Technology Bulletin 5-4-98Technology Bulletin 5-4-98

May 4, 1998

8 Min Read
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May 4, 1998 Design News

Technology Bulletin

Late developments that shape engineering

by Gary Chamberlain, Senior Editor


Mirror surfaces with nary an atom exposed?

How close can one come to perfection? In the case of Melissa Hines, an assistant professor of chemistry at Cornell University, it could be only an atom away. Her goal: a mirror surface above which not even a single atom protrudes. About five years ago, Bell Labs researchers found that by changing the acidity and composition of a chemical solution, they could produce small areas on a silicon chip that were totally flat, even at the atomic level. Surface roughness was equal to only one protruding atom out of every 30,000 surface atoms. Even on the atomic scale, however, such roughness can greatly decrease the performance of a transistor. The problem: such surface perfection is only reproducible on one type of silicon surface, silicon (111). This is a different plane from silicon (100), used for integrated circuits. Hines wants to find chemical solutions that produce perfection on different surfaces. To do this, she needs to know how a basic hydrofluoric acid solution used in her research etches away protruding atoms. To date, the most perfect surface appears through the electron tunneling microscope as a series of steps, with every step only a single atom high. The steps are the result of almost imperceptible errors in cutting a silicon wafer. If perfected, Hines sees the etching technique useful for integrated circuit technology, micromachining of very small parts, and for producing thin films. That feat, says Hines, is about five years away. E-mail [email protected].


Nanopowders, rapid compaction spur new metallurgical processes

Utron Inc. has developed a combustion gas chamber to quickly compress metallic powders into small parts, and eventually mass-produce small and big components based on the process. It's one of many efforts by powder-metallurgy scientists to take talcum, powder-size grains of metals and turn them into pressed parts. Current methods use pressure and heat to slowly press out small batches of parts. Making large parts in this fashion requires long exposure to heat, with possible undesirable molecular changes resulting. With the combustion gas chamber process, Utron hopes to mass-produce parts "on millisecond time scales," according to Dr. Arul Mozhie, Utron senior scientist. The Utron process evolved from pulsed power and high-pressure combustion technologies developed for hypervelocity launch and other defense applications. The process uses high-pressure pulses, produced by the controlled combustion of propellants, to consolidate the tiny copper and steel powders Utron made using a higher momentum flux gas medium. The work was pursued under a contract awarded by the Ballistic Missile Defense Organization. FAX (703) 369-5298.


Chaos harnessed to provide fast, 'private' communications

Researchers at the Georgia Institute of Technology have developed a system that encodes information onto chaos, transmits it, and then decodes the information away from the chaos. Rajarshi Roy, one of the researchers and chair of Georgia Tech's School of Physics, explains how it works. "In an ordinary digital signal, the message can immediately be seen," Roy reports. "But in our system, digital information is encoded in the chaos, so the message would not be obvious to a person who may intercept it." In the experimental system, a stable semiconductor diode laser produces a square wave "message" signal. That signal, amplified by an erbium-doped fiber amplifier (EDFA), is introduced into a chaotic signal produced by an erbium-doped fiber ring laser like that used in today's communications industry. The resulting combined signal, containing a mix of the message and chaotic carrier, moves through an optical fiber to a second EDFA nearly identical to the first. Upon encountering the combined signal, the receiving EDFA begins generating chaotic fluctuations synchronized with those produced by the transmitting laser. The chaotic portion of the signal, measured by a digital oscilloscope, is subtracted from the combined signal and low-pass filter to recover the original "coded" message. E-mail [email protected].


Composite wire increases power transmission capacity

A new, lightweight, high-performance conductor reinforced with an aluminum matrix composite wire developed for overhead power cables should increase transmission capacity, reduce costs, and meet environmental goals. The composite conductor, a joint endeavor of 3M and Electricite de France (EDF), will span three development phases over four years. The composite wire, reinforced with 3M's patented Nextel ceramic fibers, has the potential to provide two to three times the strength-to-weight ratio of comparable steel wire, according to 3M's Warren E. Vollmar. He anticipates the wire will have four times the electrical conductivity and less than half the thermal expansion of its steel counterpart. "These conductors are being developed for use in reconductoring applications to increase ampacity by an anticipated 40 to 100%," Vollmar adds. Both 3M and EDF will fund its own development activities. FAX (612) 736-7149.


