Surface Damage From Electrons

A scoop of rainbow sherbet floating among mini icebergs? No, the graphic at right is a snapshot of the damage that can be done to a biosensor film when it is exposed to an electron beam.

Electron beams are commonly used to view topography and to chemically analyze samples. Because electrons have much shorter wavelengths than visible light, they produce images of samples with much higher resolution than optical microscopes.

Unlike light microscopes, however, electron microscopes can damage sample surfaces in the process of analyzing them. This is especially true for organic surfaces like those used in biological sensors or diagnostic devices, such as detectors for glucose in blood or E. coli in food.

NIST researchers recently quantified the damage done by an electron beam by combining scanning electron microscopy with secondary ion mass spectrometry, or SIMS. The researchers exposed a biosensor film to an electron beam and then analyzed the film with SIMS. The SIMS instrument scans a beam of ions across the sample, knocking a row of molecules at a time off the surface. The dislodged molecules are collected and analyzed for their molecular weight by a mass spectrometer.

The resulting composite graphic shows that the electron beam removed some atoms from the biosensor film, changing the chemical composition of the surface. The heights of the raised areas in the graphic correspond to the extent of damage to those areas on the film. The NIST SEM/SIMS technique should help to better quantify the percentage of scattered electrons outside the focused area of an electron beam. This will be useful both for better understanding unintentional damage to SEM samples and for the study of electron beams as a way to deliberately etch patterns in microcircuits.

Contact: Greg Gillen, (301) 975-2190.

Spindles Cut Costs As Well as Holes

A wide range of U.S. manufacturing industries could reap substantial savings in equipment and labor costs, introduce flexible manufacturing lines, and cut cycle time using innovative spindles that in early tests appear to break new ground in machine tool performance.

Designed in a project sponsored by the National Center for Manufacturing Sciences Inc., and co-funded by NIST’s Advanced Technology Program, the prototype spindles are smaller, faster, and more flexible than conventional designs and offer new capabilities.

Spindles—the rotating shafts that hold cutters in machine tools—are critical in manufacturing because they strongly influence production rates and parts quality. The size and weight of these new spindles will make possible the construction of smaller, lighter, machine tools, providing an advantage in machine cost while enabling flexible manufacturing. The new spindles wide range of torque speeds supports flexible manufacturing, making possible the machining of a range of advanced materials with a single spindle.

The ATP project united a synergistic team of vehicle and bearing makers, machine tool builders, spindle designers, and lubrication and motor experts that devised solutions that have eluded industry for years.

The team designed and built three spindles, focusing initially on meeting the needs of the auto industry. A four-cluster spindle system may be capable of outperforming a benchmark system used in a General Motors Corp. powertrain plant. The system eliminates the expense of ball-bearing replacements and offers the potential to reduce from two to one the number of machining stations used by the auto industry to cut four cluster holes in the trial part. The new design has the potential to save more than $6 million annually in the production of a single part.

A 35-horsepower prototype spindle offers high torque over a much broader speed range than the current state of the art. Tests on a lightweight 75-hp spindle (see cutaway graphic above) demonstrated its capability to perform accurate boring of cylinders and milling of flat surfaces on a Ford Motor Co. cast iron V-8 engine block at twice the metal removal rate of current processes, a benefit that could extend to dozens more applications in many industries.

Contact: Jack McCabe, (734) 995-4919

Secure E-Commerce

NIST and 16 companies have teamed up under a cooperative R&D agreement to advance the use of “public key infrastructure” in electronic commerce. Public key infrastructure and cryptography can be used to electronically send and receive encrypted messages, including digital “signatures” that ensure the authenticity of electronic transactions.

The effort builds on specifications established by a previous NIST PKI consortium. The consortium seeks to improve interoperability of PKI products and services produced by different companies that support confidentiality. Participating companies include software, telecommunications, computer security, and credit card firms.

Contact: Donna Dodson, (301) 975-2921.

Cubic Molecules Don't Stack Up

Cubic boxes are very useful. They stack nicely and save space. They hold things for transport and protect them. When cubane, the only known cube-shaped molecule, was first synthesized in 1964, scientists hoped it would be the chemical equivalent of the versatile cubic cardboard box. Since then cubane has been touted as a potential super explosive and as a possible delivery mechanism for cancer or AIDS drugs. But it’s been slow going. The molecule is expensive to make and converts readily to a gas when heated.

NIST materials scientists are collaborating with researchers at the University of Chicago to study how cubane molecules stack together to form a solid under different conditions. They’re hoping that detailed insight into the molecule’s behavior will help cubane live up to its potential. Using a combination of X-ray and neutron scattering techniques, the NIST/UC group determined that cubane molecules stack differently at different temperatures. Heated to 121 degrees C in a specially designed furnace, the researchers found that the cube-shaped molecules do not stack on top of one another at neat 90 degree angles. Instead the molecules are rotated in space with respect to adjacent molecules just enough to flatten the stack into a rhomboid shape. This unexpected result may affect how chemists design steps for processing cubane.

