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By Gary Chamberlain, Senior Editor -- Design News, July 7, 1997
Web-thin 'miracle' fiber offers impenetrable protection
A spacecraft traverses the galaxy powered by solar sails thinner than a spider's web. Waterproof bandages inhibit bacteria and stop bleeding on contact, while allowing air through so wounds heal quickly. A soldier walks through an enemy's biological or chemical spray without a care because the clothing he wears automatically decontaminates itself. That's what scientists at the Natick (MA) Research, Development and Engineering Center hope to achieve with a technique called electrospinning. The lab's Heidi Schreuder-Gibson reports that the process involves charging to high voltage a suspended droplet of polymer solution. At a certain voltage, a fine jet of the solution shoots out toward a grounded target, forming a continuous multifilament fiber of polymer. The fiber splays as it reaches the target, dries, and is collected as an interconnected web of small fibers. The technique gives scientists the capacity to lace together a variety of polymers and fibers to produce ultra-thin layers of protection. FAX (508) 233-5390.
Fuel cell runs 9,500 hours nonstop
International Fuel Cells reports that a commercial fuel cell built by its subsidiary, ONSI Corp., has set a world record for continuous use. The fuel cell, an ONSI PC25TM Power Plant installed in a Japanese office building, operated for 9,500 hours before being shut down for scheduled inspections. The previous record, 9,477 hours, also was set by an ONSI fuel cell purchased by Tokyo Gas. The cell uses an electrochemical process to directly convert chemical energy into electricity and hot water. The chemical energy normally comes from hydrogen contained in natural gas, and, for automotive applications, could come from regular gasoline. However, the cells do not burn the gas, so they operate virtually pollution-free. The units owned by Tokyo Gas are part of an ONSI fleet of more than 100 fuel cells in operation around the world. FAX (860) 727-2216.
Hydrogen-fueled bus joins public transit fleet
Trials are under way in Georgia of a hydrogen-fueled bus that emits practically no emissions. The bus is one of the first vehicles to store hydrogen fuel in metal hydrides rather than hydrogen fuel cells. When the hydrides are heated using energy from the bus's generator, they slowly release hydrogen gas. The gas fuels a standard internal combustion engine, which drives an electrical generator that keeps the bus's batteries charged. Burning hydrogen fuel produces water vapor that contains no carbon dioxide and little or no nitrogen oxide. The H2Fuel bus was developed by a coalition that includes the Department of Energy, Augusta-Richmond County Public Transport, the Westinghouse Savannah River Co., and the Georgia Institute of Technology. E-mail charles.stancil@gtri.gatech.edu.
Single crystals move more with high voltage
High voltage causes a family of crystals known as relaxor ferroelectrics to deform 10 times more than any other material currently known, according to a Pennsylvania State University scientist. "No one has seen this large a movement before," says Thomas R. Shrout, a professor of materials at the University's Materials Research Laboratory. Ultrasound equipment, acoustic transducers, devices to position specimens under electron microscopes, and switches commonly employ such piezoelectric materials. Most common are polycrystalline like PZT--lead zirconate titanate. Relaxor ferroelectrics like PZN-PT--lead zirconate niobate lead titanate--however, can be grown as single crystals. Shrout and a post-doctoral researcher were trying to improve the piezoelectric performance of medical ultrasound devices by growing such large single crystals. They found the material deformed 1.7%. A one centimeter crystal elongates to 1.017 centimeters, 10 times more deformation than other materials. With such a material, devices can either use crystals that are 10 times smaller with the same result, or not alter the size of the piezoelectric material and achieve 10 times the effect. E-mail TShrout@alpha.mrl.psu.
Electromagnetic valves increase engine efficiency
Vehicle makers long have sought an electronic way to control engine intake and exhaust valves to meet market demands for greater engine performance and improved fuel economy. Engineers at Southwest Research Institute (SwRI) are testing a novel electromagnetic valve actuator (EVA) system that provides these benefits. The EVA system is one of a series of electromagnetic valves patented by Aura Systems, El Segundo, CA. It is being tested in a two-cylinder, 18-hp Kohler Command utility engine converted by SwRI to operate on natural gas. The system places one actuator at each valve site. Two opposing spring coils are fitted at each site, providing the primary force to open and close the valves, and to reduce power consumption and increase reliability. The spring forces are supplemented by electromagnetic force from the EVA coils. Intake and exhaust valves are independently computer controlled and timed, making it possible to fine-tune the air-fuel and exhaust flows to engine needs in a way "no camshaft can," says SwRI Principal Investigator Daniel Podnar. FAX (210) 522-3547.
