Exotic Material Shows Promise as Flexible, Transparent Electrode

Engineerblogger
March 8, 2012

An array of microcircuits made of a 10-nanometer-thick film of bismuth sulfide, an exotic material called a topological insulator, on an insulating mica substrate can be flexed without damaging its electrical properties.

Photo by Hailin Peng, Peking University.

An international team of scientists with roots at SLAC and Stanford has shown that ultra-thin sheets of an exotic material remain transparent and highly conductive even after being deeply flexed 1,000 times and folded and creased like a piece of paper.

The result could open this class of unusual materials, called topological insulators, to its first practical applications: flexible, transparent electrodes for solar cells, sensors and optical communications devices.

“It’s rare for a good conductor to be both transparent and durable as well,” said Zhi-Xun Shen of SLAC and Stanford’s Institute for Materials and Energy Sciences (SIMES).

Researchers led by Shen, Zhongfan Liu and Hailin Peng of Peking University in China, and Yulin Chen of Oxford University in England published their results last week in Nature Chemistry. Until recently, Peng and Chen were graduate students and postdoctoral researchers at Stanford and SIMES. They have continued to collaborate with Shen’s research team after being named professors at their current universities.

The researchers made and tested samples of a compound in which sheets of bismuth and selenium, each just one atom thick, alternate to form five-layer units. The bonds between the units are weak, allowing the overall material to flex while retaining its durability. And as a topological insulator – a new state of quantum matter – the material conducts electricity only on its surface while its interior remains insulating, an unexpected property with unknown potential for fundamental research and practical applications.

Since surface atoms dominate the structure of bismuth selenide, it is an exceptionally good electrical conductor – as good as gold. Unlike gold, however, bismuth selenide is transparent to infrared light, which we know as heat. While about half the solar energy that hits the Earth comes in the form of infrared light, few of today’s solar cells are able to collect it. The transparent electrodes on the surfaces of most cells are either too fragile or not transparent or conducting enough. The new material could get around that problem and allow cells to harvest more of the sun’s spectrum of wavelengths.

The researchers’ experiments also showed that bismuth selenide does not degrade significantly in humid environments or when exposed to oxygen treatments that are common in manufacturing.

“In addition to being a scientific success,” Chen said, “this demonstration should alert engineers and companies that topological insulators can also be important commercially.”

Peng added, “Infrared light pulses carry phone calls and data through optical fiber networks, so bismuth selenide may be useful in communications devices. This material could also improve infrared sensors common in scientific equipment and aerospace systems.”

Peng and colleagues made the bismuth selenide samples and conducted the flexing, conductivity and transparency tests in China. The researchers confirmed that the samples were topological insulators at the Stanford Synchrotron Radiation Lightsource’s Beam Line 5-4 at SLAC.

Theorists first proposed topological insulators in 2004, and experimentalists made the first examples, using mercury telluride at very low temperatures, two years later. Guided by theory, Chen, Shen and colleagues proved in 2009 that cheaper, more abundant and easier-to-handle bismuth telluride and similar compounds containing antimony and selenium are topological insulators at room temperature. Also in 2009, Peng, Shen and colleagues discovered important electrical conduction behavior in bismuth selenide nanoribbons.





Source:  SLAC National Accelerator Laboratory

Solved: The Mystery of the Nanoscale Crop Circles

Lawrence Berkeley National Laboratory
March 1, 2012




Almost three years ago a team of scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) was performing an experiment in which layers of gold mere nanometers (billionths of a meter) thick were being heated on a flat silicon surface and then allowed to cool. They watched in surprise as peculiar features expanded and changed on the screen of their electron microscope, finally settling into circles surrounded by irregular blisters.

The circles varied in diameter up to a few millionths of a meter, and in the center of each was a perfect square. The mysterious patterns were reminiscent of nothing so much as so‑called “alien” crop circles.

Until recently the cause of these strange formations remained a mystery. Now theoretical insights have explained what’s happening, and the results have been published online by Physical Review Letters.

Eagerly melting alloys

When two solids are combined in just the right proportions, changes in chemical bonding may produce an alloy that melts at a temperature far lower than either can melt by itself. Such an alloy is called eutectic, Greek for “good melting.” The eutectic alloy of gold and silicon – 81 percent gold and 19 percent silicon – is especially useful in processing nanoscale semiconductors such as nanowires, as well as for device interconnections in integrated circuits; it liquefies at a modest 363˚ Celsius, far lower than the melting point of either pure gold, 1064°C, or pure silicon, 1414°C.

“Gold-silicon eutectic liquid can safely solder chip layers together or form microscopic conducting wires, by flowing into channels in the substrate without burning up the surroundings,” says Berkeley Lab’s Junqiao Wu. “It’s particularly interesting for processing nanoscale materials and devices.” Wu cites the example of silicon nanowires, which can be grown from beads of eutectic liquid that form from droplets of gold. The beads catalyze the deposition of silicon from a chemical vapor and ride atop continually lengthening nanowire whiskers.

Understanding just how and why this happens has been a challenge. Although eutectic alloys are well studied as solids, the liquid state presents more obstacles, which are particularly formidable at the nanoscale because of greatly increased surface tension – the same surface forces that make it difficult to form ultra-thin films of water, for example, because they pull the water into droplets. At smaller scales the ratio of surface area to bulk increases markedly, and nanoscale structures have been described as virtually “all surface.”

These are the conditions that the team led by Wu, who is a faculty scientist in Berkeley Lab’s Materials Sciences Division and a professor in the Department of Materials Science and Engineering at the University of California at Berkeley, set out to examine, by creating the thinnest possible films of gold-silicon eutectic alloys. The researchers did so by starting with a substrate of pure silicon, on whose flat surface an extremely thin barrier layer (two nanometers thick) of silicon dioxide had formed. On this surface they laid layers of pure gold, varying the thickness from one trial to the next between just a few nanometers to a hefty 300 nanometers. The silicon dioxide barrier prevented the pure silicon from mixing with the gold.

The next step was to heat the layered sample to 600 °C for several minutes – not hot enough to melt the gold or silicon but hot enough to cause naturally existing pinholes in the thin silicon dioxide layer to enlarge into small weak spots, through which pure silicon could come in contact with the overlying gold. At the high temperature, silicon atoms quickly diffused out of the substrate and into the gold, forming a layer of eutectic gold-silicon alloy nearly the same thickness as the original gold and spreading in a virtually perfect circle from the central pinhole.

When the circular disk of eutectic alloy got large enough it suddenly broke up, disrupted by the high surface energy of the gold-silicon eutectic liquid. The debris was literally pulled to the edges of the disk, piling up around it to leave a central denuded zone of bare silicon dioxide.

In the center of the denuded zone, a perfect square of gold and silicon remained.
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Sandia National Laboratories researchers find energy storage “solutions” in MetILs

Engineerblogger
Feb 20, 2012

Chemical technologist Harry Pratt synthesizes a copper-based ionic liquid. Photo by Randy Montoya

Sandia researchers have developed a new family of liquid salt electrolytes, known as MetILs, that could lead to batteries able to cost-effectively store three times more energy than today’s batteries.

The research, published in Dalton Transactions, might lead to devices that can help economically and reliably incorporate large-scale intermittent renewable energy sources, like solar and wind, into the nation’s electric grid.

The grid was designed for steady power sources, making fluctuating electricity from intermittent renewable energy difficult to accommodate. Better energy storage techniques help even out the flow of such fluctuating sources, and Sandia researchers are studying new ways to develop a more flexible, cost-effective and reliable electric grid with improved energy storage.

“The U.S. and the world need significant breakthroughs in battery technology for renewable energy sources to replace today’s carbon-based energy systems,” said Anthony Medina, director of Sandia’s Energetic Components Realization program. “MetILs are a new, promising battery chemistry that might provide the next generation of stationary storage battery technology, replacing lead-acid and lithium-ion batteries and providing significantly higher energy storage density for these applications.”

For the past 20 years, lithium-ion batteries have been at the forefront of energy storage research. Their compact, lightweight design is well suited for cell phones, laptop computers and personal electronics, but lithium-ion batteries are expensive and degradation issues limit their use in stationary, high-capacity application on the nation’s electric grid.

Sandia researcher and inorganic chemist Travis Anderson is leading a team developing the next generation of flow batteries. A flow battery pumps a solution of free-floating charged metal ions, dissolved in an electrolyte — substance with free-floating ions that conducts electricity — from an external tank through an electrochemical cell to convert chemical energy into electricity. Flow batteries are rapidly charged and discharged by changing the charge state of the electrolyte, and the electroactive material can be easily re-used many times. Anderson said flow batteries can sustain more than 14,000 cycles in the lab, equivalent to more than 20 years of energy storage, which would be unusual in a lithium-ion battery.

