iamonds--not the kind that are a girl's best friend, but their industrial-grade cousins--are the materials of choice for durable coatings on the wear surfaces of both high-tech equipment, such as chemical reactors, and more conventional tools, like drills, grinding wheels, and saws. Besides being the hardest known coating material, diamond can also be used to produce semiconductors that are thousands of times more efficient than the standard silicon variety, resulting in electronic components that are faster, more powerful, and more rugged. Diamond is also the most transparent substance in the far infrared end of the spectrum and can be used to coat optical devices, such as windows and lens components on spacecraft, to protect them from abrasive dust and other particles.
The popularity of diamond coatings for a variety of applications has put a premium on finding faster, more efficient diamond-coating processes. One of the most promising developments in this area has been the discovery by Roland Seals and Cressie Holcombe, both of the Oak Ridge Y-12 Plant, and R. Eugene Price, of ORNL's Engineering Technologies Division, of a diamond-coating process that converts glassy carbon to diamond. Using a technique known as plasma spray deposition (PSD), these researchers can deposit thick pure diamond or diamond-boron carbide composite coatings on large, complex-shaped components.
For years, efforts to expand the applications of diamond coatings have been frustrated by the limitations of traditional chemical vapor deposition (CVD) processing, which requires very precise, ultraclean conditions and can be used only to treat relatively small surfaces. On the other hand, PSD coatings are easily applied to almost any surface using a much simpler and more economical process that produces coatings 50 times quicker and 50 times thicker than those produced using CVD. These thicker coatings are much more durable and guard against small pinhole defects that lead to complete coating failures in wear and high-abrasion applications. The simpler PSD process can also be adapted for use in the field, allowing use of diamond coatings in new areas, such as protecting drill bits for oil exploration and extending the lives of cutting blades used in industrial and farm settings.
In applications where a combination of PSD and CVD coatings would be advantageous, a thin CVD coating can be applied over a layer of plasma-spray-deposited diamond, resulting in a thick diamond coating with outer layers identical to those now provided by CVD. For example, CVD coatings are sometimes more transparent than those resulting from PSD and should yield overall better performance in certain uses, such as protective overcoats for optical mirrors. --Jim Pearce
Geomagnetic Device Probes Impacts of Solar Storms
Electric power systems in the Northeast and other U. S. areas are vulnerable to solar geomagnetic storms. ORNL researchers want to find better ways to reliably warn the nation of a solar storm so that electric utilities can protect their systems from sudden power losses and equipment damage.
A team led by Randy Barnes and Eddy Tapp, both of ORNL's Energy Division, has constructed and begun operating a geomagnetic field monitor. Scientists are using data from the ORNL monitor, along with information from the U.S. Geological Survey and Electric Power Research Institute (EPRI), to better understand the effects of solar storms on Earth's magnetic and electric fields.
Solar storms can trigger power blackouts and cause equipment damage, trips of equipment and power lines, and disturbances such as humming transformers. The Northeast and other U.S. and Canadian areas sitting on igneous rock and using long, heavily loaded transmission lines to import power are particularly vulnerable to solar storms. The reason is that the ground's high resistance causes large geomagnetically induced currents to flow in high-voltage transmission lines.
On March 13, 1989, as a result of a solar storm, a major blackout occurred in the Canadian province of Quebec. "A similar storm," Barnes says, "could cause major blackouts in the Northeast, costing between $3 billion and $6 billion in lost output."
During solar storms, Earth's magnetic field moves back and forth like a wave. These fluctuations cause small variations in the magnetic field at ground level, providing important information on solar geomagnetic storms.
"Our monitor will gather comprehensive data on the changes in the magnetic fields over time, thus filling gaps in our fundamental understanding of solar storms," Barnes said. "By comparing our data with information from other sites, we can determine how much fields vary from place to place. This knowledge can be used for developing a reliable method for warning electric utilities that a solar storm is imminent and that they should take precautions."