The group is the first to describe cubane’s structure in its high-temperature solid phase—a more energetic state that solid cubane passes through before becoming a gas. Previous attempts had failed because the molecule vaporizes so readily. NIST researchers solved the problem by mixing the solid cubane with pure amorphous carbon. The amorphous carbon slows the vaporization of the cubane and because it has no crystal structure, it doesn’t interfere with X-ray and neutron scattering data.

The graphic above shows a model of a cubane molecule superimposed on a chart based on calculations that predict cubane’s preferred stacking geometries at different temperatures. The group’s experimental confirmed these modeling predictions.

Contact: Dan Neumann, (301) 975-5252.

FQA Act Extension

The implementation date for the Fastener Quality Act of 1990—scheduled for July 26, 1998—has been extended because NIST projects that there will not be enough laboratories accredited in time to perform the volume of inspection and testing required by the act. A Federal Register notice detailing the extension was published on June 30, 1998.

NIST is extending the FQA implementation date to Oct. 25, 1998, to allow most of the remainder of the nearly 580 laboratories who have applied for accreditation to complete the process. Approximately 250 laboratories have been accredited to date.

Contact: Subhas Malghan, (301) 975-5120 or visit www.nist.gov/fqa.

Super Insulation Keeps Its Cool

If you could fit your whole house into an vacuum-insulated ice chest, you could count on lower air conditioning bills in the summer and lower heating costs in the winter.
A new kind of advanced insulation panel that has been under development for the last several years soon may provide ice-chest-like insulation to a wide range of products. The idea has applications for buildings, refrigerated trucks, home refrigerators, vending machines, shipping packages, and other products.

To help manufacturers determine the R-value or resistance to heat flow of these new panels, NIST researchers have developed an advanced insulation laboratory. The calorimeter within this laboratory is unique in that it is capable of measuring the heat conducted both through the panel and around its edges. Traditional heat flow measuring devices only take into account heat flow through the panel.

Through a cooperative research and development agreement, NIST researchers recently completed R-value measurements on a new vacuum insulation panel that utilizes a novel fill material developed by Dow Chemical. They found that the new panels had an R-value approximately six times greater than traditional glass-fiber insulation. This means that the new panels conduct heat at one-sixth the rate of glass-fiber, a significant improvement likely to lead to substantial energy savings for a variety of applications.

The new product consists of a patented, open cell foam material that is vacuum sealed within a metallized film or foil. A 2.5 cm (one-inch) thick advanced insulation panel can produce the same R value as 15 cm (6 inches) of glass-fiber insulation.

To date, these measurements represent the highest resistance to heat flow of any advanced insulation panel measured at NIST. For applications where space is at a premium, like refrigerators, the thinner advanced panels would allow greater interior space without sacrificing energy efficiency.

The U.S. Environmental Protection Agency estimates that $1 billion in annual energy savings would be realized if advanced insulation materials were incorporated into all major refrigerators and freezers.

Contact: Hunter Fanney, (301) 975-5864 or Pete Pendergast, (517) 636-7264.

No More Yucky Chemical Build Up

Semiconductor manufacturers are a fastidious bunch. They have to be. Even micrometer-sized contaminants can ruin a microcircuit. The vacuum chambers where microcircuits are made must be cleaned thoroughly at regular intervals. Molecules from gases used in these chambers gradually build up on the inside walls and on electrodes at the top and bottom of the chamber.

To remove this build up, chip makers use an ionized fluorocarbon gas called a plasma. Reactive molecules in the cleaning gas combine with silicon-containing deposits on the chamber surfaces and carry them out of the chamber.

NIST researchers recently used a sheet of ultraviolet laser light to track the concentration of the reactive fluorocarbon molecules during the cleaning process. At low pressures higher concentrations of the reactive gas were found closer to the walls of the chamber (See graphics at far left below). At higher pressures it was concentrated nearer the electrodes (See graphics at right).

The researchers plan to correlate their findings with simpler plasma monitoring systems used in industry to help manufacturers improve the efficiency of their operations and hopefully reduce their use of fluorocarbon gases that contribute to global warming.

Contact: Mark Sobolewski, (301) 975-2980.

Slicing Year 2000 Problems Down to Size

When looking for a handful of needles in a haystack it helps to know where not to look. That’s the idea behind a set of NIST-developed algorithms that have been incorporated into a commercial software product made by Blair & Associates Inc. of Hanover, Md. The new product, called the BAI Slicer, is designed to help computer programmers find “Year 2000” problems in programs written in the C language. Programs written in C—like those for controlling an automatic teller machine or a piece of manufacturing equipment—can contain tens of thousands to hundreds of thousands of lines of computer instructions. The NIST algorithm can be used to figure out which of these many lines of instructions are not related directly or indirectly to a specific function like the current date. In practice, this allows programmers to safely ignore up to 90 percent of a computer program and concentrate on the 10 percent that may need changing to conform to four-digit year dates after the year 2000. Contact: James Lyle, (301) 975-3270.

