PhysOrg.com) -- Researchers at MIT and elsewhere have succeeded in creating a synthetic crystal that can very effectively control the transmission of heat -- stopping it in its tracks and reflecting it back. This advance could lead to insulating materials that could block the escape of heat more effectively than any present insulator.

This crystal structure was built using alternating layers of silicon dioxide (the basis of the dielectric layers in most microchips) and a polymer material. The resulting two-component material successfully reflected phonons — vibrational waves that are the carriers of ordinary heat or sound, depending on their frequency. In this case, the phonons were in the gigahertz range — in other words, low-level heat.

Edwin L. Thomas, head of MIT's Department of Materials Science and Engineering and the Morris Cohen Professor of Materials Science and Engineering, was a co-author of a new paper, published on March 10 in the journal Nano Letters, that describes this creation of phononic crystals in the hypersonic range (that is, above the frequency range of sound, and thus can be considered in the range of heat).

Phonons may sometimes be thought of as particles, and sometimes as vibrational waves, analogous to the dual wave and particle nature of light. Physically, the phonons are manifested as a wave of density variation passing through a material, like the wave of compression that travels along a child's Slinky toy when you stretch it out and give one end a shove.

Phys Org