What precautions? According to "A Weather Eye on the Sun," in the December 8, 1990, issue of The Economist, "The American system relies more on long-distance transmission now than it ever has before--to a large extent because growth in demand for electricity in the Northeast has been met by importing electricity from elsewhere in the country. These long links are the most vulnerable to magnetic effects.
"If a power company got warning that a geomagnetic storm was about to hit, it might choose to rely on expensive local power rather than cheap but much-traveled power for the duration. That would reduce the risk of a gridwide failure."
Located in a field near the Laboratory, ORNL's geomagnetic monitor consists of a partially buried three-axis magnetometer, which indicates the direction and magnitude of Earth's magnetic field, and two 100-meter (328-foot) electric field sensors that measure large fluctuations in electric fields caused by ground currents. A small computer powered by a 1.2-by-3-meter (4-by-10-foot) panel of solar cells logs and temporarily stores six channels of data at the rate of one sample per second on each channel around the clock.
Researchers plan to use the system almost exclusively to monitor future solar storm activity. As the severity of geomagnetic storms peaks about every 11 years, ORNL researchers expect that the United States and Canada will face particularly serious vulnerability problems during the next solar cycle early in the 21st century.
Electric utilities, power equipment manufacturers, EPRI, and the Tennessee Valley Authority also are conducting research on developing measures for protecting systems against the effects of solar geomagnetic storms. Solar storm impacts on electric power systems were first observed in the United States in 1940.
The laboratory's geomagnetic field monitor program is funded by DOE's Office of Energy Management.--Brian Daly and Carolyn Krause
Removing Cesium-137 from Contaminated Soil
Brian Spalding and Gary Jacobs had a problem. They were working on trapping cesium-137 and other radioactive wastes in the soil using a process called in situ vitrification (ISV). This waste treatment regimen basically cooks the contaminated area--soil, contaminants, and all--into a big, glassy lump, trapping the contaminants inside. As the soil is heated, steam and other escaping gases are trapped, analyzed, and treated to remove any potential source of airborne contamination.
That's where the problem cropped up. Spalding and Jacobs, researchers in ORNL's Environmental Sciences Division, found that cooking the soil caused more cesium-137 to be released and trapped in off-gas filters than they expected. This was a bit of a surprise, considering that the near impossibility of getting cesium-137 out of soil was one of the reasons ISV was developed in the first place.
A common by-product of nuclear fission research, cesium-137 can be found in the soil and in stream, lake, and river sediments around several DOE facilities, waste disposal sites, and nuclear power plants. When it is released into the environment, cesium-137 latches onto particles of clay, eventually forming an almost permanent bond.
"A lot of people have developed techniques to take radionuclides out of the soil," says Spalding. "But cesium-137 is probably the toughest to get out of just about any soil. It has always been thought to be nearly impossible. Powerful acids had to be used to destroy half the soil to get the cesium out--that's just not practical for decontaminating large volumes of soil--the volume of contaminated waste produced was greater than the original amount."
While investigating the source of the extra cesium, Spalding and Jacobs began to suspect that as the soil was heated, polyvinylchloride (PVC) piping used to slide radioactive sludge into the ISV test trenches melted, allowing the chloride in the pipes to react with the cesium in the soil. "There's naturally a little bit of chloride in the soil in the form of salt (sodium chloride)," says Spalding, "but not enough to volatilize very much cesium. It turns out that PVC pipes are an excellent source of chloride." Future ISV tests will employ other types of plastic pipe.
Laboratory tests confirmed that what began as an ISV problem was also a potential solution to the difficult task of loosening cesium's tenacious grip on the soil. In fact, when cesium-137-contaminated soil was mixed with chloride and heated to between 800 and 1000 degrees C for at least two hours, 99% or more of the radioisotope was removed.
Of course, this shake-and-bake decontamination process takes a toll on the soil. "It's kind of like crushed brick when we're finished," Spalding admits, "But it's clean, and its alkalinity and high mineral content would probably make it a good fertilizer for other uncontaminated soil."
