Leung K.,Sandia National Laboratories
Chemistry of Materials | Year: 2017
Density functional theory and ab initio molecular dynamics simulations are applied to investigate the migration of Mn(II) ions to above-surface sites on spinel LixMn2O4 (001) surfaces, the subsequent Mn dissolution into the organic liquid electrolyte, and the detrimental effects on graphite anode solid electrolyte interphase (SEI) passivating films after Mn(II) ions diffuse through the separator. The dissolution mechanism proves complex; the much-quoted Hunter disproportionation of Mn(III) to form Mn(II) is far from sufficient. Key steps that facilitate Mn(II) loss include concerted liquid/solid-state motions; proton-induced weakening of Mn-O bonds forming mobile OH- surface groups; and chemical reactions of adsorbed decomposed organic fragments. Mn(II) lodged between the inorganic Li2CO3 and organic lithium ethylene dicarbonate (LEDC) anode SEI components facilitate electrochemical reduction and decomposition of LEDC. These findings help inform future design of protective coatings, electrolytes, additives, and interfaces. © 2016 American Chemical Society.
News Article | May 17, 2017
Decades of Sandia National Laboratories expertise on how salt domes behave went into a recent report that concluded that the U.S. Department of Energy is justified in extending the life of the Strategic Petroleum Reserve. The report, "Long-Term Strategic Review of the U.S. Strategic Petroleum Reserve," analyzed the reserve's capability to be tapped, or drawn down, and how that figures into future storage decisions. Sandia estimated the number of potential drawdowns per cavern, using computer models that consider such factors as cavern shape, relationship to surrounding caverns and salt movement, or creep, and how such parameters ultimately affect a cavern's stability. Calculating the number of drawdowns left was particularly important, said geologist Anna Lord, Sandia's project manager for the reserve. The number of times each cavern can still be tapped into affects overall design storage capacity decisions, including whether new caverns would be needed, she said. The Strategic Petroleum Reserve was established after the 1973 oil embargo to protect the United States from severe oil supply interruptions and to meet its obligations under the International Energy Program. DOE brought in Sandia five years later. The labs became geotechnical adviser in 1980, responsible for characterizing the site, including cavern and well development, geomechanical analysis, the integrity of caverns and wells, subsidence and monitoring. The reserve operates four major storage facilities in the underground salt domes of the Gulf Coast, two in Louisiana and two in Texas. The stockpile of government-owned crude oil can be tapped at the president's order when an emergency disrupts commercial oil supplies. "When the president calls up and says, 'We need to release X amount of oil,' they need to be ready to do that at a certain rate and a certain amount a day," Lord said. "All the work we do goes toward making sure they're able to do that." Sandia's work falls into two areas: geotechnical, which involves updating geologic understanding of the salt domes, modeling the caverns' geomechanical behavior and assuring the integrity of caverns and wells drilled into them; and engineering, which includes understanding fluid behavior, analyzing the leaching process that occurs during oil removal and assuring the reserve meets environmental, safety and oil quality requirements. Studying well integrity is one of Sandia's most important responsibilities, Lord said. Think of wells as a series of casings inside each other like concentric circles, with each smaller well deeper than the larger one above. The column of casing, called a string, acts as a protective barrier -- if one concentric circle goes, others remain. Well failure could cause oil to leak into the environment. In addition, a well that loses integrity can't be used to pull oil out. Sandia's team analyzes well integrity through hydrostatic column computer modeling. Reserve operators send nitrogen gas down the wells to test whether they're losing pressure, and the Sandia models provide rates and locations of any nitrogen leaks. A nitrogen leak does not necessarily mean the well will leak oil, so the model differentiates between pressure changes caused by nitrogen flow versus oil flow. Pressure tests can indicate "when do we worry, when do we need to do remediation?" Lord said. "No one's ever looked at this before, so we started a program to really try to understand what's going on behind the well. We've come up with a model that can tell us what the leak rates are and where those leaks may be," she said. "We're getting into the new area of what's going on behind the scenes. "There are well integrity issues everywhere, not just at the reserve. This happens anywhere with aging infrastructure. Geology takes over; engineering doesn't matter." Oil is removed by injecting fresh water into the brine stored at the bottom of the caverns, pushing out oil floating above the brine. But fresh water dissolves salt, changing the caverns' shape. "So we do studies to see where the water will change it, how much it will change it, does that new shape affect stability?" Lord said. Each cavern was meant to be emptied five times. But emptying a cavern makes it larger because the fresh water dissolves some of the salt. Sandia's geomechanical modeling shows, for example, "oh, you really only have three drawdowns in this cavern, you have a full five in this one, but you have none in this one, and if you take all the oil out of this one you cannot use