This impact of materials science on today's world has prompted two of the leading research institutions in the Pacific Northwest to join forces to research and develop new materials that will significantly influence tomorrow's world.
With this eye toward the future, the Department of Energy's Pacific Northwest National Laboratory and the University of Washington announced the creation of the Northwest Institute for Materials Physics, Chemistry and Technology -- or NW IMPACT -- a joint research endeavor to power discoveries and advancements in materials that transform energy, telecommunications, medicine, information technology and other fields. UW President Ana Mari Cauce and PNNL Director Steven Ashby formally launched NW IMPACT during a ceremony an January 31 at the PNNL campus in Richland, Washington.
"This partnership holds enormous potential for innovations in material science that could lead to major changes in our lives and the world," said Cauce. "We are excited to strengthen the ties between our two organizations, which bring complementary strengths and a shared passion for ground-breaking discovery."
"The science of making new materials is vital to a wide range of advancements, many of which we have yet to imagine," said Ashby. "By combining ideas, talent and resources, I have no doubt our two organizations will find new ways to improve lives and provide our next generation of materials scientists with valuable research opportunities."
The institute builds on a history of successful partnerships between the UW and the PNNL, including joint faculty appointments and past collaborations such as the Materials Synthesis and Simulations Across Scales Initiative, the PNNL-led Battery 500 consortium, and a new UW-based Materials Research Science and Engineering (MRSEC) Center. But NW IMPACT is the beginning of a long-term partnership, forging deeper ties between the UW and PNNL.
The goal is to leverage these respective strengths to enable discoveries, innovations, and educational opportunities that would not have been possible by either institution alone.
"By partnering the UW and PNNL together through NW IMPACT, the sum will truly be greater than the parts," said David Ginger, a UW professor of chemistry and chief scientist at the UW Clean Energy Institute. "We are joining together our expertise and experiences -- the best parts of ourselves, really -- to create the next generation of leaders who will create the materials of the future."
Ginger will co-lead the institution in its initial phase with Jim De Yoreo, chief scientist for Materials Synthesis and Simulation across Scales at PNNL and a joint appointee at the UW.
Over the first few years NW IMPACT aims to hire a permanent institute director, who will be based at both PNNL and the UW; create at least 20 new joint UW-PNNL appointments among existing researchers; streamline access to research facilities at the UW's Seattle campus and PNNL's Richland campus for institute projects; involve at least 20 new UW graduate students in PNNL-UW collaborations; and provide seed grants to institute-affiliated researchers to tackle new scientific frontiers in a collaborative fashion.
Some of the areas in which NW IMPACT will initially focus include:
- Materials for energy conversion and storage, which can be applied to more efficient solar cells, batteries and industrial applications. These include innovative approaches to create flexible, ultrathin solar cells for buildings or fabrics, long-lasting batteries for implantable medical devices, catalysts to enable high-efficiency energy conversion and industrial processes, and manufacturing methods to synthesize these materials efficiently for commercial applications.
- Quantum materials, such as ultrathin semiconductors or other materials that can harness the rules of quantum mechanics at subatomic-level precision for applications in quantum computing, telecommunications and beyond.
- Materials for water separation and utilization, which include processes to make water purification and ocean desalination methods faster, cheaper, and more energy-efficient.
- Biomimetic materials, which are synthetic materials inspired by the structures and design principles of biological molecules and materials within our cells -- including proteins and DNA. These materials could be applicable in medical settings for implantable devices or tissue engineering, and for self-assembled protein-like scaffolds in industrial settings.
"The science of making materials involves understanding where the atoms must to be placed in order to obtain the properties needed for specific applications, and then understanding how to get the atoms where they need to be," said De Yoreo.
NW IMPACT will draw on the unique strengths and talents of each institution for innovative collaborations in these areas. For example, PNNL has broad expertise in materials for improved batteries. The lab also offers best-in-class imaging, NMR and mass spectrometry capabilities at EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science user facility. DOE supports fundamental research at PNNL in chemistry, physics, and materials sciences that are key to materials development. The UW brings complementary facilities and equipment to the partnership, such as the Washington Clean Energy Testbeds at the Clean Energy Institute and a cryo-electron microscopy facility, as well as expertise in a variety of "big data" research and training endeavors, highly rated research and education programs, and ongoing materials research projects through the National Science Foundation-funded Molecular Engineering Materials Center.
See the PNNL press release here.
How Seashells Get Their Strength
Study shows how calcium carbonate forms composites to make strong materials such as in shells and pearls
Seashells and lobster claws are hard to break, but chalk is soft enough to draw on sidewalks. Though all three are made of calcium carbonate crystals, the hard materials include clumps of soft biological matter that make them much stronger. A study today in Nature Communications reveals how soft clumps get into crystals and endow them with remarkable strength.
The results show that such clumps become incorporated via chemical interactions with atoms in the crystals, an unexpected mechanism based on previous understanding. By providing insight into the formation of natural minerals that are a composite of both soft and hard components, the work will help scientists develop new materials for a sustainable energy future, based on this principle.
"This work helps us to sort out how rather weak crystals can form composite materials with remarkable mechanical properties," said materials scientist Jim De Yoreo of the Department of Energy's Pacific Northwest National Laboratory. "It also provides us with ideas for trapping carbon dioxide in useful materials to deal with the excess greenhouse gases we're putting in the atmosphere, or for incorporating light-responsive nanoparticles into highly ordered crystalline matrices for solar energy applications."
Beautiful and functional
Calcium carbonate is one of the most important materials on earth, crystallizing into chalk, shells, and rocks. Animals from mollusks to people use calcium carbonate to make biominerals such as pearls, seashells, exoskeletons, or the tiny organs in ears that maintain balance. These biominerals include proteins or other organic matter in the crystalline matrix to convert the weak calcium carbonate to hard, durable materials.
Scientists have been exploring how organisms produce these biominerals in the hopes of determining the basic geochemical principles of how they form, and also how to build synthetic materials with unique properties in any desired shape or size.
The strength of a material depends on how easy it is to disrupt its underlying crystal matrix. If a material is compressed, then it becomes harder to break the matrix apart. Proteins trapped in calcium carbonate crystals create a compressive force — or strain — within the crystal structure.
Unlike the strain that makes muscles sore, this compressive strain is helpful in materials, because it makes it harder to disrupt the underlying crystal structure, thereby adding strength. Scientists understand how forces, stress and strain combine to make strong materials, but they understand less about how to create the materials in the first place.
Pearls of wisdom
The leading explanation for how growing crystals incorporate proteins and other particles is by simple mechanics. Particles land on the flat surface of calcium carbonate as it is crystallizing, and units of calcium carbonate attach over and around the particles, trapping them.
"The standard view is that the crystal front moves too fast for the inclusions to move out of the way, like a wave washing over a rock," said De Yoreo.
That idea's drawback is that it lacks the details needed to explain where the strain within the material comes from. The new results from De Yoreo and colleagues do, however.
"We've found a completely different mechanism," he said.
