How does heat move through solids?

Heat and energy are interrelated. Einstein has long back discussed his ideas of transfer of heat through solids, but a recent discovery by the scientists at Oak’s ridge national laboratory has also supported Einstein’s theory. 

Energy can neither be created nor destroyed, but its forms can be changed. Heat is one such form of energy which is generated when there is friction between two objects. Though there are other means too, here we are referring to the first transfer of heat from particle to particle. 

When Einstein proposed his theory first in 1911, he stated that heat travels from atom to atom in thermal insulators and that this transfer was just an addition to the heat transfer because of vibration of molecules. This is not noticeable for materials like copper, but for other stuff, the removal of heat can be noticed as it is not so quick. Copper is an excellent conductor of electricity and heat, but wood is not. For studying the transfer of heat, it is better to use insulators as well as novel materials. 

When thallium crystal was analyzed to understand its healing properties, it revealed that the atomic vibrations in its crystal lattice were too slow to transmit a substantial amount of heat. The researchers found that another mode of heat transfer must be involved. Having information of this second mode of heat transfer, it would be easier to choose materials for heat transfer that could reduce cost, carbon emissions, and waste production. A commonly used element for heat transfer is silicon, which has a lattice of atoms chemically bound. Heat is carried through this lattice in the form of vibrations or sound waves. When these waves collide with each other, the transfer of heat is decreased.

The thallium based material has been acknowledged as the lowest category of thermal conductive. Its energy is confined to a single atom and transfer of heat is quite slow. Sound waves, as well as Einstein’s heat transfer mechanism, explains what kind of properties does metal have, because of which it can act as a conductor and an insulator. Einstein’s heat hoping mechanism is found only in excellent thermal insulators. Thermal insulation is a device that is supposed to block the transmission of heat. 

This research was authored by Saikat Mukhopadhyay, an associate at National Research Council research associate at the U.S. Naval Research Laboratory who has formerly served in the same position at ORNL as well.