that cavern again," Lord said. When the reserve started, the government wanted to store oil as quickly as possible, and bought caverns the petrochemical industry had used. The reserve still uses some of those, but most oil today is stored in caverns the Energy Department created with Sandia's feedback. "Different domes behave differently," Lord explained. "Maybe they have higher creep rates than other domes. It depends on how homogeneous it is. Is it pure salt or is it salt with shale or other impurities mixed in, such as anhydrite?" The reserve's managers can't create a cavern simply by pumping in fresh water -- the configuration of injection wells helps create the desired shape. Sandia researchers determine salt properties in an area by analyzing impurities and doing stress and strain testing, and model different leaching well configurations. From the model, they can determine how the leaching will affect the cavern's shape. They know from past studies what a cavern should look like for continued integrity. Sandia also makes recommendations for cavern operations based on their size and shape. Salt creeping to close voids causes stresses and strains on caverns and wells. Sandia's geomechanical modeling predicts where those might occur and whether they'll create a problem. The team stepped up well and cavern integrity modeling in the past couple of years, collecting and analyzing existing data to see what's going on and how one cavern's operation affects a neighboring cavern. "We're trying to bring all the pictures together into one holistic story," Lord said.
News Article | May 19, 2017
Harnessing the power of Iceland’s volcanoes to provide energy to British homes is one of those ideas that resurfaces every few years, but sounds too good – or whacky – to be true. However, interest from a clutch of international companies in a geothermal project in northern Iceland suggests the idea is not just achievable but commercially viable too. Scientists working on the Krafla Magma Testbed plan to drill more than 2km below the Earth’s crust into a molten magma lake, starting a process they say could see the UK receiving energy from Iceland’s volcanoes within 20 years. In an experiment due to begin in 2020, the researchers will drill an initial borehole down to the magma body, into which water can be pumped through reinforced U-shaped pipes. The resulting “supercritical steam” could, in theory, be used to power turbines and the energy generated sent across the North Atlantic via underwater cables. While geothermal power already generates a quarter of Iceland’s electricity production, on a global scale the sector has failed to flourish in the same way as solar or wind. Held back by high upfront development costs, it currently produces less than 1% of the world’s electricity, according to the World Energy Council. However, new technology of the type being piloted in Krafla could accelerate the sector’s growth, according to Freysteinn Sigmundsson, a geophysicist at the University of Iceland and an investigator on the project. Professor Yan Lavallée, a volcanology and magma research chair at Liverpool University, says the renewable potential is enormous. “Even a small body of magma in the order of a fraction of a cubic kilometre could power a whole country the size of the UK,” he says, adding that the possibility of storing the energy generated in large batteries or old mines is also under discussion. The promise of bountiful, clean volcano power appears to be attracting the attention of a host of large corporations, including those from the fossil fuel and mining sectors. “We have had discussions with a number of international oil and gas companies,” says John Ludden, the director of the British Geological Survey (BGS), which is coordinating the Krafla project with Iceland’s Geothermal Research Group. The Norwegian oil and gas giant Statoil confirmed an “informal dialogue” with the Krafla project, while Canada’s Falco Resources, a mining company, has part-funded a research post that is exploring collaborative work with the Krafla team. The researchers are also working with US-based Sandia National Laboratories, a nuclear contractor to the US government, to assess how to deal with magma at temperatures of 900C, says Ludden. “It’s not impossible to imagine that Iceland could send 2GW of energy at a time to the UK, Holland or Denmark via underwater cables,” he says – enough to power around 1.5m homes. “Perhaps that could happen in the next two decades.” Those underwater cables would, of course, come at a cost: one assessment (pdf) puts the price of a 1,000km-long interconnector across the North Atlantic at up to €3.5bn (£2.7bn), almost twice the cost of the London Array, one of the largest offshore wind farms in the world. Hordur Arnarson, CEO of Icelandic utility Landsvirkjun, which will develop the Krafla site, has warned that his company would need fixed price guarantees and long-term contracts, along the lines of the support given to the Hinkley Point C nuclear reactor. He has also previously raised concerns that Brexit could complicate the process. However, a UK-Iceland joint task force concluded (pdf) last July – after the referendum – that there was a viable business case for such a connector, and the European commission has put the cable on its list of “projects of common interest”. In any case, the cable would need five more years of assessments and preparatory work before construction could begin, according to Landsvirkjun, providing plenty of time for any opposition to organise. In Iceland, people living near the Krafla site have been told a risk assessment involving them will take place, says Bjarni Pálsson, a project manager for Landsvirkjun. Researchers have said, so far, that they see no risk their drilling will trigger an eruption, and that they will insert magma flow sensors specifically geared to detect future eruptions. Exporting the energy, rather than using it to boost domestic industry, is also likely to raise eyebrows. Pálsson describes exports as “just an option that the government is looking into”. “It is definitely a political issue and it will have to go through a lot of dialogue before being realised,” he says. Sign up to be a Guardian Sustainable Business member and get more stories like this direct to your inbox every week. You can also follow us on Twitter.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: STTR | Phase: Phase II | Award Amount: 996.70K | Year: 2015
