Summary of Thermal Properties

One of the outstanding characteristics of impurity-free diamond its extremely-high thermal conductivity, the highest by far of any solid at room 

Mechanism of Thermal Conductivity. The thermal conductivity in diamond occurs by lattice vibration. Such a mechanism is characterized by a flow of phonons, unlike the thermal conductivity in metals which occurs by electron transportf K l (see Ch. 3, Sec. 4.3, for the mathematical expression of thermal conductivity). 

Lattice vibration occurs in diamond when the carbon atoms are excited by a source of energy such as thermal energy. Qu2intum physics dictates that a discrete amount of energy is required to set off vibrations in a given system. This amount is equal to the frequency of the vibration times the Planck s constant (6.6256 x 10 erg-s). 

Carbon atoms are small and have low mass aruJ, in the diamond structure, are tightly and isotropically bonded to each other. As a result, the quantum energies necessary to make these atoms vibrate is large, which means that their vibrations occur mostly at high frequencies with a maximum of approximately 40 x 10 Hz.O 1 Consequently, at ordinary temperatures, few atomic vibrations are present to impede the passage of thermal waves and thermal conductivity is unusually high. 

However, the flow of phonons in diamond is not completely free. Several obstacles impede it by scattering the phonons and thus lowering the conductivityThese obstacles include  

---

TABLE 11.10 Summary of Thermal Properties of Renewable Polymers Based on PLA and PHB... 

---