To find out how calcium carbonate incorporates proteins or other strength-building components, the team turned to atomic force microscopy, also known as AFM, at the Molecular Foundry, a DOE Office of Science User Facility at Lawrence Berkeley National Laboratory. In AFM, the microscope tip delicately runs over the surface of a sample like a needle running over the grooves in a vinyl record. This creates a three-dimensional image of a specimen under the scope.
The team used a high concentration of calcium carbonate that naturally forms a crystalline mineral known as calcite. The calcite builds up in layers, creating uneven surfaces during growth, like steps and terraces on a mountainside. Or, imagine a staircase. A terrace is the flat landing at the bottom; the stair steps have vertical edges from which calcite grows out, eventually turning into terraces too.
For their inclusions, the team created spheres out of organic molecules and added them to the mix. These spheres called micelles are molecules that roll up like roly-poly bugs based on the chemistry along their bodies — pointing outwards are the parts of their molecules that play well chemically with both the surrounding water and the calcite, while tucked inside are the parts that don't get along with the watery environment.
Better composites through chemistry
The first thing the team noticed under the microscope is that the micelles do not randomly land on the flat terraces. Instead they only stick to the edges of the steps.
"The step edge has chemistry that the terrace doesn't," said De Yoreo. "There are these extra dangling bonds that the micelles can interact with."
The edges hold onto the micelles as the calcium carbonate steps close around them, one after another. The team watched as the growing steps squeezed the micelles. As the step closed around the top of the micelle, first a cavity formed and then it disappeared altogether under the surface of the growing crystal.
To verify that the micelles were in fact buried within the crystals, the team dissolved the crystal and looked again. Like running a movie backwards, the team saw micelles appear as the layers of crystal disappeared.
Finally, the team recreated the process in a mathematical simulation. This showed them that the micelles — or any spherical inclusions — are compressed like springs as the steps close around them. These compressed springs then create strain in the crystal lattice between the micelles, leading to enhanced mechanical strength. This strain likely accounts for the added strength seen in seashells, pearls and similar biominerals.
"The steps capture the micelles for a chemical reason, not a mechanical one, and the resulting compression of the micelles by the steps then leads to forces that explain where the strength comes from," said De Yoreo.
This work was supported by the Department of Energy Office of Science, National Institutes of Health.
Reference: Kang Rae Cho, Yi-Yeoun Kim, Pengcheng Yang, Wei Cai, Haihua Pan, Alexander N. Kulak, Jolene L. Lau, Prashant Kulshreshtha, Steven P. Armes, Fiona C. Meldrum & James J. De Yoreo. Direct observation of mineral-organic composite formation reveals occlusion mechanism, Nature Communications, January 6, 2016, DOI:10.1038/NCOMMS10187.
Research Collaboration for Lightweight Materials No Longer a Heavy Lift
Access to National Laboratories' Capabilities Streamlined
There is now a one-stop shop for industrial researchers who want to use the unique capabilities and talents found at select Department of Energy national laboratories in a quest to develop lighter materials. DOE is establishing a new consortium to support a vision of developing and deploying materials twice as fast, at a fraction of the cost, while increasing U.S. competitiveness in manufacturing.
DOE's Pacific Northwest National Laboratory will manage the Lightweight Materials National Lab Consortium or LightMAT — a network of nine national labs with technical capabilities that are highly relevant to lightweight materials development and use. LightMAT will provide a single point of contact which will match industry led research teams with specific expertise and equipment found only at the national labs.
"The major perceived impediments to U.S. companies working with national laboratories are the complexity and time required to identify research and development capabilities at numerous institutions throughout the country, and the difficulty of formalizing teaming agreements," said Yuri Hovanski, senior researcher at PNNL and LightMAT program director. "LightMAT will provide a more productive experience for companies that want to engage the national laboratories to accelerate deployment of lightweight materials."
PNNL, in collaboration with eight other DOE national laboratories, is developing a virtual storefront to showcase the capabilities of participating laboratories. Industry partners will now be able to engage LightMAT assistance through the LightMAT website.
Any U.S. company, large or small, is able to seek assistance to locate and use strategic resources to accelerate lightweight materials research & development. LightMAT will help with laboratory access and materials development by:
- Assisting companies to understand the unique lightweight materials capabilities housed within the consortium
- Connecting industry with laboratory technology experts to establish approaches for using these capabilities to address specific clean energy manufacturing challenges
- Aiding industry to more quickly and easily develop agreements to access national laboratory capabilities
- Providing a data repository for industry to access and leverage data and tools developed by the LightMAT consortium for expanded application and implementation.
Along with access to national laboratory capabilities, all industrial partners will be able to use collaboration tools and data aggregation tools that are being developed as part of LightMAT. This includes simplified work and technology transfer agreements, and a LightMAT non-disclosure agreement that allows access to all participating laboratories through a single document. This means additional cost and time savings for industrial participants.
"It can take as long as 20 years to get a lightweight material from concept to market," said Reuben Sarkar, deputy assistant secretary for sustainable transportation in DOE's office of Energy Efficiency & Renewable Energy. "If DOE can help cut that by 10 years, the savings and boost to U.S. industry will be substantial. With our national laboratories' expertise in lightweight materials built on a framework of industry engagement and support, LightMAT can put more of DOE's resources to work and have a real impact."
To date, the LightMAT network includes:
- Ames Laboratory
- Argonne National Laboratory
- Idaho National Laboratory
- Los Alamos National Laboratory
- Lawrence Livermore National Laboratory
- National Renewable Energy Laboratory
- Oak Ridge National Laboratory
- Pacific Northwest National Laboratory
- Sandia National Laboratories
- Processing & manufacturing
- Computational tools
- Materials characterization
Short-term goals of the consortium include creating a comprehensive online portal for industry access and participation, partnering with at least two new industry-led programs per year, and hosting or meeting with at least 10 automotive light metals companies per year to describe opportunities for accessing the resource network.
LightMAT is sponsored by DOE's Vehicle Technologies Office, which aims to increase energy efficiency and reduce emissions in vehicles. VTO is part of EERE.
Low-cost and Lightweight
Strongest titanium alloy aims at improving vehicle fuel economy and reducing CO2 emissions
An improved titanium alloy — stronger than any commercial titanium alloy currently on the market — gets its strength from the novel way atoms are arranged to form a special nanostructure. For the first time, researchers have been able to see this alignment and then manipulate it to make the strongest titanium alloy ever developed, and with a lower cost process to boot.
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.
Mixing it up
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.
"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."
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.
An improved titanium alloy — stronger than any commercial titanium alloy currently on the market — gets its strength from the novel way atoms are arranged to form a special nanostructure. For the first time, researchers at Pacific Northwest National Laboratory have been able to see this alignment and then manipulate it to make it even stronger. Using powerful electron microscopes and a unique atom probe imaging approach at EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility located at PNNL, they were able to peer deep inside the alloy’s nanostructure to see what was happening.
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.
DOE's Vehicle Technologies Office — Propulsion Materials Program supported this research using capabilities developed under PNNL's internally funded Chemical Imaging Initiative.
