By Neal Singer
The physicist’s concept that the Earth coalesced from the stuff of stars doesn’t generally raise the issue of why massive formations of banded iron — some hundreds of kilometers long — began precipitating on Earth’s surface about 3.5 billion years ago and then ceased relatively suddenly, approximately 1.7 billion years ago.
Because these deposits provide much of industry’s iron resources and also carry information about Earth’s early surface conditions and climate changes, interested researchers have cast a wide net in trying to explain why the formations exist. But attempts to pin the rap on seasonal variations, surface temperature changes, and episodic seawater mixing all have foundered on assumptions requiring the unexplained oscillations of external forces.
IRON MAN - Yifeng Wang (6772) holds a piece of banded iron during a visit to the Albuquerque Aquarium. Yifeng and colleagues have proposed an explanation - published recently in Nature Geoscience - for the precipitation of banded iron deposits in the planet's oceans billions of years ago. (Photo by Randy Montoya)
None of these theories could satisfactorily explain all the observations made by geologists, particularly the existence of structural bands in these deposits that alternate silica-rich layers with iron-rich layers.
A new solution proposed in an October issue of Nature Geoscience by principal investigator Yifeng Wang (6772) and colleagues may have the answer.
A key component of the process, Yifeng and his colleagues found in computer simulations, may have been the absence of aluminum in early oceanic rocks, an absence that chemically favored the formation of banded iron formations. The continual enrichment of oceanic crust by aluminum as Earth evolved ultimately ended the era of iron band formation.
A complete thermodynamic explanation by the researchers suggests that iron- and silicon-rich fluids were generated by hydrothermal action on the seafloor. Their calculations show that the formation of bands was generated by internal interactions of the chemical system, rather than from external forcing by unexplained changes such as ocean surface temperature variations.
“This concept of the self-organizational origin of banded iron formations is very important,” says Yifeng. “It allows us to explain a lot of things about them, like their occurrence and band thickness.
“My PhD advisor Enrique Merino [at Indiana University] was probably the first to consider banded iron formations as formed through self-organization,” says Yifeng. “We started to work on the issue about 15 years ago.” But difficulties in pinning down an actual mechanism persisted.
“Last year, Huifang Xu [at the University of Wisconsin at Madison] and I happened to talk about his work on astrobiology and then we talked about banded iron formations,” says Yifeng. “After that, I got interested again in the topic. Luckily,
I came across a very recent publication on silicic acid interactions with metals. With these new data, I did thermodynamic calculations. I looked at the results and talked to both Huifang and Enrique. The whole banded-iron-formation puzzle started to fit together nicely.”
Merino and Xu coauthored the paper with Yifeng, along with Hironomi Konishi, also at the University of Wisconsin at Madison.
“Our work has two interesting implications,” says Yifeng. “The Earth’s surface can be divided into four interrelated parts: atmosphere, hydrosphere, biosphere, and lithosphere. Our work shows that the lithosphere, that is, the solid rock part, plays a very important role in regulating the surface evolution of the Earth.
“This may have an implication to the studies of other planets such as Mars. Our work also shows that to understand such evolution requires a careful consideration of nonlinear interactions among different components in the system. Such consideration is important for prediction of modern climatic cycles.
“After all,” he says, “Earth’s system is inherently complex and the involved processes couple with each other in nonlinear fashion.” -- Neal Singer
By Patti Koning
Hydrogen getters are not sexy, but they are reliable. Sandia has been in the getter business for nearly 20 years through a flourishing partnership with Vacuum Energy Inc., which has the exclusive license to the technology.
“This is really the textbook case of how technology transfer should work,” says Tim Shepodd, manager of Materials Chemistry Dept. 8223. “We developed our hydrogen getters for applications in nuclear weapons. Then they were commercialized, which kept the program going at Sandia, and they have come back to us for plutonium transport.”
More than meets the eye — Tim Shepodd (8223) describes Sandia’s hydrogen getters program as a “sweet story of technology transfer.” Originally developed to scavenge hydrogen from nuclear weapons nearly 20 years ago, Sandia’s getters were licensed to Vacuum Energy Inc. for use in vacuum-insulated refrigerator panels, waterproof flashlights, flares, and most recently, plutonium transport. (Photo by Randy Wong)
About 15 years ago, Brad Phillip of Vacuum Energy approached Sandia for help removing gases from vacuum-insulated refrigerator panels to extend the product life, improve efficiency, and decrease size. Seeing the potential for hydrogen removal applications, Vacuum Energy licensed Sandia’s getter technology.
