June 29, 2009

Khan wins Outstanding Dissertation Award

by Tim Crosby

CARBONDALE, Ill. -- A former doctoral student’s research on new, environmentally friendly refrigeration methods is the winner of this year’s Richard and Donna Falvo Outstanding Dissertation Award at Southern Illinois University Carbondale.

Mahmud Khan, who earned his doctorate in the Department of Physics at SIUC, won for his research titled, “Magnetic Entropy Changes and Exchanges Bias Effects Associated with Phase Transitions in Ferromagnetic Heusler Alloys.” The research looked at materials that could potentially replace traditional refrigeration methods and gases, such as Freon.

The award, which carries a $1,000 prize, is named for Richard E. and Donna T. Falvo, both retired SIUC faculty members and sponsors of the competition for more than two decades.

Khan earned his master’s degree and doctorate in applied physics at SIUC and worked with a team of faculty members on a U.S. Department of Energy-funded project on metal alloys having colossal magnetocaloric properties. The term refers to metal combinations that have the ability to heat up and cool down rapidly and to below ambient temperatures when placed in a magnetic field.

Magnetic refrigeration traditionally is reserved for cooling objects that are already super cool, starting at about -450 degrees Fahrenheit. Members of the team, however, looked at ways to produce the effect in environments around room temperature, which could lead to a revolution in household cooling applications.

So-called magnetic, or “solid-state” refrigeration would offer many advantages. It would be far simpler and more efficient than traditional cooling machines, relying on far fewer moving parts. The metals used also are generally nontoxic and far more environmentally friendly than traditional units that rely on compressed gases such as Freon, which has been shown to damage ozone in the atmosphere.

The technology faces several practical challenges, however, particularly in creating the specific materials that would achieve such an effect at around room temperature as well as cause a strong enough effect to actually provide refrigeration. Researchers also need to address economic and efficiency questions.

Naushad Ali, professor of physics at SIUC, led the team on which Khan worked. In his nominating letter, Ali said Khan worked on testing the metal alloys placed in the magnetic field and discovering the underlying causes for the physical properties causing the phenomenon.

The work involved experimenting with a variety of materials and alloys -- called Heusler alloys -- and looking for a combination that could bring magnetic refrigeration into reality. After months of research, Ali said Khan experienced a “eureka” moment.

“The outcome was that Dr. Khan has designed a material which is extremely well suited for a realistic magnetic refrigerant working at usable temperatures with a very high value of refrigerant capacity,” Ali said. “And the material is relatively cheap and easy to prepare.”

Khan, who now works as a post-doctoral researcher with one of the top experts in magnetic refrigeration in the world at U.S. Department of Energy’s Ames Laboratory in Iowa, is an oft-cited source for further research in the area, Ali said.

“Dr. Khan’s quality and quantity of research accomplishments … is outstanding,” Ali said.

Aldo Migone, professor and chair of the Department of Physics at SIUC, said Khan’s abundant research has not only led to more than 20 peer-reviewed published articles so far -- an unusually high number for a doctoral student -- but also led to a pending patent.

“Magnetic cooling … would be a revolutionary new approach in the technology used for these household appliances, and one that is much more benign (to the environment),” Migone said. “Clearly Dr. Khan’s research provides a very happy marriage of the fundamental, basic research on materials with enormous potential for broader societal impact and improved new technology.”