The central feature of the Combustion Chemistry project in PLS is our development, validation, and application of detailed chemical kinetic reaction mechanisms for the combustion of hydrocarbon and other types of chemical fuels.
Defending Earth against incoming asteroids—uncommon but potentially catastrophic threats—is no easy task. Without convenient, cost-effective ways to experiment directly on asteroids in the solar system, scientists run simulations and conduct high-energy-density experiments on asteroid fragments with lasers.
September 13, 2016
A team of Lawrence Livermore National Laboratory (LLNL) physicists has performed a series of calculations shedding light on an unexpected way that iron transforms under dynamic compression.
In a paper published in Physical Review Letters, the team describes first-principle calculations on two solid phases of iron, as well as on intermediate crystal structures along the transformation path from one phase to the other. The calculations involve a carefully parameterized model for magnetic fluctuations (i.e., electron spin waves), including the effect of moving the iron nuclei as the material is squeezed in a shock experiment.
Lawrence Livermore scientists have played multiple roles in this particular problem, spanning more than a decade. A Laboratory Directed Research and Development (LDRD) Strategic Initiative project, led by Hector Lorenzana, performed pioneering shock experiments, including some on single crystal iron.
"In these original shock experiments, a single crystal of iron transforms under compression and then springs back (for the most part) to the original, intact lattice," said LLNL material scientist Michael Surh, lead author of the most recent research. "This unique, reversible behavior has defied understanding for years."
August 23, 2016
A team of Lawrence Livermore National Laboratory researchers has demonstrated the 3D printing of shape-shifting structures that can fold or unfold to reshape themselves when exposed to heat or electricity. The micro-architected structures were fabricated from a conductive, environmentally responsive polymer ink developed at the Lab.In an article published recently by the journal Scientific Reports, Lab scientists and engineers revealed a strategy for creating boxes, spirals and spheres from shape memory polymers (SMPs), bio-based "smart" materials that exhibit shape-changes when resistively heated or when exposed to the appropriate temperature.
While the approach of using responsive materials in 3D printing, often known as "4D printing," is not new, LLNL researchers are the first to combine the process of 3D printing and subsequent folding (via origami methods) with conductive smart materials to build complex structures.
In the paper, the researchers describe creating primary shapes from an ink made from soybean oil, additional co-polymers and carbon nanofibers, and "programming" them into a temporary shape at an engineered temperature, determined by chemical composition. Then the shape-morphing effect was induced by ambient heat or by heating the material with an electrical current, which reverts the part's temporary shape back to its original shape.
August 16, 2016
A new Transmission Electron Microscope (TEM) installed at the Lab earlier this year is giving LLNL researchers a clearer look at the atomic level of structures than they've had before.
The Titan 80-300 TEM, manufactured by FEI Company, was installed in December and brings an expanded capability to the existing transmission electron microscope the Lab has had for about 20 years, according to LLNL staff scientist Joe McKeown. Among the improvements include a high-angle annular dark field (HAADF) detector for scanning transmission electron microscopy (STEM), which allows for Z-contrast imaging due to enhanced scattering from high atomic number elements, and a low-voltage mode for analyzing polymers and biological samples that may be more sensitive to high-energy electrons.
"With the dark field detector, heavier elements appear brighter in contrast, so we can more easily and quickly perform both structural and compositional analysis of microstructures," McKeown said.
Postdoctoral researcher Tian (Tony) Li, one of the new TEM's primary users, said the Titan provides many new microscopy capabilities on site that he previously had to travel to Lawrence Berkeley Lab to perform. With its high-resolution imaging, Li said, researchers can see individual atomic columns, a useful tool for looking at lattice structures and doing composition analysis.
August 15, 2016
The 2016 R&D 100 awards, sponsored by the trade journal R&D Magazine, are given annually for the top 100 industrial inventions worldwide and are sometimes called the "Oscars of invention."