Tiny Bubbles May Be Key to Future Electronics

Microscopic glass bubbles filled with air, nature’s ideal insulator, may be the key to the ultrafast integrated circuits of tomorrow. A novel type of insulator called “xerogel” was incorporated recently into an integrated circuit for the first time as part of a project co-funded by NIST’s Advanced Technology Program. Following up on their ATP work, researchers at Texas Instruments and NanoPore Inc., a small New Mexico company, combined a specific xerogel formula with a new technique for replacing conventional aluminum wires in integrated circuits with copper, a better conductor. The result: a new microchip manufacturing technology that could mean a 10-fold increase in microprocessor speed and vastly more powerful computers, cellular telephones, factory control systems, and other products. The new technology demonstrates a practical solution to a critical microelectronics problem: how to pack more circuits into smaller spaces without producing “cross talk,” the jumping of signals between unconnected wires. According to TI, xerogel is so effective that it could insulate a future computer chip with a mile of wire crammed into a space the size of a fingernail. Contact: Robert Havemann, (972) 995-0271.

Company Rockets to Success with Center's Help

Turns out to make a great wheelchair, you do need to be a rocket scientist. Tom Kruse, founder and chief executive officer of Hoveround Corp., Sarasota, Fla., wanted to add a quicker, stronger, snugger wheelchair to his product line. Kruse asked the Suncoast Manufacturing Technology Center, an affiliate of the NIST Manufacturing Extension Partnership, for design and engineering help. Working with experts from the Suncoast center, NASA, and the Southern Technology Applications Center, Hoveround improved its computer-aided-design capabilities and developed a more durable, more comfortable, and more affordable wheelchair. In just one year, revenues at Hoveround rocketed from $15 million to $25 million. To meet the growing demand, Hoveround moved from a 743-square-meter (8,000-square-foot) facility to one more than five times as large and increased its workforce from 25 employees in 1995 to its current level of 180. To find the MEP center nearest them, small and mid-size companies should check the MEP web site at www.mep.nist.gov or call (800) MEP-4MFG.

Learning to Fake Photosynthesis

Plants do it all the time. They convert light to chemical energy and make organic compounds with inorganic carbon dioxide and water in the process called photosynthesis. But for chemists the task of converting carbon dioxide into something useful has been much more challenging. Now researchers at NIST, Brookhaven National Laboratory, and Howard University have successfully mastered a tricky chemical step in the photosynthesis process. Using a class of catalysts containing iron and cobalt that are similar in structure to those in plants, the group converted carbon dioxide molecules into other molecules, including organic materials. The accomplishment is a preliminary step toward technologies that would remove carbon dioxide from the Earth’s atmosphere with the help of solar energy and transform it into organic compounds, perhaps even fuels. Ultimately, by mastering fake photosynthesis, researchers may be able to reduce levels of atmospheric carbon dioxide, slow global warming, and make useful organic products at the same time. Contact: Pedatsur Neta, ( 301) 975-5635.

Making Better Concrete -- Modern concrete has evolved from years of research and field experience. NIST recently established the Partnership for High-Performance Concrete Technology to foster collaboration among private, government, and academic organizations working in this area. The partnership addresses critical high-performance concrete issues such as processing, performance prediction, characterization of HPC and its constituents, structural performance in fires, overall structural performance, and economics (including life-cycle costing models). Contact: Geoffrey Frohnsdorff, (301) 975-6706.

Price Scanning -- To help improve the accuracy of price scanning by supermarket, drug, department, and other stores, NIST weights and measures experts recently completed training for officials from 46 states. In two, three-day sessions, NIST staff members trained state weights and measures inspectors in procedures for determining the accuracy of price scanners. The training was conducted with the assistance of the Federal Trade Commission. Consumers across the county should benefit by seeing fewer overcharges at checkout, while retail businesses will lose less revenue due to undercharging. Contact: Gil Ugiansky, (301) 975-4005.

Crystal Structures -- A new agreement between NIST and two German scientific organizations, Fachinformationszentrum Karlsruhe and the Max-Planck Gesellschaft, aims to update the widely used Inorganic Crystal Structure Database. Scientists long have used the database and its collection of more than 40,000 inorganic compounds. Under the agreement, the three organizations will evaluate current and new structural data for inclusion in the database and will work to incorporate the latest in PC and web-based information technologies to make the database more versatile and easier to use. Contact: John Rumble, (301) 975-2200.

About Technology at a Glance:

NIST is an agency of the U.S. Department of Commerce's Technology Administration. NIST promotes U.S. economic growth by working with industry to develop and apply technology, measurements, and standards. Technology at a Glance is produced by Public and Business Affairs, A903 Administration Bldg., NIST, Gaithersburg, Md. 20899-0001. Any mention of commercial products is for information only; it does not imply recommendation or endorsement by NIST. Technology at a Glance Editor: Gail Porter, (301) 975-3392, email: gail.porter@nist.gov. For patent information, call (301) 975-3084.

Technology at a Glance Archive Files