Lead-free alloy exhibits high degree of machinability
Reynolds Metals Co. has introduced a patented, lead-free alloy that it claims provides superior levels of machinability compared to conventional alloys. The EZCUT AAX6030 alloy can be machined wet or dry at high rates to produce an excellent surface finish and good welding, brazing, and anodizing characteristics, according to Rodney E. Hanneman, Reynolds' VP of quality assurance and technology. The alloy also provides the corrosion resistance of AA6061 and equal or higher strengths than existing alloys in the same extruded condition without cold finish. "EZCUT AAX6030 can increase machining productivity up to 150% because it forms smaller, finer chips than other 6000-series alloys, and it is equivalent to 2011, the industry standard," Hanneman adds. E-mail rtolbrys@lanmail.rmc.com.
Material replaces multi-layer steel with 'soft' gaskets
DuPont and Frenzelit have unveiled a new material that "will revolutionize automotive gaskets." The material, Frenzelit's Novatec Engineered Graphite combined with DuPont's Kevlar® fiber, offers significant cost and ratio performance benefits over conventional multi-layer steel gaskets, according to Hans van den Hurk, DuPont Europe short fibers sector marketing manager. Multi-layer steel gaskets have been recognized for having good basic features, but require complex, high-cost production processes. Graphite, which offers the strength and ability to remain stable at up to 450C (842F), is an effective alternative that also promises an improved price/performance ratio. However, when used exclusively, graphite suffers from a certain brittleness that makes it delicate to handle and install. With the Frenzelit/DuPont partnership, adding Kevlar resulted in a material that significantly extends the handling and performance range of graphite gaskets, while providing a 100% secure seal, van den Hurk explains. FAX (810) 583-4556.
Metal-detecting molecules may aid water recycling
A biochemical technique being refined at Sandia National Laboratories may soon enable sensors that can, in seconds, detect the equivalent of one contaminant particle among a billion other molecules in waste streams. The technology makes use of molecular bundles called "liposomes" tailored to react with certain metal ions in solution. The Sandia team is looking at ways to entrap these spherical liposomes in porous silica materials--essentially whipped glasses--which may open doors to many practical inventions, including water-purity sensors in microchip factories or molecule-sized metal detectors for environmental cleanup operations. The technique eventually could result in a family of biosensors that would provide at-home detection of viruses. At Sandia, the team developed a way to entrap the elusive liposomes in sol-gels, a class of solid, lightweight, silica-based materials. E-Mail dysasak@sandia.gov.
Ultraviolet technology aimed at combating tuberculosis
New York City will serve as the site for the nation's first collective, multi-city pilot effort to use ultraviolet (UV) technology to help stop the spread of tuberculosis. The initial installation of the TB-bacteria-fighting lamps will take place at a drop-in center for the homeless in mid-town Manhattan. The national TB Coalition Project will conduct the five-year trial to examine the effects of UV germicidal irradiation (UVGI) and ventilation to curb TB in such homeless shelters. Co-sponsors include Saint Vincents Hospital, Con Edison, and the Electric Power Research Institute. New York has an overall TB rate five times the national average, with 75% more carriers than the average among homeless individuals. Combined with proper ventilation, current UVGI technology works by cleansing air of TB bacteria, often spread unwittingly by people with the active disease. UV room disinfection can be accomplished with specially designed, ceiling-mounted fixtures. The study will determine if these units, when placed at least seven feet above the floor surface, provide safe room disinfection via UV (254 nm) wavelengths, with no significant risk to occupants. FAX (415) 855-2731.
Geologists help verify nuclear test ban treaty
President Clinton, leaders of four other superpowers, and 140 other nations have signed the Comprehensive Test Ban Treaty (CTBT), prohibiting the testing of nuclear devices around the globe. But how do you enforce the treaty? Cornell University geologists hope to lend a hand. To assist in the effective monitoring of whether a nuclear bomb has been detonated, the geologists are compiling an interactive Geographic Information System (GIS), a database of global seismological, geologic, geophysical, remote sensing, and geographic information. "The treaty calls for on-site inspection if a country suspects that another country is cheating," says Muawia Barazangi, senior scientist at Cornell's Department of Geological sciences. "You need a database at hand swiftly; you can't wait weeks for a report. Otherwise the evidence may disappear." This digital database is easy to access via the World Wide Web (http://atlas.geo.cornell.edu). FAX (607) 257-6397.
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