Three technologies developed with the expertise of PLS researchers have been tapped as finalists for the awards:
The GLO Transparent Ceramic Scintillator: This instrument dramatically increases high-energy, or mega-electron-volt, radiography throughput by providing seven times faster imaging than glass scintillators and decreases the X-ray dose required to obtain detailed imagery. Mega-electron-volt radiography is used to nondestructively image the 3D volume of complex objects.
The Polyelectrolyte Enabled Liftoff (PEEL): This technology is a robust, scalable method of fabricating freestanding polymer films that are larger, stronger and thinner than what conventional methods can produce. PEEL is used at the National Ignition Facility for the daily fabrication of membranes as thin as 30 nanometers that serve as compliant, load-bearing elements for laser targets.
Solution-Grown Crystals for High-Energy Neutron Detection: This technology is a method for growing large-scale, economical stilbene crystals capable of efficiently distinguishing neutrons from gamma rays without the toxicity, flammability and handling difficulties that commercial liquid scintillators present. The technology has been licensed to Inrad Optics for commercial crystal production.
August 11, 2016
Lawrence Livermore National Laboratory scientists have combined X-ray diffraction and vibrational spectroscopy measurements together with first-principle calculations to examine the high-pressure structural behavior of magnesium chloride.
Magnesium chloride (MgCl2) is well known to be an effective de-icing agent, for example, in the aviation industry. Magnesium compounds, including MgCl2, also could function at extreme conditions as effective biocidal agents and work to neutralize biological weapons. The high pressure properties of these materials are important for understanding and predicting their behavior in complex, chemically reactive environments such as detonations that are of interest to the Defense Threat Reduction Agency (DTRA).
The team observed an extensive stability of MgCl2 under pressure that contradicts the well-established structural systematics. The research is published in the Aug. 12 edition of Scientific Reports.
The immediate technical aim of the study was to provide equations of state (EOS) and structural phase diagrams to improve the confidence of semi-empirical thermochemical calculations predicting the products and performance of detonated chemical formulations.
July 18, 2016
LLNL researchers are exploring the use of metal 3D printing to create strong, lightweight structures for advanced laser systems - an effort they say could alter the way lasers are designed in the future.
In a Laboratory Directed Research and Development (LDRD) program, physicist Ibo Matthews and his team are experimenting with a new research-based metal 3D printer, one of only four of its kind in the world, using a customized software platform capable of unprecedented design control.
The powder bed laser-melting printer, made by the Fraunhofer Institute for Laser Technology (ILT) and German startup Aconity 3D, was installed in December 2015. Lab engineers have added diagnostics and high-speed cameras to examine thermal emissions and to image the surface of parts as they're being built. Matthews said the modifications will help the researchers determine how defects or deformations occur during the 3D printing process.
"It's very flexible; it allows us to change any of the parameters we want," he said. "We're developing confidence in what we've built. If any defects occur, it is our aim that the user can have a 3D map available at the end of the build that shows what and where it happened."
May 25, 2016
Researchers at Lawrence Livermore National Laboratory (LLNL) have taken a major step toward answering a question plaguing a common metal 3-D printing technique: What interactions can lead to the porosity found in parts produced by laser powder-bed fusion processes?
In a paper published in the May 20 edition of the journal Acta Materialia online, LLNL researcher Ibo Matthews and his team discovered that gas flow, due to evaporation when the laser irradiates the metal powder, is the driving force that clears away powder near the laser's path during a build. This "denudation" phenomenon reduces the amount of powder available when the laser makes its next pass, causing tiny gaps and defects in the finished part.
"During this process you get to temperatures that are near or at the boiling point of the metal, so you have a strong vapor flux emitted from the melt pool," Matthews explained. "Prior to this study, there wasn't an understanding of what effect this flux of metal vapor had on the powder bed."
Using a custom-built microscope setup, a vacuum chamber and an ultra high-speed camera (provided by the Lab's High Explosives Applications Facility), Matthews' team observed the ejection of metal powder away from the laser during the melting process, and, through computer simulation and fluid dynamics principles, built models to help explain the particles' movement.
