RESEARCH NOTES
New class of polymeric membranes could expand gas separation uses through improved thermal and
High temperatures? Harsh chemical environments? No matter. They don't present a problem for a new type of polymeric gas separation membrane.
Photo by Stanley Leary
A new class of polymeric membranes could expand gas separation uses
through improved thermal and chemical resistance.
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Its use could potentially allow recovery of large volumes of hydrogen gas now discarded in petrochemical processing. And that recovery would reduce the environmental impact of refining processes.
Researchers from the Georgia Institute of Technology created the gas separation membrane by blending polyimide materials containing cross-linkable diacetylene groups. A solid-state cross-linking reaction initiated after formation of the membranes accounts for its improved thermal and chemical resistance, researchers say.
They believe the reaction occurs in the more ordered regions of the blend; therefore, it does not significantly increase sample density. Thus, the researchers were able to improve the membrane's mechanical properties and chemical and thermal resistance without reducing the material's gas transport and separation abilities.
"We have jumped a very large hurdle in having a material that is chemically and thermally resistant while retaining very attractive gas transport properties," says Dr. Mary E. Rezac, assistant professor in Georgia Tech's School of Chemical Engineering. "There could be a very large commercial market, but there are a number of technical hurdles still ahead of us."
The research is sponsored by the U.S. Environmental Protection Agency, the National Science Foundation and Georgia Tech. Rezac's collaborators on the project are Dr. Haskell W. Beckham, Birgit Bayer, E. Todd Sorensen and Njeri Karangu.
Rezac believes the new membranes could make the recovery of hydrogen from petrochemical processes economically feasible. The temperature of refinery gas streams — containing hydrogen, propane, methane and other hydrocarbons — exceeds the thermal operating range of current membranes. Cooling those gas streams can cost more than the recovered materials would be worth.
If the new system can operate at high temperatures unaffected by gas stream contaminants, the industry could recover hydrogen the U.S. Department of Energy has estimated would be worth several hundred million dollars a year.
"If we can achieve these types of separations, we can reduce operating energy, waste production, and the pollutants going into the atmosphere," Rezac notes. "The dollar value of the hydrogen is significant, but there are external issues in terms of recycling and pollution control that are just as important."
Beckham believes there may be other applications for such materials that can undergo crosslinking without shrinkage, he says. Dental fillings and high-strength composites are two applications that would benefit from such properties.
— John Toon
For more information, you may contact Dr. Mary Rezac, School of
Chemical Engineering, Georgia Institute of Technology, Atlanta, GA
30332-0100. (Telephone: 404-894-1255)
Ultimate Customers
New GTRI director of Research Operations focuses
Maj. Gen. George B. Harrison (USAF Ret.) has spent 5,800 hours in the pilot's seat of 68 different aircraft types, from gliders and Piper Cubs to F-16 fighters and B-1B bombers. So when the new director of Research Operations talks about "customers" for the Georgia Tech Research Institute's work, his meaning is very specific.
Gen. George Harrison
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"My real focus is on the ultimate customer, the person who has to use the equipment we help develop," he says. "Modeling and simulation to support the decision-makers is very interesting, but modeling and simulation so that the individual soldier, aviator or sailor knows how much to depend on the equipment is far more important to me. I care a lot about the lieutenants and privates, the people whose lives depend on what we do in GTRI."
During a 35-year career in the U.S. Air Force, Harrison served in a wide range of capacities. As commander of the Air Force Operational Test and Evaluation Center at Kirtland Air Force Base in New Mexico, he directed the evaluation of major Air Force systems, including the C-17, F-22, and Joint STARS.
He also commanded the Air Force Air Warfare Center at Fort Walton Beach, Florida, and was deputy chief of staff for operations with the U.S. Air Forces in Europe. His background also includes two years as commander of the Air Force Center for Studies and Analysis at The Pentagon, and 260 Vietnam combat missions.