If you’ve used a waterproof flashlight, there’s a good chance you’ve encountered one of Sandia’s getters. Each year, Vacuum Energy sells millions of Sandia’s getters to flashlight manufacturers. The getters, which are about the size of a pencil eraser, scavenge the hydrogen that accumulates in the sealed compartment to prevent an explosion.
Hydrogen is ubiquitous because moisture is always present, despite efforts to remove it. Water reacts with metals, making metal oxides and hydrogen gas. Hydrogen is also dangerous, especially when it builds up in sealed compartments, because it is chemically reactive and has a large explosive range with air and high thermal conductivity.
“Have you ever opened your TV remote to change the batteries and noticed that the old batteries are bulging slightly? That’s hydrogen pressure,” explains Tim. “A typical AA battery is semihermitically sealed, so when it fails, it fails suddenly.” That released hydrogen can be ignited with static electricity, such as static generated from sliding across a synthetic bed comforter or carpet.
The getters contain unsaturated organic compounds that react directly with the hydrogen and remove it from the atmosphere, a process called “gettering.” If oxygen is present, the getter enables the hydrogen to react with the oxygen to form water in a controlled catalytic reaction. Tim describes getters as being like ice cream, with many different flavors designed to work in high or low temperature, radioactive, or noxious gas environments. While the flashlight getters are pellets, getters are also used in powder, spray coating, and sheet form.
Easy to get rid of
“It’s easy to get rid of hydrogen,” says Tim. “The challenge is to move an explosive atmosphere below an explosive concentration in a controlled fashion. That’s what our technology does extremely effectively without igniting anything — it moderates the reaction by never letting the temperature get to the ignition point.”
About five years ago, Vacuum Energy expanded the getter application space into flares. Flares are sealed to enable a chemical reaction when they are exposed to oxygen. That sealed compartment, like a waterproof flashlight, can become explosive if too much hydrogen builds up inside.
Tim says he receives several calls each year about new uses for hydrogen getters. “The common theme is often water. I’ve been contacted repeatedly by submarine and buoy operators, even water-themed Las Vegas shows,” he explains. “We are always looking for new applications.”
In many of those calls, Tim says, people tell him they have a hydrogen problem but they have no idea how much hydrogen they are dealing with. Sandia’s getters can be used to determine the extent of hydrogen build-up, as you can count the number of hydrogen atoms absorbed by a getter over a set period of time.
Last year Sandia’s getter passed rigorous DOE testing for use in plutonium transport. Tim says that without getter commercialization, Sandia never would have been able to develop the technology for this application. Vacuum Energy is now supplying getters to DOE’s Savannah River Site.
“The biggest hurdle was that the plutonium shipping container contains a mixture of carbon dioxide and air, and getters had never been used in that environment before,” says April Nissen (8223), who oversaw the testing for Sandia. “We had to ensure that the getters would perform perfectly in those conditions. Failure is not an option.”
An important component of the testing was how the getters performed as they aged in the radioactive environment. Recently, April ran tests on a getter that had been in service for two years and found that they performed better than the laboratory-aged samples, which were subjected to worst-case conditions. “The getters sailed through a very rigorous set of tests,” says April. “We knew the technology would perform, but you never expect this sort of thing to come off without a hitch.”
Another potential getter application is in radar sources, which can degrade and malfunction when exposed to hydrogen. “A lot of people have an issue with hydrogen-sensitive devices that are placed with or in microchips and sealed,” says Tim. “Existing technology used for radar sources deactivates very quickly when exposed to room air, making this technology very difficult to work with.”
Tim presented Sandia’s getter solution at the Advanced Technology Workshop on RF and Micro-wave Packaging, sponsored by the International Microelectronics and Packaging Society last month in San Diego, Calif. An advantage of Sandia’s technology is that it can be worked on in air for several hours before it needs to be sealed. “Our technology also has orders of magnitude less equilibrium water vapor over the surface of the material, minimizing the chance of corrosion, and it passes low ionic content test,” says Tim. “Our presentation was very well received. We are definitely expanding this line of business.
