By Neal Singer
Naturally occurring structures like birds’ wings or tree trunks are thought to have evolved over eons to reach the best possible balance between stiffness and density.
But in a June paper in Nature Materials, the Brinker and Fan groups at Sandia and the University of New Mexico (UNM), in conjunction with researchers at Case Western Reserve and Princeton universities, show that nanoscale materials self-assembled in artificially determined patterns can improve upon nature’s designs.Finer scale than found in nature
“Using self-assembly we can construct silica materials at a finer scale than those found in nature,” says principal investigator Jeff Brinker (1002). “Because, at very small dimensions, the structure and mechanical properties of the materials change, facile fabrication of stiff, porous materials needed for microelectronics and membrane applications may be possible.”
Nuclear magnetic resonance and Raman spectroscopic studies performed by Roger Assink (ret.) and Dave Tallant (1822), along with molecular modeling studies performed by Dan Lacks at Case Western Reserve University showed that, as the ordered porous films became more porous, the silica pore walls thinned below 2 nm, rearranging the silica framework to become denser and stiffer.
Less sensitive to increasing porosity
While the stiffness of evolved optimized bone declines proportional to the square of its density, mechanical studies performed by Thomas Buchheit (1814) working with University of New Mexico student Christopher Hartshorn showed that the stiffness/modulus of self-assembled materials was much less sensitive to increasing porosity: For a material synthesized with a cubic arrangement of pores, the modulus declined only as the square root of its density.
The silica nanostructures — basically a synthetic analogue of bone-like cellular structures, replicated at the nanoscale using silica compounds — thus may improve performance where increased pore volume is important.
These include modern thin-film applications such as membrane barriers, molecular recognition sensors, and low-dielectric-constant insulators needed for future generations of microelectronic devices.
Closely examined bones
“Bone, closely examined, is a structured cellular material,” says Jeff, a Sandia Fellow and chemical engineering professor at UNM. “Because, using self-assembly, we had demonstrated the fabrication of a variety of ordered cellular materials at the nanoscale with worm-like (curving cylinders), hexagonal (soda
straw packing) and cubic sphere arrangements of pores (Lab News, Oct. 6, 2000, we wondered whether the modulus-density scaling relationships of these nanoscale materials would be similar to the optimized evolved materials [like bone].
“We found that both material structure and pore sizes matter,” says Jeff. “At all densities we observed that the cubic arrangement was stiffer than the hexagonal arrangement, which was stiffer than the worm-like.”
For each of these structures, increasing porosity caused a reduction in modulus, but the reduction was less than for theoretically optimized or naturally evolved materials due to the attendant stiffening of the thinning nanoscale silica walls resulting from the formation of small stiff silica rings.
“This change in ring structure only happens at the nanoscale,” says Jeff.
Hongyou Fan (1815-1 ) created cubic, cylindrical, and worm-like (or disordered) pores to evaluate differences in stiffness resulting from these differently shaped internal spaces.
Other paper authors include Dave Kissel of UNM, Regina Simpson (1822), and Salvatore Torquato of Princeton.
Funding was provided by DOE's Office of Science and Sandia's Laboratory Directed Research and Development office. -- Neal Singer
By Mike Janes
A partnership of three national laboratories — including Sandia — and three research universities in the San Francisco Bay Area has been chosen to host one of three national bioenergy research centers, Secretary of Energy Samuel Bodman announced last week.
The center will be funded by DOE through its Biological and Environmental Research Genomics: GTL research program in the Office of Science.
Lawrence Berkeley National Laboratory (Berkeley Lab) will lead the new center, which will be known as the DOE Joint BioEnergy Institute (JBEI). It is expected to receive $125 million in DOE funding over its first five years.
The DOE JBEI’s other partners are Lawrence Livermore National Laboratory (LLNL), the University of California (UC) campuses in Berkeley and Davis, and Stanford University. Plans call for the center to be headquartered in a leased building in the East Bay area, central to all partners. Initial work will take place at the West Berkeley Biocenter in Berkeley.
“The DOE bioenergy research centers will provide the transformational science needed for bio-energy breakthroughs to advance President Bush’s goal of making cellulosic ethanol cost-competitive with gasoline by 2012, and assist in reducing America’s gasoline consumption by 20 percent in 10 years,” Bodman says. “The collaborations of academic, corporate, and national laboratory researchers represented by these centers are truly impressive and I am very encouraged by the potential they hold for advancing America’s energy security.”
Two Sandians on management team
Two Sandians will serve on the JBEI management team: Blake Simmons (8755) as vice president of deconstruction and Kathe Andrews-Cramer (8333) as vice president of strategic integration. Other members include Jay Keasling, CEO of Berkeley Lab, vice president of fuels synthesis; Harvey Blanch, Berkeley Lab/UC Berkeley, chief science and technology officer; Wolf Frommer, Stanford University, vice president of feedstocks; and Paul Adams, Berkeley Lab, vice president of technology.
Research at the institute will focus on biofuels — liquid fuels derived from the solar energy stored in plant biomass. Harnessing even a tiny fraction of the total solar energy available each year could meet most if not all of the nation’s annual transportation energy needs.
Transforming biofuels research
“Diversifying our energy supply is a critical priority for the nation. Achieving that goal will require new scientific breakthroughs and rapid translation of science into scalable technologies,” says Sandia President Tom Hunter. “This partnership will enable a synthesis of biosciences and engineering that will transform the nation’s biofuel research capabilities. With the Joint BioEnergy Institute, Sandia joins California’s extraordinary national laboratories and leading research universities as we move forward to set a new standard for renewable energy research.”
