What is the best material for thermal conductivity?

The best material for thermal conductivity is diamond, which has a thermal conductivity of 1300~2400 W/(m*K).

Metal: Silver has the best thermal conductivity, followed by copper, gold and aluminum.

Nonmetal: diamond has the best thermal conductivity, followed by silicon (si).

The process of transferring heat from a high-temperature region to a low-temperature region due to the thermal movement of microscopic particles, such as molecules, atoms, and electrons, within an object without macroscopic displacements of the substances that make up the object is called thermal conductivity.

Thermal conductivity relies on the thermal movement of electrons, atoms, molecules and lattices in the material to transfer heat . However, the nature of the material is different, its main thermal conductivity mechanism is different, the effect is not the same. Generally speaking, the thermal conductivity of metal is greater than non-metal, pure metal thermal conductivity is greater than alloy. In the three states of matter, the solid state thermal conductivity is the largest, followed by the liquid state, the gas state is the smallest. For example, the thermal conductivity of ice, water and water vapor at 0°C under standard atmospheric pressure is 2.22W/(m-K), 0.55W/(m?K) and 0.183W/(m?K) respectively.

Metal thermal conductivity mainly relies on the thermal movement of free electrons, conductive metal materials with good thermal conductivity is also large. Metal thermal conductivity range of 2.3 ~ 420W / (m?K), silver is 420W / (m-K). However, the addition of other elements within the pure metal to become an alloy, due to the embeddedness of these elements, seriously impede the movement of free electrons, so that the thermal conductivity is greatly reduced. For example, pure copper λ = 398W / (m? K), after adding 30% of zinc pure copper into brass, λ is only 109W (m? K).

Nonmetallic materials thermal conductivity mainly rely on the lattice structure vibration to produce elastic waves to transfer energy. Physics calls it phonon transfer of energy. In the transfer process, if there are phonon scattering factors, such as crystal gaps, cracks, thermal conductivity will be significantly reduced. The thermal conductivity of liquids is in the range of 0.07-0.7 W/(m?K), and the mechanism of thermal conductivity of liquids is more complicated. The thermal conductivity of gases relies on molecular thermal motion, the speed of molecules in the high-temperature region is higher than that in the low-temperature region, and energy is transferred to molecules in the low-temperature region through molecular collisions. The thermal conductivity of gas is in the range of 0.006-0.7W/(m?K). Gas molecules have a greater impact on thermal conductivity, the smaller the molecular weight, the lighter the weight, the faster the speed of movement, the greater the thermal conductivity. Power plant generators using hydrogen cooling instead of air cooling, cooling effect is better is this reason.

Reference:

Baidu Encyclopedia-Thermal Conductivity