Reference: Arun Devaraj, Vineet V. Joshi, Ankit Srivastava, Sandeep Manandhar, Vladimir Moxson, Volodymyr A Duz, Curt Lavender A Low Cost Hierarchical Nanostructured β-Titanium Alloy for Lightweighting Applications, Nature Communications, April 1, 2016, DOI: 10.1038/NCOMMS11176.
Of Catalysts and Coke
Researchers peer inside catalyst used in biofuel processing to investigate why it clogs
Catalysts known as zeolites are vital to fuel production and other processes. Coke deposits in zeolites are a costly problem in petroleum refinement and in petrochemical production.
"Understanding coke molecules in zeolites will provide broad benefits across the refinery and renewable energy industries, and zeolite is one of the most highly utilized catalysts," said Karthikeyan Ramasamy, a chemical engineer at the Department of Energy's Pacific Northwest National Laboratory.
To explore ways to fix the issue, Ramasamy and other researchers from PNNL, with help from DOE's Lawrence Berkeley National Laboratory, zoomed in at the highest resolution yet on these problematic carbon-based deposits.
They found zeolites's porous nature makes it a great chemical catalyst, but also traps tiny clusters of carbon-containing molecules that can ultimately disrupt the catalysis process. An uneven distribution of aluminum in the fresh zeolite catalyst causes an uneven distribution of coke deposits during chemical reactions.
"We wanted to understand this coking mechanism and where it blocks the reaction and how it blocks it. By using a combination of techniques we could compare them to one another and form a complete story," said PNNL materials scientist Arun Devaraj, who co-led the study with Ramasamy.
Read more in Lawrence Berkeley National Laboratory's news release.
Reference: Arun Devaraj, Vijayakumar Murugesan, Jie Bao, Mond F. Guo, Mirosław A. Derewinski, Zhijie Xu, Michel J. Gray, Sebastian Prodinger, Karthikeyan K. Ramasamy. Discerning the Location and Nature of Coke Deposition from Surface to Bulk of Spent Zeolite Catalysts, Scientific Reports, November 23, 2016, DOI: 10.1038/srep37586.
PNNL Scientists among Most Influential in the World
Six researchers named in top one percent of citations
Six researchers with the Department of Energy's Pacific Northwest National Laboratory are among the most highly cited scientists in the world.
The PNNL researchers are included on the 2016 Highly Cited Researcher list from Clarivate Analytics (formerly Thomson Reuters), which analyzed publication and citation statistics between 2004-2014. The list features scientists from around the world whose citations rank in the top one percent within 22 subject areas. Citations accrue when newly published scientific papers refer back to previously published research findings.
Three of the PNNL scientists were recognized in the geosciences category. Richard Easter, Steven Ghan, and Philip Rasch are developing new ways to understand a very important climate issue that currently poses a lot of uncertainty: What is the impact of clouds and small particles in the atmosphere as the climate changes. The particles can be natural, such as from a volcano or from waves breaking on the ocean, or they can come from processes such as energy production. The particles form the nucleus of clouds, which have a huge influence on the Earth's energy balance; the chemistry and physics involved in understanding the process are formidable. At PNNL, Easter, Ghan and Rasch are part of one of the world's top teams studying these processes.
Chemistry, materials science, and microbiology
The other three researchers were recognized for important contributions in chemistry, materials science, and microbiology.
- Janet Jansson, microbiology: Jansson focuses on the use of molecular approaches (omics) to study complex microbial communities, such as those residing in soil, sediments, and the human gut. Specific contributions include using an array of technologies to show the versatility of microbes that live in permafrost, which is a reservoir for a huge amount of carbon. The fate of that carbon as the climate warms and permafrost thaws is a huge issue for scientists trying to understand the planet's future. The work, published in Nature, yielded one of the most detailed looks ever at the microbes active in permafrost.
- Jun Liu, chemistry, materials science: Liu was recognized in both chemistry and materials science related to materials synthesis, characterization and applications, including energy storage — batteries that are smaller, more efficient, less expensive, and even fundamentally different than current technologies. Developing better batteries is key not only for common devices like laptops and cell phones; it's central to the world's ability to move away from traditional fossil fuels and to renewable forms of energy such as wind and solar energy,.
- Yuehe Lin, chemistry: Lin is a Washington State University professor with a joint appointment to PNNL. He studies nanotechnology, particularly the development of new nanobioelectronic devices and nanomaterials for biomedical diagnosis and drug delivery. His other research activities include developing integrated microanalytical systems for environmental and biomedical analysis, and synthesizing functional nanomaterials for energy and environmental applications.
This year's list includes 3,100 researchers with global and scientific impact. The complete list can be viewed on Clarivate Analytics' website.
Sawdust Reinvented into Super Sponge for Oil Spills
Environmentally friendly material tweaked to soak up to 5 times its weight in oil, float 4 months in icy, rough waters
Lowly sawdust, the sawmill waste that's sometimes tossed onto home garage floors to soak up oil spilled by amateur mechanics, could receive some new-found respect thanks to science.
Researchers at the Department of Energy's Pacific Northwest National Laboratory have chemically modified sawdust to make it exceptionally oil-attracting and buoyant, characteristics that are ideal for cleaning oil spills in the icy, turbulent waters of the Arctic. The nontoxic material absorbs up to five times its weight in oil and stays afloat for at least four months.
"The chance of an oil spill in the Arctic is real. We hope materials like our modified sawdust can help if an accident happens."
"Most of today's oil remediation materials are designed for warm water use," said PNNL microbiologist George Bonheyo, who leads the modified sawdust's development from PNNL's Marine Sciences Laboratory.
"But as ice retreats in the Arctic Sea, fossil fuel developers are looking north, and we need new oil spill response methods that perform well in extreme conditions," added Bonheyo, who also holds a joint appointment in bioengineering with Washington State University.
"The chance of an oil spill in the Arctic is real," said fellow PNNL microbiologist Robert Jeters, who is also part of the project. "We hope materials like our modified sawdust can help if an accident happens."
Fire & ice
Containing oil spills in cold waters is especially tricky, as bobbing ice chunks push oil below the water's surface, making it difficult to collect. The same goes for rough waters, whose tall, clashing waves disperse oil.
The modified saw dust pulls double duty. Beyond absorbing oil, it also enhances another approach to combatting oil spills — controlled burns. If changing weather or tides move spilled oil toward a sensitive area fast, oil can be burned before it can cause further harm. Called in-situ burning, the practice can significantly reduce the amount of oil in water and minimize its adverse environmental effects.
Bonheyo and his team looked to develop an environmentally friendly and inexpensive material that floats despite rough or freezing waters and can support in-situ burning. Not wanting to create more pollution if emergency responders can't retrieve oil cleanup material, Bonheyo's team considered other natural ingredients like rice hulls and silica. But they ultimately found their winner in a fine dust called wood flour. A woodworking byproduct, wood flour is often used to make wood composites.