However, flow battery grid storage systems are roughly the size of a house and can cost more than equivalent lithium-ion batteries. The goal of researchers is to make flow batteries smaller and cheaper, while increasing the amount of energy stored for a given volume, or energy density.

Flow batteries have been fielded in the U.S., Japan and Australia. A number of systems – up to 25 MW – are in the process of being demonstrated under the American Recovery and Reinvestment Act (ARRA) administered by DOE’s Energy Storage Systems Research program. Zinc bromine and vanadium redox systems are among the top contenders. But the materials involved are moderately toxic, and vanadium is subject to major price fluctuations. In addition, the aqueous solution limits the amount of material that can be dissolved and how much energy can be stored, and outside temperature can hurt performance.

Sandia is pioneering research on flow batteries that avoid these problems by not using water. Anderson assembled a multidisciplinary team of experts from the Labs, including electrochemist David Ingersoll, organic chemist Chad Staiger and chemical technologists Harry Pratt and Jonathan Leonard. What they’ve designed is a new family of electrochemically reversible, metal-based ionic liquids, or MetILs, which are based on inexpensive, non-toxic materials that are readily available within the U.S., such as iron, copper and manganese.

“Instead of dissolving the salt into a solvent, our salt is a solvent,” Anderson said. “We’re able to get a much higher concentration of the active metal because we’re not limited by saturation. It’s actually in the formula. So we can cost-effectively triple our energy density, which drastically reduces the necessary size of the battery, just by the nature of the material.”

The electrochemical efficiency, or ability to reverse charge, in MetILs is far greater than anything else published to date. The team has prepared nearly 200 combinations of cations, anions and ligands, and of those, five outperform the electrochemical efficiency of ferrocene, which has long been considered the gold standard.

A common problem when mixing positively and negatively charged species is that these species will start aggregating together, eventually causing the solution to turn gummy and clog the battery membrane and electrode surfaces. The team addressed that challenge by developing asymmetric cations, or positively charged ions, that resemble a soccer ball. In this analogy, the black pentagons represent negatively charged areas and the white hexagons represent positively charged regions. Such an arrangement lowers the melting point by preventing the ionic liquid constituents from bonding and becoming a solid, while the partial charge still allows electrons to flow freely through the cell to generate a current.

Sandia researchers have discovered a new family of liquid salt electrolytes that could lead to batteries with three times greater energy density than other available storage technologies. The MetILs are, from left to right: copper-based compound, cobalt-based compound, manganese-based compound, iron-based compound, nickel-based compound, and vanadium-based compound. Photo by Randy Montoya

The team is funded by the Department of Energy’s Office of Electricity Delivery and Energy Reliability. Imre Gyuk, energy storage systems program manager for that office, has been a champion of Sandia’s efforts and provided the necessary funding.

“The MetILs approach represents an ingenious, out-of-the-box solution to the cathode/electrolyte paradigm. Because it is based on readily available, inexpensive precursors, it may well lead to innovative, cost-effective storage systems with major impacts on the entire U.S. grid,” said Gyuk.

The findings apply to new flow battery cathode materials. The next step for the Sandia team is to find similar materials for flow battery anodes, and researchers are encouraged by their progress.

“There are three things you’re juggling at the same time, and they aren’t always related: viscosity, electrical conductivity and the fundamental electrochemical efficiency,” Anderson said. “The excitement of having all three things go right at the same time, it’s like finding the treasure, but without the map. We’re creating that map, and we’re very excited by the possibilities.”

Source: Sandia National Laboratories

Small modular reactor design could be a 'SUPERSTAR'

Argonne National Laboratory
Feb 9, 2012

Credit: ANL

Though most of today's nuclear reactors are cooled by water, we've long known that there are alternatives; in fact, the world's first nuclear-powered electricity in 1951 came from a reactor cooled by sodium. Reactors cooled by liquid metals such as sodium or lead have a unique set of abilities that may again make them significant players in the nuclear industry.

At the U.S. Department of Energy's (DOE) Argonne National Laboratory, a team led by senior nuclear engineer James Sienicki has designed a new small reactor cooled by lead—the Sustainable Proliferation-resistance Enhanced Refined Secure Transportable Autonomous Reactor, or SUPERSTAR for short.

Small modular reactors, or SMRs, are small-scale nuclear plants that are designed to be factory-manufactured and shipped as modules to be assembled at a site. They can be designed to operate without refueling for 15 to 30 years. The concept offers promising answers to many questions about nuclear power—including proliferation, waste, safety and start-up costs.

SUPERSTAR is an example of a so-called "fast reactor," a type fundamentally different from the light-water reactors common today. Light-water reactors use water both as a coolant and as a moderator to slow down neutrons created in the fuel as it fissions. Instead, fast reactors use materials that don't slow down neutrons—often a liquid metal, such as sodium or lead.

Like all new generations of reactors, SUPERSTAR has "passive" safety systems—backup safety measures that kick in automatically, without human intervention, in case of accidents. For example, all reactors have control rods incorporating substances that absorb neutrons and stop nuclear chain reactions. SUPERSTAR's rods can be suspended above the reactor core held in place by electricity. If the plant loses power, the control rods will automatically drop into the core and stop the reaction.

In addition, SUPERSTAR's lead coolant is circulated around the core by a process called natural circulation. While existing plants use electrically-driven pumps to keep the water moving, SUPERSTAR exploits a law of physics to move the coolant.

"In any closed loop, with heat at the bottom and cooling on top, a flow will develop, with the heated stream rising to the top and cooled stream going down," explained Anton Moisseytsev, an Argonne nuclear engineer also working on the reactor design. "The SUPERSTAR design takes advantage of this feature—its lead coolant is circulated solely by natural circulation, with no pumps needed. And of course, having no pumps means no pump failures." This means that if the plant loses power, as happened at the Fukushima Daiichi plant in Japan, the reactor does not need electricity to cool the core after shutdown.
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Hydrogen from Acidic Water: Researchers Develop a Potential Low Cost Alternative to Platinum for Splitting Water

Engineerblogger
Feb 10, 2012

Using a molybdenite complex and the PY5Me2 ligand, Berkeley Lab researchers synthesized a molecule that mimics catalytically active triangular molybdenum disulfide edge-sites. The result is an entire layer of catalytically active material. Molybdenum atoms are shown as green, sulfur as yellow.

A technique for creating a new molecule that structurally and chemically replicates the active part of the widely used industrial catalyst molybdenite has been developed by researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). This technique holds promise for the creation of catalytic materials that can serve as effective low-cost alternatives to platinum for generating hydrogen gas from water that is acidic.

Christopher Chang and Jeffrey Long, chemists who hold joint appointments with Berkeley Lab and the University of California (UC) Berkeley, led a research team that synthesized a molecule to mimic the triangle-shaped molybdenum disulfide units along the edges of molybdenite crystals, which is where almost all of the catalytic activity takes place. Since the bulk of molybdenite crystalline material is relatively inert from a catalytic standpoint, molecular analogs of the catalytically active edge sites could be used to make new materials that are much more efficient and cost-effective catalysts.

“Using molecular chemistry, we’ve been able to capture the functional essence of molybdenite and synthesize the smallest possible unit of its proposed catalytic active site,” says Chang, who is also an investigator with the Howard Hughes Medical Institute (HHMI). “It should now be possible to design new catalysts that have a high density of active sites so we get the same catalytic activity with much less material.”

Says Long, “Inorganic solids, such as molybdenite, are an important class of catalysts that often derive their activity from sparse active edge sites, which are structurally distinct from the inactive bulk of the molecular solid. We’ve demonstrated that it is possible to create catalytically active molecular analogs of these sites that are tailored for a specific purpose. This represents a conceptual path forward to improving future catalytic materials.”

Chang and Long are the corresponding authors of a paper in the journal Science describing this research titled “A Molecular MoS2 Edge Site Mimic for Catalytic Hydrogen Generation.” Other authors are Hemamala Karunadasa, Elizabeth Montalvo, Yujie Sun and Marcin Majda.

Molybdenite is the crystalline sulfide of molybdenum and the principal mineral from which molybdenum metal is extracted. Although commonly thought of as a lubricant, molybdenite is the standard catalyst used to remove sulfur from petroleum and natural gas for the reduction of sulfur dioxide emissions when those fuels are burned. Recent studies have shown that in its nanoparticle form, molybdenite also holds promise for catalyzing the electrochemical and photochemical generation of hydrogen from water. Hydrogen could play a key role in future renewable energy technologies if a relatively cheap, efficient and carbon-neutral means of producing it can be developed.