His service to GTRI began in July 1997, when he was chosen to lead the Electronic Systems Laboratory, one of nine GTRI research units. On Dec. 19, GTRI Director Edward K. Reedy chose Harrison to fill the Research Operations position. In that capacity, he is responsible for operation of all GTRI research laboratories.
With this unique background, Harrison has had an opportunity to view GTRI's work from both sides of the production cycle.
"I've spent a lot of time actually using the equipment that GTRI either produces or supports," he explains. "I am here because my field experience has convinced me that GTRI and Georgia Tech are committed to excellence and quality."
Harrison believes GTRI has a bright future. He feels the organization's primary challenge is to broaden its sponsor base while continuing to meet the needs of its long-time customers in the Department of Defense.
— John Toon
Letting the Flip-Chips Fall as They May
New technique reduces cost of
Researchers in Georgia Tech's Packaging Research Center have developed a novel, no-flow underfill material and process that eliminates long underfilling and curing process times. The innovations significantly reduce flip-chip manufacturing cost and provide for throughputs compatible with surface mount assembly.
Led by Dr. Daniel F. Baldwin, an assistant professor in the Woodruff School of Mechanical Engineering, and Dr. C.P. Wong, a professor in the School of Materials Science and Engineering, the research team created this new, no-flow assembly process and material. Wong's group has filed two U.S. patents for the materials' invention.
"The process and material contain a self-fluxing agent and a latent catalyst that eliminates the flip-chip fluxing, cleaning, and long underfilling and curing times," Wong says. "It simultaneously reflows and cures the solder joints and underfill using a conventional surface mount reflow furnace."
Conventional underfill flow lasts from 15 seconds to 30 minutes, Baldwin says, depending on the material, die size and temperature. Curing commercially available underfill materials takes one to two hours and involves several time-consuming cleaning steps before underfill application.
In contrast, the no-flow underfills flow simultaneously with chip placement, typically 0.5 to 5 seconds, and the cycle times during cure and reflow last 3 to 5 minutes. Also, this process allows for interconnect testing and flip-chip repair, before the high value-added solder reflow joining process.
"Our analysis of the cost and processing times indicates a two- to six-fold reduction in assembly cost and at least a 50 percent reduction in processing cycle time over conventional flip-chip processing," Baldwin said. "Once the no-flow underfill has been printed onto the organic substrate, and the flip-chip is placed piercing the underfill, the assembly is reflowed, forming the solder interconnects and curing. No further post-curing of the underfill is required."
— Jackie Nemeth
Microrelay Breakthroughs
New type of magnetically actuated microrelay
offers
A new type of magnetically actuated microrelay could have applications in automobile electronics, test equipment and other areas where low actuation voltages are required.
photo by Stanley Leary
New type of magnetically-actuated microrelay could have applicatons in
automobile electronics, test equipment and other areas requiring
low actuation voltages.
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The devices, which are smaller than a dime, have set records for their low contact resistance and ability to switch large current loads. Developed by researchers at the Georgia Institute of Technology, the microrelays can be integrated with circuit boards because their fabrication techniques are compatible with standard microelectronic processing. The design allows similar configurations to be used for both normally-on and normally-off relays, as well as for multi-pole relays.
"The significant issue in using a magnetically-actuated relay is that you can achieve larger forces and a greater air gap between contacts when compared to electrostatic relays," says William P. Taylor, a former researcher in Georgia Tech's School of Electrical and Computer Engineering. "The larger gap holds off a higher voltage, which allows you to switch higher voltage signals than would be permitted with other types of microrelays."
Competing microrelay technologies use electrostatic forces that require higher actuation voltages than magnetic relays, though they operate with lower currents. The magnetic and electrostatic approaches offer advantages that depend on the specific application, Taylor notes.
The Georgia Tech microrelays operate at less than five volts, which would allow them to be driven by digital logic circuits and used as part of equipment for which higher voltages could be undesirable. Their contact resistance of less than 100 milliohms and ability to switch currents of up to 1.2 amperes set a new record for microrelays, Taylor says.
