Thermal conductivity electrons. In this case the mean velocity is the Fermi velocity which is temperature independent. The mean free path is determined by the impurities and the crystal imperfections which are temperature independent as well. So the only temperature-dependent quantity is the heat capacity "c", which, in this case, is proportional to "T". So with "k" a constant. For pure metals such as copper, silver, etc. "l" is large, so the thermal conductivity is high. At higher temperatures the mean free path is limited by the phonons, so the thermal conductivity tends to decrease with temperature. In alloys the density of
Two-dimensional materials material. This is due to the two forms of molybdenum sulfide monolayers having different electrical properties. The 1T polymorph of molybednum sulfide is metallic in character while the 2H form is more semiconducting. However, molybdenum disulfide layers produced by electrochemical lithium intercalation are predominantly 1T and thus metallic in character as there is no conversion to the 2H form from the 1T form. The thermal conductivity of molybdenum disulfide monolayers at room temperature is 34.5W/mK while the thermal conductivity of few-layer molybdenum disulfide is 52W/mK. The thermal conductivity of graphene, on the other hand, is 5300W/mK. Due to the rather