Currently, the best available technique for producing hydrogen is to split water molecules into molecules of hydrogen and oxygen using platinum as the catalyst. However, with platinum going for more than $2,000 an ounce, the market is wide open for a low cost alternative catalyst. Molybdenite is far more plentiful and about 1/70th the cost of platinum, but poses other problems.

“Molybdenite has a layered structure with multiple microdomains, most of which are chemically inert,” Chang says. “High-resolution scanning tunneling microscopy studies and theoretical calculations have identified the triangular molybdenum disulfide edges as the active sites for catalysis; however, preparing molybdenite with a high density of functional edge sites in a predictable manner is extremely challenging.”

Chang, Long and their research team met this challenge using a pentapyridyl ligand known as PY5Me2 to create a molybdenum disulfide molecule that, while not found in nature, is stable and structurally identical to the proposed triangular edge sites of molybdenite. It was shown that these synthesized molecules can form a layer of material that is analogous to constructing a sulfide edge of molybdenite.

“The electronic structure of our molecular analog can be adjusted through ligand modifications,” Long says. “This suggests we should be able to tailor the material’s activity, stability and required over-potential for proton reduction to improve its performance.”

In 2010, Chang and Long and Hemamala Karunadasa, who is the lead author on this new Science paper, used the PY5Me2 ligand to create a molybdenum-oxo complex that can effectively and efficiently catalyze the generation of hydrogen from neutral buffered water or even sea water. Molybdenite complexes synthesized from this new molecular analog can just as effectively and efficiently catalyze hydrogen gas from acidic water.

“We’re now looking to develop molecular analogs of active sites in other catalytic materials that will work over a range of pH conditions, as well as extend this work to photocatalytic systems” Chang says.

Adds Long, “Our molecular analog for the molybdenite active site might not be a replacement for any existing catalytic materials but it does provide a way to increase the density of active sites in inorganic solid catalytic materials and thereby allow us to do more with less.”

This research was supported by the DOE Office of Science, in part through the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub.


Source: Lawrence Berkeley National Laboratory

Tool determines value of solar photovoltaic power systems

Engineerblogger
Feb 1, 2012

Sandia National Laboratories researcher Geoff Klise worked with Solar Power Electric to develop a tool that can be used to appraise photovoltaic installations on homes and businesses. (Photo by Randy Montoya)

Consistent appraisals of homes and businesses outfitted with photovoltaic (PV) installations are a real challenge for the nation’s real estate industry, but a new tool developed by Sandia National Laboratories and Solar Power Electric and licensed by Sandia addresses that issue. Sandia scientists, in partnership with Jamie Johnson of Solar Power Electric, have developed PV Value, an electronic form to standardize appraisals. Funded by the Department of Energy’s Office of Energy Efficiency and Renewable Energy, the tool will provide appraisers, real estate agents and mortgage underwriters with more accurate values for PV systems.

“Previous methods for appraising PV installations on new or existing construction have been challenging because they were not using standard appraisal practices,” said Geoff Klise, the Sandia researcher who co-developed the tool. “Typically, appraisers develop the value of a property improvement based on comparable properties with similar improvements as well as prevailing market conditions. If there aren’t PV systems nearby, there is no way to make an improvement comparison. When a PV system is undervalued or not valued at all, it essentially ignores the value of the electricity being produced and the potential savings over the lifetime of the system. By developing a standard methodology for appraisers when comparables are not available, homeowners will have more incentive to install PV systems, even if they consider moving a few years after system installation.”

The tool uses an Excel spreadsheet, tied to real-time lending information and market fluctuations, to determine the worth of a PV system. An appraiser enters such variables as the ZIP code where the system is located, the system size in watts, the derate factor – which takes into account shading and other factors that affect a system’s output – tracking, tilt and azimuth, along with a few other factors, and the spreadsheet returns the value of the system as a function of a pre-determined risk spread. The solar resource calculation in the spreadsheet is based on the PVWatts simulator developed by the National Renewable Energy Laboratory, which allows the spreadsheet to value a PV system anywhere in the U.S.

“With PV Value, appraisers can quickly calculate the present value of energy that a PV system can be estimated to produce during its remaining useful lifetime, similar to the appraisal industry’s income approach,” said Johnson. “Additionally, a property owner thinking about installing PV can now estimate the remaining present value of energy for their future PV system and what it could be worth to a purchaser of their property at any point in time in the event a sale of the property takes place before the estimated payback date is reached.”

The tool is being embraced by the Appraisal Institute, which is the nation’s largest professional association of real estate appraisers. “From my perspective as an appraiser, I see that this is a great tool to assist the appraiser in valuations, and it connects to the Appraisal Institute’s recent Residential Green and Energy Efficient Addendum. It’s an easy, user-friendly spreadsheet that will not bog the appraiser down with a lot of extra time in calculations, and if they fill out the addenda properly, they’ll be able to make the inputs and come up with some numbers fairly quickly,” said Sandy Adomatis, SRA, a real estate appraiser and member of the Appraisal Institute.

Although the tool is licensed for solar PV installations, it could be used for other large green features in a home that generate income, such as wind turbines.

Source: Sandia National Laboratories

Additonal Information:

• The spreadsheet, user manual and webinar explaining the tool are available for download at http://pv.sandia.gov/pvvalue.

Self-guided bullet prototype can hit target a mile away

Engineerblogger
Jan 30, 2012

A tiny light-emitting diode, or LED, attached to a self-guided bullet at Sandia National Laboratories shows a bright path during a nighttime field test that proved the battery and electronics could survive the bullet's launch. (Photo courtesy of Sandia National Laboratories)

Take two Sandia National Laboratories engineers who are hunters, get them talking about the sport and it shouldn’t be surprising when the conversation leads to a patented design for a self-guided bullet that could help war fighters.

Sandia researchers Red Jones and Brian Kast and their colleagues have invented a dart-like, self-guided bullet for small-caliber, smooth-bore firearms that could hit laser-designated targets at distances of more than a mile (about 2,000 meters).

“We have a very promising technology to guide small projectiles that could be fully developed inexpensively and rapidly,” Jones said.

Sandia is seeking a private company partner to complete testing of the prototype and bring a guided bullet to the marketplace.

Researchers have had initial success testing the design in computer simulations and in field tests of prototypes, built from commercially available parts, Jones said.

While engineering issues remain, “we’re confident in our science base and we’re confident the engineering-technology base is there to solve the problems,” he said.

Sandia’s design for the four-inch-long bullet includes an optical sensor in the nose to detect a laser beam on a target. The sensor sends information to guidance and control electronics that use an algorithm in an eight-bit central processing unit to command electromagnetic actuators. These actuators steer tiny fins that guide the bullet to the target.

Most bullets shot from rifles, which have grooves, or rifling, that cause them to spin so they fly straight, like a long football pass. To enable a bullet to turn in flight toward a target and to simplify the design, the spin had to go, Jones said.

The bullet flies straight due to its aerodynamically stable design, which consists of a center of gravity that sits forward in the projectile and tiny fins that enable it to fly without spin, just as a dart does, he said.

Computer aerodynamic modeling shows the design would result in dramatic improvements in accuracy, Jones said. Computer simulations showed an unguided bullet under real-world conditions could miss a target more than a half mile away (1,000 meters away) by 9.8 yards (9 meters), but a guided bullet would get within 8 inches (0.2 meters), according to the patent.

Plastic sabots provide a gas seal in the cartridge and protect the delicate fins until they drop off after the bullet emerges from the firearm’s barrel.

The prototype does not require a device found in guided missiles called an inertial measuring unit, which would have added substantially to its cost. Instead, the researchers found that the bullet’s relatively small size when compared to guided missiles “is helping us all around. It’s kind of a fortuitous thing that none of us saw when we started,” Jones said.

The four-inch-long bullet has actuators that steer tiny fins that guide it to its target. (Photo by Randy Montoya)

As the bullet flies through the air, it pitches and yaws at a set rate based on its mass and size. In larger guided missiles, the rate of flight-path corrections is relatively slow, so each correction needs to be very precise because fewer corrections are possible during flight. But “the natural body frequency of this bullet is about 30 hertz, so we can make corrections 30 times per second. That means we can overcorrect, so we don’t have to be as precise each time,” Jones said.

Testing has shown the electromagnetic actuator performs well and the bullet can reach speeds of 2,400 feet per second, or Mach 2.1, using commercially available gunpowder. The researchers are confident it could reach standard military speeds using customized gunpowder.

And a nighttime field test, in which a tiny light-emitting diode, or LED, was attached to the bullet showed the battery and electronics can survive flight, Jones said.

Researchers also filmed high-speed video of the bullet radically pitching as it exited the barrel. The bullet pitches less as it flies down range, a phenomenon known to long-range firearms experts as “going to sleep.” Because the bullet’s motions settle the longer it is in flight, accuracy improves at longer ranges, Jones said.