Sandia’s role in the center will build on the Labs’ expertise in science-based engineering, computational science, and microsystems.
Sandia’s capabilities in enzyme engineering, systems biology, membrane transport, protein expression, and hyperspectral imaging are expected to contribute significantly to the JBEI mission.
Sandia’s Center for Integrated Nanotechnologies (jointly operated with Los Alamos National Laboratory), the Microsystems and Engineering Sciences Applications (MESA) complex, and the Combustion Research Facility will play leading roles. Current bioenergy-related research at Sandia expected to enhance DOE JBEI efforts includes the examination of the photosynthetic properties of various plants and microbes; analysis of extremophile enzymes; and related engineering methods that can facilitate the processing of cellulosic biomass.
Scientific studies have consistently ranked biofuels among the top candidates for meeting large-scale energy needs, particularly in the transportation sector. However, the commercial-scale production of clean, efficient, cost-effective bio-fuels will require technology-transforming scientific breakthroughs.
Converting biomass to biofuel
Researchers at the DOE JBEI intend to meet this challenge through the conversion of lignocellulosic biomass into biofuels. Lignocellulose, the most abundant organic material on the planet, is a mix of complex sugars and lignin that gives strength and structure to plant cell walls. By extracting simple fermentable sugars from lignocellulose and producing biofuels from them, the potential of the most energy-efficient and environmentally benign fuel crops can be realized.
Researchers will tackle key scientific problems that currently hinder the cost-effective conversion of lignocellulose into biofuels and other important chemicals. They will also develop the tools and infrastructure to accelerate future biofuel research and production efforts, and help transition new technologies into the commercial sector. The goal of the center is to achieve measurable success within the next five years.
The organization of the center will feature four interdependent science and technology divisions:
In addition to maintaining an Industry Partnership Program, research at the center will be guided by an Industry Advisory Board whose membership will come from key sectors, including feedstocks, enzymes, fuels production, biotechnology, genetics, and chemistry.
Each of the member institutes of the DOE JBEI brings unique capabilities to the partnership. The national laboratory partners operate state-of-the-art scientific instrumentation and research facilities. In addition to the Sandia facilities, other assets include the Molecular Foundry, the Advanced Light Source, and the National Center for Electron Microscopy at Berkeley Lab; and the Center for Accelerator Mass Spectrometry and the MicroArray Center at LLNL.
The other two DOE Bioenergy Research Centers are the DOE BioEnergy Research Center, led by the Oak Ridge National Laboratory in Oak Ridge, Tenn., and the DOE Great Lakes Bioenergy Research Center, led by the University of Wisconsin in Madison, Wisc., in close collaboration with Michigan State University in East Lansing, Mich.
By Mike Janes
Researchers at Sandia/California have emerged as key players in a US Army program that focuses on the design and manufacture of a lightweight, high-caliber, self-propelled cannon system.
The weapon system, known as the Non-Line-of-Sight Cannon (NLOS cannon), is fully automated and can fire at a sustained rate of six rounds per minute. The artillery system, once completed, must be light and agile enough to fit three vehicles comfortably onto a C-17 cargo aircraft.
According to project manager Nipun Bhutani (8774), Sandia’s primary contribution in the program to date has been a critical adjustment to a laser ignition system that serves as the heart of the NLOS cannon vehicle. The cannon is part of Future Combat Systems (FCS), the Army’s premier modernization program.
BAE Systems is developing this system as part of The Boeing Company/SAIC-led FCS program.
The laser ignition system was developed by the Army’s Armament Research, Development, and Engineering Center (ARDEC), in collaboration with Kigre, Inc. The ignition unit is mounted on the back of the cannon’s gun barrel, where a laser beam is fired through an opening mechanism (the breech) to ignite a charge and launch an artillery shell.
However, says Nipun, the recoil force and shock of the projectile (bullet) discharge had caused an increase in observed failures during early prototype testing.
“The laser ignition system offers much better precision, rapid fire, and automation than the mechanical method, and it’s safer,” Nipun says. “But it’s obviously not going to be an effective long-term solution if reliability cannot be maintained.”
Instead of abandoning the laser ignition concept in favor of traditional, mechanical ignition, the Army called in experts at Sandia who deal with shock issues surrounding a wide range of components.
To absorb the force from the discharge, Sandia proposed a new isolation system between the laser and the breech. Vibration isolation systems are widely used to protect sensitive devices from vibrations or shock produced in their environment. Typical examples include isolating delicate laboratory experiments from floor-borne vibrations, or isolating a car body or airplane frame from engine vibrations.
Sandia, in collaboration with BAE Systems and ARDEC, is developing an isolation system for the NLOS cannon that acts much like a filter and results in much lower shock levels.
In addition to working on the isolation system, Sandia researchers have applied the Labs’ modeling and experimental capabilities to hardening the laser igniter.
In an effort to develop the most effective isolation system possible, the Sandia team needed to model the physics and inner workings of the laser system components. This involved modeling the gun loads and other physical dynamics inside the laser ignition system, particularly as it is fired.
“In keeping with Sandia tradition, we developed an entire systems approach to the problem,” says Nipun. That approach included not only analysis and modeling of the isolation system but building a prototype and further researching the system’s performance and reliability. Sandia also did modeling work on the laser and breech. Sandia is supporting BAE Systems’ test efforts.
One of Sandia’s long-term objectives with its NLOS cannon work, says Nipun, is to enhance its reputation for customer service and strengthen alliances with BAE Systems, ARDEC, Benet Laboratories, and others.
“We want to be known among our current and future customers as the ‘go-to’ lab,” says Bhutani.
-- Mike Janes