Leveraging the results of our Phase I work, the Torch Team proposes to execute laboratory-based experiments to elucidate fundamental micro-debris formation mechanisms to improve optical modeling of impacts. Optical signatures from impacts collected over the last decade have identified definitive micro-debris parameter trends. However, current theories have difficulty reproducing these optical observations. Our Phase II work plan includes the development of innovative particle sizing instrumentation. Moreover, a novel experiment will be conducted to validate radiometric inversion methodologies for determining micro-debris properties in ground and flight tests, thereby leveraging existing optical data collected on impacts. Our proposed experimental approach will address critical micro-debris characterization data gaps in a timely and cost effective manner to improve hypervelocity impact electro-optic/infrared (EO/IR) modeling. Approved for Public Release, 15-MDA-8303 (1 July 15)
Agency: National Science Foundation | Branch: | Program: STTR | Phase: Phase I | Award Amount: 225.00K | Year: 2016
This Small Business Technology Transfer Phase I project will advance the development of new portable gas analysis systems. Portable analysis systems can provide timely information about the surroundings, leading to better decisions in critical situations. For law enforcement, a portable detector based on the proposed technology will enable officers to focus an investigation on specific targets, whether narcotics or explosives. Likewise, for military and civil defense operations, trace explosives can be detected even when the bulk of the material is well concealed. A portable system with the proposed detector will easily be able to identify and quantify chemical warfare agents and pesticides at single part-per-billion levels in complex backgrounds. With precise agent detection at these low levels, the users of these systems will have better information and more time to act on that information. In agriculture, a better detector will lead to a more judicious use of pesticides and thereby increase their effectiveness while reducing human exposure. Considering all of the potential applications, the proposed work could lead to significant advancements in a $600 million segment of the $2 billion annual gas detection market. The intellectual merit of this project is based on the years of work that Sandia National Laboratories and Defiant Technologies have invested in the development of micro components and systems for chemical detection. The proposal objective is to develop a new ionization source that can replace radioactive materials, and other larger and more power hungry thermionic sources. The new thermionic ionization source will use micro-electro-mechanical systems (MEMS) fabrication techniques to form a millimeter-scale heating element that operates efficiently at 600 degrees C. New techniques to formulate and deposit low function work materials on these heaters will be developed and exploited to construct the ionization sources. The research will entail an exploration of alkali metal formulations for the low-work function material, heater fabrication for longevity, and source operating conditions for possible failure mechanisms. At the end of this Phase I effort, the goal is to develop an ionization source that can be coupled with portable gas chromatograph and portable ion mobility systems for the detection and analysis of explosives, chemical warfare agents, pesticides, and narcotics.
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase II | Award Amount: 911.40K | Year: 2016
During Phase I and Phase II, M4 Engineering, Inc. and Sandia National Laboratories have created a unique bonded joint analysis methodology and associated software. During Phase II.5, the developed techniques will be further enhanced and a fully functional commercial analysis code (SIMULIA/Abaqus) plug-in will be created. The software plug-in will make the advanced technology accessible to all levels of practicing engineers via integrated pre- and post-processing modules. The technology is based upon a world class nonlinear constitutive equation for polymers developed over a decade at Sandia. A two-pronged approach consisting of concise surrogate models (i.e., traction-separation interface models) for design and analysis and high fidelity models that can be used along with experimental data for surrogate model parameterization will provide the Navy a comprehensive bond modeling method. During Phase I and Phase II, ductile and brittle adhesives for metal bonding have been studied. The upcoming Phase II.5 work will include looking at an additional adhesive, as well as composite substrates. Hence, a key part of this work will also include an experimental program to populate the high fidelity models and validate the surrogate traction-separation models.
