A collaborative effort between researchers from the Massachusetts Institute of Technology, IBM, the University of California at Berkeley, and the University of Athens has resulted in the creation of an intricate ceramic nanostructure (see the figure). The double-strand matrix, known as a gyroid structure, is being eyed as a potential component in integrated circuits and magnetic storage media. It also may find its way into selective membranes, next-generation catalysts, photonic materials, and other applications.
Mathematicians had created a theoretical version of this structure 30 years ago. But limitations in tools and technologies made it virtually impossible to replicate in real life. That is, it was impossible before the Air Force Office of Scientific Research and the National Science Foundation Center for Polymer Interfaces and Macromolecular Assemblies at IBM decided to fund a project to investigate the creation of inorganic materials.
Researchers discovered that by carefully controlling the molecular weight and volume fraction of block copolymers—a type of polymer made up of two or more different monomer units linked together in blocks—nanostructures with highly ordered and complex pore structures could be produced. When they used a purely hydrocarbon block and a block containing inorganic substances, two materials were synthesized. These materials then formed two different structures. The inorganic block dominated one, while the organic block was dominant in the other. Oxidation removed the hydrocarbon block, and the inorganic block was converted to a ceramic.
While it's not a conventional processing technique, researchers were able to show how subjecting two materials to a one-step, room-temperature oxidation process could convert the materials into nanoporous or nanorelief ceramic films. The nanoporous structure is a ceramic matrix interpenetrated with connected, ordered, tortuous pores. The nanorelief film is an open structure comprised of intricate 3D ceramic-strut networks. The interconnected struts that make up the nanorelief ceramic film form a 3D structure that is mostly air. The struts are only 300 Å in diameter, or about one-thousandth the width of a human hair.
As a ceramic, the films can be subjected to temperatures up to 400°C, which is much higher than the temps traditional polymers can withstand. And while most ceramics are powders and binders, researchers believe the double-gyroid ceramic film will prove to be solvent-resistant. This alone expands the structure's potential uses.
For more information, check out MIT's web site at www.mit.edu.