For more information, you may contact Dr. Mark G. Allen, School of
Electrical and Computer Engineering. Georgia Institute of Technology,
Atlanta, Ga., 30332-0269. (Telephone: 404-894-9419)
Georgia Tech electrical engineer receives prestigious
Dr. Steven W. McLaughlin, assistant professor in the School of Electrical and Computer Engineering (ECE) at the Georgia Institute of Technology, received a $500,000 Presidential Early Career Award for Scientists and Engineers (PECASE) during a White House ceremony last November.
photo by Stanley Leary
Research by Georgia Tech scientist Steven McLaughlin has led to increases in the storage capacity of CDs — 50 gigabytes on a disk.
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The PECASE awards were presented to 60 young researchers from a variety of disciplines. The awards are the highest honor bestowed by the U.S. government on outstanding scientists and engineers who are beginning their careers.
"I am extremely surprised and honored to receive this award," says McLaughlin, who joined Tech's faculty in 1996 after spending four years at the Rochester Institute of Technology in Rochester, N.Y. "While the award appears to single out individual accomplishments, it is really a tribute to the support I have received from the School of ECE and Georgia Tech."
A member of ECE's telecommunications faculty, McLaughlin will use his $500,000 award over a five-year period to support his research in optical recording systems, similar to compact discs (CDs) and digital video discs (DVDs). Optical recording systems are capable of storing information in high-capacity, non-binary formats.
"The storage capacity of CDs (about 680 megabytes on a 4.5-inch disc) makes their useful lifespan about 15 years. DVDs just coming into today's market have sufficient capacity (up to 17 gigabytes on a 4.5-inch disc) to be useful for an additional 15 years. Beyond that, new approaches are beginning to be proposed. Both CD and DVD systems currently store about 1 to 1.5 bits in every 'pit' stored on the surface of the disc," McLaughlin says. "We are developing techniques that increase the storage density to between 3 to 5 bits per pit, resulting in an overall storage capacity of over 50 gigabytes on the same size disc. As a result, discs will be able to hold much more audio and video information."
He describes his research as reasonably high risk, because his ideas and technologies go against conventional wisdom. But they are of great interest to optical recording companies. Recently, the National Institute of Standards and Technology funded a $10 million project in which McLaughlin will collaborate with the University of Arizona, Calimetrics Inc., Energy Conversion Devices Inc. and Polaroid Corporation. The partners will develop high-capacity optical storage media and high-speed data transfer systems for desktop digital media systems or even low-cost portable devices.
— Jackie Nemeth
A Case for Microwave Packaging
Research provides inexpensive way to maintain
As consumer electronics continue to use higher and higher operating frequencies for personal communications, low-cost microwave packages are becoming a major concern.
Traditional microwave packages, well-suited for high-performance and low-volume applications, are expensive and often not well-suited for mass production. Plastic surface mount packages are adequate for components operating below 5 GHz, but they do not meet the performance needs of microwave/millimeter-wave applications.
To meet the consumer electronic needs of the near future, Dr. Joy Laskar, assistant professor in Georgia Tech's School of Electrical and Computer Engineering, and his wireless electronics team have designed a low-cost microwave package. They have leveraged current plastic package technologies, but modified the physical footprint. Researchers engineered this low-cost, shielded vertical interconnect package (VIP) in collaboration with Hewlett-Packard Company to maintain radio- frequency signal integrity.
"The surface mount package footprint has been redesigned to provide near waveguide-like properties with the potential for operation to millimeter wave frequencies," Laskar says. "The initial VIP prototype has been designed, fabricated and characterized, and represents a significant breakthrough for low-cost microwave packaging."
His team has measured a 10-decibel improvement in return loss with a non- optimized design, resulting in improved signal-to-noise ratios.