Despite the technology's remarkable success in decontaminating soil in the laboratory, Spalding and Jacobs have taken the technology about as far as they can and are planning to refocus their efforts on ISV. "We did this research to explain the cesium releases during the ISV process, and we've shown that, as a decontamination process, it has all the desirable features. We hope there's someone out there who wants to develop it and demonstrate that it is a realistic technology in field tests."--Jim Pearce
On-Site Tests for PCB Contamination
A much less expensive test for detecting toxic polychlorinated biphenyls (PCBs) in environmental samples has been developed at ORNL. This simplified "spot test" can be performed at one-tenth the cost of the conventional laboratory method because it provides almost immediate results at the site of the PCB contamination. As a result, sample transport to the laboratory, costly laboratory procedures, and extra work time are eliminated.
The newly developed and patented test uses strips of chemically treated paper that glow if exposed to PCBs and then excited by a certain light. The tests, based on room-temperature phosphorescence (RTP) and enhanced photoluminescence (EPL), were developed by Tuan Vo-Dinh, leader of the Advanced Monitoring Development Group in ORNL's Health Sciences Research Division. Vo-Dinh has developed several applications using RTP, including spot tests for other pollutants. Other researchers involved in the projects included Anjahi Pal, Lorna Ramirez, Wendi Watts, Lisa Ford, and Jean Pierre Alarie.
PCBs were manufactured in the United States from 1929 to 1977 for various uses, including electrical equipment, hydraulic fluids, and lubricants for industrial equipment. Through such products, PCBs entered the environment.
The disposal of PCBs was not regulated until the late 1970s, when studies started to show that these toxic compounds do not degrade readily in the environment and can cause adverse health effects. "PCB contamination is now one of the environment's most pressing global issues," Vo-Dinh says.
In the new test, a sample of material is applied to a paper test strip coated with special chemicals and then ultraviolet (UV) light is shone on it. If PCBs are present in the sample, the PCB molecules on the test strip retain the UV energy, interact with the chemicals, and glow. Such UV analysis has become increasingly popular in recent years. Examples of other spot tests that rely on luminescence and fluorescence include UV-reactive threads woven into currency to provide a means for identifying counterfeit bills or amusement park handstamps that show up only under UV light.
Previous phosphorescence tests relied on frozen samples because ordinary molecular movement in a room-temperature sample would dissipate UV energy and prevent the sample from glowing. Vo-Dinh's RTP and EPL methods use chemicals that stimulate light emission from the test strip, making it glow if PCBs are present.
This development was sponsored by DOE's Office of Environmental Technology Development and Office of Health and Environmental Research and by the Environmental Protection Agency's Environmental Monitoring Systems Laboratory at Las Vegas, Nevada.--Travis Parman
ORNL Physicists Find New Laser-Based Optical Effect
ORNL physicists have discovered a new laser-based optical effect, a phenomenon of light's interaction with matter, that provides an entirely new principle for several uses of laser technology.
The discovery, published in the June 1993 edition of Physical Review Letters, could lead to measurement methods tens to hundreds of times more accurate than those currently used for measuring gas concentrations in mixtures. The effect also could be used in enriching materials with rare isotopes by relatively inexpensive lasers instead of traditional mass spectrometry. Another application could be laser control of certain chemical reactions, creating a "laser-induced catalyst."
"What we have done is reveal new ways in which the characteristic emissions and absorptions of light by atoms and molecules can be greatly modified," says W. Ray Garrett, a senior research scientist in ORNL's Health Sciences Research Division.
Garrett explains that normal emissions occur in characteristic, sharply defined "colors," or spectra, that distinctly identify the chemical species that are present. "Until now, scientists could do little to change these emitted colors, although color shifts have been observed in the stars. But the newly discovered effect can, with proper laser setup, produce big changes in the emissions," he says.
When the laser beam strikes and excites a gas sample in a particular type of excitation mode, a shift in wavelength (change in color) is observed in the reemitted light for the specific chemical being analyzed. The amount of this color change, which is easily measured, provides researchers with an accurate analysis of the sample because it is directly and linearly proportional to the concentration of the gas species being measured and independent of the intensity of the exciting laser.