"(Matthews) has discovered a phenomenon that we didn't know was present in metal powder-bed additive manufacturing, and this is an effect that has important implications for part quality and build speed," said Chris Spadaccini, director of Additive Manufacturing Initiatives for the Lab. "It is also something we now know we will have to capture with our models, so new physics is being added to the simulation codes."
Wayne King, director of the Accelerated Certification of Additively Manufactured Metals project at LLNL, called the findings a "big step forward" for the process.
May 16, 2016
Around 13 times per century, Mercury passes between Earth and the sun in a rare astronomical event known as a planetary transit. The 2016 Mercury transit occurred on May 9 between roughly 4:12 a.m. and 11:42 p.m. PDT.
NASA's stunning video of the transit of Mercury across the sun was made possible in part by work done by Lawrence Livermore scientists. Regina Soufli, a member of the Physics Division, led her LLNL team, including Jeff Robinson, Eberhard Spiller, Sherry Baker and Jay Ayers, and collaborated with Eric Gullikson of Lawrence Berkeley National Laboratory's Center for X-Ray Optics, Reflective X-ray Optics, LLC and other institutions, on the design, development, fabrication and calibration of the multilayer mirrors used in the extreme ultraviolet (EUV) telescopes of NASA's Solar Dynamics Observatory (SDO) mission.
The SDO multilayer mirrors act as reflective lenses and are responsible for capturing the images and movies of the sun produced by SDO at seven extreme ultraviolet (EUV) wavelengths, including those shown in NASA's video of the Mercury transit.
April 27, 2016
Lawrence Livermore National Laboratory (LLNL) material scientists have found that 3D-printed foam works better than standard cellular materials in terms of durability and long-term mechanical performance.
Foams, also known as cellular solids, are an important class of materials with applications ranging from thermal insulation and shock-absorbing support cushions to lightweight structural and floatation components. Such material is an essential component in a large number of industries, including automotive, aerospace, electronics, marine, biomedical, packaging and defense. Traditionally, foams are created by processes that lead to a highly non-uniform structure with significant dispersion in size, shape, thickness, connectedness and topology of its constituent cells.
As an improved alternative, scientists at the additive manufacturing lab at LLNL recently demonstrated the feasibility of 3D printing of uniform foam structures through a process called direct-ink-write. However, since 3D printing requires the use of polymers of certain properties, it is important to understand the long-term mechanical stability of such printed materials before they can be commercialized. This is especially vital in applications such as support cushions, where the foam material is subjected to long-term mechanical stresses.
To address the stability question, the LLNL team performed accelerated aging experiments in which samples of both traditional stochastic foam and 3D-printed materials were subjected to a set of elevated temperatures under constant compressive strain. The stress condition, mechanical response and permanent structural deformation of each sample were monitored for a period of one year and, in some cases, even longer. A method called time-temperature-superposition was then used to quantitatively model the evolution of such properties over a period of decades under ambient conditions.
March 21, 2016
Material scientists at Lawrence Livermore National Laboratory have found certain metal oxides increase capacity and improve cycling performance in lithium-ion batteries.
The team synthesized and compared the electrochemical performance of three graphene metal oxide nanocomposites and found that two of them greatly improved reversible lithium storage capacity.
The research appears on the cover of the March 21 edition of the Journal of Materials Chemistry A.
Graphene-metal oxide (GMO) nanocomposites have become renowned for their potential in energy storage and conversion, including capacitors, lithium-ion batteries, sensors and catalysis (for fuel cells, water splitting and air cleaning).
For applications in lithium-ion batteries, nanosized metal oxide (MO) particles and highly conductive graphene are considered beneficial for shortening lithium diffusion pathways and reducing polarization in the electrode, leading to enhanced performance.