Sandia’s getter work has taken Tim and other researchers in some unusual directions. About a year and a half ago, a salmon supplier asked Sandia for help in maintaining a specific environment in shipping containers that were cooled using a technology that leaked a little hydrogen.
“If the supplier could keep the fish at a certain pressure and temperature consistently, they could change their shipping method and save a lot of money,” he says. “So for a few months we had refrigerators out in the lab with trays full of salmon and getters as we worked on the environment.”
Another aspect of the project was quantifying the odor emitted by the salmon to determine what factors might be changed to keep the fish fresher. “That’s the beauty of working at Sandia,” says Tim. “You never know what kind of project you’ll be working on next — salmon or radar sources or something else totally unexpected.” . -- Patti Koning
By Mike Janes
Sandia researchers and others at the University of New Mexico (UNM), the Joint BioEnergy Institute (JBEI), Novozymes, and North Carolina State University’s Center for Integrated Fungal Research (NCSU-CIFR) have received a DNA sequencing award from the DOE Joint Genome Institute (JGI) to study microbial genes in arid grasslands. The research combines interests in fundamental microbial ecology with DOE goals to exploit microbes in the production of biofuels.
“This award positions a very talented team to collaboratively apply DOE’s unique facilities in genomics and systems biology to the important challenge of sustainable bioenergy production,” says Grant Heffelfinger (8630), manager of molecular and computational biology. “We normally think of biofuels-relevant ecosystems as those where substantial amounts of biomass are produced and broken down, but this is an excellent example of the relevance of biodiversity across ecosystems — both for the advancement of systems biology as well as biofuels production.”
MORE THAN 400 genome sequencing instruments (some shown here at the Joint Genome Institute’s Walnut Creek, Calif., headquarters) are among the platforms to be used in the grasslands project. (Photo courtesy of Roy Kaltschmidt, Lawrence Berkeley National Laboratory)
Microorganisms in arid land ecosystems have evolved high-efficiency recycling systems to cope with severe nutrient scarcity, extreme temperatures, and low water availability. Genes underlying these adaptations offer great potential in industrial-scale processes designed to convert plant material cheaply and efficiently into biofuels.
The project’s sequencing effort will focus on microorganisms associated with the roots of a common grass species, blue grama, and will interface with ongoing environmental change experiments at UNM’s Sevilleta Long Term Ecological Research site in central New Mexico.
“This award will enable us to better understand the metabolic potential of microbial communities native to extreme environments,” says Don Natvig, professor of biology at UNM. “This understanding can in turn be applied to real-world problems, such as biofuels production inefficiencies and greenhouse gas management technologies.”
Biofuels research and environmental change studies are united by the urgent need to develop sustainable energy sources, and to understand and mitigate the environmental effects of spiraling greenhouse gas emissions. In terms of renewable energy, the study will drive the commercial development of new products useful in the breakdown of lignocellulosic biomass, the starting material for production of biofuels.
From an environmental sciences perspective, the award will enable researchers to study and monitor the effects of altered patterns of fire, precipitation, increasing temperatures, and atmospheric pollution on ecosystem structure and function.
The scientific team includes Amy Powell and Bryce Ricken (both 8622) from Sandia; Don Natvig, Scott Collins, Robert Sinsabaugh, Andrea Porras-Alfaro, and Diego Martinez from the UNM Department of Biology; Blake Simmons (8625) of Sandia and JBEI; Ralph Dean of NCSU-CIFR; and Randy Berka of Novozymes.
Advancing green technology innovation
“It is tremendously exciting for us to establish a genomics-based research program at Sandia to study the value of microbes endemic to extreme environments for the development of biofuels and in understanding carbon cycling and sequestration. Climate and energy eclipse all other science and engineering issues now, and will for the foreseeable future. Our studies are timely and will advance green technology innovation,” says Amy.
The total sequencing resources allocated to the project by DOE will be the equivalent of that required to analyze several microbial genomes or a significant fraction of the human genome, which contains approximately three billion base pairs of DNA.
Established in 2005, the JGI’s Community Sequencing Program (CSP) provides the scientific community at large with free access to high-throughput sequencing at DOE JGI for projects of relevance to DOE missions. Sequencing projects are chosen based on scientific merit — judged through independent peer review — and relevance to issues in bioenergy, global carbon cycling, and biogeochemistry. For more information, see www.jgi.doe.gov/CSP/index.html. -- Mike Janes