The phenomenon is free of the normal masking effects of other gases present, revealing the presence and concentration of a given chemical, independent of other components in the sample. "That advantage over existing technology," Garrett says, "could greatly improve accuracy during remote measurement of chemical concentrations in a vapor plume from an exhaust vent, smokestack, or leaky container." Experimental results have been obtained for metal vapors and for noble gases in exact agreement with theoretical predictions.
Garrett says the underlying physics of the discovery at ORNL is "part of the burgeoning field of nonlinear optics," a field that embraces a variety of effects associated with the interaction of high-intensity laser light with matter in all of its forms--gases, liquids, solids, and plasmas.--Brian Daly
ORNL Scientists Win Three R&D 100 Awards
R & D magazine has cited three ORNL inventions among 1993's top 100 new technologies, bringing the total R&D 100 awards for Martin Marietta Energy Systems, Inc., to 82. Oak Ridge is still first among all DOE sites in the total number of R&D 100 awards.
The Energy Systems developers who have received a 1993 R&D 100 Award are Francois G. Pin of ORNL's Engineering Physics and Mathematics Division and Stephen M. Killough of the Robotics and Process Systems Division, for a new means of locomotion for wheeled vehicles; Peter Mazur, a cryobiologist in ORNL's Biology Division, for a new technique for deep-freezing fruit fly embryos for genetic research; and John Googin and Ben Davis, both of the Y-12 Plant, William Huxtable of Energy Systems' Central Engineering Services, and Alicia Compere and Bill Griffith, both of ORNL's Chemical and Analytical Sciences Division, for a new way to degrade chlorine bleach in industrial process streams.
New means of locomotion for wheeled vehicles. So often, an invention's success is a consequence of its elegant simplicity. So it is with the Omnidirectional Holonomic Platform (OHP). This new technology, developed by ORNL's Francois Pin and Stephen Killough, promises big improvements for wheeled devices such as motorized wheelchairs, factory and plant equipment, robots, and even household vacuum cleaners.
Conventional wheeled vehicles can't move in all directions from a given starting position while simultaneously rotating--a capability arising from a property known as holonomy. The OHP can do this. For this reason, some manufacturers say it may displace their existing wheel technology because it is much more efficient and dexterous.
Despite its weighty name, the OHP's basic structure and function are elementary. Its parts are easy to manufacture and assemble, yielding a readily accessible, low-cost item.
"This is not a complicated piece of equipment," says Pin, leader of the Autonomous Robotic Systems Group in ORNL's Engineering Physics and Mathematics Division. "That's what is so beautiful about it and what makes it so widely applicable."
For devices such as motorized wheelchairs, the virtue of holonomic motion will offer unprecedented mobility. Starts and stops for changing direction will be eliminated, and getting into tight quarters will be easier. Similarly, on the factory floor, transport vehicles such as forklifts and wheeled carts stand to gain exceptional dexterity, saving both time and trouble.
The platform is a disk approximately a meter (3 feet) in diameter that sits on a Y-shaped rolling system. Unique wheel assemblies and their individual motors make up the three arms of the "Y." The wheels have very little hub area with an almost completely spherical rolling surface. In appearance, they resemble croquet balls that have had an inch sliced off each side. Each arm of the Y-shaped rolling system has a set of two wheels that are either side-by-side (perpendicular to the arm) or end-to-end (in line with the arm) and at 90-degree angles to one another. This clever configuration allows the whole contraption to move about holonomically.
"This is the big advantage of this type of system," says Killough. "It offers exceptional mobility and precision." Until now, nobody has been able to devise a wheeled platform or conveyor-type system to master this movement without using wheels that require steering.
The OHP owes its deftness to the 90-degree angle wheel assemblies and the innovative computer technology developed at ORNL that controls them. "We didn't reinvent the wheel," Pin says, "We found a smart way of controlling several of them."
By appropriately combining the speed of the three motors that drive the wheels, the computer's program controls the platform and permits its unique means of locomotion. It can be teleoperated using a joystick control, or it can move about autonomously using sensors to avoid obstacles.