To turn the dust into a thirsty oil mop, researchers chemically attach components of vegetable oil onto the material's surface. These attachments make the modified material oil-grabbing and water-shunning. The final product is a light, fluffy, bleached powder. The team is also trying out adding tiny, oil-eating microbes — fungi and bacteria — to the powder's surface so any left-behind material could naturally break down oil over time.
Just a sprinkle
Applying the modified sawdust is simple: sprinkle a thin layer over oil on the water's surface. The material immediately starts soaking up oil, creating a concentrated and solid slick that stays afloat thanks to the material's buoyant nature. The oil-soaked material can either be burned or retrieved.
The team is using PNNL's unique Arctic simulation lab in Sequim, Washington to evaluate the material in icy waters. The facility is a customized shipping container that cools down to as low as 5 degrees Fahrenheit, which prompts researchers to don snowmobile suits and ski masks while they work. Ice slush forms on the surface of water that circulates inside a 290-gallon raceway pond placed inside the bitterly cold lab space. Oil is spilled on the slushy surface, followed by a sprinkle of modified sawdust. Tests have shown the material's water-repellent nature prevents ice from forming on it, allowing it to soak up oil and remain at the surface.
Researchers are also testing how well the material performs in controlled burns. They conducted initial burns this fall at the U.S. Coast Guard and Naval Research Laboratory's Joint Maritime Test Facility near Mobile, Alabama. Burn tests continue today at PNNL's Marine Science Laboratory. Early results indicate a small amount of material enables burning of both thin and thick layers of spilled oil.
In the coming months, PNNL will further evaluate the modified sawdust. The material will need additional testing and approval by multiple agencies before it can be used at actual oil spills.
PNNL is developing the material for the Department of Interior's Bureau of Safety of Environmental Enforcement. BSEE is the lead federal agency charged with improving safety and ensuring environmental protection related to the offshore energy industry, primarily oil and natural gas on the U.S. Outer Continental Shelf.
The material's development team includes Bonheyo, Jeters, Yongsoon Shin, Jiyeon Park, Andrew Avila and Maren Symes.
The Contradictory Catalyst
Researchers find the key to speeding up the rate of reaction of a potential catalyst for energy storage lies in making the reactive parts of the catalyst move more slowly
One reason we can't bottle summer sunshine and save the solar energy for rainy days is that we don't have an efficient way to store it. Nature stores energy in chemical bonds, like when plants photosynthesize our food. Researchers are trying to design catalysts based on inexpensive metals to store energy like nature does.
The chemical bonds in hydrogen gas, for example, could power fuel cells, internal combustion engines, or generators. Using a natural catalyst from bacteria for inspiration, researchers have now developed the fastest synthetic catalyst for hydrogen production — producing 45 million molecules per second. Instead of a costly metal, this catalyst uses inexpensive, abundant nickel at its busy core.
"This work gave us some insight into the movement of the catalyst, and how to control that movement to make it more efficient."
Although the catalyst requires more energy to run than a conventional platinum catalyst, the insight garnered from this result might eventually help make hydrogen fuel in an environmentally friendly, affordable way, the researchers report in the chemistry journal Angewandte Chemie International Edition.
"The next thing we'll work on is making it more efficient," said chemist Molly O'Hagan at the Department of Energy's Pacific Northwest National Laboratory. "We still have to feed it too much electricity to produce the hydrogen."
To make sustainable hydrogen fuel cells for your car or your home, we need to produce hydrogen fuel from a source other than fossil fuel. PNNL Chemist Molly O'Hagan explains in 90 seconds.
The team at PNNL has been developing a nickel-based catalyst modeled on an enzyme from nature called a hydrogenase for several years. Back in 2011, working in the Center for Molecular Electrocatalysis, a DOE Energy Frontier Research Center, they made a synthetic catalyst that was 10 times faster than the natural one. That natural one clocked in at 100,000 hydrogen molecules per second.
As they worked on the catalyst development, the scientists would test their catalysts in reactions by combining the catalyst and acids in different media. One thing they noticed was that the synthetic catalyst produced hydrogen faster in a viscous liquid as opposed to a free-flowing liquid.
"We used this medium that was like pancake syrup and saw very fast rates," said O'Hagan. "The catalyst has arms that move around to position the pieces of the chemical reaction. Normally they are flopping around like crazy and the pieces don't always hit the right target. When this happens, the arms can actually get stuck in a position where the catalyst can't put the pieces together at all. We thought that this thick syrup might be slowing down the flopping, letting the arms put the pieces together more efficiently."
To test this hypothesis, the team designed the catalyst to have longer arms that would drag and slow down the flopping. They tested different arm lengths and found the longer the arms, the faster the catalyst produced hydrogen molecules.
They also measured how fast the arms were swinging around. The longer the arms, the slower the movement, allowing them to attribute the faster hydrogen production to the slower arm movements. Like excited children playing catch, calming down a bit lets them hit their mark more often.
"This work gave us some insight into the movement of the catalyst, and how to control that movement to make it more efficient," said O'Hagan.
Some computational work for this research was performed in EMSL, the Environmental Molecular Sciences Laboratory a DOE Office of Science User Facility at PNNL. The study was supported by the Department of Energy Office of Science.
Reference: Allan Jay P. Cardenas, Bojana Ginovska, Neeraj Kumar, Jianbo Hou, Simone Raugei, Monte L. Helm, Aaron M. Appel, R. Morris Bullock, and Molly O'Hagan. Controlling Proton Delivery through Catalyst Structural Dynamics, Angew. Chem. Int. Ed., Sept. 27, 2016, DOI: 10.1002/anie.201607460.
Tweaking Electrolyte Makes Better Lithium-metal Batteries
A pinch of electrolyte additive gives rechargeable battery stability, longer life
Scientists have found adding a pinch of something new to a battery's electrolyte gives the energy storage devices more juice per charge than today's commonly used rechargeable batteries.
New, early-stage research shows adding a small amount of the chemical lithium hexafluorophosphate to a dual-salt, carbonate solvent-based electrolyte can make rechargeable lithium-metal batteries stable, charge quickly and have a high voltage.
"A good lithium-metal battery will have the same lifespan as the lithium-ion batteries that power today's electric cars and consumer electric devices, but also store more energy so we can drive longer in between charges," said chemist Wu Xu of the Department of Energy’s Pacific Northwest National Laboratory. Xu is a corresponding author on a paper published today in the journal Nature Energy.
Most of the rechargeable batteries used today are lithium-ion batteries, which have two electrodes: one that's positively charged and contains lithium, and another negative one that's typically made of graphite. Electricity is generated when electrons flow through a wire that connects the two.
To control the electrons, positively charged lithium atoms shuttle from one electrode to the other through another path, the electrolyte solution in which the electrodes sit. But graphite can't store much energy, limiting the amount of energy a lithium-ion battery can provide smart phones and electric vehicles.
When lithium-based rechargeable batteries were first developed in the 1970s, researchers used lithium metal for the negative electrode, called an anode. Lithium was chosen because it has ten times more energy storage capacity than graphite. Problem was, the lithium-carrying electrolyte reacted with the lithium anode. This caused microscopic lithium nanoparticles and branches called dendrites to grow on the anode surface, and led the early batteries to fail.