“Nobody had ever seen that, but we’ve got high-speed video photography that shows that it’s true,” he said.

Potential customers for the bullet include the military, law enforcement and recreational shooters. In addition to Jones and Kast, Sandia researchers who helped develop the technology are: engineer Brandon R. Rohrer, aerodynamics expert Marc W. Kniskern, mechanical designer Scott E. Rose, firearms expert James W. Woods and Ronald W. Greene, a guidance, control and simulation engineer.

Sandia's self-guided bullet

Source: Sandia National Laboratories

Novel Materials for Hydrogen Storage

Engineerblogger
Jan 27, 2012

Berkeley Lab scientist Jeffrey Long co-leads a project to develop novel materials for hydrogen storage. (Credit: Roy Kaltschmidt/Berkeley Lab)

The biggest challenge with hydrogen-powered fuel cells lies in the storage of hydrogen: how to store enough of it, in a safe and cost-effective manner, to power a vehicle for 300 miles? Lawrence Berkeley National Laboratory (Berkeley Lab) is aiming to solve this problem by synthesizing novel materials with high hydrogen adsorption capacities.

The U.S. Department of Energy recently awarded Berkeley Lab a three-year, $2.1 million grant for the project, which will also include contributions by the National Institute of Standards and Technology (NIST) and General Motors (GM). The grant was part of more than $7 million awarded by DOE last month for hydrogen storage technologies in fuel cell electric vehicles.

“We’re working on materials called metal-organic frameworks to increase the capacity of hydrogen gas in a pressure cylinder, which would be the fuel tank,” said Jeffrey Long, a Berkeley Lab scientist who co-leads the project along with Berkeley Lab chemist Martin Head-Gordon. “With these materials, we’re working on storing the hydrogen without the use of very high pressures, which will be safer and also more efficient without the significant compression energy losses.”

Metal-organic frameworks (MOFs) are three-dimensional sponge-like framework structures that are composed primarily of carbon atoms and are extremely lightweight. “What’s very special about these materials is that you can use synthetic chemistry to modify the surfaces within the materials and make it attractive for hydrogen to stick on the surface,” Long explained.

Separately, Long is also using MOFs in a carbon capture project, in which the material would selectively absorb carbon dioxide over nitrogen. For the fuel cell project, the trick lies not in getting the MOF to select hydrogen out of a mixture but to store as much hydrogen as possible.

Currently, vehicles using hydrogen fuel cells can achieve a range of close to 300 miles—but only if the hydrogen is stored at extremely high pressures (600 to 700 bar), which is expensive and potentially unsafe. It is also energy intensive to pressurize the hydrogen.

So far Long has succeeded in more than doubling hydrogen capacity, but only at very low temperatures (around 77 Kelvin, or -321 Fahrenheit). “It’s still very much basic research on how to create revolutionary new materials that would boost the capacity by a factor of four or five at room temperature,” he said. “We have an idea of what kinds of frameworks we might make to do this.”

Long’s approach is to create frameworks with lightweight metal sites on the surface, making it attractive for hydrogen molecules to bind to the sites. “Our approach has been to make some of the first metal-organic frameworks that have exposed metal cations on the surface,” he said. “Now we need to figure out ways of synthesizing the materials so that instead of one hydrogen molecule we can get two or three or even four hydrogen molecules per metal site. Nobody’s done that.”

This is where Head-Gordon, a computational chemist, comes in. He will work on theoretical understanding of MOFs so that he can try to predict their hydrogen storage properties and then instruct Long’s team as to what kind of material to synthesize. “He can do calculations on a lot of different target structures and say, here’s the best one for you guys to spend time trying to make, because synthetic chemistry is very cost and labor intensive,” Long said.

The scientist at GM will aid in providing accurate high-pressure measurements. The NIST scientist is an expert in neutron diffraction and neutron spectroscopy, which will allow Long and his team to pinpoint where exactly the hydrogen is going and verify that it is binding to the metals.

Source: Lawrence Berkeley National Laboratory (Berkeley Lab)

Nanotube bundles could make good solar cells

Engineerblogger
Jan 17, 2012

Photon hitting a bundle of carbon nanotubes

Bundles of carbon nanotubes could increase the efficiency of thin-film solar cells. So say researchers at the Los Alamos National Laboratory in the US who have used high-speed spectroscopy to show that the bundles can not only generate electron-hole pairs when exposed to sunlight but can separate these pairs of charge carriers too. This is the first time that these two crucial functions have been demonstrated in a single thin-film photovoltaic material.

Thin-film photovoltaic materials are better than conventional solar-cell materials, such as silicon, in that they are cheaper to make, are lighter and more flexible. They work by absorbing photons from sunlight and converting these into electron-hole pairs (or excitons). To generate electric current, an electron and hole must then be separated in the brief space of time it takes before the two particles come back together and are reabsorbed into the material. In solar cells, the exciton must quickly travel to another layer in the device (where the charge separation will occur), but it is normally reabsorbed too fast, something that ultimately leads to low light absorption efficiencies.

Semiconducting carbon nanotube bundles could come into their own here, say Jared Crochet and colleagues. Individual semiconducting nanotubes (which are tubules of the semi-metal graphene) suffer from the low efficiency mentioned above, but this problem can be overcome when the tubes are aggregated into bundles of tubes that have the same chirality. Chirality is the direction in which the graphene sheet has been twisted to form a tube – from left to right, or right to left.

Light absorption and charge separation
Such nanotube bundles respond to absorbed light in the same way as the parent material graphene, and charge separation can thus be very efficient. "This effect is promising for incorporating carbon nanotubes into photovoltaic devices as active layers where both light absorption and charge separation can occur," Crochet told nanotechweb.org.

The materials used in these experiments were produced by centrifuging individual carbon nanotubes so that tubes of the same twist direction and diameter aggregated together. The researchers chose bundles with a diameter and twist that strongly absorb light at a wavelength of about 570 nm – ideal for exposing to sunlight.

High-speed spectroscopy
By exposing the samples to a brief flash of laser light and recording spectra every tens of femtosecond, Crochet's team was able to observe signals that are characteristic of excitons being formed, plus additional peaks that indicated the production of free electrons and holes. In samples made of non-bundled individual carbon nanotubes, only the peak corresponding to exciton creation was seen.

The team now plans to incorporate single chirality semiconducting carbon nanotube networks into real-world photovoltaic devices as active layers. "We would ideally like to see an all-carbon solar cell made of graphene, graphene oxide and carbon nanotubes," said Crochet.

The researchers are also busy trying to better understand exciton dissociation and charge transport in the nanotube bundles using the high-speed spectroscopy technique. "The advantage of having the material in a device is that we can investigate every step, from photon absorption to charge collection," concluded Crochet.

The work was reported in Physical Review Letters.


Source: Nanotechweb.org

Broad scientific approach to studying rare earth materials needed to ensure continued deployment of clean energy technologies

Lawrence Berkeley National Laboratory
Jan 11, 2012 

The top matrix shows the supply risk and importance to clean energy of certain elements in the short term (present-2015). The bottom matrix shows the medium term (2015-2025). (Source: DOE)

A few short decades ago, few could have imagined that the world would be seriously concerned over something called dysprosium. Also known as number 66 on the periodic table, dysprosium was once just another element for chemistry students to memorize but is now one of the most sought-after and critically needed materials on the planet.

Belonging to a family of elements known as lanthanides—also called rare earths—dysprosium and other rare earths are used in almost every high-tech gadget and clean energy technology invented in the last 30 years, from smart phones to wind turbines to hybrid cars. Although the United States was self-sufficient in rare earths or obtained them on the free market until the early 2000s, the vast majority are now mined in China and the supply has been subject to fluctuations. The Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) aims to change the status quo by reviving the study of these critical materials to better understand how to extract them, use them more efficiently, reuse and recycle them and find substitutes for them.

In its 2011 Critical Material Strategy released last month, the DOE said that “supply challenges for five rare earth metals (dysprosium, neodymium, terbium, europium and yttrium) may affect clean energy technology deployment in the years ahead.” It also recommended enhanced training of scientists and engineers to “address vulnerabilities and realize opportunities related to critical materials.”

“If we are going to achieve what we need to do in terms of managing climate change, we absolutely have to fix the materials problem—it’s the linchpin for clean energy technologies,” said Frances Houle, a Berkeley Lab scientist who is Director of Strategic Initiatives in the Chemical Sciences Division. “Because Berkeley Lab is such a broad institution, many of the pieces required are already here. We have the chemistry, the earth science, the materials science, the theory. Not very many institutions can say that.”