Welding process delivers lighter, more compact metal parts

Dana Corp.'s Driveshaft Div. has introduced a magnetic-pulse welding process for joining ferrous and non-ferrous material to form lighter, more compact--and in some cases--previously non-producible driveshaft configurations. "The process results in a metallurgical attachment that outperforms conventional MIG welding and competing mechanical attachment processes," says Jim Duggan, Dana's chief engineer of advanced design. The process creates an intense magnetic field by downloading large amounts of electrical energy into a specifically designed coil over a very short period of time. When an aluminum tube, for example, is subjected to the field, it collapses inward with sufficient force to weld itself onto a stationary component, such as a steel or aluminum shaft. The solid-state weld process requires no heat, with the component orientation controlled by machine tooling. FAX (419) 866-2616.


Simulation predicts shrinkage and warpage in resins

A common problem in molding high-precision plastics involves getting the molds sized so that parts come out in the correct size and shape. C-MOLD, a producer of CAE tools, thinks it has solved the problem, particularly for such unwieldy semi-crystalline materials as nylons or PETs, based on new simulation software it has developed. The "scientific procedure" for capturing the effect of crystallinity on material properties is based on research done by C-MOLD, the Cornell Injection Molding Program (CIMP), and experimental validation performed by the Polymers Department of the GM Research and Development Center. With the simulation, "we can now capture the cooling rate dependence of (shrinkage and warpage) properties by incorporating crystallization kinetics," says Manju Mahishi, project leader. No other simulation software uses fundamental material properties that yield this level of accuracy." E-mail [email protected].


Spray cooler technology bolsters combustion-turbine output

A low-cost technology introduced by the Electric Power Research Institute (EPRI) has substantially increased the output of an Australian combustion-turbine power plant. Using the EPRI technology, air passing through compressors at the Ecogen Jeeralong Power Station in Victoria is sprayed with a fine mist of demineralized water. This cools the inlet temperatures, increasing flow through the combustion turbine. In all, 2,500 fine nozzle sprays per unit are fitted to the turbine inlet air duct. The result: a 10% increase in power output during peak summer demand. Moreover, on hot, dry summer days, when industries and households switch on their air conditioners, the station can be brought to its peak load capacity of 465 MW within a half hour. In another installation in Missouri, the Utilicorp Energy Group estimates a similar system will save the utility more than $3 million through the year 2010. "With EPRI's aid, we identified ways of raising our plant capacity at a fraction of the cost of building a new plant or buying expensive power," notes Mike Jonagon, superintendent of gas turbines at Utilicorp. E-mail [email protected].


Composites processing system stabilizes 'live' chemicals

"In one quantum leap forward, incremental changes of the past in the composites industry are giving way to a total system breakthrough," says Gene Kirila, CEO of Pyramid Operating Systems. Kirila refers to his firm's new VECTM operating system, the VEC 5.5Cell. The "Virtual Engineered" composites system links materials, equipment, process control, human interface, and advanced technology in one program. A key component of the operating system is Floating MoldTM, a patent-pending, closed-mold technique that uses two composite laminate skins in a liquid, air-tight seal of two pressure vessels filled with non-compressible fluid. The system collects and analyzes materials data, then creates complete histograms of the resin environment during the composite-producing process. Control parameters include: temperature, viscosity, flow rate, mass density, gel times, and peak exotherms on a real-time basis. Visit www.pyracomp.com.


'Moses' lends a big voice to little machines

Sandia National Laboratories' tiny micromachines now have a spokesman who's bigger than life. Charlton Heston provides onscreen and voice-over narration for a promotional video about micromachine and integrated microelectronics R&D performed at the lab. (Also, see Design News, 3/2/98, p. 126.) On the video, Heston taps into a half-century's worth of

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