Many have tweaked rechargeable batteries over the years in an attempt to resolve the dendrite problem. Researchers switched to other materials such as graphite for the anode. Scientists have also coated anodes with protective layers, while others have created electrolyte additives. Some solutions eliminated dendrites but also resulted in impractical batteries with little power. Other methods only slowed, but didn't stop, dendrite growth.
Thinking today's rechargeable lithium-ion batteries with graphite anodes could be near their peak energy capacity, PNNL is taking another look at the older design with lithium metal as an anode. Xu and colleagues were part of earlier PNNL research seeking a better-performing electrolyte. The electrolytes they tried produced either a battery that didn't have problematic dendrites and was super-efficient but charged very slowly and couldn't work in higher-voltage batteries, or a faster-charging battery that was unstable and had low voltages.
Next, they tried adding small amounts of a salt that's already used in lithium-ion batteries, lithium hexafluorophosphate, to their fast-charging electrolyte. They paired the newly juiced-up electrolyte with a lithium anode and a lithium nickel manganese cobalt oxide cathode. It turned out to be a winning combination, resulting in a fast, efficient, high-voltage battery.
The additive enabled a 4.3-volt battery that retained more than 97 percent of its initial charge after 500 repeated charges and discharges, while carrying 1.75 milliAmps of electrical current per square centimeter of area. It took the battery about one hour to fully charge.
The battery performed well largely because the additive helps create a robust protective layer of carbonate polymers on the battery's lithium anode. This thin layer prevents lithium from being used up in unwanted side reactions, which can kill a battery.
And, because the additive is already an established component of lithium-ion batteries, it's readily available and relatively inexpensive. The small amounts needed — just 0. 6 percent of the electrolyte by weight — should also further lower the electrolyte's cost.
Xu and his team continue to evaluate several ways to make rechargeable lithium-metal batteries viable, including improving electrodes, separators and electrolytes. Specific next steps include making and testing larger quantities of their electrolyte, further improving the efficiency and capacity retention of a lithium-metal battery using their electrolyte, increasing material loading on the cathode and trying a thinner anode.
This research was supported by the Department of Energy's Office of Energy Efficiency and Renewable Energy. Researchers performed microscopy and spectroscopy characterizations of battery materials at EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science national User Facility at PNNL. The battery electrodes were made at DOE's Cell Analysis, Modeling, and Prototyping Facility at Argonne National Laboratory.
Reference: Jianming Zheng, Mark H. Engelhard, Donghai Mei, Shuhong Jiao, Bryant J. Polzin, Ji-Guang Zhang & Wu Xu, "Electrolyte Additive Enabled Fast Charging and Stable Cycling Lithium Metal Batteries," Nature Energy, March 1, 2017, DOI: 10.1038/nenergy.2017.12.
WSU Grad Students and the Pacific Northwest National Laboratory – a Winning Combination
Institutions grow collaboration
Over the years, doctoral candidates have interned at the Pacific Northwest National Laboratory, conducting research in areas ranging from energy to national security to fundamental science. Some students have even co-authored scientific papers and presented at conferences before completing their doctorate.
But now, the Department of Energy lab and Washington State University are upping the ante with a formalized program that enhances the benefits to both institutions.
Twelve doctoral candidates have been selected to participate in the PNNL-WSU Distinguished Graduate Research Program that will put them to work in the lab to gain valuable and relevant research experience. The benefit to PNNL goes far beyond an extra pair of hands in the lab.
"These doctoral students are not only bright, they will come with new questions and ideas that will enhance the culture of creativity and innovation at the Lab," said Malin Young, deputy director for science and technology at PNNL. "We have dozens of researchers who are excited to host and mentor WSU graduate students in these areas of vital national importance."
WSU graduate students may pursue research related to clean energy, chemistry, environmental sustainability, national security and biotechnology — or other areas of PNNL's broad range of capabilities.
PNNL will provide the students' stipends and benefits. The participants are selected by both the lab and WSU, and it's anticipated the program will be an incentive to attract the best and brightest doctoral candidates. The graduate students will spend approximately two years at PNNL after completing their coursework at any of the WSU campuses.
"Engaging graduate students with the talented energy, environment, national security and fundamental science researchers at our institutions will increase the scientific and research capacity in our region," said Chris Keane, vice president for research at WSU.
The program adds to the long-standing partnership between the two institutions, which includes joint research programs and joint faculty appointments.
The first group of students is comprised of 12 current doctoral candidates who will begin work at PNNL this year. A new group of doctoral students is expected each year. This year's participants are:
- Jenny Voss, Chemical Engineering
- Nadia Panossian, Mechanical Engineering
- Ernesto Martinez-Baez, Chemistry
- Priyanka Ghosh, Computer Science
- Christina Louie, Chemical Engineering
- Justine Missik, Engineering Science
- Xu Liu, Computer Science
- Stephen Taylor, Soil Science
- Trent Graham, Chemical Engineering
- Isaac Johnson, Material Science & Engineering
- Austin Winkelman, Chemistry
- Anthony Kyzysko, Chemistry
Learn more on the PNNL-WSU Distinguished Graduate Research Program website.
PNNL Researcher Elected MRS Fellow
A materials science researcher at the Department of Energy's Pacific Northwest National Laboratory has been elected to the rank of fellow of the Materials Research Society. Chongmin Wang was recognized for his contributions to the development of transmission electron microscopy tools enabling direct observation of lithium-ion batteries during operation, leading to insights in designing better battery materials.
Wang is a chief scientist at EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility at PNNL. His research focuses on correlating the structural and chemical evolution of materials, especially energy storage materials, with their functional properties. He received the MRS Innovation in Materials Characterization Award in 2016 and the Journal of Materials Research Paper of the Year award in 2015. He is also an R&D 100 award winner for implementing graphene based materials in lithium battery applications and was named the Alexander von Humboldt Research Fellow in 1994. He earned a bachelor's degree in physics and a master's in condensed matter physics from Lanzhou University in China, and a doctorate in materials science and engineering from Leeds University in the United Kingdom. He will be recognized at the organization's spring meeting in Phoenix in April.
MRS has nearly 16,000 members from 90 countries around the world. Election as a fellow recognizes members for notable research contributions that advance the field of materials science. No more than 0.2% of members may be elected to the rank of fellow each year.
Chemists Tackling Carbon Challenges at Next Week's American Chemical Society Meeting
It's like throwing away money. Carbon dioxide released by power plants could supply carbon atoms to create fuels and chemicals, or be used to push out leftover fuels from the subsurface. All these options rely heavily on economically viable technologies to capture the carbon dioxide. Such technologies exist but are still too costly for power plants. Scientists from diverse disciplines have been working on these carbon challenges, each with a different approach to finding answers.
Vanda Glezakou and Roger Rousseau at the Department of Energy's Pacific Northwest National Laboratory decided it was important to get everyone in the same room and talking about their approaches and findings. So they've organized a symposium to encourage a spirited exchange of ideas around computational chemistry. Titled Computations for CO2 Capture, Conversion & Sequestration, the event will be held at the American Chemical Society's national meeting on Sunday, April 2.