Like coal and gold, the rare earths are mined out of the ground. However, in any given ore, they are mixed together with other rare earths. So although they are not actually rare, they are difficult to mine. “They’re in low concentration, and it’s very hard to mine them and separate them out, so it’s challenging and extremely energy-intensive to produce rare earth materials ready for industrial manufacturers; it requires a lot of electricity, water and chemicals,” said Berkeley Lab Senior Scientist David Shuh. “This area of study has been ignored over the last two decades, largely due to insufficient research and development support.”
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Battery, heal thyself: Inventing self-repairing batteries

Engineerblogger
Jan 12, 2012

These microcapsules, filled with liquid metal, sit on a gold conductive layer. If the circuit is mechanically damaged, the capsules burst to restore the conductive pathway. Each is just 10 microns across; 10 could fit side by side in a human hair. Image by Amanda Jones and Ben Blaiszik. Credit: Argonne National Laboratory

Imagine dropping your phone on the hard concrete sidewalk—but when you pick it up, you find its battery has already healed itself.

A team of researchers from the University of Illinois at Urbana-Champaign (UIUC) and the U.S. Department of Energy's (DOE) Argonne National Laboratory are exploring ways to design batteries that heal themselves when damaged.

"This would help electronics survive daily use—both the long-term damage caused by charging over and over again, and also the inevitable physical damage of everyday life," said Jeff Moore, a UIUC scientist on the team.

Scientists think that loss of electrical conductivity is what causes a battery to fade and die. Theories abound on the specific molecular failures; perhaps chemicals build up on electrodes, or the electrodes themselves pull away. Perhaps it's simply the inevitable stress fractures in materials forced to expand and contract repeatedly as the battery is charged and used.

In any case, the battery's storage capacity drops due to loss of electrical conductivity. This is what the team wants to address.

The idea is to station a team of "emergency repairmen" already contained in the battery. These are tiny microspheres, each smaller than a single red blood cell, and containing liquid metal inside. Added along with the battery components, they lie dormant for most of the battery's lifetime.

But if the battery is damaged, the capsules burst open and release their liquid metal into the battery. The metal fills in the gaps in the electrical circuit, connecting the broken lines, and power is restored.

Capsules could be designed to be triggered by different events—some that respond to physical damage and others that respond to overheating, for example. This would allow scientists to tailor the contents of the different capsules to repair specific situations.

Microcapsules have been manufactured in large scale since the 1950s. When you press your pencil down on carbonless copy paper, microcapsules full of ink burst open to leave an imprint on the paper layers beneath. Microcapsules full of perfume burst when you rub a scratch-and-stiff sticker.

"We hope that using microcapsules, which are a well-known technology, could make this technology easy to scale up for commercial use," Moore said.

The team's first step was to test the system in a simple system, connecting an electrode with a wire to see if the capsules could "heal" the circuit if cut. (Watch a demonstration of this in the video below).

"Our new self-healing materials can completely repair the circuit in less than a millisecond," Moore said.

The next step, which the researchers are beginning, is to test the capsules in a prototype battery. Argonne materials scientist and battery expert Khalil Amine is helping the team adapt the capsules for lithium-ion batteries. Other collaborators are UIUC scientists Nancy Sottos and Scott White.

The work is funded through the Center for Electrical Energy Storage (CEES), one of three Argonne-led Energy Frontier Research Centers (EFRCs). Established in 2009 by a special block grant from DOE, the EFRCs are five-year interdisciplinary programs focused around specific scientific challenges that are believed to be key to breakthroughs in energy technology.

The CEES is addressing the problems that limit electrochemical energy storage technologies—such as batteries and supercapacitors—for transportation, residential and commercial use.




Source: Argonne National Laboratory 
  

Additional Information: 

• The results have been published in a paper, "Autonomic Restoration of Electrical Conductivity", in the journal Advanced Materials. Moore's co-authors on the paper are Benjamin Blaiszik, Sharlotte Kramer, Martha Grady, David McIlroy, Nancy Sottos and Scott White.

Renewable Energy: Clearing a Potential Road Block to Bisabolane

Engineerblogger
Jan 11, 2012

JBEI researchers determined the structure of the AgBIS enzyme and found it to consist of three helical domains, the first three-domain structure ever found in a synthase of sesquiterpenes. This discovery holds importance for advanced biofuels and other applications. Credit: Lawrence Berkeley National Laboratory

The recent discovery that bisabolane, a member of the terpene class of chemical compounds used in fragrances and flavorings, holds high promise as a biosynthetic alternative to D2 diesel fuel has generated keen interest in the green energy community and the trucking industry. Now a second team of researchers with the U.S Department of Energy (DOE)’s Joint BioEnergy Institute (JBEI) has determined the three-dimensional crystal structure of a protein that is key to boosting the microbial-based production of bisabolane as an advanced biofuel.

The JBEI research team, led by bioengineers Paul Adams and Jay Keasling, solved the protein crystal structure of an enzyme in the Grand fir (Abies grandis) that synthesizes bisabolene, the immediate terpene precursor to bisabolane. The performance of this enzyme – the Abies grandis α-bisabolene synthase (AgBIS) – when engineered into microbes, has resulted in a bottleneck that hampers the conversion by the microbes of simple sugars into bisabolene.

“Our high resolution structure of AgBIS should make it possible to design changes in the enzyme that will enable microbes to make bisabolene faster,” says Adams, a leading authority on x-ray crystallography. “It should also enable us to engineer out inhibition effects that slow throughput, and perhaps also engineer the enzyme to produce other kinds of fuels similar to bisabolane.”

Adams, who heads JBEI’s Technologies Division, is the corresponding author of a paper describing this work in the Cell Press journal Structure. The paper is titled “Structure of a Three-Domain Sesquiterpene Synthase: A Prospective Target for Advanced Biofuels Production.” Co-authoring it with Adams and Keasling were Ryan McAndrew, Pamela Peralta-Yahya, Andy DeGiovanni, Jose Pereira and Masood Hadi.

JBEI is one of three DOE Bioenergy Research Centers established by DOE’s Office of Science to advance the technology for the commercial production of advanced biofuels. It is a multi-institutional partnership led by the Lawrence Berkeley National Laboratory (Berkeley Lab) and headquartered in Emeryville, CA.

This past fall, JBEI researchers identified bisabolane as a potential new advanced biofuel that could replace D2 diesel, today’s standard fuel for diesel engines, with a clean, green, renewable alternative that’s produced in the United States. Using the tools of synthetic biology, the researchers engineered strains of bacteria and yeast to produce bisabolene from simple sugars, which was then hydrogenated into bisabolane. While showing much promise, the yields of bisabolene have to be improved for microbial-based production of bisabolane fuel to be commercially viable.

“The inefficient terpene synthase enzyme is one of the bottlenecks in the metabolic pathway used by the engineered microbes,” says Peralta-Yahya, a lead member of the earlier JBEI team as well as the current team. “Knowing the AgBIS crystal structure will guide us in engineering it for improved catalytic efficiency and stability, which should bring our bisabolene yields closer to economic competitiveness.”

Peralta-Yahya and her colleagues determined that the AgBIS enzyme consists of three helical domains, the first three-domain structure ever found in a synthase of sesquiterpenes – terpene compounds that contain 15 carbon atoms. The discovery of this unique structure holds importance on several fronts, as co-lead author of the Structure paper McAndrew explains.

“That we found the structure of AgBIS to be more similar to diterpene (20 carbon terpene compounds) synthases not only provides us with insight into the function of these less well characterized enzymes, it also provides us with clues to the evolutionary heritage as the archetypal three-domain terpenoid synthases became two-domain sesquiterpene synthases in plants. Furthering our knowledge of the structures and functions of terpenoid synthases may prove to have abundant practical applications aside from advanced biofuels because these enzymes produce a wide variety of specialized chemicals.”

Solving the three-dimensional crystal structure of AgBIS was made possible by the protein crystallography capabilities of Berkeley Lab’s Advanced Light Source (ALS), a DOE Office of Science national user facility for synchrotron radiation, and the first of the world’s third generation light sources. For this work, the JBEI team used three of the five protein crystallography beamlines operated by the Berkeley Center for Structural Biology (BCSB) – beamlines 8.2.1, 8.2.2, and 5.0.3.

“We needed to use multiple beamlines because we collected data on several crystals – the protein by itself, and the protein with different inhibitors/cofactors,” says Adams, who headed the BCSB from 2004 to 2011. “Also, the approach we used to solve the AgBIS structure required high flux tunable x-rays such as those provided at 8.2.1 and 8.2.2, which are superbend beamlines.”

This research was supported by the DOE Office of Science.

