|
|
Click
on image for larger view. |
|
Visualizing first images of soot forming in a flame may lead to advances in health and in industry. |
Studying soot may minimize health hazards |
|
Tiny soot particles, created when materials burn, create health problems and may contribute to thousands of premature deaths each year, according to the U.S. Environmental Protection Agency. Researchers from Argonne and Brigham Young University have used the Advanced Photon Source (APS) to see for the first time the birth and growth of the tiniest soot particles in a living flame. This work promises to contribute to a comprehensive model of how soot forms and grows. Such a model may help to reduce the health hazards associated with soot production, to improve the efficiency and performance of industrial devices that rely on burning hydrocarbons and to devise efficient production processes that use soot, such as the industrial manufacture of carbon black. Over the years, researchers have used a variety of techniques to study soot particles. But until now, it has been difficult or impossible to study the structure of particles in the 1 nanometer to 100 nanometer size range as they are formed. (A nanometer is about 1/50,000 the diameter of a human hair.) Yet this size range covers most of the initial formation and growth of soot particles. Soot originates in the incomplete combustion of hydrocarbons. Studies at other laboratories suggest that soot begins with the chemical growth of large aromatic (benzene-based) hydrocarbons to about 0.5 to 2 nanometers in diameter. This substrate or nucleus grows into an elementary soot particle about 4 nanometers in diameter and then clusters into small chains. The chains merge to produce primary particles, 20 to 50 nanometers in diameter, that coagulate to form larger soot aggregates. This formation and growth occurs as a series of chemical and physical interactions within a flame. Thanks to the high intensity of APS X-rays, scientists have been able to study for the first time the initial distribution of soot particles as they form within the flames of such fuels as toluene and hexane. “We've been able to observe particles between 0.8 and 15 nanometers in diameter,” said Argonne chemist Randall Winans. “Thanks to the APS, we're able to observe pre-soot particles 10 times smaller than anything previously observed with a synchrotron X-ray source.” This research was funded by the U.S. Department of Energy's Office of Basic Energy Sciences and was carried out at the Basic Energy Sciences Synchrotron Radiation Center beamline at the APS. For more information, please contact Catherine Foster. |