Valuable Clues from Old Objects in the Solar System
A research collaboration involving Livermore scientists has found that calcium-aluminum-rich inclusions (CAIs), some of the oldest objects in the solar system, formed far from the Sun and later fell back into the midplane of the solar system. Findings from this study may lead to a greater understanding of how our solar system—and possibly thers—have evolved.
CAIs formed some 4.57 billion years ago, millions of years before the planets began to take shape. Because CAIs are enriched with the lightest oxygen isotope relative to planetary materials, they may provide a record of the oxygen composition of the solar nebular gas in areas where they grew. The collaboration, led by researchers at the National Aeronautics and Space Administration’s Johnson Space Center, studied a specific CAI from a sample of the Allende carbonaceous chondrite meteorite, which fell to Earth in 1969 and is an abundant source of CAIs. Using NanoSIMS (a nanometer-scale secondary-ion mass spectrometer), the Livermore team examined the rims surrounding CAIs in the Allende sample and measured the concentration of oxygen isotopes in each inclusion. Results showed that late in a CAI’s evolution, it was in a nebular environment distinct from where it originated. This later environment was similar to the environment in which the building materials for terrestrial planets originated.
These findings imply that CAIs formed from several oxygen reservoirs, likely located in distinct regions of the solar nebula. The research also indicates that the inclusions had contact with nebular gas, either as solid condensates or as molten droplets. The collaboration, which included researchers from the University of California at Berkeley and the University of Chicago, published its results in the March 4, 2011, issue of Science.
Contact: Ian Hutcheon (925) 422-4481 (email@example.com).
A Batteryless Chemical Detector
A research team led by materials scientist Yinmin (Morris) Wang in Livermore’s Physical and Life Sciences Directorate has developed the first generation of detectors using one-dimensional semiconductor nanowires that do not need external batteries. The nanosensor takes advantage of a unique interaction between chemical species and semiconductor nanowire surfaces to stimulate an electrical charge between the two ends of nanowires or between the exposed and unexposed nanowires. The highly sensitive device can quickly distinguish various molecules and chemical species and determine their concentration levels.
Working with colleagues from the University of Shanghai for Science and Technology, the Livermore team ran experiments on two platforms—a zinc oxide and a silicon nanosensor—using an ethanol solvent as a testing agent. In the zinc oxide sensor, the electric voltage between the two nanowire ends changed when a small amount of ethanol was placed on the detector. “The rise of the electric signal is almost instantaneous and decays slowly as the ethanol evaporates,” says Wang. In tests with more than 15 solvents, the team observed different voltages for each type. The silicon nanosensor showed a similar response to the various solvents, although the voltage decay rate differed from that of the zinc oxide sensor.
Because the new detector does not require an external power source, its development could be the first step in making a chemical sensor that is easy to deploy on a battlefield. According to Wang, the team must next test the sensors with more complex molecules such as those from explosives and biological systems. Results from this work appeared in the January 4, 2011, issue of Advanced Materials.
Contact: Yinmin Wang (925) 422-6083 (firstname.lastname@example.org).
Carbon Aerogels Designed for Energy Applications
Laboratory research on advanced carbon aerogels for energy applications was featured in the March 2011 issue of Energy and Environmental Science. Carbon aerogels are a unique class of high-surface-area materials derived by solgel chemistry in which the liquid component of a polymer gel has been replaced with a gas. Because of their high surface area, electrical conductivity, environmental compatibility, and chemical inertness, carbon aerogels are promising materials for many energy-related applications from hydrogen and electrical storage to desalination and catalysis.
In one Livermore project, researchers are developing carbon aerogels that improve the storage capacity of electrical double-layer capacitors. In these devices, charge is stored in the form of ions that accumulate on the aerogel’s surface, creating an intermediate type of capacitor between batteries and electrostatic capacitors. Such capacitors are an ideal complement to batteries when a device has a peak power demand above the base level because they extend battery life.
Carbon aerogels are also important in capacitive deionization, a desalination method in which ions are removed from electrolytes (seawater or brackish water flowing between electrode pairs) to create a clean water source. Livermore researchers first used carbon aerogels in a capacitive deionization system in the 1990s. Since then, they have found that by adjusting the pore-size distribution in carbon aerogels, they can reduce ionic transport losses while maintaining a high capacitance and thus improve the system’s energy efficiency.
Another promising energy application for carbon aerogels is their use as electrode materials and catalyst support in proton-exchange membrane fuel cells. The advantage in this application is that an aerogel’s surface area, pore size, and pore volume can be tailored independently. In addition, the three-dimensional morphology of carbon aerogels reduces the electrode’s electric losses, thus improving electrical conductivity for the fuel cell.
Contact: Juergen Biener (925) 422-9081 (email@example.com).
New Research Capability for High Explosives Facility
The Laboratory’s High Explosives Applications Facility (HEAF) has activated a new high-velocity research gun (above right) for shock physics research. Such guns are used to study the behavior of materials under sudden high pressures and temperatures. The new gas gun, which operates in two stages, can launch a projectile to velocities of 8,000 meters per second. (In comparison, a typical rifle bullet travels about 1,000 meters per second.) This speed gives it the ability to generate precise one-dimensional shock waves up to several million atmospheres of pressure.
In a two-stage gas gun, the first stage uses gunpowder and a piston to compress a light drive gas, typically hydrogen, to very high pressures. A rupture disk releases the drive gas into a smaller diameter launch tube holding the experimental projectile. The launch tube guides the projectile to the end of the gun where the target chamber contains a target connected to diagnostic instruments outside the chamber.
One mission of HEAF’s two-stage gun is to prove out experimental methodologies and diagnostics prior to testing actinides at the Joint Actinide Shock Physics Experimental Research (JASPER) Facility at the Nevada National Security Site (formerly known as the Nevada Test Site). An actinide is one of 15 chemical elements in the actinide series of the periodic table. The elements in this series are radioactive and release energy when activated through nuclear reactors and nuclear weapons. Earlier this year, the Stockpile Stewardship Program used the HEAF gas gun to conduct a joint experiment in which Livermore and Los Alamos national laboratories participated in diagnostics development for upcoming experiments at JASPER.
Contact: John J. Scott (925) 422-8720 (firstname.lastname@example.org).