Source: Lawrence Berkeley National Laboratory

ORNL technology could mean improved prosthesis fitting, design

Engineerblogger
Jan 4, 2012

ORNL biomedical engineers Boyd Evans and John Mueller are working to improve prosthetic fitting and design for young military amputees. (Photo: Jason Richards)

Soldiers returning from war who have lost a leg could lead a more active lifestyle with the help of a technology being developed by Oak Ridge National Laboratory researchers.

ORNL biomedical engineers Boyd Evans and John Mueller are perfecting a portable, wearable system to measure walking patterns that can be applied to real-world activities in a variety of settings.

"For example, if an amputee soldier wants to train and return to active duty, we need to understand how he or she would fare on a military training course, which you can't measure in a laboratory setting," said Evans, who leads the project.

Evans and Mueller are collaborating with Center for the Intrepid at Brooke Army Medical Center to improve prosthesis performance for young soldiers. Wounded soldiers tend to be between ages 18-25, need a prosthetic that will last a long time and are active so they are putting more stress on their healthy limb.

"Lower leg amputees in the military population are typically young, athletic and, besides their injuries, in top physical condition," Mueller said. "For this reason, most military patients want to remain active and in some cases return to active military duty. We are looking at how we can improve prosthesis fit, alignment and function."

Additionally, Evans and Mueller want to develop a gait analysis system that can be utilized outside of a confined laboratory setting. Typically, motion- capture gait analysis is performed in a large, multimillion dollar laboratory using controlled conditions and limited activities.

"The goal of our research is to use the recent advances made in video game technology to develop inexpensive tools for amputee rehabilitation," said Evans. "This will allow advanced rehabilitation techniques to both be used in smaller clinics and to be taken outside the clinic."

To monitor the motion and force of walking patterns, Evans and Mueller are collaborating with BAMC to utilize inertial measurement units and other sensors that can be strapped onto segments of a subject's leg, such as the thigh, calf and foot. The data collected from the IMU transfers to a computer, and algorithms calculate the motions and forces associated with specific joints.

To test the effectiveness of IMUs, Evans and Mueller use a robot leg, which has been programmed with data from a walking person. Evans and Mueller plan on going to the Gait and Motion Analysis Laboratory at Center for the Intrepid in a few months to test their system on a human subject with a prosthetic and healthy leg.

If the prosthesis is not fit or aligned correctly, it could affect a patient's walking patterns, resulting in "asymmetric" gait. These abnormal gait patterns can increase the stress on the healthy limb, leading to problems later in life such as arthritis.

"We have high expectations for this system once it is fully developed," Mueller said. "We think it will improve the prosthetic fitting and aligning process and help lower the risk of chronic joint disease in this group of wounded warriors."

A subset to this overall project, called "Using Kinect for Xbox 360 and Computer Vision to Analyze Human Gait," won the Siemens Competition for Math, Science and Technology in early December. The multi-camera Kinect is connected to a computer that uses body-tracking algorithms to measure how different parts of the leg move when someone's walking. Summer interns Cassee Cain and Ziyuan Liu, who worked with Evans and Mueller, received the top Siemens team award for their project.

Evans and Mueller's work represent an overall collaboration with Otto Bock Healthcare and the Center for the Intrepid at Brooke Army Medical Center. ORNL researcher Randy Lind is developing an advanced platform to measure the forces associated with motion, and researchers Nance Ericson and Ethan Farquhar are integrating the entire system to incorporate wireless data collection.

Source:  Oak Ridge National Laboratory

N.E. Chemcat Corporation Licenses Brookhaven Lab's Electrocatalyst Technology for Fuel Cells in Electric Vehicles

Engineerblogger
Jan 4, 2012

(From left) Brookhaven National Laboratory chemists Kotaro Sasaki, Radoslav Adzic, Jia Wang, and Miomir Vukmirovic work on the recently licensed electrocatalysts using a new electron microscope in their laboratory.

N.E. Chemcat Corporation, Japan’s leading catalyst and precious metal compound manufacturer, has licensed electrocatalysts developed by scientists at the U.S. Department of Energy’s Brookhaven National Laboratory that can reduce the use of costly platinum and increase the effectiveness of fuel cells for use in electric vehicles. In addition, the license includes innovative methods for making the catalysts and an apparatus design used in manufacturing them.

Platinum is the most efficient electrocatalyst for fuel cells, but platinum-based catalysts are expensive, unstable, and have low durability. The newly licensed electrocatalysts have high activity, stability, and durability, while containing only about one tenth the platinum of conventional catalysts used in fuel cells, reducing overall costs.

The electrocatalysts consist of a palladium or a palladium alloy nanoparticle core covered with a monolayer – one-atom thick – platinum shell. This palladium-platinum combination notably improves oxygen reduction at the cathode of a hydrogen/oxygen fuel cell. This type of fuel cell produces electricity using hydrogen as fuel, and forms water as the only byproduct.

Radoslav Adzic, the Brookhaven Lab senior chemist who led the team that developed the catalysts, said, “We are delighted that N.E. Chemcat Corporation has licensed our platinum monolayer electrocatalyst technology. We hope that it will facilitate the development of affordable and reliable fuel cell electric vehicles, which would be very beneficial for the environment since they produce no harmful emissions. Also, the use of nonrenewable fossil fuels for transportation that contribute to global warming would be greatly reduced, prolonging their availability for other uses in the future.”

Source:  Brookhaven National Laboratory

7 things you may not know about catalysis

Engineerblogger
Dec 19, 2011

The ice-like hexagonal structure of water molecules interacting with and above a model platinum catalyst surface is determined from quantum chemical calculations. Oxygen atoms in water shown as red, hydrogen atoms as white; platinum atoms are shown in bluish-grey. High-level details of the structure can be seen in the reflections of each atom surface.  Rees Rankin (Argonne's Center for Nanoscale Materials) Photo courtesy of Argonne National Laboratory.

Catalysts are all around us.

Catalysts are one of those things that few people think much about, beyond perhaps in high school chemistry, but they make the world tick. Almost everything in your daily life depends on catalysts: cars, Post-It notes, laundry detergent, beer. All the parts of your sandwich—bread, cheddar cheese, roast turkey. Catalysts break down paper pulp to produce the smooth paper in your magazine. They clean your contact lenses every night. They turn milk into yogurt and petroleum into plastic milk jugs, CDs and bicycle helmets.

What is catalysis?

Catalysts speed up a chemical reaction by lowering the amount of energy you need to get one going. Catalysis is the backbone of many industrial processes, which use chemical reactions to turn raw materials into useful products. Catalysts are integral in making plastics and many other manufactured items.

Even the human body runs on catalysts. Many proteins in your body are actually catalysts called enzymes, which do everything from creating signals that move your limbs to helping digest your food. They are truly a fundamental part of life.

Small things can have big results.

In most cases, you need just a tiny amount of a catalyst to make a difference. Even the size of the catalyst particle can change the way a reaction runs. Last year, an Argonne team including materials scientist Larry Curtiss found that one silver catalyst is better at its task when it's in nanoparticles just a few atoms wide. (The catalyst turns propylene into propylene oxides, which is the first step in making antifreeze and other products.)

It can make things greener.

Industrial manufacturing processes for plastic and other essential items often produce nasty by-products which can pose hazards to human health and the environment. Better catalysts can help solve that problem. For example, the same silver catalyst actually produces fewer toxic by-products—making the whole reaction more environmentally friendly.

At its heart, a catalyst is a way to save energy. And applying catalysts on a grand scale could save the world a lot of energy. Three percent of all of the energy used in the U.S. every year goes into converting ethane and propane into alkenes, which are used to make plastics, among other things. That's the equivalent of more than 500 million barrels of gasoline.

Catalysts are also the key to unlocking biofuels. All biomass—corn, switchgrass, trees—contains a tough compound called cellulose, which has to be broken down to make fuel. Finding the perfect catalyst to disintegrate cellulose would make biofuels cheaper and more viable as a renewable energy source.

Often, we have no idea why they work.

The precise reasons why catalysts work are often still a mystery to scientists. Curtiss works in computational catalysis: using computers to tackle the complicated interplay of physics, chemistry and math that explains how a catalyst operates.

Once they've figured out the process, scientists can try to build a catalyst that works even better by simulating how different materials might work instead. Potential configurations for new catalysts can run to thousands of combinations, which is why supercomputers are best at dealing with them.

When Edison was building the lightbulb, he tested literally hundreds of different filaments (likely testing the patience of his lab assistants as well) before discovering the carbonized filament. By taking advantage of supercomputers and modern technology, scientists can speed up the years of testing and expense to get to breakthroughs.

Curtiss runs simulations on Argonne's Blue Gene/P supercomputer to design possible new catalysts. "As supercomputers have gotten faster, we've been able to do things we'd never have been able to do 10 years ago," he said.