In the experiments, the team dipped prefabricated graphene aerogel electrodes in metal ion solutions where all metal oxide nanoparticles appear to be anchored on the surface of graphene and are fully accessible to the electrolyte (i.e., open pore space).
February 9, 2016
For the first time ever, scientists at Lawrence Livermore National Laboratory and UC Santa Cruz have successfully 3D-printed supercapacitors using an ultra-lightweight graphene aerogel, opening the door to novel, unconstrained designs of highly efficient energy storage systems for smartphones, wearables, implantable devices, electric cars and wireless sensors.
Using a 3D-printing process called direct-ink writing and a graphene-oxide composite ink designed at the Lab, the LLNL team was able to print micro-architected electrodes and build supercapacitors able to retain energy on par with those made with electrodes 10 to 100 times thinner.
"We're pioneering the marriage of 3D-printing and porous materials," said material and biomedical scientist Fang Qian , a co-author on the paper. "Think of a supercapacitor as a portable energy device, so anything that needs electricity would benefit from such a supercapacitor. If we can replace the standard (technology) with our lightweight, compact and high-performance supercapacitor, that would be a radical change."
January 20, 2016
Lawrence Livermore National Laboratory researchers have created a library of nanoporous gold structures on a single chip that has direct applications for high-capacity lithium ion batteries as well as neural interfaces.
Nanoporous gold (np-Au), a porous metal used in energy and biomedical research, is produced through an alloy corrosion process known as dealloying that generates a characteristic three-dimensional nanoscale network of pores and ligaments.
In the cover article in the Jan. 14 issue of Nanoscale, a journal published by the Royal Society of Chemistry, LLNL researchers and their University of California, Davis collaborators describe a method for creating a library of varying np-Au morphologies on a single chip via precise delivery of tunable laser energy. UC Davis professor Erkin Seker served as the principal investigator (PI) of the UC Fees project that primarily funded the work, along with co-PI Monika Biener of LLNL's Materials Science Division.
Laser microprocessing (e.g. micromachining) provides spatial and temporal control while imposing energy near the surface of the material.
"Traditional heat application techniques for the modification of np-Au are bulk processes that cannot be used to generate a library of different pore sizes on a single chip," said LLNL staff scientist Ibo Matthews, co-author of the paper. "Laser microprocessing offers an attractive solution to this problem by providing a means to apply energy with high spatial and temporal resolution."
July 27, 2015
By tightly integrating experimental and theoretical techniques, a PLS team has provided fundamentally new insights into the specific factors that determine the absorption characteristics of copper complexes.
The results demonstrate that conventional interpretations based on "ligand field theory" – a staple concept in inorganic chemistry – are insufficient for capturing the full characteristics of the absorption profile. Instead, the team matched up computational simulation results with experimental spectroscopic data to identify how specific spectral characteristics are triggered by the dynamics of the surrounding chemical environment.
"The results are a first step toward being able to create optically tunable materials for filters and for energy-efficient 'smart window' technologies. They also could help us to better understand the role of metal-ligand complexes in photobiology," said Roger Qiu, the lead LLNL author of a paper appearing on a recent cover of the journal, Physical Chemistry Chemical Physics .
This new research also demonstrates the power of combining experimental and quantum chemistry simulation capabilities residing within the laboratory to tackle challenging and high impact scientific questions.
July 7, 2015
Early Earth was an inhospitable place where the planet was often bombarded by comets and other large astrophysical bodies.
Some of those comets contained complex prebiotic materials, such as amino acids and peptides (chains of amino acids), which are some of the most basic building blocks of life on Earth.
"The survivability of these compounds under impact conditions is mostly unknown," said Lawrence Livermore's Nir Goldman, who recently received a NASA grant to continue his astrobiology research. "Our research hopes to answer these questions and give an indication for what types of potentially life-building compounds would be produced under these conditions."
Basically, Goldman is trying to figure out if life on Earth really did come from out of this world.