Stavila V.,Sandia National Laboratories |
Talin A.A.,Sandia National Laboratories |
Allendorf M.D.,Sandia National Laboratories
Chemical Society Reviews | Year: 2014
Metal-organic frameworks (MOFs) are a class of hybrid materials with unique optical and electronic properties arising from rational self-assembly of the organic linkers and metal ions/clusters, yielding myriads of possible structural motifs. The combination of order and chemical tunability, coupled with good environmental stability of MOFs, are prompting many research groups to explore the possibility of incorporating these materials as active components in devices such as solar cells, photodetectors, radiation detectors, and chemical sensors. Although this field is only in its incipiency, many new fundamental insights relevant to integrating MOFs with such devices have already been gained. In this review, we focus our attention on the basic requirements and structural elements needed to fabricate MOF-based devices and summarize the current state of MOF research in the area of electronic, opto-electronic and sensor devices. We summarize various approaches to designing active MOFs, creation of hybrid material systems combining MOFs with other materials, and assembly and integration of MOFs with device hardware. Critical directions of future research are identified, with emphasis on achieving the desired MOF functionality in a device and establishing the structure-property relationships to identify and rationalize the factors that impact device performance. This journal is © the Partner Organisations 2014.
Sheps L.,Sandia National Laboratories
Journal of Physical Chemistry Letters | Year: 2013
We present the time-resolved UV absorption spectrum of the B̃ ( 1A′) ← X̃ (1A′) electronic transition of formaldehyde oxide, CH2OO, produced by the reaction of CH2I radicals with O2. In contrast to its UV photodissociation action spectrum, the absorption spectrum of formaldehyde oxide extends to longer wavelengths and exhibits resolved vibrational structure on its low-energy side. Chemical kinetics measurements of its reactivity establish the identity of the absorbing species as CH2OO. Separate measurements of the initial CH2I radical concentration allow a determination of the absolute absorption cross section of CH2OO, with the value at the peak of the absorption band, 355 nm, of σabs = (3.6 ± 0.9) × 10-17 cm2. The difference between the absorption and action spectra likely arises from excitation to long-lived B̃ (1A′) vibrational states that relax to lower electronic states by fluorescence or nonradiative processes, rather than by photodissociation. © 2013 American Chemical Society.
Leonard F.,Sandia National Laboratories |
Talin A.A.,U.S. National Institute of Standards and Technology
Nature Nanotechnology | Year: 2011
Existing models of electrical contacts are often inapplicable at the nanoscale because there are significant differences between nanostructures and bulk materials arising from unique geometries and electrostatics. In this Review, we discuss the physics and materials science of electrical contacts to carbon nanotubes, semiconductor nanowires and graphene, and outline the main research and development challenges in the field. We also include a case study of gold contacts to germanium nanowires to illustrate these concepts. © 2011 Macmillan Publishers Limited. All rights reserved.
Leung K.,Sandia National Laboratories
Journal of Physical Chemistry C | Year: 2013
We review recent ab initio molecular dynamics studies of electrode/electrolyte interfaces in lithium ion batteries. Our goals are to introduce experimentalists to simulation techniques applicable to models which are arguably most faithful to experimental conditions so far, and to emphasize to theorists that the inherently interdisciplinary nature of this subject requires bridging the gap between solid and liquid state perspectives. We consider liquid ethylene carbonate (EC) decomposition on lithium intercalated graphite, lithium metal, oxide-coated graphite, and spinel manganese oxide surfaces. These calculations are put in the context of more widely studied water-solid interfaces. Our main themes include kinetically controlled two-electron-induced reactions, the breaking of a previously much neglected chemical bond in EC, and electron tunneling. Future work on modeling batteries at atomic length scales requires capabilities beyond state-of-the-art, which emphasizes that applied battery research can and should drive fundamental science development. © 2012 American Chemical Society.