They've brought together experts from catalysis, materials chemistry, environmental sciences, geochemistry, computational chemistry, and physics to share their latest research and discuss future research directions. Several PNNL researchers will showcase their expertise as well, including David Heldebrant, known for his research in carbon dioxide capture solvents, Simone Raugei, known for modeling chemical and biochemical processes for energy production, and Sebastien Kerisit, known for his work in modeling geochemical processes.
Read more in this highlight.
Geochemists Reveal How Nanoparticles Evolve and Change
Geochemistry examines chemical reactions within earth systems and affects everything from recovering oil to producing food. Researchers from the Department of Energy's Pacific Northwest National Laboratory have organized a symposium that explores how the reactivity of nanoparticles changes as the particles morph through different stages of life. The talks will be presented at the American Chemical Society's national meeting.
PNNL researchers Jennifer Soltis, Michele Conroy, and Frances Smith, along with R. Lee Penn from the University of Minnesota, have organized a symposium on nanoparticle reactivity, which is vital for areas including nuclear materials processing. Understanding the evolution of nanoparticle reactivity as conditions change is a fundamental step in developing a detailed picture of the role of nanoparticles in environmental and industrial settings.
At PNNL, Soltis uses different kinds of microscopy to better understand the nucleation and growth of nanoparticles — both geochemical and radiochemical. Conroy studies the different life stages of metal nanoparticles from when they first begin to form through when they disintegrate. Smith studies materials and geochemistry, including the long-term storage of nuclear materials.
Titled Evolving Nanoparticle Reactivity throughout Nucleation, Growth & Dissolution, the symposium begins Wednesday at 8:30 am.
Read more in this highlight.
International Press Seeks Expertise of PNNL's Devanathan
Multiple news outlets quote PNNL scientist as an expert in membrane separation
International and national news outlets are quoting a researcher at the Department of Energy's Pacific Northwest National Laboratory as they report on a new nano-sieve developed by the University of Manchester in the U.K.
The outlets quoted materials scientist Ram Devanathan as an outside expert not involved in the membrane's development after the journal Nature Nanotechnology invited him to pen a News & Views column on the technology. The sieve is made of the nanomaterial graphene oxide and filters salts from water, turning seawater into clean drinking water.
He's been quoted by several news outlets, including:
Devanathan has extensively studied membranes for selective separation. Through his research, he has advanced fundamental understanding of the transport of protons, small molecules and ions through membranes, including those made with graphene oxide. Devanathan is currently involved in a project under PNNL's Materials Synthesis and Simulation Across Scales Initiative that uses computational simulations integrated with experiments to scale up graphene oxide membranes for selective water and ion transport.
He is also serving as the acting director of PNNL's earth systems science division. Devanathan is a fellow of the American Ceramic Society and holds a doctorate in materials science and engineering from Northwestern University in Illinois.
Researchers resolve key question on titanium oxide, water interactions
When a molecule of water comes in for a landing on the common catalyst titanium oxide, it sometimes breaks up and forms a pair of molecule fragments known as hydroxyls. But scientists had not been able to show how often the breakup happened. Now, researchers have determined that water is only slightly more likely to stay in one piece as it binds to the catalyst surface than it is to form the hydroxyl pairs.
The result — water's advantage is so small — might surprise some chemists. But understanding that small advantage has wide-ranging significance for a variety of potential applications in industries that use titanium dioxide. These industries include alternative fuel production, solar energy and food safety, and even self-cleaning windows. It will also help scientists better understand how acids behave and expand their knowledge of how molecules split.
"How water binds was the big question," said chemist Zdenek Dohnalek at the Department of Energy's Pacific Northwest National Laboratory. "Chemists had mixed information from a lot of different methods, and theorists also had ideas. Using a unique combination of instruments, we've finally solved it."
The team reported the work in the Proceedings of the National Academy of Sciences.
Land of mystery
Even though many industries use titanium oxide to help speed up chemical reactions, scientists have not uncovered all of its secrets. A key mystery, researchers have long debated, is the way in which water interacts with titanium oxide. The interaction is important in its own right to split water, but it also influences the course of many reactions in general.
On titanium oxide's surface, molecules of water switch between being intact and splitting into hydroxyls. Even though there are many different ways of measuring the ratio of intact water to hydroxyls at any given time, scientists have not been able to nail it down for decades.
To explore the problem, PNNL researchers combined different tools in a new way. They sent beams of water at various speeds onto cold titanium oxide sitting under a very high resolution microscope known as a scanning tunneling microscope.
The microscope let them visualize the catalyst's titanium and oxygen atoms. The atoms appear as bright and dark rows, like a cornfield with tall rows of corn alternating with ditches, and individual molecules of water appear as bright spots that don't align with the rows.
In addition to viewing water molecules as they hit the surface, the team simulated details of the atoms interacting in exacting detail on a high performance computer. Combining experiments and simulations allowed the team to settle the long-standing debate.
Shaped like a V, a water molecule has a fat oxygen atom in the middle bound to two smaller hydrogen atoms on either side. Titanium oxide helps break the bonds between the atoms to push a chemical reaction forward: the titanium atoms trap water molecules, while nearby oxygen, also part of the catalyst surface, draws away then captures one of the hydrogen atoms.
When this happens, two hydroxyls are formed, one from a surface oxygen combining with the hydrogen and the other leftover from the water molecule.
The scientists needed to know how often the hydroxyls formed. Do water molecules largely stay intact on the surface? Or do they immediately convert to hydroxyls? How likely water will stay intact on titanium oxide — and how easily the hydroxyls reform into water — sets the stage for other chemical reactions.
To find out, the chemists had to develop technologies to measure how often the hydroxyls arose on the surface. Using resources developed within EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility at PNNL, they shot a beam of water molecules at a titanium oxide surface at low energy — the beam shooting slowly, and at high energy — moving fast like out of a firehose.
They ended up with bright spots on the surface, and the higher the energy, the more spots. But the spots did not look bright enough to include both hydroxyls, as expected, so they performed additional experiments to determine what the spots were.
The team shot water at the titanium dioxide surface and then froze the water in place. Then they slowly warmed everything up. Raising the temperature revealed the spots — which they thought were at least one hydroxyl — changing into water molecules. This meant that each spot had to actually be a pair of hydroxyls because the evidence showed that all the raw materials needed to make a water molecule were sitting there, and both hydroxyls were needed.
They performed various other experiments to determine the temperature at which a landing water molecule converts into hydroxyl pairs and vice versa. From that they learned that water is only slightly more stable than the hydroxyl pairs on the surface — 10 percent more, if we go by the amount of energy it takes to disrupt them.
Simulating the water landings on a high performance computer, also at EMSL, the researchers found out the only water molecules that stuck to the catalyst were ones that landed in a figurative ditch within a cornfield, where the water's oxygen faced a titanium atom down in the ditch.