— Jackie Nemeth
Cough, Choke, Wheeezzzzeee
U.S. air unhealthy under new pollution standard,
A day in the country may not be as healthy as you think, according to a Georgia Tech study analyzing the impact of an air pollution standard proposed by the U.S. Environmental Protection Agency (EPA).
U.S. EPA data shows acceptable sites in black for current ozone standards (top) and for proposed standards (bottom).
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The proposal sets a standard for ground-level ozone, a pollutant associated with photochemical smog. The new standard could cause large portions of the rural eastern United States to be cited as ozone non-attainment areas, according to the study, led by Dr. William L. Chameides, a Regents professor in the School of Earth and Atmospheric Sciences.
The journal Science published the results of the study last year. Chameides collaborated on the research with Dr. Rick D. Saylor of Georgia Tech and Dr. Ellis B. Cowling at North Carolina State University.
If enacted, the new standard will require a major change in the nation's air pollution control strategies, which until now have largely focused on urban pollution, Chameides said.
Ground-level ozone is produced from chemical reactions in the atmosphere fueled by air pollutants such as hydrocarbons and nitrogen oxides. The federal Clean Air Act empowers the EPA to establish a National Ambient Air Quality Standard (NAAQS) for ozone to protect human health. In response to new medical data indicating adverse health effects at lower ozone concentrations, the EPA has proposed a new NAAQS.
Analysis of ozone levels measured at rural locations in the eastern half of the United States indicates that nearly half the sites would not meet the new ozone standard.
"This implies that the harmful effects of air pollution may be a lot more ubiquitous in the United States than previously thought," Chameides says. "Non-attainment of the current standard is mostly limited to urban areas, and thus most people's perception is that air pollution is an urban problem. But if EPA's new standard better reflects the health effects of ozone pollution, it suggests that you could probably go just about anywhere in the eastern United States during the summer and encounter unhealthy air."
— John Toon
Researchers Honored
Phillips, Bayor, Hertel, Scranton and Cowan are
honored by awards
Dr. Michael Phillips, a faculty research associate in the College of Engineering, was appointed director of the Electronic Data Application Division for SOLE — The International Society of Logistics. As director, Phillips will work to achieve the Society's goal of fostering the professional development of its members.
Dr. Ronald H. Bayor, who co-edited the book "The New York Irish," received the James S. Donnelly Sr. Prize for the best book in history and social sciences. The American Conference for Irish Studies presented the award. Bayor is a professor of history in the Georgia Tech History, Technology and Society Department.
Dr. Nolan Hertel, a professor in the George W. Woodruff School of Mechanical Engineering, was a co-winner of the 1997 Protection and Shielding Best Paper Award at the 1997 American Nuclear Society winter meeting. Hertel and his co-authors (Drs. Dominic Napolitano, Nick Romano, and Y. J. Yu) won the award for their paper titled "Shielding Analysis of the NAC-MPC Storage System." Hertel won the same award at the 1996 winter meeting for a paper on which he was co-author.
Dr. Philip Scranton, Kranzberg professor of the history of technology, authored "Endless Novelty: Specialty Production and American Industrialization, 1865-1925," which was released in December 1997 by Princeton University Press. "Endless Novelty" was profiled as a "hot topic" book in the publication Lingua Franca earlier this year. It is expected to alter the ways in which Americans understand the dynamics of industrial growth.
Richard Cowan, program manager of the Multiuniversity Center for Integrated Diagnostics at the School of Mechanical Engineering, is participating in the Congressional Science and Engineering Fellowship Program coordinated by the American Association for the Advancement of Science. The program is a cooperative effort of about 25 national engineering and scientific organizations, each of whom sponsors one or more mid-career professionals for a one-year fellowship in Washington, D. C. Cowan's fellowship, which began in January, is sponsored by the American Society of Mechanical Engineers. Fellows are selected in a national competititon from among outstanding, mid-career scientists and engineers.
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