Goldman's early research found that the impact of icy comets crashing into Earth billions of years ago could have produced a variety of small prebiotic or life-building compounds. His work using quantum simulations predicted that the simple molecules found in comets (such as water, ammonia, methanol and carbon dioxide) could have supplied the raw materials, and the impact with early Earth would have yielded an abundant supply of energy to drive the synthesis of compounds like protein forming amino acids. In later work, researchers from Imperial College in London and University of Kent conducted a series of experiments very similar to Goldman's simulations in which a projectile was fired using a light gas gun into a typical cometary ice mixture. The result: Several different types of amino acids formed.
"Impact events could have not only delivered prebiotic precursors to the primitive planet, but the sudden increase in pressure and temperature from the impact itself was likely a driving factor in synthesizing their assembly into these primary structures," Goldman said.
May 4, 2015
A team of researchers from Lawrence Livermore and UC Davis have found that covering an implantable neural electrode with nanoporous gold could eliminate the risk of scar tissue forming over the electrode's surface.
The team demonstrated that the nanostructure of nanoporous gold achieves close physical coupling of neurons by maintaining a high neuron-to-astrocyte surface coverage ratio. Close physical coupling between neurons and the electrode plays a crucial role in recording fidelity of neural electrical activity.
"Our results show that nanoporous gold topography, not surface chemistry, reduces astrocyte surface coverage," said Monika Biener, one of the LLNL authors of the paper. Nanoporous gold has attracted significant interest for its use in electrochemical sensors, catalytic platforms, fundamental structure−property studies at the nanoscale and tunable drug release. It also features high effective surface area, tunable pore size, well-defined conjugate chemistry, high electrical conductivity and compatibility with traditional fabrication techniques.
April 21, 2015
A new type of graphene aerogel will make for better energy storage, sensors, nanoelectronics, catalysis and separations.
Lawrence Livermore National Laboratory researchers have made graphene aerogel microlattices with an engineered architecture via a 3D printing technique known as direct ink writing. The research appears in the April 22 edition of the journal, Nature Communications.
The 3D printed graphene aerogels have high surface area, excellent electrical conductivity, are lightweight, have mechanical stiffness and exhibit supercompressibility (up to 90 percent compressive strain). In addition, the 3D printed graphene aerogel microlattices show an order of magnitude improvement over bulk graphene materials and much better mass transport.
Aerogel is a synthetic porous, ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas. It is often referred to as "liquid smoke."
March 4, 2015
A systematic study of the effects on National Ignition Facility (NIF) implosions of the ultra-thin mounting membranes that support target capsules inside NIF hohlraums was reported by LLNL researchers in a Physics of Plasmas paper, published online Feb. 4.
The performance of NIF's inertial confinement fusion targets depends on the symmetric implosion of highly compressed fuel. The target capsule is held at the center of the hohlraum by two plastic membranes called tents. On early NIF shots, the tent membrane was 300 nanometers (nm) thick; as technology improved, targets were built with 110-nm, 45-nm, 30-nm, and most recently as thin as 12-nm tents (as the tent becomes thinner it becomes less reliable as a support).
March 3, 2015
Lawrence Livermore researchers have identified electrical charge-induced changes in the structure and bonding of graphitic carbon electrodes that may one day affect the way energy is stored.
The research could lead to an improvement in the capacity and efficiency of electrical energy storage systems, such as batteries and supercapacitors, needed to meet the burgeoning demands of consumer, industrial and green technologies.
October 30, 2014
A team led by the Lawrence Livermore scientists has created a new kind of ion channel consisting of short carbon nanotubes, which can be inserted into synthetic bilayers and live cell membranes to form tiny pores that transport water, protons, small ions and DNA.
October 17, 2014
Lawrence Livermore researchers have turned to graphene aerogel for enhanced electrical energy storage that eventually could be used to smooth out power fluctuations in the energy grid..
September 15, 2013
A group of international scientists including a PLS researcher have confirmed that life really could have come from out of this world.