If the water came in with just the right speed, the water reoriented and docked one of its hydrogens towards a nearby oxygen, forming the hydroxyl pairs seen in the experiments. If not, the water molecule just bounced off.
"We discovered that electrostatics — the same static that makes sparks when you rub your feet on the carpet — helped steer the water molecules onto the surface," said theoretical chemist and coauthor Roger Rousseau.
All of these details will help researchers understand catalysis better and improve our understanding of chemical reactions. In addition, the results reveal a value that scientists have long tried to nail down — how easy or hard it is for water to lose a hydrogen on titanium oxide.
This work was supported by the American Recovery and Reinvestment Act and the Department of Energy Office of Science.
Reference: Zhi-Tao Wang, Yang-Gang Wang, Rentao Mu, Yeohoon Yoon, Arjun Dahal, Gregory K. Schenter, Vassiliki-Alexandra Glezakou, Roger Rousseau, Igor Lyubinetsky, and Zdenek Dohnálek. Probing Equilibrium of Molecular and Deprotonated Water on TiO2(110), Proc Natl Acad Sci U S A Early Edition February 6, 2017, DOI: 10.1073/pnas.1613756114.
Tweaking a Molecule's Structure Can Send it Down a Different Path to Crystallization
Insights could lead to better control of drug development, energy technologies. And food.
Silky chocolate, a better medical drug, or solar panels all require the same thing: just the right crystals making up the material. Now, scientists trying to understand the paths crystals take as they form have been able to influence that path by modifying the starting ingredient.
The insights gained from the results, reported April 17 in Nature Materials, could eventually help scientists better control the design of a variety of products for energy or medical technologies.
"The findings address an ongoing debate about crystallization pathways," said materials scientist Jim De Yoreo at the Department of Energy's Pacific Northwest National Laboratory and the University of Washington. "They imply you can control the various stages of materials assembly by carefully choosing the structure of your starting molecules."
From floppy to stiff
One of the simplest crystals, diamonds are composed of one atom — carbon. But in the living world, crystals, like the ones formed by cocoa butter in chocolate or ill-formed ones that cause sickle cell anemia, are made from molecules that are long and floppy and contain a lengthy well-defined sequence of many atoms. They can crystallize in a variety of ways, but only one way is the best. In pharmaceuticals, the difference can mean a drug that works versus one that doesn't.
Chemists don't yet have enough control over crystallization to ensure the best form, partly because chemists aren't sure how the earliest steps in crystallization happen. A particular debate has focused on whether complex molecules can assemble directly, with one molecule attaching to another, like adding one playing card at a time to a deck. They call this a one-step process, the mathematical rules for which scientists have long understood.
The other side of the debate argues that crystals require two steps to form. Experiments suggest that the beginning molecules first form a disordered clump and then, from within that group, start rearranging into a crystal, as if the cards have to be mixed into a pile first before they could form a deck. De Yoreo and his colleagues wanted to determine if crystallization always required the disordered step, and if not, why not.
Clump, snap and ...
To do so, the scientists formed crystals from a somewhat simplified version of the sequence-defined molecules found in nature, a version they call a peptoid. The peptoid was not complicated — just a string of two repeating chemical subunits (think "ABABAB") — yet complex because it was a dozen subunits long. Based on its symmetrical chemical nature, the team expected multiple molecules to come together into a larger structure, as if they were Lego blocks snapping together.
In a second series of experiments, they wanted to test how a slightly more complicated molecule assembled. So, the team added a molecule onto the initial ABABAB... sequence that stuck out like a tail. The tails attracted each other, and the team expected their association would cause the new molecules to clump. But they weren't sure what would happen afterwards.
The researchers put the peptoid molecules into solutions to let them crystallize. Then the team used a variety of analytical techniques to see what shapes the peptoids made and how fast. It turns out the two peptoids formed crystals in very different fashions.
A tail of two steps
As the scientists mostly expected, the simpler peptoid formed initial crystals a few nanometers in size that grew longer and taller as more of the peptoid molecules snapped into place. The simple peptoid followed all the rules of a one-step crystallization process.
But thrusting the tail into the mix disrupted the calm, causing a complex set of events to take place before the crystals appeared. Overall, the team showed that this more complicated peptoid first clumped together into small clusters unseen with the simpler molecules.
Some of these clusters settled onto the available surface, where they sat unchanging before suddenly converting into crystals and eventually growing into the same crystals seen with the simple peptoid. This behavior was something new and required a different mathematical model to describe it, according to the researchers. Understanding the new rules will allow researchers to determine the best way to crystallize molecules.
"We were not expecting that such a minor change would make the peptoids behave this way," said De Yoreo. "The results are making us think about the system in a new way, which we believe will lead to more predictive control over the design and assembly of biomimetic materials."
This work was supported by the Department of Energy Office of Science and PNNL's Laboratory Directed Research and Development program.
Reference: Xiang Ma, Shuai Zhang, Fang Jiao, Christina Newcomb, Yuliang Zhang, Arushi Prakash, Zhihao Liao, Marcel Baer, Christopher Mundy, Jim Pfaendtner, Aleksandr Noy, Chun-Long Chen and Jim De Yoreo, Tuning crystallization pathways through sequence-engineering of biomimetic polymers. Nature Materials, April 17, 2017, DOI: 10.1038/nmat4891.
Video Captures Bubble-blowing Battery in Action
Researchers propose how bubbles form, could lead to smaller, more stable lithium-air batteries
With about three times the energy capacity by weight of today's lithium-ion batteries, lithium-air batteries could one day enable electric cars to drive farther on a single charge.
But the technology has several holdups, including losing energy as it stores and releases its charge. If researchers could better understand the basic reactions that occur as the battery charges and discharges electricity, the battery's performance could be improved. One reaction that hasn't been fully explained is how oxygen blows bubbles inside a lithium-air battery when it discharges. The bubbles expand the battery and create wear and tear that can cause it to fail.
A paper in Nature Nanotechnology provides the first step-by-step explanation of how lithium-air batteries form bubbles. The research was aided by a first-of-a-kind video that shows bubbles inflating and later deflating inside a nanobattery. Researchers had previously only seen the bubbles, but not how they were created.
"If we fully understand the bubble formation process, we could build better lithium-air batteries that create fewer bubbles," noted the paper's corresponding author, Chongmin Wang, of the Department of Energy's Pacific Northwest National Laboratory. "The result could be more compact and stable batteries that hold onto their charge longer."
PNNL researchers used an environmental transmission electron microscope to record a first-of-a-kind video that shows bubbles inflating and later deflating inside a tiny lithium-air battery. The video helped researchers develop the first step-by-step explanation of how lithium-air batteries form bubbles. The knowledge could help make lithium-air batteries that are more compact, stable and can hold onto a charge longer.
Wang works out of EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science user facility located at PNNL. His co-authors include other PNNL staff and a researcher from Tianjin Polytechnic University in China.
The team's unique video may be a silent black-and-white film, but it provides plenty of action. Popping out from the battery's flat surface is a grey bubble that grows bigger and bigger. Later, the bubble deflates, the top turning inside of itself until only a scrunched-up shell is left behind.
