Naturally produced boric acid in Boron, Calif., gives the town a frosted appearance.
Boric Acid Is Amazing!
August / September 2007
Volume 5 Number 4
How can we help to preserve the environment, reduce our dependence on foreign oil and yet keep on driving just as much as we do now? The answer probably isn't being discussed in a think tank in Washington or being assembled on a factory floor in Detroit—€”but it just might be sitting in your mother's medicine cabinet.
Scientists at Argonne National Laboratory have begun to combine infinitesimal particles of boric acid—€”known primarily as a mild antiseptic and eye cleanser—€”with traditional motor oils to improve their lubricity and by doing so increase energy efficiency. Ali Erdemir, senior scientist at Argonne, has spent nearly 20 years investigating the lubricious properties of boric acid. In 1991, he received an R&D 100 award for showing that microscopic particles of boric acid could dramatically reduce friction between automobile engine parts. Metals covered with a boric acid film exhibited coefficients of friction lower than that of Teflon, making Erdemir's films the slickest solids in existence at that time.
"Ali was looking at large, micron-sized, particles," said George Fenske, who works alongside Erdemir at Argonne. "He was just sprinkling boric acid onto surfaces."
But driven by a conviction that he could fashion boric acid into an even better lubricant, Erdemir continued to chase the ultimate frontier: a perfectly frictionless material. Glimpsing the potential of nanotechnology, Erdemir went smaller—€”ten times smaller—€”and was astonished by the behavior of much thinner boric acid films. "If you can produce or manufacture boric acid at the nanoscale, its properties become even more fantastic," he said. "This is probably one of the very first commercial success stories in nanolubrication."
Reducing the size of the particles to as tiny as 50 nanometers in diameter—€”less than one one-thousandth the width of a human hair—€”solved a number of old problems and opened up a number of new possibilities, Erdemir said. In previous tests, his team had combined the larger boric acid particles with pure poly-alpha-olefin, the principal ingredient in many synthetic motor oils. While these larger particles dramatically increased the lubricity of the pure oil, within a few weeks gravity had started to cause the mixture to separate. By using smaller particles, Erdemir created a stable suspension of boric acid in the motor oil.
Through the application of smaller grains of boric acid, the Argonne scientists also found that they needed less of the substance to produce the slick films.
This could help to reduce costs of boric acid motor oil additives, which currently retail for around $40, according to Fenske. In laboratory tests, these new boric acid emulsions have been shown to cut the coefficient of friction to less than 0.05, dramatically reducing the amount of energy lost through friction as heat. The implications for fuel economy are not hard to imagine, Erdemir said. "You're easily talking about a four or five percent reduction in fuel consumption," he said. "In a given day, we consume so many millions of barrels of oil, and if you can reduce that number by even one percent, that will have a huge economic impact—€”not to mention reducing our dependence on foreign oil, which is the biggest political problem that we are now facing."
Argonne is currently in talks with two major additive companies in an attempt to bring boric acid technology to market. While these new additives need to pass a battery of environmental and safety tests, they will probably be available within two years, Erdemir said.
Erdemir's first experiments with boric acid represented an enormous breakthrough in tribology, which is the study of friction and lubrication. He demonstrated that the compound had the potential to substantially diminish friction, but more importantly he showed boric acid to be every industrial technologist's dream: it came from naturally abundant minerals, was cheap to manufacture, and posed no health hazards or threats to the environment. By comparison, Teflon (otherwise known as polytetrafluoroethylene) was synthetic, relatively expensive to make, and caused flu-like symptoms if heated above 650 degrees Fahrenheit.
Boric acid owes its lubricious properties to its unique natural structure. The compound consists of a stack of crystallized layers in which the atoms tightly adhere to each other. However, these layers stack themselves relatively far apart, so that the intermolecular bonds (called van der Waals forces) are comparatively weak. When stressed, the compound's layers smear and slide over one another easily, like a strewn deck of playing cards. The strong bonding within each layer prevents direct contact between sliding parts, lowering friction and minimizing wear.
Until recently, most of Erdemir's work in boric acid lubrication had been restricted to motor oils, principally because of the relative bulk of the larger particles. The move to the nanoscale, however, has opened up other possible uses of the chemical. Through a simple chemical reaction known as alkylation, nano-boric acid can be transformed into a liquid relative of boric acid that has shown potential to increase fuel lubricity. "If you put this liquid into the existing unadditized fuel, you'll see additional improvements in fuel economy," Erdemir said.
Using this liquid analog of solid boric acid as a fuel additive would greatly benefit the environment, both because it would help to increase fuel efficiency and because it would replace existing environmentally-hazardous fuel lubricants, Erdemir claimed. By themselves, most fuels—€”especially diesel—€”contain some sulfur and other special chemical additives to boost lubricity. When burned, however, some of these additives along with sulfur may cause harmful emissions and acid rain. However, the lack of a suitable alternative complicated efforts to cut sulfur content.
"If you take the sulfur out, the fuel's lubricity comes down to almost zero. You have to put something in to restore the lubricity," Erdemir said. This liquid analog of nano-boric acid technology seems to be able to do just that."
While Fenske explained that Argonne's new fuel additive is intended primarily for diesel fuels, it may also help to assist with the introduction of fuels with higher ethanol contents. "I don't know what the lubricity of E-85 is compared to gasoline, but it can't be any better than gasoline. The lubricity of ethanol is going to be a main cause of problems, so you may need a different additive package for the alcohol-based fuels. And boric acid is nicely soluble in alcohol," he said.
The substitution of liquid boric acid for sulfur-containing additives preserves the health of the car as well as that of the environment. Sulfur exhaust gradually coats the surface of a car's catalytic converter, the part which helps to reduce the toxicity of a car's emissions through a set of chemical reactions. Eventually, the converter becomes so choked with sulfur that it is no longer able to process any more exhaust. "Sulfur not only hurts the environment; it hurts your car," Erdemir said.
Even though he has just begun to unleash the potential of boric acid, Erdemir believes that nanoscale synthetic compounds may prove to be even more effective lubricants. "The next step is to use the basic knowledge that we have gained out of this particular compound to come up with more exotic compounds that will work even better," he said.
"Better," said Erdemir, means entering a physical regime in which friction nearly vanishes. By achieving this "superlubricious" state, scientists will have reshaped the entire field of lubrication science while reaping enormous economic rewards. "There are just so many mechanical systems," Erdemir said.
"If you can actually make these surfaces frictionless, we're talking about achieving a level of not only fuel savings but also economic savings of up to five to seven percent of our national GDP. That's about $600 billion just in the United States alone."
Whether scientists can actually eliminate friction entirely, like electric resistance in a superconductor, is not yet known. But Erdemir is convinced that he can continue to make progress.
Jared Sagoff is an Argonne science writer.
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