Oxygen-Free High Thermal Conductivity

Q1) OFHC Copper is an oxygen-free highly conductive copper alloy. Usually it is a pure copper alloy. OFHC is a metal material of nonferrous metal alloys known to have high electrical and thermal properties. OFHC is manufactured by directly converting the refined cathode and casting selected under carefully controlled conditions to prevent contamination of pure oxygen-free metals during processing. The method of manufacturing OFHC copper guarantees ultra high grade metals with a copper content of 99.98%.

Constant of k 0 In the case of pure metals such as copper and silver, the thermal conductivity is high because l is large. At higher temperatures, the mean free path is limited by phonons, so the thermal conductivity tends to decrease with temperature. For alloys, the density of impurities is so high that l and k are therefore small. Therefore, alloys such as stainless steel can be used as insulation.

Pure alloys have high thermal conductivity. Alloys consisting of two metals with thermal conductivities k 1 and k 2 are expected to have a conductivity k between k 1 and k 2. Surprisingly, this is not a fact. The thermal conductivity of the two metal alloys is usually much lower than this. For example, copper and aluminum have thermal conductivities of 401 W / m ° C and 237 W / m ° C, respectively. In liquids, the molecules are relatively denser than the density in the gas. Therefore, the thermal conductivity of the liquid depends mainly on the molecular diffusion effect, that is, the random motion of the molecule. As we saw earlier, an increase in the random motion of a molecule can interfere with the heat flow through the liquid.

In the case of metal and nonmetal, the influence of temperature on thermal conductivity is different. For metals, the thermal conductivity is mainly due to free electrons. According to Wiedemann-Franz's law, the thermal conductivity of a metal is approximately proportional to the absolute temperature (Kelvin) multiplied by the conductivity. For pure metals, the conductivity decreases with increasing temperature, so the product of these two (thermal conductivity) remains nearly constant. However, as the temperature approaches absolute zero, the thermal conductivity drops dramatically. For alloys, the change in conductivity is usually small, so the thermal conductivity increases with temperature and is usually proportional to temperature. Many pure metals have a peak thermal conductivity between 2 K and 10 K