They could be essential for the next big revolution in batteries.

Newly efficient lithium-ion batteries helped turn clunky car phones into the slim, elegant cell phones and laptops available today. But scientists are already searching for the next revolution in batteries—one that could someday make a battery light and powerful enough to take a car 500 miles at a go. A promising idea is lithium-air batteries, which use oxygen from the air as a primary component. But this new battery will require totally revamping the internal chemistry, and it will need a powerful new catalyst to make it work. A lithium-air battery works by combining lithium and oxygen atoms and then breaking them apart, over and over. That is a situation tailor-made for a catalyst, and a good one would make the reaction faster and make the battery more efficient.

How do you make a new catalyst?

Understanding the chemistry behind reactions is the first step; then scientists can use modeling to design potential new catalysts and have them tested in the lab. But that first step is difficult unless you can get down to the atomic level to see what is happening during a reaction. This is where big scientific facilities like Argonne's Advanced Photon Source (APS) shine. At the APS, scientists can use the brightest X-rays in the United States to track the reactions in real time. At the laboratory's Electron Microscopy Center, researchers take photos of the atoms while they react. Curtiss and the team have used both of these in their search for better catalysts.

Source: Argonne National Laboratory (ANL)

Making molecular hydrogen more efficiently

Engineerblogger
Dec 12, 2011

This image depicts the series of reactions by which water is separated into hydrogen molecules and hydroxide (OH-) ions.   The process is initiated by nickel-hydroxide clusters (green) embedded on a platinum framework (gray).

When it comes to the industrial production of chemicals, often the most indispensable element is one that you can't see, smell, or even taste. It's hydrogen, the lightest element of all.

Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory have developed an extraordinarily efficient two-step process that electrolyzes, or separates, hydrogen atoms from water molecules before combining them to make molecular hydrogen (H2), which can be used in any number of applications from fuel cells to industrial processing.

Easier routes to the generation of hydrogen have long been a target of scientists and engineers, principally because the process to create the gas requires a great deal of energy. Approximately 2 percent of all electric power generated in the United States is dedicated to the production of molecular hydrogen, so scientists and engineers are searching for any way to cut that figure. "People understand that once you have hydrogen you can extract a lot of energy from it, but they don't realize just how hard it is to generate that hydrogen in the first place," said Nenad Markovic, an Argonne senior chemist who led the research.

While a great deal of hydrogen is created by reforming natural gas at high temperatures, that process creates carbon-dioxide emissions. "Water electrolyzers are by far the cleanest way of producing hydrogen," Markovic said. "The method we've devised combines the capabilities of two of the best materials known for water-based electrolysis."

Most previous experiments in water-based electrolysis rely on special metals, like platinum, to adsorb and recombine reactive hydrogen intermediates into stable molecular hydrogen. Markovic's research focuses on the previous step, which involves improving the efficiency by which an incoming water molecule would disassociate into its fundamental components. To do this, Markovic and his colleagues added clusters of a metallic complex known as nickel-hydroxide—Ni(OH)2. Attached to a platinum framework, the clusters tore apart the water molecules, allowing for the freed hydrogen to be catalyzed by the platinum.

"One of the most important points of this experiment is that we're combining two materials with very different benefits," said Markovic. "The advantage of using both oxides and metals in conjunction dramatically improves the catalytic efficiency of the whole system."

According to Argonne materials scientist George Crabtree, who helped to initiate the establishment of Argonne's energy conversion program, the researchers' success is attributable to their ability to work on what are known as "single-crystal" systems—defect-free materials that allow scientists to accurately predict how certain materials will behave at the atomic level. "We have not only increased catalytic activity by a factor of 10, but also now understand how each part of the system works. By scaling up from the single crystal to a real-world catalyst, this work illustrates how fundamental understanding leads quickly to innovative new technologies."

Source: Argonne National Laboratory

The Next Generation of Nuclear Reactors

Engineerblogger
Nov 29, 2011

The nuclear-power-generation future is quietly taking shape, at least virtually, through the labors of several hundred scientists and technicians working on the Next Generation Nuclear Plant (NGNP) at the Idaho National Laboratory (INL) in Idaho Falls, ID. Scattered through several research facilities and operating sites, these experts are wrestling with dozens of questions—from technology evaluations to site licensing to spent fuels—that accompany any extension of nuclear power.

High-temperature gas-cooled reactor.
Image courtesy of Idaho National Laboratory (INL).

NGNP is far more than an extension: it is a radical step forward for nuclear power. It will be the first truly new reactor design to go into commercial service in the U.S. in decades; it is to be up and running by September 2021. The way forward may not be smooth. Cost estimates range from $4 billion to nearly $7 billion and who pays for what remains unsettled. Nevertheless, barring a technical crunch, a licensing snag, or a financial meltdown, NGNP could become a cornerstone of an energy future with abundant electricity and drastically reduced carbon emissions.

The reactor initiative is for a high-temperature gas-cooled reactor or HTGC (sometimes abbreviated as HTGR), a graphite-moderated and helium-cooled design backed by considerable engineering development in Japan, China, Russia, South Africa, and, in the U.S. by General Atomics, Inc. The primary goal of the project is to commercialize HTGCs. Experts put the potential market at several hundred reactors if most coal-fired power plants are replaced.

Researcher at Idaho National Laboratory (INL).

Running NGNP is what the U.S. Department of Energy calls the NGNP Industry Alliance. Members include many of power-generation’s biggest names: General Atomics; Areva NP; Babcock & Wilcox; Westinghouse Electric Co.; SGL Group, a German producer of graphite and carbon products; and Entergy Nuclear. Entergy owns, operates, or manages 12 of the 104 power-gen reactors in the U.S. and is expected to handle licensing. These firms’ operations and expertise span the industry.

Further backing comes from the consortium that operates INL itself. Its members are Battelle Energy Alliance / Battelle Memorial Institute; Babcock & Wilcox; Washington Group International / URS Corp.; Massachusetts Institute of Technology; and the Electric Power Research Institute.

The high-temperature reference is to the reactor’s outlet temperature, about 1,000 °C, or very roughly three times higher than most of today’s reactors. That means HTGCs can be a source of low-carbon, high-temperature process heat for petroleum refining, biofuels production, the production of fertilizer and chemical feedstocks, and reprocessing coal into other fuels, among other uses. This is why the NGNP alliance includes Dow Chemical, Eastman Chemical, ConocoPhillips, Potash Corp., and the Petroleum Technology Alliance of Canada. All are potential customers for NGNP’s clean heat.

The NGNP Industry Alliance’s HTGC is an integral part of the Generation IV International Forum (GIF). Founded in 2000, GIF is a broadly based international effort to put nuclear power to widespread use for base-load electricity generation and low-cost heat for industrial processes. The other five Generation IV designs are molten-salt reactors, sodium-cooled fast, supercritical water-cooled, gas-cooled fast, and lead-cooled fast. (“Fast” refers to a portion of the neutron spectrum.)

Improvements to existing reactors of 2000 and later are classed as Generation III reactors. They have:

• standardized type designs to expedite licensing, reduce capital costs, and speed construction. Gen II’s were largely custom-built.

• simpler, more rugged designs for less complicated operation and lower vulnerability to operational problems.

• higher availability with fewer, shorter outages and operating lives stretching 60 years.

• better resistance to damage from possible core melts and aircraft impact.

• "grace periods" of 72 hours; a shutdown plant requires no active intervention for the first 72 hours in part because of passive or inherent safety features that rely on gravity, natural convection, or resistance to high temperatures.

• higher "burn up" to reduce fuel use and the amount of waste.

There is also a Gen III-plus group of about a dozen reactor designs in advanced planning stages. Today’s operating units, mostly built since 1970, are second generation. The first generation was 1950 - 1970 prototypes and demonstration units.

Despite optimistic long-term prospects for NGNP and Gen-IV, the nuclear industry’s critics raise two objections. First, safety risks may be greater initially with new reactor types as reactor operators will have had little experience with the new design. Second, fabrication, construction, and maintenance of new reactors can be expected to have a steep learning curve. Advanced technologies always carry a higher risk of accidents and mistakes than predecessors. Established technologies grow safer with accumulated experience and lessons-learned.

The NGNP program envisions dozens of these reactors by 2050. In contrast to today’s power-generation reactors and their enormous concrete-and-steel containment structures, these reactors may be nearly invisible. They will be underground in concrete silos 150 feet deep.

Meanwhile, ASME is playing a major role in NGNP research on metal alloys that can withstand the reactors’ extremely high outlet temperatures. The alloys under consideration are 800H (iron-nickel-chromium), Grade 91 steel (chromium–molybdenum) and Haynes International’s Hastelloy XR (nickel-chromium-iron-molybdenum). The work is being carried out by ASME Standards Technology LLC under an agreement with the U.S. Department of Energy.