The popcorn-worthy flick was captured with an in-situ environmental transmission electron microscope at EMSL. Wang and his colleagues built their tiny battery inside the microscope's column. This enabled them to watch as the battery charged and discharged inside.
Video evidence led the team to propose that as the battery discharges, a sphere of lithium superoxide jets out from the battery's positive electrode and becomes coated with lithium oxide. The sphere's superoxide interior then goes through a chemical reaction that forms lithium peroxide and oxygen. Oxygen gas is released and inflates the bubble. When the battery charges, lithium peroxide decomposes, and leaves the former bubble to look like a deflated balloon.
This finding was the focus of a Nature News & Views column written by researchers at Korea's Hanyang University, who describe the research as "a solid foundation for future Li-O2 battery designs and optimization."
This research was supported by DOE's Office of Energy Efficiency and Renewable Energy.
Reference: Langli Luo, Bin Liu, Shidong Song, Wu Xu, Ji-Guang Zhang, Chongmin Wang, Revealing the reaction mechanisms of Li-O2 batteries using environmental transmission electron microscopy, Nature Nanotechnology, March 27, 2017, DOI: 10.1038/nnano.2017.27.
Read more in this News & Views article: Yang-Kook Sun and Chong S. Yoon, Lithium-oxygen batteries: The reaction mechanism revealed, Nature Nanotechnology, March 27, 2017, DOI: 10.1038/nnano.2017.40.
For First Time, Researchers Measure Forces that Align Crystals and Help them Snap Together
Understanding crystal growth is important for designing new materials
Like two magnets being pulled toward each other, tiny crystals twist, align and slam into each other, but due to an altogether different force. For the first time, researchers have measured the force that draws them together and visualized how they swivel and align.
Called van der Waals forces, the attraction provides insights into how crystals self-assemble, an activity that occurs in a wide range of cases in nature, from rocks to shells to bones.
"It's provocative in the sense that from these kinds of measurements one can build a model of 3-D assembly, with particles attaching to each other in select ways like Lego bricks," said chemist Kevin Rosso of the Department of Energy's Pacific Northwest National Laboratory. "Crystals are most everywhere in nature, and this work will help us take advantage of these forces when we design new materials."
Crystals form supporting structures in a variety of natural and synthetic materials. Larger crystals can build up from smaller ones. Although generally shaped like cubes, crystals have several different sides, some of which match well with each other and others that don't. When matching sides are oriented properly, crystals can fuse seamlessly, growing larger and larger.
But what makes crystals get close enough to fuse in the first place, and can they self-align? Many types of forces have been hinted at through the years, but the tools to narrow down the correct ones have not existed.
Now, Rosso and teams at PNNL, EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility at PNNL, and the University of Pittsburgh developed a new approach by combining an environmental transmission electron microscope, called an ETEM, with nanocrystal force probes that allows scientists to watch crystals interact in a life-like situation. PNNL post-doctoral chemist Xin Zhang and EMSL user Yang He, a Ph.D. student from the University of Pittsburgh, used resources within EMSL to examine how titanium oxide crystals couple.
To understand their experiment, imagine holding two magnets and moving them toward each other. When they're so close that the attractive force overcomes the effort you're using to hold them apart, they will jump together. The PNNL team did this, but on a much smaller scale and with a force that isn't magnetism.
One small jump
The team needed to use very tiny crystals that wouldn't overwhelm the weak forces they expected to see. They attached titanium oxide crystals a hundred to a thousand times thinner than a human hair (depending on the hair) to either side of an instrument that measures force. The team then moved the crystals toward each other, twisted at several different angles between them, until the two snapped together.
The team also pulled the crystals apart and measured how much force that took as well. These measurements allowed the researchers to characterize the force in detail. There are several different kinds of forces that work for objects of this size, and with additional analyses the team concluded forces called van der Waals were the ones at work causing self-alignment.
Researchers slowly pull apart tiny bits of a titanium oxide mineral called rutile, about a thousand times skinnier than a human hair. The red dots near the top show the starting point. As the bottom half is pulled down, the top half stays attached by van der Waals forces — until, that is, the pull becomes too great.
And a twist
In addition, they wanted to put a face to a name, in a manner of speaking, of a theoretical prediction of van der Waals forces made in the 1970s. The theory allowed scientists to calculate the torque between crystals that are being twisted relative to each other (imagine twisting a baguette to pull a piece of bread off) based on the angle between them.
So the team also measured the force between two crystals held at a constant distance apart but twisted in opposite directions from each other. Co-author computational physicist Maria Sushko compared the data to predictions the theory made and showed that the theory held up.
"This is the first measure and proof that the force depends on how the crystals are rotated relative to each other, what we call rotationally dependent," said Rosso. "If they are rotationally dependent, this implies that this force will contribute to aligning free crystals that bump together in a liquid environment, for example, increasing the rate of successful sticking."
In addition, proving the connection means it will be easier to determine such attractive forces for crystals made of different materials, such as calcium carbonate found in seashells. Scientists will be able to determine these forces by plugging in numbers to an equation rather than re-doing all of the experiments.
This work was supported by the Department of Energy Office of Science and PNNL Laboratory Directed Research and Development program. The experimental work was done at EMSL, one of a handful of DOE Office of Science User Facilities equipped with the technology and scientific expertise to conduct this research.
Reference: Xin Zhang, Yang He, Maria L. Sushko, Jia Liu, Langli Luo, James J. De Yoreo, Scott X. Mao, Chongmin Wang, Kevin M. Rosso. Direction-specific van der Waals attraction between rutile TiO2 nanocrystals, Science April 28, 2017, DOI: 10.1126/science.aah6902.
DOE's Environmental Management Leader Visits PNNL Glass Lab
Glass scientists at Pacific Northwest National Laboratory hosted the Department of Energy's Acting Assistant Secretary for Environmental Management, Sue Cange earlier this month. DOE's Office of Environmental Management's mission is to complete the safe cleanup of the environmental legacy brought about from five decades of nuclear weapons development and government-sponsored nuclear energy research.
Cange was visiting the Hanford nuclear site along with her chief of staff Betsy Connell and associate principle deputy assistant secretary for field operations Stacy Charboneau. They took time out to tour the laboratory where PNNL researchers study the science underpinning vitrification — the process of turning nuclear waste into glass. PNNL scientists support DOE's Waste Treatment and Immobilization Plant, under construction now, where the waste will be mixed with glass-forming materials and melted into a durable glass form for safe, long-term storage.
Cange learned how the challenges of Hanford's chemically diverse waste are met using scientific glass formulation methods to increase waste loading in the glass and minimize the volume of glass and hence reduce the cost of the clean-up effort. Cange also saw the Laboratory Scale Melter system which is being used to understand the dynamic process of converting the liquid waste into solid glass.
PNNL is world-renowned for its expertise in glass formulation and processing — knowledge that is instrumental to the work done in partnership with the DOE Office of River Protection to develop the vitrification process.
The PNNL Director's Column has more information on how the laboratory supports Hanford cleanup efforts.
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