The first applications of the OHP may be for autonomous robots used for inspecting crowded and reach-restricted spaces in factories and plants. "Robotics manufacturers with whom we have spoken see this as an attractive alternative to the current wheel technology, particularly when simultaneous rotational and translational motions (in a straight line) of the robot are required," Pin says.
"We can instantly take off in a new direction or spin around without stopping to steer the wheels," Killough adds, "and can maneuver very precisely in a minimal amount of space."
Other promising applications include autonomous transport vehicles in warehouses, outdoor vehicles, construction equipment, and maybe even home vacuum cleaners. Groupings of the wheel assemblies (when pointed up) could serve as an improved conveyor belt on which objects can be smoothly transported, manipulated for precise machining, and loaded as cargo where minimal shear or strain on the object being carried is desired.
Research on the OHP was supported by DOE's Office of Basic Energy Sciences and was carried out in ORNL's Center for Engineering Systems Advanced Research.
Freezing fruit flies for future research. Millions of dollars could be saved each year through use of a new technique for deep-freezing fruit fly embryos for genetic research, developed by ORNL biologists Peter Mazur in cooperation with University of Chicago scientists.
The new method can preserve embryos for an estimated 1000 years and hatch 20% of the thawed embryos into fertile adult flies. Attempts to freeze, thaw, and hatch fruit flies had been unsuccessful before 1990.
Mazur, a Martin Marietta Energy Systems Corporate Fellow and senior staff biologist in ORNL's Biology Division, says that cryopreservation--preservation through the use of extremely low temperatures--also could reduce research costs and ensure a more genetically consistent stock of the flies for future study.
"As it stands now, thousands of genetic strains of fruit flies must be maintained through constant breeding about every two weeks," Mazur says. "That runs into millions of dollars each year and poses the risk of not being able to maintain a stock that is genetically pure over time."
Since the early 1900s, geneticists have been enthusiastic about the fruit fly's usefulness for research. Because of its genetic likeness to the human genome (the whole of an organism's genetic information), the fly's genome has been listed as one of the five most significant genomes to be sequenced as part of the worldwide Human Genome Project. Sequencing involves identifying and putting into sequential order the genetic building blocks of DNA at the most fundamental level.
The Drosophila fly (scientific name for the fruit fly) has several attractive qualities: It flourishes in a laboratory setting, its chromosomes are often large enough in size to be easily seen through a microscope even at the larval stage, and, particularly appealing to geneticists, it has only a 10-day life cycle.
"This short lifespan makes it relatively easy to study genetic mutations throughout many generations," Mazur explains. However, he adds, the drawback to such a short lifetime is the need to constantly breed the flies to maintain sufficient laboratory stocks--an expensive and risky proposition.
Maintaining a single stock costs roughly $200 a year, and 10,000 to 30,000 different genetic stocks are now being maintained. The major risk is "genetic drift"--spontaneous changes in the organism's genetic blueprint that can occur from generation to generation. "And," says Mazur, "there always exists the possibility of flies being incorrectly labeled. Such mistakes could contaminate the stock."
Compounding the ordeal of keeping thousands of stocks of fruit flies is the frustrating fact that only about 20% of them are in use at any given time. The remaining 80% must be maintained, though, because they are either a testament of past research or the topic of future studies.
Given 15,000 stocks of fruit flies, cryogenic preservation of the 80% not in use could save a conservatively estimated $2.4 million a year. The amount rises to $6 million per year if all 30,000 stocks were frozen.
For decades, scientists have searched in vain for an effective method for deep-freezing fruit fly embryos without damaging them, but the eggs' high sensitivity to cold has foiled most every attempt. The eggs also are shrouded in a protective, waxy membrane that resists water and other solutions used in the cryogenic process.
"Peter Steponkus was actually the first to achieve some amount of success in 1990 in preserving Drosophila cryogenically," Mazur says, pointing out that the Cornell University scientist's research laid the foundation for successful cryopreservation of the organism.
But on average, only about 0.5% of Steponkus' cryopreserved embryos were able to develop into adult fruit flies (see photo above). Mazur's 20% recovery rate represents a 40-fold improvement. Steponkus has recently reported still further improvement.