Source: ASME

Reliable nuclear device to heat, power Mars Science Lab

Engineerblogger
Nov 24, 2011

NASA's Mars Science Laboratory mission, which is scheduled to launch this week, has the potential to be the most productive Mars surface mission in history. That's due in part to its nuclear heat and power source.

When the rover Curiosity heads to space as early as Saturday, it will carry the most advanced payload of scientific gear ever used on Mars' surface. Those instruments will get their lifeblood from a radioisotope power system assembled and tested at Idaho National Laboratory. The Multi-Mission Radioisotope Thermoelectric Generator is the latest "space battery" that can reliably power a deep space mission for many years.

The device provides a continuous source of heat and power for the rover's instruments. NASA has used nuclear generators to safely and reliably power 26 missions over the past 50 years. New generators like the one destined for Mars are painstakingly assembled and extensively tested at INL before heading to space.

"This power system will enable Curiosity to complete its ambitious expedition in Mars' extreme temperatures and seasons," said Stephen Johnson, director of INL's Space Nuclear Systems and Technology Division. "When the unit leaves here, we’ve verified every aspect of its performance and made sure it’s in good shape when it gets to Kennedy Space Center."

The power system provides about 110 watts of electricity and can run continuously for many years. The nuclear fuel is protected by multiple layers of safety features that have each undergone rigorous testing under varied accident scenarios.

The INL team began assembling the mission's power source in summer 2008. By December of that year, the power system was fully fueled, assembled and ready for testing. INL performs a series of tests to verify that such systems will perform as designed during their missions. These tests include:

• Vibrational testing to simulate rocket launch conditions.
• Magnetic testing to ensure the system's electrical field won't affect the rover's sensitive scientific equipment. 
• Mass properties tests to determine the center of gravity, which impacts thruster calculations for moving the rover.
• Thermal vacuum testing to verify operation on a planet’s surface or in the cold vacuum of space.

INL completed its tests in May 2009, but by then the planned September 2009 launch had been delayed until this month because of hurdles with other parts of the mission. So INL stored the power system until earlier this summer, when it was shipped to Kennedy Space Center and mated up with the rover to ensure everything fit and worked as designed.

The system will supply warmth and electricity to Curiosity and its scientific instruments using heat from nuclear decay. The generator is fueled with a ceramic form of plutonium dioxide encased in multiple layers of protective materials including iridium capsules and high-strength graphite blocks. As the plutonium naturally decays, it gives off heat, which is circulated through the rover by heat transfer fluid plumbed throughout the system. Electric voltage is produced by using thermocouples, which exploit the temperature difference between the heat source and the cold exterior. More details about the system are in a fact sheet here: http://www.inl.gov/marsrover/.

Curiosity is expected to land on Mars in August 2012 and carry out its mission over 23 months. It will investigate Mars' Gale Crater for clues about whether environmental conditions there have favored the development of microbial life, and to preserve any evidence it finds.

NASA chose to use a nuclear power source because solar power alternatives did not meet the full range of the mission's requirements. Only the radioisotope power system allows full-time communication with the rover during its atmospheric entry, descent and landing regardless of the landing site. And the nuclear powered rover can go farther, travel to more places, last longer, and power and heat a larger and more capable scientific payload compared to the solar power alternative NASA studied.

Source: Idaho National Laboratory (INL)

Related Article:

• NASA launching 'dream machine' to explore Mars

Biofuels from Switchgrass: Researchers Boost Switchgrass Biofuels Potential by Adding a Maize Gene to Switchgrass

Engineerblogger
Nov 21, 2011

Introducing a maize gene into switchgrass substantially boosted the potential of the switchgrass biomass as an advanced biofuel feedstock. (Photo courtesy of USDA/ARS)

Many experts believe that advanced biofuels made from cellulosic biomass are the most promising alternative to petroleum-based liquid fuels for a renewable, clean, green, domestic source of transportation energy. Nature, however, does not make it easy. Unlike the starch sugars in grains, the complex polysaccharides in the cellulose of plant cell walls are locked within a tough woody material called lignin. For advanced biofuels to be economically competitive, scientists must find inexpensive ways to release these polysaccharides from their bindings and reduce them to fermentable sugars that can be synthesized into fuels.

An important step towards achieving this goal has been taken by researchers with the U.S. Department of Energy (DOE)’s Joint BioEnergy Institute (JBEI), a DOE Bioenergy Research Center led by the Lawrence Berkeley National Laboratory (Berkeley Lab).

A team of JBEI researchers, working with researchers at the U.S. Department of Agriculture’s Agricultural Research Service (ARS), has demonstrated that introducing a maize (corn) gene into switchgrass, a highly touted potential feedstock for advanced biofuels, more than doubles (250 percent) the amount of starch in the plant’s cell walls and makes it much easier to extract polysaccharides and convert them into fermentable sugars. The gene, a variant of the maize gene known as Corngrass1 (Cg1), holds the switchgrass in the juvenile phase of development, preventing it from advancing to the adult phase.

“We show that Cg1 switchgrass biomass is easier for enzymes to break down and also releases more glucose during saccharification,” says Blake Simmons, a chemical engineer who heads JBEI’s Deconstruction Division and was one of the principal investigators for this research. “Cg1 switchgrass contains decreased amounts of lignin and increased levels of glucose and other sugars compared with wild switchgrass, which enhances the plant’s potential as a feedstock for advanced biofuels.”

The results of this research are described in a paper published in the Proceedings of the National Academy of Sciences (PNAS) titled “Overexpression of the maize Corngrass1 microRNA prevents flowering, improves digestibility, and increases starch content of switchgrass.”

Lignocellulosic biomass is the most abundant organic material on earth. Studies have consistently shown that biofuels derived from lignocellulosic biomass could be produced in the United States in a sustainable fashion and could replace today’s gasoline, diesel and jet fuels on a gallon-for-gallon basis. Unlike ethanol made from grains, such fuels could be used in today’s engines and infrastructures and would be carbon-neutral, meaning the use of these fuels would not exacerbate global climate change. Among potential crop feedstocks for advanced biofuels, switchgrass offers a number of advantages. As a perennial grass that is both salt- and drought-tolerant, switchgrass can flourish on marginal cropland, does not compete with food crops, and requires little fertilization. A key to its use in biofuels is making it more digestible to fermentation microbes.

“The original Cg1 was isolated in maize about 80 years ago. We cloned the gene in 2007 and engineered it into other plants, including switchgrass, so that these plants would replicate what was found in maize,” says George Chuck, lead author of the PNAS paper and a plant molecular geneticist who holds joint appointments at the Plant Gene Expression Center with ARS and the University of California (UC) Berkeley. “The natural function of Cg1 is to hold pants in the juvenile phase of development for a short time to induce more branching. Our Cg1 variant is special because it is always turned on, which means the plants always think they are juveniles.”

Chuck and his colleague Sarah Hake, another co-author of the PNAS paper and director of the Plant Gene Expression Center, proposed that since juvenile biomass is less lignified, it should be easier to break down into fermentable sugars. Also, since juvenile plants don’t make seed, more starch should be available for making biofuels. To test this hypothesis, they collaborated with Simmons and his colleagues at JBEI to determine the impact of introducing the Cg1 gene into switchgrass.

In addition to reducing the lignin and boosting the amount of starch in the switchgrass, the introduction and overexpression of the maize Cg1 gene also prevented the switchgrass from flowering even after more than two years of growth, an unexpected but advantageous result.

“The lack of flowering limits the risk of the genetically modified switchgrass from spreading genes into the wild population,” says Chuck.

The results of this research offer a promising new approach for the improvement of dedicated bioenergy crops, but there are questions to be answered. For example, the Cg1 switchgrass biomass still required a pre-treatment to efficiently liberate fermentable sugars.

Overxpression of the Cg1 gene in switchgrass (left) compared to Wild-type of switchgrass of the same age and grown under the same conditions. (Photo courtesy of USDA/ARS)

“The alteration of the switchgrass does allow us to use less energy in our pre-treatments to achieve high sugar yields as compared to the energy required to convert the wild type plants,” Simmons says. “The results of this research set the stage for an expanded suite of pretreatment and saccharification approaches at JBEI and elsewhere that will be used to generate hydrolysates for characterization and fuel production.”

Another question to be answered pertains to the mechanism by which Cg1 is able to keep switchgrass and other plants in the juvenile phase.

“We know that Cg1 is controlling an entire family of transcription factor genes,” Chuck says, “but we have no idea how these genes function in the context of plant aging. It will probably take a few years to figure this out.”

Source: Lawrence Berkeley National Laboratory