New nanocomposite process improves capacitors

A new technique for creating films of barium titanate (BaTiO3) nanoparticles could allow lead to capacitors able to store twice as much energy as conventional devices, according to researchers at Georgia Tech in Atlanta.

The improved capacitors could be used in consumer devices, such as cellular telephones, and in defense applications requiring both high energy storage and rapid current discharge, the team says.

Barium titanate has long been of interest for use in capacitors, but until recently, materials scientists had been unable to produce good dispersion of the material within a polymer matrix. By using tailored organic phosphonic acids to encapsulate and modify the surface of the nanoparticles, researchers at the Georgia Institute of Technology’s Center for Organic Photonics and Electronics were apparently able to overcome the particle dispersion problem to create uniform nanocomposites.

“Our team has developed nanocomposites that have a remarkable combination of high dielectric constant and high dielectric breakdown strength,” said Joseph W. Perry, a professor in the Georgia Tech School of Chemistry and Biochemistry and the Center for Organic Photonics and Electronics. “For capacitors and related applications, the amount of energy you can store in a material is related to those two factors.”

The new encapsulation technique could have broad applications.

“This work opens a door to effectively exploit this type of particle in nanocomposites using the coating technology we have demonstrated,” explained Perry. “There are many ways we can envision making advances beyond what we’ve done already.”

Though the new materials may already offer enough of an advantage to justify commercializing, Perry believes there are additional opportunities for boosting their performance. The research team also wants to scale up production to make larger samples—now produced in two-inch by three-inch films—available to other researchers who may wish to develop additional applications.

Because of their ability to store and rapidly discharge electrical energy, capacitors are used in a variety of consumer products, such as computers and cellular telephones. And because of the increasing demands for electrical energy to power vehicles and new equipment, they also have military applications.

The results were reported in the April 2007 edition (Vol. 19, issue 7) of the journal Advanced Materials. The research was supported by the Office of Naval Research and the National Science Foundation. Georgia Tech has filed a patent application on the nanoparticle encapsulation technique.