Technology Bulletin

Sounding off on fastener cracks

A new inspection device developed at the Department of Energy's Pacific Northwest National Laboratory detects cracks in bolts more easily and less expensively than alternatives. The device relies on ultrasonic electronics to retrieve more accurate readings by limiting background noise. Also, the device allows fasteners to be inspected while in place, thereby reducing inspection time and allowing periodic monitoring. Inspectors have greater opportunity to interpret the data and make repair decisions with a complementary computer tool that gives a visual representation of the fastener and any fractures or degradation.

Mobile radar is 'active' worldwide

The proliferation of international military air threats is expected to dominate demand for mobile radar in the next several years, according to a report issued by Frost & Sullivan entitled World Markets for Military and Commercial Land-Based Surveillance Radar. The report says that NATO, spurred on by realization of problems surrounding commonality of existing radar networks, represents the highest near-term market growth for manufacturers. Several eastern-European nations-Poland, Turkey, Greece, the Czech Republic, and Hungary-are involved in air defense radar procurements. At the forefront of manufacturer development efforts is active array radar, which exhibits both the operating efficiency and the necessary performance capabilities for coping with multiple threats. "In an active-array radar antenna, the beam transmitting and receiving elements operate from small modules present on the antenna itself, rather than down in an antenna support structure such as a building," says Katrina Herrick, author of the report and a Frost & Sullivan consultant for the company's Defense Aerospace Group. "These modules allow an alternative to the beam-phase shifting method present in phased-array antennas, which means that each radiating element operates independently, allowing increased flexibility in beam forming as well as improved response time. Active-array technology is particularly well suited to the growing market for highly mobile military radar," she says. Mobility allows for less dependence on static air-defense radar installations that have proven their vulnerability in intense conflicts during recent years. Fax: (210) 348-1003.

Silicon + gold = future of electronics?

"They have no idea how they are going to be making the next generation of electronic devices ten years from now. That's what we are working on," says Brian Korgel, a University of Texas College of Engineering researcher. Korgel believes that the electronics industry is reaching the limits of miniaturization. "In five to ten years, the way we make computer chips will hit the end of the miniaturization road," he says. Korgel and his colleague Steve Johnston believe they are defining the future of electronics. The two researchers produced "nanowires" using gold and silicon heated to 500C under 5,000-psi pressure. "Our components are only four nanometers long," says Korgel. The researchers produce their nanowires by heating silicon atoms in the presence of gold. "The silicon atoms congregate together or dissolve in the gold. As the silicon dissolves inside the gold and the concentration of silicon becomes great enough, the gold "ejects" the silicon in the form of a wire. The properties of the nanowires are affected by quantum rules that apply only in the nanoworld, according to Korgel. "When we make things this small, silicon no longer behaves like silicon," he says. For example, silicon normally does not emit light, but in the nanoworld, silicon can emit light. It can be used in the construction of extremely high-resolution light-emitting devices for computer monitors and television screens. Researchers are testing what happens when the nanowires form live circuits. "We are now trying to make a transistor using these nanowires as a conduit for electrons," he says. In addition to computer monitors and television screens, both optoelectronic devices and sensors may also use nanowires. The National Science Foundation and the US Department of Energy fund the research. Call (512) 471-7272.

Metals benefit from plastic process

A team of researchers at Pacific Northwest National Lab (PNNL), Washington State University, and Boeing is developing a new "superplastic forming" (SPL) process suitable for making complex structures from aluminum, stainless steel, titanium, and other metals for automotive and other applications. SPL uses laser welding for joining multiple-layer sheet components in a single-step process that produces stiffened structures and reduces part and fastener counts. After welding sheets in a predetermined pattern, a given structure is heated in a forming die where pressurized gas is introduced between the layers. The internal sheets form stiffening members between the outer sheets. Laser welding patterns deter- mine the structure's geometry, which can include truss core, sinusoidal, egg-grate, and other patterns. "Low forming pressures and single-step processing significantly reduce tooling costs compared to conventional methods," says PNNL's Staci Maloof. She also says that the technology is practical for high-volume manufacturing. Contact PNNL at (888) 375-7665.

Scientist shakes up 'particle packing' notions

The performance characteristics of a material depend on how the particles from which it is made stack up. How particles stack is important because it defines how molecules order themselves in all types of materials. The question scientists have never been able to fully answer is how spheres, whether they are oranges or molecules, stack up when randomly poured into a vessel or container. "The trouble is that no one has ever really defined exactly what is meant by randomness," says Sal Torquato, a chemistry and materials science professor at Princeton. The long-standing belief is that, given enough shaking and stirring, particles will settle to maximum density, a state known as "random close packing." Particles in this state have a density of about 64%. "But 64% is not at all universal," he says. "Sometimes you might get 66 or 68%. Other times you might get 58%." Torquato argues that the concept of "random close packing" is flawed. The best packing strategies yield a density of up to 74%. Using a combination of computer simulations and observations with professor Pablo Debenedetti and graduate student Tom Truskett, Torquato demonstrated that the density of a randomly packed structure depends on how the particles are shaken and stirred. Marbles, for example, may fit perfectly in a container if poured one way, but may not fit if poured another way. According to Torquato, this observation negates the idea that there is a fixed concept called random close packing. "One day I just said, ok, what's wrong here. Then, it hit me. Random close packing is an oxymoron," he says. "The idea of randomness conflicts with the idea of close packing, which implies the most ordered structure," according to the professor. He proposes a new concept called "maximally random jammed state." The idea is to look for the most random particle arrangements so tightly packed that none of the particles can move. Although additional work is required, Torquato believes this new approach is important for the design of new materials. "Understanding the nature of disorder in material microstructures is one of the holy grails because of the intimate connection between the microstructure and the bulk physical properties of materials." Contact Torquato at (609) 258-3341 or via e-mail at torquato@princeton.edu .

Quantum leap for computing

Christopher Monroe, a staff physicist at the National Institute of Standards and Technology (NIST), says that the world may be one step closer to development of a quantum computer. A quantum computer is a device with computing capabilities defined by the laws of quantum physics that would far surpass any conventional computer in power and efficiency when applied to certain problems. "They are only useful for particular tasks," explains Monroe. "The most important problem quantum computing seems to be good for is number factoring and subsequent code breaking. To factor a 200-digit number, we need perhaps a 10,000 quantum-bit memory and we'd have to carry out maybe a billion operations. We have done only several operations on just four quantum bits," he says. Researchers at NIST recently made the first observation of quantum entanglement-an experiment considered an essential step toward the development of a quantum computer. The researchers confined four singly ionized beryllium atoms, spaced along a line, in an electromagnetic trap. Lasers cooled the atoms to near absolute zero. The atoms were then forced into the same spin state. Next, laser light entangled the atoms, creating a superposition of all four atoms. "Our technique is scalable to a lot more atoms. If we get to that level, we may have a quantum computer," says Monroe. Although the quantum computer is years away, he notes that big companies are paying attention. "Presently, the big guns like Microsoft, HP, and Intel have people working in this area, but I believe they are just passively following what's going on," says Monroe. FAX: (303) 497-7375.