Mazur and his ORNL research team, in consultation with Drosophila expert Anthony P. Mahowald at the University of Chicago, identified critical steps in the freeze-thaw process to realize the impressive results.
When the eggs are about an hour old, the researchers wash them, then put them in a bath of cool water overnight to slow their growth rate. The next morning, they remove the eggs from the cool-water bath and then use bleach, alcohol, and a gasoline-like liquid called heptane to remove the two membranes that coat the eggs.
Once the coating has been removed and the embryos are permeable, a solution of ethylene glycol is introduced into the cells of the eggs. "The ethylene glycol is similar to a concentrated form of antifreeze," Mazur says. It is used to protect the embryos from fatally freezing when they are plunged into a thermos of liquid nitrogen slush.
In an instant, the embryos are frozen at about -205 degrees C. The ethylene glycol, instead of crystallizing like ice, vitrifies into a glasslike substance, and the eggs are preserved.
"This rapid freezing actually outraces the chilling effect that normally would kill the eggs," Mazur says. "When we thaw the embryos, we have to do it at an equally rapid pace."
Mazur's work was initially funded by the National Science Foundation (NSF). He is now continuing to study cryopreservation techniques for mosquitoes through the support of NSF and DOE's Office of Health and Environmental Research.
Breaking down bleach in waste streams. Martin Marietta Energy Systems researchers have invented a new way to break down hypochlorite, or chlorine bleach, in industrial waste streams. The new method is environmentally safe, and it costs less and is more effective than currently available chemical methods.
Chlorine ranks eighth in production among manufactured chemicals worldwide. It is used to make plastics, pharmaceuticals, paper, and agricultural products and to disinfect swimming pools, cooling towers, and drinking water. Hypochlorite is a by-product or waste of many industrial and environmental processes that use chlorine.
To meet environmental standards, industrial firms making chlorine or chlorine-containing products must filter escaping chlorine gas through a caustic scrubber. This treatment produces sodium hypochlorite (NaOCl), which can kill fish and other aquatic life when discharged to lakes and rivers.
The new hypochlorite degradation process, patented by DOE, was invented by researchers from ORNL and the Y-12 Plant. The process was originally developed to break down sodium hypochlorite in Y-12 Plant waste streams. The waste hypochlorite was produced by scrubber treatment of chlorine released in the electrolytic separation of lithium from chlorine in the feed material, lithium chloride. This material has been used in the production of lithium metal for nuclear weapons.
(The hypochlorite treatment process is not used at the Y-12 Plant because of a beneficial arrangement in which waste liquids containing sodium hypochlorite are loaded in tanks in Oak Ridge and delivered by truck to a Knoxville sewage plant. This facility uses the waste as a source of chlorine for sewage treatment. However, the new process is an alternative solution.)
R&D Solutions, a company based in Oak Ridge, obtained a license for the process from DOE. The catalyst used in the process is manufactured for R&D Solutions by United Catalyst, Inc., of Louisville, Kentucky. Personnel from Martin Marietta, R&D Solutions, and United Catalyst received an R&D 100 Award for the chlorine removal technology. Besides Energy Systems researchers Googin, Davis, Huxtable, Compere, and Griffith, other winners were Chet Thornton of ORNL's Plant and Equipment Division, who is president of R&D Solutions, and other ORNL staff members who also work for R&D Solutions--Bob Walker of the Health Sciences Research Division, Arnold Beal of the Instrumentation and Controls Division, Deborah Davidson of the Chemical Technology Division, and Scott Beck of the Plant and Equipment Division.
According to R&D Solutions, the new process can reduce 26,500 parts per million (ppm) of chlorine bleach in a waste stream to less than 0.1 ppm in minutes. Using a catalyst invented by Compere, Griffith, and Huxtable, the process simply converts a toxic waste stream containing chlorine bleach into a harmless one containing recyclable oxygen and salt. Furthermore, the catalyst lasts for many months before becoming inactive, compared to just a few days with others.--Wayne Scarbrough and Carolyn Krause
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